Cost-Constrained Optimization of Energy Efficiency for Multi-family and Commercial BuildingsDavid Vernon, Mazen Daher, Mark ModeraProject Report2023This project provides California stakeholders with cost-optimized selections of technology packages for building cost-effective and high-efficiency multi-family residential and commercial buildings. A detailed cost and energy performance analysis was used to identify measures and packages that most closely approach zero-net energy for each building type in each state climate zone.Read PaperCalifornia Energy Commission (CEC)
Analysis of Refrigerant Use for AC Equipment MaintenanceTheresa Pistochini, Roger Silveira, Derrick Ross, Robert McMurry, Adarsh UmaraniAcademic Journal Paper2022Understanding refrigerant emissions from air-conditioning (AC) equipment is critical for accurately estimating its global warming impacts. The goal of the study described in this article was to develop a primary data collection method to estimate average refrigerant emission rates of R-22 and R-410A in AC equipment by examining historical refrigerant used relative to the initial refrigerant charge of the AC equipment inventory.Read PaperDaikin U.S.
Timing is Everything: Optimizing Load flexibility of Heat Pump Water Heaters for Cost, Comfort, and Carbon EmissionsCaton Mande, Aref Aboud, Loren dela Rosa, Rachael Collins, Matthew J. EllisConference Paper2022As California continues to decarbonize the electrical grid and more customers electrify, load flexibility among heat pumps is becoming critical for maximizing the use of carbon-free electricity sources, stabilizing the electricity grid, and minimizing operating costs to end-users. Economic model predictive control (MPC) is an advanced control technique that can provide automated load flexibility due to its ability to account for time-varying electric tariffs and available energy storage. A new configurable control framework is motivated and described to address the challenges of configuring economic MPC for deployment in heat pump water heaters.Read Paper
Concurrent Space Cooling and Hot water Heating through Compact Heat Pumps for All-electric Residential BuildingsSubhrajit Chakraborty, Robert Mcmurry, Curtis HarringtonConference Paper2022Multi-function heat pumps can use the compressor heatduring a space cooling operation, which is otherwise wasted to the ambient through the condenser coil, to heat up water for domestic use. This project tested a multi-function heat pump that combines space cooling, dehumidification, ventilation, and domestic hot water (DHW) in a compact system (POD).Read Paper
Aerosol Sealing of Existing ResidencesCurtis Harrington, Frederick Meyers, David Bohac, Melissa Anders, and Lindsay GentyConference Paper2022This paper describes the air leakage reductions achieved in an ongoing U.S. Department of Energy Building America project that integrates an aerosol-based sealing technology used primarily for new residential construction into existing home retrofits.Read Paper
Technology Characteristics that Influence Adoption of Residential Distributed Energy Resources: Adapting Rogers’ FrameworkSarah Outcault, Angela Sanguinetti, Leslie NelsonAcademic Journal Paper2022Distributed energy resources (DERs) present an important opportunity to lower the carbon intensity of residential buildings but face numerous barriers to adoption. This paper extends and adapts Rogers' theory of the role of technology characteristics in the diffusion of innovation (Rogers, 1962) to address the unique features of residential DERs. Read Report
Building Lower-Carbon Affordable Housing: Case Studies from CaliforniaSarah Outcault, Eli Alston-Stepnitz, Angela Sanguinetti, Ashley N. DePew, Cinthia MagañaAcademic Journal Paper2022This research explores developers’ experiences with lower-carbon multi-family affordable housing in California using three case studies that illustrate different pathways to decarbonization – improving efficiency, eliminating fossil fuel combustion for end-uses, and adopting a zero-net energy design.Read Report
Modeling Impacts of Ventilation and Filtration Methods on Energy Use and Airborne Disease Transmission in ClassroomsTheresa Pistochini, Caton Mande, Subhrajit ChakrabortyAcademic Journal Paper2022The benefits of increased ventilation and filtration for reducing disease transmission compared to drawbacks of reduced thermal comfort and increased energy consumption and electricity demand are not well described. A comprehensive simulation of outdoor air ventilation rates and filtration methods was performed with a modified Wells-Riley equation and EnergyPlus building simulation to understand the trade-offs between infection probability and energy consumption for a simulated classroom in 13 cities across the US.Read Report
Packaged Roof Top Unit with Integrated Heat Pump and Indirect/Direct Evaporative CoolingTheresa Pistochini, Robert McMurryTechnical Report2022The emerging technology assessed in this study is a packaged RTU that integrates a heat pump (HP) with an indirect-direct evaporative cooling(IDEC) system that is designed as a direct replacement for a traditional RTU. This project evaluates the packaged heat pump with IDEC in a field study and compares its performance to a baseline packaged RTU. Read ReportSouthern California Edison, Pacific Gas and Electric
Greenhouse Gas Analysis of Proposed HVAC Designs for the Davis Innovation Sustainability CampusDr. David Vernon, Mazen DaherTechnical Report2022The Davis City Council has required that the proposed Davis Innovation Sustainability Campus use an all-electric, high efficiency HVAC design that would be 30% more efficient than Title 24 code requirements using the Time Dependent Valuation metric. To meet this requirement, the HVAC design would use packaged air source heat pumps on each of the buildings. Upgrading the HVAC systems to a district energy system with all electric central equipment including a chiller, heat pump, thermal energy storage tanks, and a geothermal bore field has the potential to be even more efficient than the required design.Read Report
Occupant Non-Energy Impact Identification Framework: A human-centered approach to understanding residential energy retrofitsSarah Outcault, Angela Sanguinetti, Nermin Dessouky, Cinthia MagañaAcademic Journal Paper2022Residential energy retrofits have the potential to generate significant non-energy impacts (NEIs) on occupants, but the understanding of those NEIs has been hampered by the lack of a shared approach to studying them. A detailed literature review revealed several common tendencies that limit the generalizability of findings, including a focus on benefits, different categorization schemes, varied scope and specificity, the conflation of impacts across occupant groups, and conflation of retrofits’ functional outcomes with occupant impacts. This paper suggests a more systematic way of conceptualizing NEIs is needed and proposes a new framework that supports a comprehensive, unbiased, human-centered, and standardized approach. Read Report (paywall)
Characterizing the performance of a do-it-yourself (DIY) box fan air filterRachael Dal Porto, Monet N. Kunz, Theresa Pistochini, Richard L. Corsi & Christopher D. CappaAcademic Journal Paper2022Air filtration serves to reduce concentrations of particles in indoor environments. Most standalone, also referred to as portable or in-room, air filtration systems use HEPA filters, and cost generally scales with the clean air delivery rate. A “do-it-yourself” lower-cost alternative, known as the Corsi-Rosenthal Box, that uses MERV-13 filters coupled with a box fan has been recently proposed, but lacks systematic performance characterization. We have characterized the performance of a five-panel Corsi-Rosenthal air cleaner using both research-grade instrumentation (an aerodynamic particle sizer, APS) and a low-cost particle sensor.Read Report
Understanding teachers' experiences of ventilation in California K- 12 classrooms and implications for supporting safe operation of schools in the wake of the COVID-19 pandemicAngela Sanguinetti, Sarah Outcault, Theresa Pistochini, Madison HoffackerAcademic Journal Paper2022Classrooms are often under-ventilated, posing risks for airborne disease transmission as schools have reopened amidst the COVID-19 pandemic. While technical solutions to ensure adequate air exchange are crucial, this research focuses on teachers’ per-ceptions and practices that may also have important implications for achieving a safe classroom environment.Read Report
Greenhouse Gas Emission Forecasts for Electrification of Space Heating in Residential Homes in the USGTheresa Pistochini, Mitchal Dichter, Subhrajit Chakraborty, Nelson Dichter, Aref AboudAcademic Journal Paper2022This study aims to inform policymakers about the greenhouse gas emission impacts of heat pump deployment in residential homes. Electric heat pumps eliminate direct burning of fossil fuels in homes but result in indirect emissions due to fossil fuels burned for electricity production. This paper presents the first detailed emission forecasts for operating either a heat pump or gas furnace for residential heating over a 15-year period, starting in year 2022 through 2036, in six regions across the US. Read Report
R-466A Refrigerant DemonstrationCurtis Harrington, Fred MeyersCase Study2022Refrigerants used in vapor-compression air conditioners and heat pumps have been the subject of environmental regulations requiring the need to develop alternative solutions with lower global warming potential (GWP). In general, there is a trade-off when choosing alternative refrigerants between performance, GWP, and safety.Download
Residential solar water heating: California adopters and their experiencesAngela Sanguinetti, Sarah Outcault, Eli Alston-Stepnitz, Mithra Moezzi, Aaron IngleAcademic Journal Paper2021 This research surveyed 227 single-family households with solar water heating across the state of California to understand their motivations and experiences, and draw implications regarding barriers to adoption. The survey explored households’ experiences across five stages of adoption, as outlined in Rogers’ Diffusion of Innovation theory: Knowledge, Persuasion, Decision, Implementation, and Confirmation.Download (Paywall)
Considerations for Use and Selection of Portable Air Cleaners for ClassroomsTheresa PistochiniWhite Paper2021Portable Air Cleaners with High Efficiency Particulate Air (HEPA) filtration are widely available. They are measured in terms of their “Clean Air Delivery Rate” (CADR) which is a measure of the cleaning speed of the system in removing particles in a controlled environment2. Portable air cleaners have CADR’s ranging from about 25-400 CFM (depending on size), and more than one could be used in a classroom to increase the amount of filtration provided.Read ReportCalifornia Energy Commission (CEC)
Low-Cost, Large-Diameter Shallow Ground Loops for Ground-Coupled Heat Pumps Curtis Harrington, Antash Najib, Vinod Narayanan, Mitchal Dichter, David Springer, Michael Slater, Peter Grant, Ada Liu, James Haile, Moncef Krarti, Joseph HuangProject Report2021This project developed and validated modeling tools for simulating a ground heat exchanger technology that provides a less expensive method for implementing ground-source heat pumps and significantly reduces energy use in many California climate zones, furthering attainment of California’s energy goals.Read ReportCalifornia Energy Commission (CEC)
Using non-invasive MEMS pressure sensors for measuring building envelope air leakageArmando Casillas, Mark Modera, Marco PritoniAcademic Journal Paper2021Micro-electromechanical systems (MEMS)-based sensors have seen significant improvements in accuracy and cost over the past several years, and due to the need for altitude sensing in unmanned aerial vehicles and wearable technologies, absolute pressure sensors have shown the most dramatic improvements. This paper investigates applications of MEMS sensors in commercial buildings.Download (Paywall)
Techno-economic parametric analysis of large diameter shallow ground heat exchanger in California climatesAntash Najib, Angelo Zarrella, Vinod Narayanan, Richard Bourne, Curtis HarringtonAcademic Journal Paper2020A parametric study of a large diameter, shallow bore ground heat exchanger system coupled to a water-to-air heat pump is presented. The performance of this system is compared to an equivalent air-to-air heat pump system. Building loads from a single-family home in two different climate zones with different magnitudes and ratio of winter and heating loads are used in this study. In the first climate zone (Sacramento, CA), the winter load is two times the summer load while in the second climate zone (Riverside, CA), the winter and heating loads are nearly balanced.Read Article (paywall)California Energy Commission (CEC)
Analysis of Greenhouse Gas Emissions from Residential Heating Technologies in the USANelson Dichter, Aref AboudTechnical Report2020Greenhouse gases (GHGs) are a group of compounds that have a high transmittance of most electromagnetic wavelengths of solar radiation but low transmittance of infrared (heat) radiation. The earth is continuously heated by solar radiation from the sun and cooled by emitting infrared radiation to the sky. When higher levels of GHGs are present in the atmosphere, more of the radiation being emitted by the earth is reflected back on its surface rather than escaping into space while solar radiation is still able to penetrate the atmosphere. Read ReportTrane Technologies
Improving Ventilation and Indoor Environmental Quality in California SchoolsTheresa Pistochini, Caton Mande, Mark Modera, Sarah Outcault, Angela SanguinettiProject Report2020This project developed and demonstrated approaches to synergistically improve ventilation and indoor environmental quality during replacements of packaged heating, ventilation, and air conditioning (HVAC) systems in California schools.Read ReportCalifornia Energy Commission (CEC)
An Experimentally Validated Model of a Cross-Flow Sub-Wet Bulb Evaporative ChillerYahui Yang, Vinod Narayanan, Theresa Pistochini, Derrick RossAcademic Journal Paper2020A simplified model to predict the performance of a novel sub-wet bulb evaporative chiller (SWEC) for producing chilled water is presented. The SWEC design uses a daisy-chained arrangement of cross-flow heat exchangers (HXs) with evaporative media located in between the heat exchangers to chill water below the outdoor wet bulb temperature (WB) in either a one-pass or two-pass arrangement.Read ReportCalifornia Energy Commission (CEC)
