Authors Subhrajit Chakraborty, David Vernon, Apoorva Jha and Vinod Narayanan analyze the potential of utilizing a novel indirect evaporative cooler (IEC) that can efficiently cool building ventilation air in the hot summer months, and be used as a heat recovery ventilator in winter months. Their laboratory testing of this equipment showed significant energy savings potential, and validated their IEC physics-based model. Ultimately, this will lead to accurate modeling of this energy saving technology over a variety of buildings and climates.
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Seeley Climate Wizard Hybrid: Packaged Roof Top Unit with Integrated Heat Pump and Indirect/Direct Evaporative Cooling
A packaged heating, ventilation, and air conditioning (HVAC) system is an integrated piece of mechanical equipment that provides all three mechanical functions for a space. Packaged roof top units (RTUs), which are the baseline technology assessed in this study, are the predominant method of building conditioning in California. It is estimated that 75% of commercial building floor area in California is conditioned with packaged systems [1]. The emerging technology assessed in this study is the Seeley Climate Wizard (CW) Hybrid, which is a packaged RTU that integrates a heat pump with an indirect-direct evaporative cooling (IDEC) system that is designed as a direct replacement for a traditional RTU. This project evaluates the Climate Wizard (CW) Hybrid, manufactured by Seeley International, in a field study and compares its performance to a baseline packaged RTU.
The CW Hybrid combines an indirect-direct evaporative cooling (IDEC) system with a heat pump, which results in the energy saving benefits of evaporative cooling with the capabilities of a heat pump. The IDEC system portion of the CW Hybrid operates with 100% outdoor air filtered by MERV 13 filters on the inlet. The system operates using both indirect and direct cooling in series by passing the air through an indirect evaporative heat exchanger followed by direct evaporative media. The resulting supply air is below the wet bulb temperature of the ambient air, meaning that comfort can be maintained in buildings in dry climates like California using significantly less electricity than compressor-based air conditioners. The single-speed heat pump side of the system can provide either heating or cooling based on the position of the reversing valve. The supply air on the heat pump is recirculated from the room and filtered with a MERV 13 filter.
Addressing Need for Low-Cost Ventilation Screening Tool in a Pandemic World
COVID-19 has permanently or temporarily altered numerous aspects of our lives. As a testing, adjusting and balancing provider, NorthWest Engineering Service, Inc. was one of many entities to immediately recognize the importance of ventilation and ASHRAE recommended air changes per hour in mitigating the effects of coronavirus. In fact, ventilation is arguably one of the more important recommendations being discussed in the first months of the crisis.
Unfortunately, the answer was not as simple as maximizing outside air and walking away – that is a temporary solution at best. It is important to recognize the energy and equipment lifetime impacts that can happen when HVAC systems are called upon to operate beyond design intent.
The ideal solution, technically, would be to undertake a full room-by-room TAB project to make sure all building occupants are breathing properly diluted air in every part of every room.
But this is certainly not the ideal solution from the standpoint of budget. In particular, clients with many, multi-story buildings, like hospitals, colleges and large school districts, don’t typically plan for a campus-wide TAB project in a single year. And even if money can be found, more time cannot.
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Research Team Selected for $4.6 M Department of Energy Award to Advance Concentrating Solar-Thermal Power
Concentrating solar-thermal power technologies can help eliminate carbon dioxide emissions from the energy sector. UC Davis and eight partnering institutions were selected to receive $4.6 M from the Department of Energy to advance high temperature receiver development for industrial process heat and solar thermal power generation. The team, led by Vinod Narayanan and Erfan Rasouli at UC Davis, will design, develop, and de-risk a 150-kilowatt solar-thermal receiver able to heat supercritcal carbon dioxide or air to temperatures from 600-900°C.
A District Energy System Design Could Cut More Emissions for Proposed Davis Innovation Sustainability Campus
Report analyzes greenhouse gas emissions of two heating and cooling systems
Homes and businesses use over 25 percent of California’s energy. With a number of different space heating and cooling technologies available to developers, it is important to understand and quantify potential greenhouse gas (GHG) impacts.
A study, completed by the UC Davis Western Cooling Efficiency Center (WCEC), analyzed the GHG emissions for two different heating and cooling options for a proposed development in Davis – the Davis Innovation Sustainability Campus (DiSC). Researchers analyzed GHG emissions for: 1) the proposed all-electric, high-efficiency design, which would use packaged heat pump equipment for heating and cooling the buildings and 2) a potential upgrade to an all-electric, very high efficiency design, which would use a district energy system. A district energy system uses a central plant heat pump and chiller to heat and cool water that is piped to buildings for heating and cooling.
“Based on predicted energy consumption data provided be Trane, we found that a district energy system could further improve energy efficiency by 26%, reduce total energy consumption by 14%, and reduce GHG emissions by 16% over the already highly efficient proposed design,” said lead researcher David Vernon, Co-Director of Engineering for the UC Davis Western Cooling Efficiency Center.
DiSC energy system options
DiSC is a proposed development that would build new residential, office, laboratory, and manufacturing buildings on the eastern edge of Davis. The developer team is required by the Davis City Council to build an all-electric design with an energy efficiency level 30% more efficient than required by Title 24 building codes.
“The developer funded us to look at a district energy