Analysis of Greenhouse Gas Emissions Reductions Using Functional Storage Options in CaliforniaNelson DichterTechnical Report2020This research investigates the potential impact thermal energy storage systems can have on greenhouse gas (GHG) emissions by shifting the electric load associated with vapor-compression systems from peak to off-peak hours. DownloadTrane Technologies
Transient simultaneous heat and mass transfer model to estimate drying time in a wetted fur of a cowElizabeth Chen, Vinod Narayanan, Theresa Pistochini, Erfan RasouliAcademic Journal Paper2020To reduce heat stress that contributes to complications in milk production and breeding, dairy cows are typically cooled by intermittent water sprays coupled with fan-induced air flow. Industry currently utilises fixed duration on and off-cycles; however, water efficiency may be improved by matching the sprinkler off-time to the cow drying time that corresponds to current outdoor environmental conditions. Electricity use can also be reduced by varying fan speeds to achieve the required heat rejection rate for a given set of conditions. To achieve savings in water and electricity, a transient, one-dimensional simultaneous heat and mass transfer model of evaporation within the wetted fur layer of a dairy cows was developed to estimate drying time and heat rejection rate based on ambient conditions. Read ArticleCalifornia Energy Commission (CEC)
Testing, Adjusting and Balancing HVAC Systems: An Overview of Certification AgenciesFredrick Meyers, Theresa PistochiniTechnical Report2020In this report, we will examine the benefits of using a certified contractor for TAB and describe the three main certifying agencies and differences between them.DownloadICB/TABB
Performance Evaluation of a Residential Indirect-Direct Evaporative Cooler (IDEC)Curtis Harrington, Derrick RossProject Report2020The purpose of this project was to conduct laboratory testing of a residential Indirect-Direct Evaporative Cooler (IDEC) to characterize its performance across typical cooling season weather conditions in climate zones 7 and 10. This technology provides cooling very efficiently using only two sets of fans and water pumps. Relying on evaporative cooling eliminates the need for high global warming potential refrigerants, and the associated compressor which consumes much of the electricity used by a traditional air conditioner. DownloadSan Diego Gas & Electric (SDG&E)
Analysis of NOx Emissions from Hybrid Heating Technologies in CaliforniaNelson DichterProject Report2020Nitrogen oxides (NOx), harmful and toxic greenhouse gases, are released when gas is burned at high heat in a furnace. Whole-building annual energy simulations were conducted using EnergyPLus to estimate NOx annual emissions from low NOx furnaces (40 ng/J), ultra-low NOx (14 ng/J) furnaces and hybrid heating systems (a heat pump with a low NOx furnace for auxiliary heat) in single-family residential buildings in California. Carbon dioxide (CO2) emissions were also estimated for these systems. When the results were averaged across California, weighted by the population in each California climate zone, the hybrid heating system reduced NOx emissions by 95% 100% and CO2 emissions by 67%-69% compared to a low NOx furnace.DownloadTrane Technologies
A revised capacitance resistance model for large diameter shallow bore ground heat exchangerAntash Najib, Angelo Zarrella, Vinod Narayanan, Peter Grant, Curtis HarringtonAcademic Journal Paper2019Ground heat exchangers (GHE) for residential heat pumps have the advantage of rejecting (extracting) heat to a lower (higher) temperature sink (source) as compared with air source heat pumps. The thermal performance of shallow GHEs with larger diameter and of helical shape is modelled in this study using both a lumped parameter numerical model and a commercially available computational fluid dynamics (CFD) software. Measurements in a real test site single-family residence are also used for soil property calibration.Download (paywall)California Energy Commission (CEC)
Laboratory and Field Testing of RTU Optimization Package Combining a Condenser-Air Pre-Cooler with Compressor Speed ReductionTheresa Pistochini, Caton MandeProject Report2018This report describes a laboratory and field evaluation of a retrofit package to optimize the performance and efficiency of packaged air conditioning and heating Roof Top Units (RTUs). The package included Variable-Frequency Drive(s) (VFDs) to reduce the speed of the compressor(s) to 48 Hertz (Hz), and a condenser-air pre-cooler. This retrofit package is being considered as a method to save energy associated with air conditioning at all conditions, reduce peak electricity demand, and permanently reduce load on the compressor.
Download From ETCC WebsiteSouthern California Edison (SCE)
Characterizing the Transient and Aggregate Response of Dispatchable Condenser Air Pre-CoolersCaton Mande, Derrick Ross, Robert McMurry, Theresa PistochiniProject Report2018Evaporative condenser air pre-coolers, or “pre-coolers,” use evaporative cooling methods to pre-cool the inlet air to the condenser of an air conditioning system. This results in a lower temperature for air conditioner heat rejection, reducing power demand and increasing air conditioning process efficiency. While significant work has been done to demonstrate precoolers as an energy efficiency measure, this project studied the technology as a dispatchable demand response resource, controlled by the utility for grid management.Download From ETCC WebsiteSouthern California Edison (SCE)
Software-Controlled Switch Reluctance MotorsTheresa Pistochini, Caton Mande, Matthew StevensProject Report2018This project measured the performance of an emerging technology nominal threehorsepower (3HP) high rotor pole Switched Reluctance Motor (SRM) with softwarecontrolled inverter, compared to a baseline nominal 3HP baseline induction motor controlled by a Variable-Frequency Drive (VFD) in laboratory testing, and a nominal 3HP baseline single-speed induction motor for field testing. The difference in performance between the two motors was used to forecast annual energy and demand savings expected to result from replacing the baseline technology with the emerging technology.
Download From ETCC WebsiteSouthern California Edison (SCE)
Laboratory Testing of Software-Controlled Switched Reluctance MotorsCaton Mande, Matthew StevensCase Study2019Testing the efficacy of a high rotor pole switched reluctance motor (SRM) driven by a software-controlled inverter.Download PDFSouthern California Edison (SCE)
Using Videos to Promote Evaporative Cooling AdoptionSarah Outcault, Paul FortunatoCase Study2018Providing better information and communication is needed to encourage stakeholder adoption of ECTs. This WCEC study compared two methods of communicating information: outreach videos and manufacturer websites.Download PDFSouthern California Edison (SCE)
Design and Performance Characterization of a Micro-pin fin sCO2 RecuperatorCameron Naderi, Erfan Rasouli, Vinod NarayananSymposium Proceeding Paper2018Design, fabrication, and thermal-fluidic characterization of a compact three-layered recuperator unit cell (RUC) was presented in this study. The supercritical carbon dioxide (sCO2) streams flowed through microscale pin arrays on the hot and cold sides. A detailed design using Computational fluid dynamics (CFD) and structural analysis simulations was then performed to develop a final design of the RUC. An experimental facility was assembled to characterize the thermal-fluidic performance of the RUC. Results indicated that effectiveness of 90 percent or higher could be achieved at low approach temperatures. The correlation-based model predicted the overall heat transfer coefficient to within 20 percent of the experimental data. Based on the performance of the RUC, preliminary scaling estimated for a multiple-unit cell recuperator was also provided.Download PDFU.S. Department of Energy
Design and Performance Characterization of an Additively Manufactured Primary Heat Exchanger for sCO2 Waste Heat Recovery CyclesErfan Rasouli, Samikshya Subedi, Colt Montgomery, Caton W. Mande, Matthew Stevens, Vinod Narayanan, Anthony D. RollettSymposium Proceeding Paper2018Design, fabrication and characterization of an additively manufactured (AM) Inconel 718 Primary Heat Exchanger (PHX) for waste heat recovery was discussed in this paper. Design details including considerations of pressure drop on the hot side, high internal pressure on the sCO2 side and the near-counter flow design for high effectiveness were discussed. The fabricated AM PHX was pressure tested at temperature for verification of structural integrity. Preliminary results of pressure drop and heat transfer rate were also presented.Download PDFOffice of Naval Research and U.S. Department of Energy
Pitch and Aspect Ratio Effects on Single-Phase Heat Transfer through Microscale Pin Fin Heat SinksErfan Rasouli, Cameron Naderi, Vinod NarayananAcademic Journal Paper2018Heat transfer and pressure drop of single-phase liquid flow was characterized in eight micro pin fin heat sinks with varied pitch and aspect ratios. Flow visualization was performed on all the heat sinks and flow transition into unsteady vortex shedding was observed only in those with specific pitch and aspect ratios. The existence of vortex shedding in micro pin fin heat sinks enhanced the heat transfer and affected the prediction error of heat transfer correlations in literature. Separate correlations were developed to predict Nusselt number in the steady and unsteady regimes.Download From Journal WebsiteU.S. Department of Energy
High Flux Thermal Receiver and Method of UseMonte Kevin Drost, Sourabh Apte, Thomas L'estrange, Vinod Narayanan, Charles Rymal, Eric Truong, Erfan Rasouli, Kyle Ryan Zada, Brian M FronkUS Patent Application2018A thermal receiver, such as a solar flux thermal receiver, is disclosed comprising a modular arrangement of arrayed microchannels or micropins to heat a working fluid by heat transfer. Disclosed solar receivers provide a much higher solar flux and consequently a significant reduction in thermal losses, size, and cost, relative to known receivers. Unit cell receivers can be numbered up and combined in parallel to form modules, and modules combined to form full scale receivers.Download PDFU.S. Department of Energy
Efficiency optimization of a variable-capacity/variable-blower-speed residential heat-pump system with ductworkSreenidhi Krishnamoorthy, Mark Modera, Curtis HarringtonAcademic Journal Paper2017The purpose of this study was to evaluate the cooling operation of a variable-capacity/variable-fan-speed residential heat-pump connected to a typical single-zone duct system located outside the conditioned space in a hot-dry climate. This was accomplished through full-scale laboratory testing of prototype heat-pump equipment connected to a complete residential duct system within a climatic chamber wherein a range of summer conditions were simulated. Compressor speeds and evaporator airflows were manipulated over a range of practical combinations to characterize the efficiency of the entire system.Download From Journal WebsiteCalifornia Energy Commission
Can You Take the Heat? A Cross-National Comparison of Thermal Comfort Strategies and Energy-Saving Field ExperimentsSarah Outcault, Marco Pritoni, Kristin Heinemeier, Ayako MikamiWhite PaperThis paper presents a cross-cultural comparison of cooling strategies in sustainable communities in the United States and Japan to deepen our understanding of occupant behavior within the broader social context. We describe the “social potential” for energy conservation that could be tapped if alternatives to A/C were viewed through that lens. The paper draws on the lessons learned from a pair of interventions to encourage passive cooling strategies and reduce A/C use in an American community of zero energy buildings and a Japanese “smart home” community.Download PDFACEEE
Impacts of Duct Leakage on central outdoor-air conditioning for commercial-building VAV systemsSreenidhi Krishnamoorthy, Mark ModeraAcademic Journal Paper2016The purpose of this study was to estimate the energy losses due to duct leakage during central heating and cooling of outdoor air in commercial buildings with VAV systems. This was accomplished by calculating the required cooling and pre-heating of outdoor air with and without duct leakage for hot, moderate and cold climates. Our simplified model uses hourly weather data, along with leakage level, outdoor air fraction,and fan flow profiles to estimate heating and cooling loads associated with conditioning outdoor air for a typical office building.Download From Journal WebsiteSouthern California Edison
Design of Compact Heat Exchangers for Supercritical Carbondioxide CyclesErfan Rasouli, Samikshya Subedi, Vinod Narayanan, Anthony D. Rollett, Jack Beuth, Kevin DrostConfrence Proceeding Paper2016Supercritical carbondioxide (sCO2) cycles are being proposed in recent years for power generation from a variety of heat sources including fossil, nuclear, solar and geothermal. Advantages of using sCO2 include smaller power block size, high efficiency at moderate temperatures, and potential simplicity in power plant controls. In an indirect cycle, the working fluid is contained within a high pressure closed loop; heat is added into the working fluid in a high temperature high pressure primary heat exchanger. Designs of compact primary heat exchanger in such cycles were discussed in this paper. The designs include considerations for maximizing heat transfer rate while reducing pressure drop, uniform flow distribution, mechanical integrity of the HX, and fabrication approaches.Download From Journal WebsiteU.S. Department of Energy
Phase-Change Heat Transfer Characterization In Microscale-pin fin Heat SinksErfan Rasouli, Vinod NarayananAcademic Journal Paper2017Subcooled and saturated flow boiling of Performance Fluid PF5060 through four micro pin fin heat sinks (μPFHSs) with varied pitch and aspect ratios was investigated in this study. The phenomenon of vortex shedding observed in single phase flows for the higher pitch ratio heat sinks was seen to result in increased two-phase heat transfer coefficients in the nucleate boiling dominant regime. Additionally, the unsteady vortex shedding eliminated the wall temperature overshoot in the range of experiments performed. Download From Journal WebsiteU.S. Department of Energy
Laboratory Testing of an Energy Efficient Dehumidifier for Indoor FarmsTheresa Pistochini, Robert McMurry, Derrick Ross, Paul FortunatoCase Study2017Traditional dehumidification systems provide dehumidification and increase the air temperature, as opposed to the desired dehumidification and reduction of air temperature. An alternative is MSP Technology’s dehumidification system that uses a plate air-to-air heat exchanger and a cooling coil that is part of a split compressor-based refrigeration system.Download PDFXcel Energy
Energy-Efficient Clothes Dryers: Automatic Cycle Termination ControllerTheresa Pistochini, Caton MandeCase Study2017This project developed an automatic dryer cycle termination controller that utilized the relationship between dryer drum inlet temperatures and outlet temperatures to accurately predict the end of the drying cycle. The technology promises to be more accurate and robust in performance under different load and environmental conditions in comparison to existing technology. The low-cost automatic controller was demonstrated in the laboratory to reduce energy use in gas clothes dryers by accurately terminating the drying cycle. In addition, information obtained in the drying cycle can be used to predict real-time energy efficiency metrics to track dryer performance over time as a means for fault detection and to provide information to the consumer.Download PDF
Performance Testing of DR-55 As A Replacement for R-410A RefrigerantCurtis HarringtonCase Study2017One part of that solution is to reduce the global warming potential of the refrigerants used in these systems. Accidental release of refrigerant to the atmosphere is inevitable with these systems so it is imperative to identify a working fluid that has low GWP while also achieving acceptable performance and low safety risk to occupants. The predominant refrigerant used in air conditioning equipment today is R-410A. While R-410A provided a good alternative to R-22, recent advances in refrigerant blends are showing further reductions in global warming potential, while also demonstrating comparable performance.Download PDF
Water-Use Efficiency for Alternative Cooling Technologies in Arid ClimatesTheresa Pistochini, Mark ModeraAcademic Journal Paper2011 Evaporative cooling technologies are generally valued for their reduced energy consumption in comparison to compressor-based air conditioning systems. However, two concerns that are often raised with respect to evaporative cooling equipment are their on-site water use and the impact of poor water quality on their performance. Download From Journal WebsiteCalifornia Energy Commission
Laboratory Testing of Aerosol for Enclosure Air SealingCurtis Harrington, Mark ModeraResearch Report2012Space conditioning energy use can be significantly reduced by addressing uncontrolled infiltration and exfiltration through the envelope of a building. A process for improving the airtightness of a building envelope by sealing shell leaks with an aerosol sealing technology is presented. Download PDFU.S. Department of Energy
Automated Fault Detection & Diagnostics for Rooftop Packaged Air ConditionersKristin HeinemeierCase Study2012 Automated Fault Detection & Diagnostics (AFDD) for RTUs is a technology class that senses key system operating parameters, detects performance degradation, and triggers an alarm that is communicated to some form of fault management tool, the zone thermostat, or appropriate facility personnel. California’s Energy Efficiency Strategic Plan urges the broader application of this technology, and Title 24 requires AFDD as a mandatory measure for all new commercial RTUs. Download PDFCalifornia Energy Commission
Aerosol Duct Sealing in Central Exhaust SystemsJonathan WoolleyCase Study2012 Aeroseal is a cost effective method to seal leaks in ducts; it uses a vinyl polymer adhesive sprayed into the duct as an aerosol. Developed at Lawrence Berkeley National Laboratory, Aeroseal is designed to quickly repair leaks that are otherwise inaccessible without significant building renovation. Download PDFCalifornia Energy Commission
Advanced Diagnostics & Service for Rooftop Air ConditionersJonathan WoolleyCase Study2013 AirCare Plus® is a third-party energy efficiency program that provides contractors with the necessary training, tools, and incentives to conduct quality in-field assessment of efficiency for commercial rooftop air conditioners. Service provided through the program is different from that of typical maintenance contractors especially in that evaluation of equipment performance is conducted using the Service Assistant™ developed by Field Diagnostics. This field tool is a hand held data acquisition device that measures pressure, temperature, and humidity at ten key points in an air conditioner and automates thermodynamic diagnosis of the vapor compression cycle. Download PDFCalifornia Energy Commission
Making Energy Savings Easier: Usability Metrics for ThermostatsMarco Pritoni, Daniel Perry, Cecilia Aragon, Alan Meier, Therese PefferAcademic Journal Paper2011U.S. residential thermostats control approximately 9% of the nation’s energy use. Many building codes now require programmable thermostats (PTs) because of their assumed energy savings. However, several recent field studies have shown no significant savings or even higher energy use in households using PTs compared to those using non-PTs. These studies point to usability problems that lead to incorrect use and wasted energy.Download From Journal WebsiteU.S. Department of Energy
Facilitating Energy Savings with Programmable Thermostats: Evaluation and Guidelines for the Thermostat User InterfaceMarco Pritoni, Therese Peffer, Daniel Perry, Cecilia Aragon, Alan Meier Academic Journal Paper2013After conducting a usability study of programmable thermostats, we reviewed several guidelines from ergonomics, general device usability, computer-human interfaces, and building control sources. We analyzed the characteristics of thermostats that enabled or hindered successfully completing tasks and in a timely manner. Subjects had higher success rates with thermostat displays with positive examples of guidelines, such as visibility of possible actions, consistency and standards, and feedback. We suggested other guidelines that seemed missing, such as navigation cues, clear hierarchy, and simple decision paths. Download From Journal WebsiteU.S. Department of Energy
Usability of Residential Thermostats: Preliminary InvestigationsMarco Pritoni, Therese Peffer, Daniel Perry, Cecilia Aragon, Alan Meier Academic Journal PaperPersonal interviews revealed widespread misunderstanding of thermostat operation. The on-line surveys found that most thermostats were selected by previous residents, landlords, or other agents. The majority of occupants operated thermostats manually, rather than relying on their programmable features and almost 90% of respondents reported that they rarely or never adjusted the thermostat to set a weekend or weekday program. Photographs of thermostats were collected in one on-line survey, which revealed that about 20% of the thermostats displayed the wrong time and that about 50% of the respondents set their programmable thermostats on “long term hold” (or its equivalent). Download From Journal WebsiteU.S. Department of Energy
Home Energy Management: Products & TrendsMarco Pritoni, Janelle LaMarche, Katherine Cheney, Kurt Roth, Olga SachsResearch PaperHome Energy Management (HEM) describes a class of technologies including sensors, smart thermostats, and feedback devices seeking to manage residential energy consumption profiles to reduce peak electric demand and consumers’ electric bills. Download PDF
Folk Labeling: Insights on Improving Usability and Saving Energy Gleaned from After-Market Graffiti on Common AppliancesMarco Pritoni, Therese Peffer, Jessica Granderson, Gari Kloss, Alan Meier, Cecilia AragonResearch PaperThe after-market labeling of a device by its users often indicates problematic usability, which can affect the device's energy consumption. For example, when people find a lighting control panel difficult to use, they often write instructions on a piece of paper and affix it nearby as a reminder to themselves and to help others. Download PDF
How People Actually Use ThermostatsMarco Pritoni, Alan Meier, Cecilia Aragon, Becky Hurwitz, Dhawal Mujumdar, Therese Peffer, Daniel PerryResearch PaperResidential thermostats have been a key element in controlling heating and cooling systems for over sixty years. However, today’s modern programmable thermostats (PTs) are complicated and difficult for users to understand, leading to errors in operation and wasted energy. Four separate tests of usability were conducted in preparation for a larger study. These tests included personal interviews, an on-line survey, photographing actual thermostat settings, and measurements of ability to accomplish four tasks related to effective use of a PT. Download PDFU.S. Department of Energy
Principal Agent Problems in Energy Efficient Computing in a University SettingMarco Pritoni, Siva Gunda, Tracy HsiehResearch PaperAbout 10% of the energy usage on a typical university campus is spent to meet Information Technology (IT) demands such as powering desktops, severs, printers, laptops, and other peripheral equipment. At UC Davis, the annual energy expenditure on IT alone was approximately $3 million (~$1.3 million excluding servers and related usage) in 2008. Download PDF
How People Use Thermostats in Homes: A ReviewMarco Pritoni, Therese Peffer, Alan Meier, Cecilia Aragon, Daniel PerryAcademic Journal PaperResidential thermostats control a substantial portion of both fuel and electrical energyd9% of the total energy consumption in the U.S. Consumers install programmable thermostats to save energy, yet numerous recent studies found that homes with programmable thermostats can use more energy than those controlled manually depending on how or if they are used. At the same time, thermostats are undergoing a dramatic increase in capability and features, including control of ventilation, responding to electricity price signals, and interacting with a home area network. These issues warrant a review of the current state of thermostats, evaluating their effectiveness in providing thermal comfort and energy savings, and identifying areas for further improvement or research. Download From Journal WebsiteU.S. Department of Energy
Contractors Walk on the Wild Side... Why?Kristin HeinemeierResearch Paper It has been estimated that permits are obtained for fewer than 5% of air conditioner replacements in California homes. This means that 95% of jobs never comply with nor verify the energy efficiency measures of California’s energy code (not to mention the health and safety concerns with unpermitted work!). The Western HVAC Performance Alliance—an innovative Industry-Utility alliance comprised of contractors, manufacturers, distributors, unions, code officials, utility program managers, verification providers, and researchers—has posited that there are substantial behavioral elements to the problem.Download PDFCalifornia Energy Commission
Uncertainties in Achieving Energy Savings from HVAC Maintenance Measures in the FieldKristin Heinemeier, Marshall Hunt, Marc Hoeschele, Elizabeth Weitzel, Brett CloseResearch Paper2012 HVAC maintenance measures have been demonstrated in the laboratory to have the potential to save a significant amount of energy. For example, Mowris et al. 2012 shows that by combining charge adjustment, airflow improvement, duct sealing, and elimination of non-condensables, over 30% of HVAC energy use can be saved. Download PDFCalifornia Energy Commission
Demand Control Kitchen VentilationDavid GruppCase Study2013 This study is a summarized compilation of select SPEED case studies to demonstrate the efficacy of demand control kitchen ventilation in different environments ranging from 7 to 40 horsepower. Installations have been performed for combined hood and make-up air motor nameplate ratings up to 90 horsepower. Download PDFCalifornia Energy Commission
Demand Control Kitchen Ventilation BUSINESS CASEDavid GruppBusiness Case Study2013This business case provides 3 different scenarios for estimated savings, incentives and on bill financing information for Demand Control Kitchen ventilation. Title 24 changes take effect January 1, 2014 and will significantly alter the baseline for calculating incentives. Download PDFCalifornia Energy Commission
Swimming pools as heat sinks for air conditioners: Model design and experimental validation for natural thermal behavior of the poolCurtis Harrington, Mark Modera, Jonathan WoolleyAcademic Journal Paper2011Swimming pools as thermal sinks for air conditioners could save approximately 40% on peak cooling power and 30% of overall cooling energy, compared to standard residential air conditioning. Heat dissipation from pools in semi-arid climates with large diurnal temperature shifts is such that pool heating and space cooling may occur concurrently; in which case heat rejected from cooling equipment could directly displace pool heating energy, while also improving space cooling efficiency.Download From Journal WebsiteCalifornia Energy Commission
Swimming pools as heat sinks for air conditioners: California feasibility analysisCurtis Harrington, Mark ModeraAcademic Journal Paper2013Earlier studies used field testing of swimming pool temperatures to validate a mathematical model for predicting the temperature of an unheated pool. Combining those results with manufacturers’ data on the performance of vapor-compression air conditioners as a function of heat rejection temperature, the analyses in the paper suggest that rejecting air conditioning heat to a swimming pool can save approximately 25–30% of single-family residential cooling electricity use and reduce cooling electricity demand during peak conditions by 30–35%, as compared to using the same compressor to reject the heat to ambient air.Download From Journal WebsiteCalifornia Energy Commission
Condenser Air Pre-Cooler RetrofitsJonathan Woolley, David GruppCase Study2013Evaporative pre-coolers are effective retrofits to reduce the temperature of air that cools the condenser coil in air-cooled chillers, RTUs and other DX equipment. In these systems, the outside air stream passes over a wetted surface before it reaches the condenser, heat from the outside air is absorbed by water evaporation thus cooling the air stream. Evaporative condenser pre-coolers are applicable to most all climate zones, but have even more energy impact in lower humidity areas, such as California. Download PDFCalifornia Energy Commission
Condenser Air Pre-Cooler Retrofits For Rooftop UnitsJonathan Woolley, David GruppProject Report2013A CSGS and BAFB working team was established to recommend and install PIER solutions at the Contrails Inn Dining Facility as the first step to show how these technologies might be successfully implemented at other Air Force bases and facilities. As part of this task, the team evaluated base energy loads, occupant usage patterns and facility operation schedules. Based on this data, the working team was able to present lighting and HVAC retrofit recommendations.

This document summarizes the evaporative condenser air pre-cooler retrofit on a 50-ton Trane® chiller portion of the demonstrations at the 15,000 square foot Contrails Dinning Facility.
Download PDFCalifornia Energy Commission
Multi-Tenant Light Commercial Preliminary ReportJohn Markley, Marco PritoniProject Report2013The UC Davis Multi-Tenant Light Commercial project intends to establish a building level retrofit package that will substantially improve energy performance by collectively improving the envelope, lighting and HVAC systems. The primary goals of the UC Davis Multi-Tenant Light Commercial project are to increase the overall energy efficiency and permanently reduce the peak energy consumption of MTLC buildings. Simultaneously, the Multi-Tenant Light Commercial project aims to make these packages more economically feasible by leveraging the economy of scale through maximizing purchase potential, and by minimizing the cost through reducing the required contractor visits necessary to perform the work. Download PDFPacific Gas & Electric
Application for Entry to the Western Cooling ChallengeWCCWestern Cooling ChallengePlease submit a cover letter expressing your company’s intent to submit an entry to the Western Cooling Challenge.WCC ApplicationWCEC
Western Cooling Challenge Program RequirementsWCCWestern Cooling ChallengeThe Western Cooling Challenge (WCC), hosted by the Western Cooling Efficiency Center (WCEC) at the University of
California Davis, is a multiple winner competition that encourages HVAC manufactures to develop climate‐appropriate
rooftop packaged air conditioning equipment that will reduce electrical demand and energy use in Western climates by at
least 40% compared to DOE 2010 standards.
Download PDFWCEC
Trane Voyager DC Laboratory ResultsWCCProject Report2012Trane’s Voyager DC shows a savings of 43%. The explicit goal of the effort reported here was to laboratory test the Trane Voyager DC according to Western Cooling Challenge test protocol. The protocol evaluates equipment performance in hot-dry climate conditions, operating under realistic airflow resistances and with an outside air ventilation rate that would be encountered in typical commercial retail applications. A secondary goal was to laboratory test the equipment across a broad range of operating conditions in order to characterize performance in various scenarios, and to evaluate function of each major system sub-component and operating mode.Download PDFSouthern California Edison
Development of Test Protocol for Direct Evaporative Condenser Air PrecoolersTheresa E. Pistochini, Perry L. Young, Mark ModeraAcademic Journal2014Evaporative precoolers for air-cooled condensing units have been demonstrated to reduce electricity demand and save energy, particularly in arid climates. However, no objective, standardized test data for these products exists in the United States, making it difficult for end-users and utilities to evaluate expected performance prior to purchase and installation. This paper proposes a test protocol for evaporative precoolers installed on condensing units up to 70 kW, and then executes the protocol using three precooling products designed for residential split system air conditioners.Read the ArticleCalifornia Energy Commission
Recent Applications of Aerosol Sealing in BuildingsCurtis Harrington, Mark ModeraAcademic Journal2014This paper describes two recent applications of aerosol sealing techniques in buildings for improving indoor air quality and reducing energy required for heating, cooling, and ventilation.Download PDFCalifornia Energy Commission
Coolerado H80 Field Report at China Lake, CAWCCProject Report2013Field test results for the Coolerado H80 hybrid indirect evaporative air conditioner at NAWS China Lake, California.Download PDFState Partnership for Energy Efficiency Demonstrations (SPEED)
Coolerado H80 Field Test at UC DavisJonathan Woolley, Paul Fortunato, David GruppCase Study2013Field test results for the Coolerado H80 hybrid indirect evaporative air conditioner at the University House, at UC Davis.Download PDFState Partnership for Energy Efficiency Demonstrations (SPEED)
Shut the Sash: Fume Hood Ventilation in LaboratoriesDavid GruppCase Study2013One of the simplest ways to reduce the energy required by operating laboratory fume hoods is to ensure that the sash—the moveable pane in front of the fume hood that controls the exhaust flow from an experiment—is always in the lowest possible operating position. This simple action can in some circumstances lower the amount of energy used substantially and will in all cases provide for the safest working environment, even in cases where energy use is not reduced. Behavioral change programs to promote being mindful of sash heights have been dubbed “Shut-the-sash” (STS). WCEC observed the effect of such behavioral programs at two university campuses. Download PDFState Partnership for Energy Efficiency Demonstrations (SPEED)
RTU Efficiency OptimizersDavid GruppCase Study2013Several new retrofit controllers are now available for single-zone rooftop-unit (RTU) air conditioners that take advantage of energy saving techniques not previously economically possible. These retrofits work by replacing the simplistic stock control unit with new digital controls, new sensors, and often upgrade the single speed supply fan motor to take advantage of variable frequency drive (VFD) motor controllers. WCEC observed the performance of the CATALYST RTU Optimizer system at two university campuses.Download PDFState Partnership for Energy Efficiency Demonstrations (SPEED)
Multifamily Ventilation Code Change Proposal: Final ReportJohn Markley, Curtis Harrington, Nelson DichterProject Report2014This final report proposes changes to the 2016 California Title 24 Building Energy Efficiency Standards regarding indoor air quality ventilation of multifamily buildings. In summary, we recommend (a) unifying all multifamily residential ventilation requirements by extending current requirements for new low-rise multifamily buildings to new high-rise multifamily buildings, and (b) for high-rise multifamily buildings that use central shaft ventilation systems, two new requirements that are necessary to ensure that these systems perform as energy efficiently as possible and do not under- or over-ventilate homes. Download PDFCalifornia Energy Commission
Thermostats Can't Fix This: Case Studies on Advanced Thermostat Field TestsSarah Outcault, Claudia Barriga, Kristin Heinemeier, John Markley and Dan BermanCase Study2014The technology for thermostats has changed significantly in the past decade. More advanced features such as programmability offer great potential for energy savings. But with this increased technical complexity has come a corresponding complexity in the user interface. Some manufacturers have attempted to deal with this by adopting a deployment model that transfers to the installing contractor responsibility for the initial setup and user instruction.Download PDFACEEE
Transformation Partnerships for Crossing the “Valley of Death”
Karl Johnson, David Weightman, Chris Scruton, Pedram Arani, Jonathan WoolleyProject Report2012Between the lab and the marketplace, new energy-efficient technologies often succumb to the "valley of death," a set of perilous barriers to market introduction that can prevent best practice technologies (with typical energy savings of 50% to 80%) from entering and transforming the market. The California Energy Commission created the State Partnership for Energy Efficient Demonstrations (SPEED) Program in 2004 to transform the market for deep energy-efficient products developed or enhanced with Public Interest Energy Research (PIER) Program funding. Download PDFState Partnership for Energy Efficiency Demonstrations (SPEED)
Speakman Hybrid Rooftop Unit Performance: Western Cooling Challenge Laboratory Test ResultsWCC, Jonathan WoolleyProject Report2011This report documents the results of Western Cooling Challenge laboratory tests of the Speakman Hybrid, a rooftop air conditioner that uses indirect evaporative cooling, direct evaporative cooling, and conventional vapor compression cooling. The Western Cooling Efficiency Center (WCEC) orchestrated the laboratory tests, which were conducted by the National Renewable Energy Laboratory under a commitment from the US Department of Energy Office of Building Technology to provide laboratory testing for advanced cooling technologies submitted to the Western Cooling Challenge. Download PDFSouthern California Edison
Western Cooling Challenge Test Protocol DevelopmentWCC, Jonathan Woolley, Mark ModeraResearch Paper2011This paper outlines and discusses the development of the test protocol and performance criteria for the Challenge. The choice of laboratory test conditions is discussed. The rationale for and calculation of performance metrics including nominal cooling capacity and credited cooling capacity are presented. Additionally, the assumptions underlying requirements for minimum sensible energy efficiency are summarized, and key non-performance-based criteria for the program are explained.Download PDFCalifornia Energy Commission
Occupancy Sensing Adaptive Thermostat Controls – A Market Review and Observations from Multiple Field Installations in University Residence HallsJonathan Woolley, Therese PefferResearch Paper While both occupancy sensors and the Internet have been around for many decades, recently both have been applied to programmable thermostats to reduce energy consumption and to improve usability and control. This paper explores the implications of coupling these technologies, and the role the added capabilities play on the efficiency and effectiveness of building conditioning. The research focuses on various installations of occupancy-sensing mesh-networked web-programmable thermostats in university residence halls, with a focus on the results from installation in multiple dormitories at the University of California, Davis. Download PDFACEEE
Modeling Ventilation in Multifamily BuildingsJohn Markley, Curtis Harrington, Garth TorvestadResearch Paper2014Proper ventilation is an essential component of multifamily building design due to its effects on occupant health and comfort. Though the concept of providing fresh air is straightforward, multifamily buildings pose several unique challenges that require special consideration in order to avoid excessive ventilation and energy waste. Two issues in particular that must be addressed in multifamily buildings are minimizing the air that moves between tenant spaces and ensuring that each individual space receives the required ventilation. In an effort to address these topics the UC Davis Western Cooling Efficiency Center, as part of a Public Interest Energy Research project, evaluated potential improvements to mechanical ventilation of multifamily buildings. This paper outlines the results from energy models of several multifamily building configurations to improve airflow balancing and energy efficiency in high-rise multifamily buildings with central shaft exhaust ventilation. Download PDFACEEE
One Machine for Heating Cooling & Domestic Hot Water: Multi-Function Heat Pumps to Enable Zero Net Energy HomesMark Modera, Jonathan Wolley, David Grupp, Bill Dakin, Michael KoenigResearch PaperWhile traditional residential mechanical design uses multiple systems and fuels to provide thermal services, the emerging generation of heat-pump technologies can provide heating, cooling and domestic hot water with a single appliance. These heat pumps operate over a wider temperature range than their predecessors, offer substantial efficiency improvements, and introduce opportunities for waste heat recovery. Download PDFACEEE
Improving Cost Effectiveness of Radiant Floor CoolingRichard Bourne, Theresa Pistochini, Jonathan WoolleyProject Report2014Radiant floors can reduce annual cooling energy costs up to 70% in comparison with conventional forced air cooling systems. Savings result from reducing blower energy use, improving cooling efficiency, and facilitating non-compressor cooling sources. The technology was developed in partnership with Walmart. It is suitable for use by most major retailers, and in other “large area” slabs in new retail malls, offices, and schools. Prior to this project, a related system was developed with Walmart by the UC Davis Western Cooling Efficiency Center and Viega LLC. That system is now marketed by Viega as “Climate Mat.”Climate Mat is the first “large area” pre-fabricated tubing array designed for low-cost installation of radiant cooling arrays in large buildings. Climate-Mat systems can be installed for approximately $2/sq.ft.; the goal of this project was to value-engineer the design toward lowering the installed cost by 50%, to $1/sq.ft. Download PDFCalifornia Energy Commission
Energy and Demand Savings from Sealing ExhaustJonathan Woolley, Joshua Gottlieb, Theresa Pistochini, Mark ModeraProject Report2009The goal of this project was to help the state of California address the energy losses associated with leakage in exhaust ductwork in commercial buildings and dormitory style residences. The study coupled computer modeling of zone pressures and flows as impacted by transient meteorological conditions with field research to answer a number of questions about the potential for energy savings from sealing leaks or reducing flows in exhaust ducts. Computer simulations were conducted in a multizone airflow modeling package and used to characterize the relationship between outdoor air infiltration and changes in exhaust flow. Download PDFCalifornia Energy Commission
Why Occupancy-responsive Adaptive Thermostats do not Always Save--and the Limits for When They ShouldJonathan Woolley, Marco Pritoni, Therese Peffer, Mark ModeraResearch Paper2014So-called ‘smart thermostats’ are beginning to fill the gap left in efficiency programs after researchers and policy makers discovered that in practice, simple programmable thermostats do not guarantee energy savings. As a result, EPA ended EnergyStar certification of programmable thermostats in 2010. Many recent pilots for communicating thermostats, occupancy-responsive thermostats, and adaptive control schemes have shown significant annual HVAC savings on the order of 10-20%. However, the form and function for technologies in this space vary widely. Download PDFACEEE
Reducing Maintenance-Water Consumption in Evaporative Cooling EquipmentMark ModeraASHRAE Summer 2013 Presentation2013This presentation explains why calcium and magnesium behave differently in the production of scale in evaporative cooling equipment. With this knowledge, proper maintenance techniques that diminish scale production can actually reduce water consumption while increasing equipment longevity.Download PDFASHRAE
Internet-Connected, Occupancy-Responsive, Adaptive Thermostats for University Residence HallsMarco Pritoni, David Grupp, Jonathan Woolley, Karl JohnsonProject Report2014Many recent field evaluations for communicating and occupancy-responsive thermostats have shown significant annual HVAC savings on the order of 10-20%. However, the form and function for technologies in this space vary widely. Occupancy responsive thermostats adjust mechanical system operating parameters to reduce energy consumption when a conditioned space is vacant. Unlike occupancy controls for lighting, the value of occupancy control applied to heating and cooling depends on a range of dynamic factors that are difficult to measure and assess with precision. For instance, the efficiency of heating and cooling equipment changes with weather conditions and part- or full-load runtime capacity, while thermal loads depend on the aggressiveness of indoor temperature set-points, and their dynamic relationship to a variety of physical and environmental factors.Download PDFState Partnership for Energy Efficiency Demonstrations (SPEED)
New Building Efficiency Evaluation at UC DavisDavid Grupp, Paul Fortunato, Karl JohnsonProject Report2012Gallagher Hall and Conference Center is an 86,000 square-foot building at the University of California Davis. The building, opened in 2009 houses the Graduate School of Management and contains a mixture of classrooms, office space and conferencing facilities. The building is located outside of the central campus and does not have access to the campus district heating and cooling systems. This presented a challenge to the designers – but also an opportunity to think creatively and design a building for high efficiency from the ground up. The result was a building design that achieved LEED Platinum recognition. Many systems and design features made this possible, but most can be grouped into three main categories – the radiant heating and cooling system, the dedicated outside air system, and the solar management features.
Download PDFState Partnership for Energy Efficiency Demonstrations (SPEED)
RTU Efficiency OptimizersDavid Grupp, Karl JohnsonCase StudyPackaged cooling equipment also known as Rooftop Units (RTUs) are used in 46% of all commercial buildings, and serves approximately 69% of the commercial building cooled floor space in the U.S. The ubiquitous use of these pieces of equipment is due to the ease by which they can be designed into a building, low capital cost, and a modular nature that allows for easy demarcation of energy billing and maintenance responsibility between multiple tenants of a single building. However, RTUs are notoriously inefficient because they’re often oversized, improperly installed, and inadequately maintained. In addition, even though the technology for improving RTU energy efficiency is well understood, the forces driving design tend to favor low first costs and ease of installation rather than energy efficiency and robust design. Several new retrofit controllers are now available for single-zone rooftop-unit (RTU) air conditioners that take advantage of energy saving techniques not previously economically possible.State Partnership for Energy Efficiency Demonstrations (SPEED)
Laboratory Performance Results: Munters EPX 5000 Hybrid DOASWCC, Jonathan WoolleyProject Report2014The primary goal for this project was to characterize energy efficiency of the Munters EPX 5000 in all modes of operation, in all possible configurations, and across a full range of operating conditions. Laboratory test results were carefully analyzed to consider the technical opportunities and challenges related to the equipment and to identify opportunities for additional improvements to the technology. These results provide the basis for recommendations about how utility efficiency programs, design engineers, and customers might proceed to apply this type of technology for management of indoor environmental quality in commercial buildings while simultaneously reducing energy consumption and peak demand. Download PDFPG&E
Dual-Evaporative Pre-Cooling Retrofit Field ResultsWCC, Jonathan Woolley, Paul FortunatoCase Study2015The product tested in this project takes advantage of indirect evaporative cooling to cool the ventilation air stream on a conventional rooftop unit, and uses direct evaporative cooling to cool air at the condenser inlet. This dual design reduces energy by reducing the temperature of incoming ventilation air and by lowering the condensing temperature. Since the dual evaporative pre-cooling technology incorporates with a conventional air conditioner, the combined system still maintains latent cooling capacity for applications where dehumidification is required. These dual processes work together to increase cooling capacity and to improve efficiency for the vapor compression system. The second effect is mainly caused by a lower heat sink temperature for the refrigeration cycle. Laboratory measurements for the dual evaporative pre-cooling technology installed on a similar rooftop air conditioner indicated 43% reduction in power draw at peak.Download PDFSouthern California Edison (SCE)
Title 24 Credit for efficient Evaporative CoolingSpencer Dutton, Jonathan Woolley, Nelson DichterProject Report2014develop a new model for the EnergyPlus building energy simulation tool that can be used to simulate a new generation of high efficiency air conditioners that combine different cooling technologies in order to leverage the strengths of each. These “hybrid” cooling systems have the potential to use substantially less energy than conventional air conditioning systems. However, there are currently no modeling tools or methods to accurately project energy savings for these systems. Accordingly, there is not currently a suitable Title-24 compliance pathway for hybrid air conditioning systems. The development of this model should provide the basis to support simulations for Title 24, or for the evaluation of programs and efforts that support the California Energy Efficiency Strategic Plan goal to advance the market transfer of “climate appropriate” cooling strategies.Download PDFCalifornia Energy Commission (CEC)
Condenser Air Evaporative Pre-Cooler Test Protocol
Theresa Pistochini, Mark Modera, Jay MaddenProject Report2012Systems are being introduced to the market that bring the advantages of this evaporative cooling process to small scale air-cooled AC systems. These systems are designed to be retrofitted onto existing units. They operate by evaporating water in the condenser air stream, cooling the incoming condenser air. While there are established test standards for rating the performance of air-cooled AC systems, a test standard to objectively compare the performance of condenser air evaporative pre-coolers doesn’t exist. The purpose of this study is to develop a test protocol for these systems, and to evaluate this protocol in a laboratory setting.Download PDFSouthern California Edison
Automated Duct Sealing DemonstrationWill Allen, Karl JohnsonProject Report2014This report details the sealing of the UC Davis Art building duct system using the Aeroseal process, and describes the savings that can be expected based on measurements of the pre-seal airflows and historic energy usage, combined with measurements of the degree of sealing achieved. Savings are predicted due to both reduced fan energy required to deliver air to the registers, and to the elimination of loss of conditioned air.
Download PDFState Partnership for Energy Efficiency Demonstrations (SPEED)
Side-By-Side Evaluation of Two Indirect Evaporative Conditioners Added to Existing Packaged Rooftop UnitsJonathan Woolley, Caton Mande & Mark ModeraWestern Cooling Challenge Project Report2014The overarching goal of this pilot demonstration project was to explore and document the field application of indirect evaporative cooling applied as a retrofit to existing commercial HVAC equipment. Climate appropriate cooling is a key goal within the California Energy Efficiency Strategic plan. Download PDFPG&E
Dualcool Hybrid Rooftop Unit Field TestWCCWestern Cooling Challenge Case Study2014Hybrid air conditioners, like the variable speed multi-stage rooftop unit with dual-evaporative pre-cooling observed in this study,
can significantly reduce overall cooling energy and reduce peak demand energy through a combination of climate appropriate
technologies and efficient part-load operation. Previous laboratory testing for this technology demonstrated 43% peak demand
savings compared to the stated performance for ASHRAE 90.1 compliant equipment operating in California’s hot-dry conditions. The
measured performance qualified this technology for the Western Cooling Challenge - a multiple winner competition hosted by UC
Davis that encourages HVAC manufactures to develop air conditioners that reduce peak demand by at least 40% (Woolley 2012).
Download PDFSouthern California Edison (SCE)
Smart Power for the Smart HomeNelson Dichter, G.P. Li, Mark Modera, Keyue Smedley, Jonathan Woolley, Linyi Xia Project Report2015Typical American households have a dynamic power quality factor varying from 0.8 to 0.95 depending on the signature of loads and their use at the time. (Appliances such as HVAC, motors, and lighting generate reactive and harmonic power, which is typically about 20% of the power consumption.) While photovoltaic (PV) panels via inverter provides mostly real power to home loads, the reactive power consumed by the loads would need to come from the electric grid and thus lowering the energy efficiency of the total system. Surging demand on reactive power at peak hours further induces instability to the grid. In this study, three aspects of this challenges and solutions are investigated, active power filter (APF) design, load disaggregation system design, energy modeling and testing of the systems above.Download PDFCalifornia Energy Commission (CEC)
Field Evaluation of Daikin Rebel Advanced Heat Pump Rooftop UnitJonathan Woolley, Ben Homquist, Caton MandeProject Report2015The HVAC industry, policy leaders, and market stakeholders are making a concerted effort to improve efficiency for HVAC. The Daikin Rebel represents an important step in this direction. The use of variable speed vapor compression systems will almost certainly become a mainstay in future HVAC standards. However, these solutions are currently new to the market; manufacturers and practitioners do not yet fully understand the proper approach to design, installation, control, and optimization; nor do most recognize the practical limitations and the extended implications of their application. This study develops a deeper understanding about this class of variable speed multistage rooftop units, and provides insight into the real benefits that can be expected from such technologies. Download PDFSacramento Municipal Utilities District (SMUD)
Field Evaluation of an Evaporative Condenser Air Pre-Cooler Retrofit Jonathan Woolley, Robert McMurry, Christian Young, David GruppProject Report2015This study set out to carefully measure the in-field performance improvements for one evaporative condenser air pre-cooler, applied to improve the cooling efficiency for a data center. A secondary objective was to observe and document the real world experiences with this technology, and to develop some understanding about the longevity and maintainability for the technology. Download PDFSouthern California Edison (SCE)
Field Evaluation of an Indirect Evaporative Air ConditionerJonathan Woolley, Christian Young & Caton MandeProject Report2015This study evaluates the performance of one product – the Climate Wizard indirect evaporative air conditioner. For this project, the system was installed as a retrofit for a small restaurant in Rocklin, California. The technology was setup to operate in parallel with three existing rooftop air conditioners, and to provide all ventilation for the space.Download PDFPacific Gas and Electric Company (PG&E)
Field Evaluation for a Dual-Evaporative Pre-Cooling RetrofitWCC, Mark Modera, Jonathan Woolley, and Zhijun LiuProject Report2014The purpose of this project was to gather field data to demonstrate and understand the performance improvement associated with adding an evaporative pre‐cooler for condenser‐inlet‐air and ventilation‐air to conventional RTUs. The tested retrofit was expected to save energy two ways: a) by cooling the outdoor air being delivered to the RTU indoor coil, and thereby reducing how much cooling it needs to perform, and b) by reducing the air temperature seen by the RTU condenser coil, thereby decreasing refrigerant pressure and the work that needs to be done by the compressor. The key metrics used to characterize the performance of the retrofit include: a) sensible Coefficient of Performance (COP), b) sensible cooling capacity, and c) electric power draw, all as a function of outdoor weather conditions. In addition, the project was designed to measure the on‐site water consumption associated with achieving those performance improvements, as well as to calculate key intermediate parameters, such as the sensible cooling capacity delivered to the ventilation air, and the maximum observable wet‐bulb effectiveness of the pre‐cooling system. Wet‐bulb effectiveness is a measure the ability of the evaporative media to cool the air entering the condenser toward the wet‐bulb temperature of the outside air, and is the key parameter used to characterize the performance of evaporative coolers for condenser air in the laboratory. The measured sump‐water temperature represents the coolest temperature produced by the pre-cooler, and therefore the highest observable wet bulb effectiveness. Download PDFSouthern California Edison (SCE)
Field Performance Evaluation of Trane Voyager with DualCoolWCC, Jonathan Woolley, Caton Mande, and Mark Modera Project Report2014The approach chosen for this evaluation was a field test conducted on three identical packaged rooftop units (RTUs) installed in Ontario, California. Two of these RTUs serve interior office space and the third unit serves a kitchen of a restaurant and bakery. The measure was factory-installed on the RTUs before they were installed on the buildings in September 2012. Monitoring involved minute-by-minute data collection on the RTUs, fitted with the measure and later with the measure removed. The evaluation focused on these key performance parameters: sensible COP, sensible cooling capacity, and electric power draw. Download PDFSouthern California Edison (SCE)
Market Barriers to Widespread Diffusion of Climate-Appropriate HVAC Retrofit TechnologiesSarah Outcault, Jennifer Kutzleb, Jonathan Woolley, and Kristin HeinemeierProject Report2015This study seeks to identify market barriers and other factors impeding adoption and promotion of downstream climate-appropriate HVAC retrofit technologies, as well as develop opportunities to increase adoption and promotion by addressing market barriers.Download PDFSouthern California Edison
Can A/C Use Be Reduced?Sarah Outcault, Kristin Heinemeier, Marco Pritoni, Jennifer Kutzleb, Qiwei WangProject Report2015The behavioral research team at UC Davis’ Western Cooling Efficiency Center (WCEC) was asked by the Tokyo Gas Company Ltd. to establish an ongoing research exchange focusing on two zero-net energy communities: E-Sogo in Yokohama, Japan and West Village in Davis, CA. The research focused on the impact of behavioral strategies and interventions on energy consumption in these two different communities. Interventions were designed for each community to understand the impacts of behavior on energy usage. The results from these different interventions are were then compared and used to develop recommendations for Tokyo Gas and future research studies on behavior‘s impact on energy usage.Download PDFTokyo Gas
Energy Efficiency and the misuse of programmable thermostatsMarco Pritoni, Alan K. Meier, Cecilia Aragon, Daniel Perry, Therese PefferAcademic Journal2015Programmable thermostats are generally sold as energy-saving devices controlling heating and cooling systems, but can lead to energy waste when not operated as designed by the manufacturers. We utilized Amazon Mechanical Turk, an online crowdsourcing service, to investigate thermostat settings and behavior in households. We posted a survey and paid respondents to upload pictures of their thermostats to verify self-reported data. About 40% of programmable thermostat owners did not use programming features and 33% had programming features overridden. Respondents demonstrated numerous misconceptions about how thermostats control home energy use. Moreover, we found that 57% of households were occupied nearly all the time, limiting the potential energy savings. The study revealed flaws in selfreported data, when collected solely from traditional surveys, which raises concerns about the validity of current thermostat-related research using such data.Download From Journal Website
Cloudfridge: A Cloud-Based Control System for Commercial Refrigeration SystemsMarco Graziano, Marco PritoniResearch Paper2014This paper presents a novel hardware and software architecture that allows advanced control algorithms for commercial refrigerators to be developed, tested and deployed inexpensively. The aim of this new control framework is to optimize energy consumption as a software task, utilizing the benefits of lower cost computational resources inherent to cloud computing, minimizing on net overall energy usage of the refrigeration system. A prototype of the proposed system has been developed and tested under a California Energy Commission grant. Download PDFCalifornia Energy Commission
Open Software-Architecture for Building Monitoring and ControlCarl Blumstein, David Culler, Gabe Fierro, Therese Peffer, Marco PritoniResearch PaperInformation technology can increase energy efficiency by improving the control of energy-using devices and systems. Awareness of this potential is not new—ideas for applications of information technology for energy efficiency have been promoted for more than 20 years. But much of the potential gain from the application of information technology has not yet been realized. Today a combination of new requirements for the operation of the electricity system and the development of new technology has the potential to cause a rapid increase in the pace of adoption of improved controls. In this paper we discuss one promising avenue for technology advancement. First, we review some basic concepts with emphasis on open software-architecture. Then we describe the components of XBOS, a realization of this open software-architecture. XBOS has the ability to monitor and control many different sensors and devices using both wired and wireless communication and a variety of communication protocols. Finally, we illustrate the capabilities of XBOS with examples from an XBOS installation in a small commercial office building in Berkeley California. Download PDFACEEE
Method for Discovering Functional Relationships Between Air Handling Units and Variable-Air-Volume Boxes From Sensor DataMarco Pritoni, Arka Bhattacharya, David Culler, Mark ModeraResearch PaperIn Building Automation Systems contextual information about sensors is frequently missing or hard-coded in the control code. Retrieving this data is time consuming and error-prone, but necessary to write any type of control application. Automating metadata acquisition is a new and active area of research. Methods to infer metadata from sensor labels or from recorded data have been previously proposed. However, these methods are ineffective in uncovering the association between HVAC components. In fact, measured variables (pressures, temperatures, flows, valve positions) have slow and attenuated responses to changes in input variables, thus impairing the efficacy of correlation methods. In addition, sensor readings are frequently constrained between physical limits and kept around setpoints by nested control loops. For this reason, pure statistical methods fail to capture the differences between sensor streams and are unable to classify them. In this article, we propose a new method for discovering functional relationships between Air Handling Units and Variable-Air-Volume Boxes from sensor data. Download PDF
The Wholesale Market Value of Dispatchable Efficiency for Commercial Air ConditioningJonathan Woolley, Thomas JawinResearch Paper2015We explore the demand response opportunity through dispatchable, efficient air conditioning technologies that reduce peak electricity demand from cooling by 40%. Download PDF
Climate Appropriate Cooling for a Grocery Store: Hybrid Unitary DOAS System in San Ramon, CAJonathan Woolley, Robert McMurryProject Report2015The research reported herein directly supports California Energy Efficiency Strategic Plan goals to accelerate marketplace penetration of climate appropriate air conditioning technologies. The report presents results from a field assessment of a dedicated outdoor air supply (DOAS) air hander that uses both indirect evaporative cooling and vapor compression to cool ventilation air for commercial buildings. This hybrid system was installed for an existing food store in San Ramon, California in combination with a whole building systems controls revision, and a closed door medium temperature refrigerated case lineup. In the year since installation, the project has demonstrated 20% whole building peak demand reduction, and 20% annual energy savings.
The research work was executed by the UC Davis Western Cooling Efficiency Center and the PG&E Emerging Technology Program in collaboration with the major grocery chain, and with technical support from the technology manufacturer, and the project engineering, installation, controls and commission teams.
Download PDFPacific Gas & Electric (PG&E)
Hybrid Rooftop Air Conditioners For a Mall, Fairfield CANelson Dichter, Jonathan Woolley, Caton MandeProject Report2015An inordinate amount of energy is wasted each year as a result of the fact that packaged commercial air conditioners are designed as ‘one-size fits-all’ products that can function in any climate and are not designed to achieve maximum efficiency for a specific climate. Climate appropriate solutions recognize unique opportunities for efficiency that arise from the climatic patterns and characteristics in particular regions. In California, these solutions include technologies that use water evaporation strategically to achieve substantial gains in cooling efficiency.

The research reported herein directly supports California Energy Efficiency Strategic Plan goals to accelerate marketplace penetration of climate appropriate air conditioning technologies. The report presents results from a field assessment of two Trane Voyager RTUs that have been retrofitted with an Integrated Comfort Dual-Cool. The Dual-Cool retrofit uses direct evaporative cooling to precool the condenser air and indirect evaporative cooling to cool the ventilation air. Two of these hybrid systems were installed on a mall in Fairfield, California. One of the units serves tenant spaces and the other serves the common areas in the mall. When compared to manufacturer data for a similar RTU the field data showed an improvement in peak capacity by as much as 48% and an improvement in average capacity by as much as 45%. The field data showed an improved overall efficiency in all modes of operation and a decrease in power consumption by as much as 19%. However, some modes of operation showed an increased power draw of as much as 10%.
Download PDFPacific Gas & Electric (PG&E)
Laboratory Performance Results: Indirect Evaporative Air Conditioning & Condenser Pre-Cooling as Climate Appropriate Retrofits for Packaged Rooftop UnitsCurtis Harrington, Jonathan Woolley, Robert DavisProject Report2015This report records results of a detailed laboratory evaluation of an indirect evaporative cooler and coupled to a rooftop packaged air conditioner (RTU) that was retrofit with a condenser air pre-cooler. The scheme reduces air conditioner compressor energy use in two main ways:

1. By reducing condenser inlet temperature and improving efficiency for the vapor compression cycle
2. By providing a substantial portion of the building cooling needs with indirect evaporative cooling
Download PDFSouthern California Edison (SCE)
Water Treatment and Management for Evaporatively Cooled CondensersTheresa Pistochini, Curtis Harrington, Mark Modera, Erica R. McKenzieProject Report2012The primary goal of this investigation was to provide long term laboratory test data to assess the longevity of an evaporatively-cooled condensing unit (ECCU) and to provide recommendations for operation and maintenance of the system to maintain performance and energy efficiency. A secondary objective was to evaluate water management strategies to minimize the use of bleed water and reduce the water consumption of the system.Download PDFSouthern California Edison (SCE)
Evaporative Condenser Air Pre-CoolersMark Modera, Theresa Pistochini Project Report2015In order to understand the energy benefits associated with evaporative pre-coolers, the American Society for Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) formed a Standard Project Committee (SPC-212P) to develop a Method of Test for “Determining Energy Performance and Water-Use Efficiency of Add-On Evaporative Pre-Coolers for Unitary Air Conditioning Equipment”. This report describes laboratory testing of five evaporative condenser air pre-cooler products on a packaged roof top unit and provided feedback to the ASHRAE SPC-212P.Download PDFSouthern California Edison (SCE)
Laboratory Testing of Variable Speed Compressor and Fan Controls for RTU OptimizationTheresa Pistochini, Robert McMurryProject Report2015This report describes a laboratory evaluation to optimize the performance and efficiency of a packaged air-conditioning and heating roof top unit (RTU) with a variable speed electrically communicated motor (ECM) controlling the blower speed and a retrofitted variable speed drive controlling the compressor speed. This technology is being considered as a method to save energy associated with air conditioning at part load conditions. It also may have potential to reduce peak electricity demand in buildings with over-sized equipment or when combined with condenser-air evaporative pre-cooling technology.Download PDFSouthern California Edison (SCE)
Directional-Bore Ground Source Heat Pump Field ReportDavid GruppProject Report2014The project at Rio Mondego was a demonstration of a ground
source heat pump system utilizing directional boring technology.
The construction of the heat exchanger utilized 5 directionally
bored holes of approximately 130’ in length emanating from a
single point manifold. Into these bores a conventional u-tube heat
exchanger was placed and the bore was filled with grout.
Download PDFSacramento Utility Municipal District (SMUD)
Performance Assessment of a Wide Diameter Shallow Bore Ground Source Heat ExchangerJose Garcia, Jonathan Woolley, Theresa PistochiniProject Report2016This study investigated the in-situ performance of a new ground heat exchanger technology installed as the source for a water-to-water heat pump in a single family residence. The technology is different from traditional ground heat exchangers because it is installed in a shallow wide diameter bore (20’ deep x 24” diameter). This design reduces the cost and complexity of drilling compared to deeper heat exchanger bores. Whereas traditional systems consist of a U-shaped pipe in a small diameter bore, the technology studied here consists of a single pipe wound into a 24” diameter helix – in this way, roughly 300’ of heat exchanger pipe are fit into each shallow bore. Download PDFSacramento Utility Municipal District (SMUD)
Central Hotel Guest Room Energy ControlsTheresa Pistochini, Curtis Harrington, Mark ModeraProject Report2010During the summer of 2010, occupancy controls and an energy management system (EMS) were installed at the
Best Western Island Palms hotel in San Diego, CA. The study included 12 rooms that were instrumented with
temperature and current loggers collecting data every 15 minutes. Four rooms were used as a base case with the
occupancy and EMS controls turned off while the other eight rooms utilized the controls. The data was analyzed
between three groups: Baseline, occupancy controls, and occupancy with EMS controls.
Download PDFSan Diego Gas & Electric (SDGE SDG&E)
HVAC Field Evaluation at SDG&E's Energy Innovation CenterCaton MandeProject Report2015During the timeframe of March 2013 – September 2014, WCEC performed the diagnostic measurements and recorded observations while on-site at the facility. Information regarding normal building maintenance, HVAC set up, building controls, and building settings were determined from conversations with both the building manager of the Energy Innovation Center (EIC) and the HVAC technician that services the building. Download PDFSan Diego Gas & Electric (SDGE SDG&E)
Polymer Bead LaundryWill AllenProject Report2015The WCEC performed a year long field study that monitored the performance of the Xeros laundry machines in real world operations. The study was conducted at a local athletic club. The study found that the Xeros laundry machine reduces water consumption by roughly 60%. Additionally, it found that energy savings, primarily due to not needing hot water, were roughly 87% when measured on a source energy basis. Significant cost advantages were also found, especially when used for high volume laundry operations.Download PDFSo Cal Gas (Sempra)
Gas Engine Heat Pump TechnologyNelson DichterProject Report2015The gas engine driven heat pump (GEHP) is a relatively new (first produced in 1985) heat pump technology whose purpose is to increase energy efficiency in water and space heating/cooling. This report details the results of a modeling study that compared the relative performance of three different building HVAC systems. The systems compared were a conventional AC and natural gas furnace, an electric heat pump system, and a gas engine driven heat pump. Each system was modeled in all of the California climate zones. Results for site energy, source energy, peak electrical draw, and annual cost in a time-of-use pricing structure were reported.Download PDFSo Cal Gas (Sempra)
Sub Wet-Bulb Evaporative Chiller (Nexajoule)Theresa Pistochini, Robert McMurryProject Report2015Several unique designs exist that are considered sub wet-bulb evaporative chillers, and this report focuses on one such design. The SWEC utilizes a two stage evaporative cooling system to chill water below the web-bulb temperature of the outdoor air. The theoretical limit for the supply water temperature is the dew point of the outdoor air. Download PDFSouthern California Edison (SCE)
Hybrid Rooftop Air Conditioners with Dual Evaporative Pre-Cooling Performance EvaluationJonathan Woolley, Caton MandeProject Report2015The purpose of this project was to gather field data to demonstrate and understand the performance of a hybrid rooftop air conditioner that uses dual-evaporative pre-cooling, essentially an RTU that employs the technology used to define the Western Cooling Challenge.Download PDFSouthern California Edison (SCE)
Performance Evaluation for Indirect Evaporative Cooling on Cellular SitesJonathan Woolley, Caton MandeProject Report2015The objective of this study is to conduct field evaluations of Indirect Evaporative Coolers (IECs) in California Climate Zone 8. IECs were installed at two different cellular sites in the cities of Cudahy, CA and Placentia, CA during the summer of 2014. The evaluation studied real-world equipment operation and developed characterizations of the overall system performance and energy efficiency across a range of operating conditions. The study is designed to investigate performance characteristics that cannot be captured by steady-state laboratory testing.Download PDFSouthern California Edison (SCE)
Laboratory Test of a Sub Wet-Bulb Evaporative Chiller (Tsinghua)Theresa Pistochini, Robert McMurryProject Report2015Several unique designs exist that are considered sub wet bulb evaporative chillers, and this report focuses on one such design. The SWEC cools an outdoor air stream using an indirect evaporative cooling process. Part of this cooled, dry, outdoor air is delivered to the building as ventilation air; the rest is exhausted as part of the evaporative cooling process, which also chills a water supply used to cool the building.Download PDFSouthern California Edison (SCE)
Laboratory Performance Results: Indirect Evaporative Air Conditioning and Condenser Pre-Cooling As Climate-Appropriate Retrofits for Packaged Rooftop UnitsJonathan WoolleyProject Report2015This report documents and discusses results of a detailed laboratory evaluation of an indirect evaporative cooler (IEC) coupled to a rooftop packaged air conditioner (RTU) that was retrofit with a condenser air pre-cooler.Download PDFSouthern California Edison (SCE)
Do occupancy-responsive learning thermostats save energy? A field study in university residence hallsMarco Pritoni, Jonathan M. Woolley, Mark ModeraAcademic Journal2016Occupant presence and behavior can and should influence energy use in buildings. If occupancy is measured, predicted, or otherwise inferred, building controls can automatically adjust system operating parameters to use less energy without sacrificing user services. However, previous field evaluations and simulation studies appear to have overestimated the energy savings associated with this type of smart control. In this article we present results from a carefully controlled field evaluation of occupancy-responsive learning thermostats installed in every bedroom of three high rise university residence halls. While a standard practice energy model developed prior to the retrofit estimated 10–25% savings for cooling and 20–50% savings for heating, measurements reveal that the control scheme only reduced energy consumption by 0–9% for cooling, and by 5–8% for heating for normal operation during academic periods. However, for non-academic periods when the residence halls were sparsely populated,the scheme reduced cooling energy consumption by 20–30%. We analyzed these observations in relation to occupancy patterns, room temperature records, ambient conditions, and equipment run time. The findings provide novel insight about how to improve field evaluations and refine model assumptions to better predict the impact of occupancy-responsive thermostat controls. Notably, while analysts often use fractional building occupancy trends to simulate building energy performance, this study highlights the importance of accounting accurately for both the temporal and spatial variation of vacancy events throughout a building.Download From Journal WebsiteCalifornia Energy Commission (CEC)
Energy-Efficiency Clothes Dryers: Self-Calibrating Automatic Cycle Termination ControllerTheresa Pistochini,
Caton Mande
Project ReportThis project developed an automatic dryer cycle termination controller that utilized the relationship between dryer drum inlet temperatures and outlet temperatures to accurately predict the end of the drying cycle. The technology promises to be more accurate and robust in performance under different load and environmental conditions in comparison to existing technology.Download PDFCalifornia Energy Commission (CEC)
Occupant Thermal Feedback for Improved Efficiency in University BuildingsMarco Pritoni, Kiernan Salmon, Angela Sanguinetti, Joshua Morejohn, Mark ModeraAcademic Journal2017Despite the significant amount ofenergy spent on HVAC operations, thermal comfort conditions in campus buildings are frequently poor.Faulty assumptions or a lack of data regarding occupant comfort can lead to energy waste from over-heating or overcooling. Additionally, inadequate operational procedures and outdated technology makeit difficult for occupant needs to inform temperature management.

This paper describes the campus-wide deployment of TherMOOstat, a software tool that solicits thermal feed-back from students, and analyzes its impact on energy use and energy management procedures. Thermalfeedback can be submitted any time from any building on central campus. Over 10,000 feedback submis-sions were received across one year, transforming occupants into meaningful sensors. The research teamexplored manual and automatic methods to link occupant thermal feedback to the energy managementsystem, resulting in improved efficiency and comfort.
Download From Journal WebsiteCenter for Information Technology Research in the Interest of Society (CITRIS)
Modeling and Design Analysis of a Regenerative Indirect Evaporative Heat Exchanger Using an Effectiveness MethodZhijun Liu, William Allen, Mark ModeraAcademic JournalIndirect evaporative cooling (IEC) is a water-based cooling technology that is attractive for space cooling in dry and hot climates due to its lower energy consumption (compared to vapor compression air conditioners) and lack of humidification (compared to direct evaporative cooling). The key component of advanced IEC or hybrid IEC/DX (Direct eXpansion vapor compression) systems(Elberling 2006) is the IEHX (indirect evaporative heat exchanger). A practical accurate model of an IEHX is needed to characterize the thermal behavior of these coolers and to support their implementation by HVAC designers.DownloadCalifornia Energy Commission
A Simplified CFD Model for Steady Transitional Flow in Narrow U-shaped ChannelsZhijun Liu, Jean-Jacques Chattot, Mark ModeraConference Paper2014A simplified CFD model that facilitates rapid analysis of steady transitional flow in narrow U-shaped channels is proposed, formulated, and numerically implemented. A depth-averaging technique is used to reduce the original three-dimensional (3-D) Navier-Stokes (N-S) equations to two-dimensions
(2-D) with a unique treatment of the viscous terms, which are expressed in terms of the local wall shear stress and computed through a use of the Colebrook correlation for transitional and turbulent flow in channels.
DownloadCalifornia Energy Commission
Simplified Thermal Modeling of Indirect Evaporative Heat ExchangersZhijun Liu, William Allen, Mark ModeraAcademic Journal2013A simplified model using a modified effectiveness–Number of Transfer Units (NTU) method for thermal performance simulation of indirect evaporative heat exchangers is presented and then validated utilizing experimental data from the literature. The objective of this model is to facilitate efficient computer simulation of indirect evaporative cooling or hybrid indirect evaporative cooling/direct expansion vapor compression systems, both of which include an indirect evaporative heat exchanger as a core component. Through some approximations, the governing differential equations that describe indirect evaporative heat exchanger heat/mass transfer behavior are modified to produce a methodology that is analogous to the effectiveness–NTU method for sensible-only heat exchangers.DownloadCalifornia Energy Commission
Improving System Efficiency for a Variable-Capacity/Variable-Blower-Speed Residential Heat Pump System with Multizone DuctworkSreenidhi Krishnamoorthy, Mark Modera, Curtis HarringtonAcademic Journal Paper2018This article describes efficiency improvements resulting from incorporating zonal airflow control into a variable-capacity/variable-fan-speed residential air-conditioning system. The results described are based on full-scale laboratory testing of prototype heat-pump equipment connected to a “typical-design” residential duct system located within a climatic chamber used to produce a range of summer climate conditions.Download
Advancing Development of Hybrid Rooftop Packaged Air Conditioners: Test Protocol and Performance Criteria for the Western Cooling ChallengeJonathan Woolley, Mark ModeraASHRAE Journal2011This paper outlines and discusses the development of the test protocol and performance criteria for the Western Cooling Challenge. The choice of laboratory test conditions is discussed. The rationale for and calculation of performance metrics including nominal cooling capacity and credited cooling capacity are presented. Additionally, the assumptions underlying requirements for minimum sensible energy efficiency are summarized, and key nonperformance-based criteria for the program are explained.DownloadCalifornia Energy Commission
An investigation of coupling evaporative cooling and decentralized graywater treatment in the residential sectorErica McKenzie, Theresa Pistochini, Frank Loge, Mark ModeraAcademic Journal Paper2013Total electricity and water burdens, including both direct and indirect uses, were modeled for newly constructed and 15-year-old homes in six California climate zones for three air conditioning systems: standard air-cooled condensing unit, evaporatively pre-cooled condensing unit, and an evaporative condensing unit. Compared to the air-cooled condensing unit, average annual direct electricity savings were 17.7% and 11.3% for an evaporatively pre-cooled condensing unit and an evaporative condensing unit, respectively. The evaporative condensing unit provided greater savings at peak load than the evaporatively pre-cooled condensing units (peak power savings were 30.9% and 23.8%, respectively),
which is promising for hot arid climates.
DownloadCalifornia Energy Commission
Low Pressure Air-Handling System Leakage in Large Commercial Buildings: Diagnosis, Prevalence, and Energy ImpactsMark Modera, Craig Wray, Darryl DickerhoffAcademic Journal Paper2013Air-handling system leakage reduces the amount of air delivered to conditioned spaces and in most cases wastes energy and money. Standards exist for where and how to measure system airtightness, but they tend to focus on new construction, and only on the high-pressure (1500 Pa to 2500 Pa (6 to 10 in. w.c.))/ medium-pressure (500 to 1500 Pa (2 to 6 in. w.c.)) portions of the system. This paper investigates air leakage in the “low-pressure” (≤500 Pa (≤2 in. w.c.)) portions of large commercial-building air-handling systems (i.e., downstream of variable-air-volume box inlet dampers).DownloadCalifornia Energy Commission
Technical and economic feasibility of unitary, horizontal ground-loop
geothermal heat pumps for space conditioning in selected california
climate zones
Steven Wiryadinata, Mark Modera, Bryan Jenkins, Kurt KornbluthAcademic Journal Paper2016This work investigates the viability of unitary 3.5 kWt, ground-source terminal heat pumps (GTHP) employing horizontally drilled geothermal heat exchangers (GHX) relative to air-source packaged terminal heat pumps (PTHP) in hotels and motels and residential apartment buildings in California’s coastal and inland climates. The GTHP can reduce hourly peak demand for the utility by 7–34% compared to PTHP, depending on the climate and building type. The annual energy savings of up to 5% are highly dependent on the water-pump energy consumption relative to savings associated with the ground-air temperature difference (T). In mild climates with small T, the pump energy use may overcome savings from utilizing a GHX. The levelized cost savings, ranging from $1.7/yr-m2 to $3.6/yr-m2, were mainly due to reduced maintenance and lifetime capital costs. Without these reductions, the GTHP does not appear to offer significant advantages over PTHP in the climates studied. The GTHP levelized cost was most sensitive to variation in installed cost and system efficiency. These results can inform installers and decision makers about the viability of this technology, which is highly dependent on climate and building type.DownloadNSF
CAT on a Hot Tin Roof: Getting Climate Appropriate Technologies onto Rooftops in Hot Dry ClimatesJerine Ahmed, Edwin Hornquist, Mark ModeraConference PaperApproximately 65% of the commercial building sector is cooled by roof top units (RTUs) that are designed and optimized for nation-wide application. California has a long-standing commitment to meeting aggressive carbon reduction objectives. Can RTU performance be optimized for California’s unique climate? Would manufacturers be willing to produce solutions to meet these regional needs? To address these needs, the California investor-owned utilities and the Statewide Emerging Technologies program began a decade long effort to meet the challenge of getting climate appropriate RTUs onto California rooftops. This paper presents an accounting of the challenges along the way and the solutions that were employed to meet this goal, starting with the Western Cooling Challenge (WCC) to manufacturers, with efficiency targets based upon adding indirect evaporative cooling to direct expansion RTUs; >40% improvement in seasonal efficiency, and >50% improvement in peak efficiency relative to DOE 2010 minimum efficiency standard. The WCC incorporated lessons learned through research and demonstrations on RTU retrofits and has evolved towards innovative, less-costly solutions that add indirect evaporative cooling to existing RTUs. This paper presents the technical design of the WCC, laboratory and field test results for WCC technologies, laboratory and field test results for evaporative pre-coolers for RTUs. The paper also presents the development of an ASHRAE standard for testing RTU evaporative pre-coolers, including addressing value-chain acceptance issues, and water consumption concerns. The authors conclude with a discussion of the future of HVAC efficiency in California.Download
Evaluation of the Next Generation Residential Space Conditioning System for CaliforniaSara Beaini, Ammi Amarnath, Walter Hunt, Ronald Domitrovic, Sreenidhi Krishnamoorty, Curtis Harrington, Mark Modera, Robert Davis, Ryohei HinokumaConference PaperThe ‘Next Generation’ Residential Space Conditioning System (Next-Gen RSCS) for California (CA) is an integration of multiple advanced HVAC technologies including: variable capacity heat pump compressor, variable speed blower fan, alternative refrigerant (R-32), automated demand response, fault detection and diagnostics, intelligent dual fuel heating (gas/electric), integrated ventilation, and zonal control. Along with the technology evaluation, an assessment was performed on duct losses for single versus multi-zone duct configurations with variable capacity equipment. The experimental results, from 3 leading laboratories, inform the industry on optimizing the system for efficiency, utility integration, and homeowner comfort.DownloadCalifornia Energy Commission
University of California Strategies for Decarbonization: Replacing Natural GasAlan Meier, Steven J. Davis, David G. Victor, Karl Brown, Lisa McNeilly, Mark Modera, Rebecca Zarin Pass, Jordan Sager, David Weil, David Auston, Ahmed Abdulla, Fred Bockmiller, Wendell Brase, Jack Brouwer, Charles Diamond, Emily Dowey, John Elliott, Rowena Eng, Stephen Kaffka, Carrie V. Kappel, Margarita Kloss, Igor Mezić, Josh Morejohn, David Phillips, Evan Ritzinger, Steven Weissman, Jim WilliamsWhite Paper2018Having pledged to become carbon neutral by 2025, the University of California has embarked on a large-scale effort to evaluate options for achieving this goal. For UC, the central challenge to deep decarbonization lies in reducing and, perhaps, ultimately eliminating the use of natural gas, a fossil fuel consisting primarily of methane. Nearly all CO2 emissions (96%) from UC operations come from direct combustion of natural gas (a “Scope 1” emission) and from purchased electricity generated from fossil fuels (a “Scope 2” emission). Therefore, a cost-effective exit strategy for conventional natural gas is vital to achieving the carbon neutrality goal. The UC carbon neutrality goal does not include “Scope 3” emissions, which are other emissions indirectly related to the University’s activities, such as from gasoline burned in employee-owned vehicles.DownloadTomKat Charitable Trust
Turning Paris into reality at the University of CaliforniaDavid G. Victor, Ahmed Abdulla, David Auston, Wendell Brase, Jack Brouwer, Karl Brown, Steven J. Davis, Carrie V. Kappel, Alan Meier, Mark Modera, Rebecca Zarin Pass, David Phillips, Jordan Sager, David WeilAcademic Journal Paper2018The Paris Agreement highlights the need for local climate leadership. The University Of California’s approach to deep decarbonization offers lessons in efficiency, alternative fuels and electrification. Bending the emissions curve globally requires efforts that blend academic insights with practical solutions.DownloadTomKat Charitable Trust
Performance Testing of R-466A: A Low Global Warming Potential Alternative RefrigerantDerrick RossCase Study2019The Western Cooling Efficiency Center (WCEC) tested the cooling performance of a unitary heat pump with R-410A and with a new, low GWP R-466A refrigerant. Researchers tested the heat pump equipment in cooling mode at six outdoor air conditions from 75°F-115°F using R-410A to obtain a baseline and repeated the tests after a drop-in replacement with the R-466A refrigerant. The cooling tests measured the total capacity, total system power, and coefficient of performance (COP) of the heat pump to determine what impact the new refrigerant had on the system’s performance.DownloadTrane
Ventilation rates in California classrooms: Why many recent HVAC retrofits are not delivering sufficient ventilationWanyu R.Chan, Xiwang Li, Brett C.Singer, Theresa Pistochini, David Vernon, Sarah Outcault, Angela Sanguinetti, Mark ModeraAcademic Journal Paper2020Previous research has shown that under-ventilation of classrooms is common and negatively impacts student health and learning. To advance understanding of contributing factors, this study visited 104 classrooms from 11 schools that had recently been retrofitted with new heating, ventilation, and air-conditioning (HVAC) units. CO2 concentration, room and supply air temperature and relative humidity, and door opening were measured for four weeks in each classroom.Download (Paywall)California Energy Commission (CEC)
Valuation of Thermal Energy Storage for Utility Grid OperatorsNelson Dichter, Michael Day, Mark ModeraProject Report2018This research investigates the potential impact on peak electric load that thermal energy storage systems can have on the electric grid by displacing vapor-compression systems and shifting the associated electric load from peak to off-peak hours. Whole building computer simulations were used to estimate the accuracy of two methods used by California utilities to quantify the value of thermal energy storage systems, the “10-Day Average Baseline” method and the “permanent load shift” method. DownloadIngersoll Rand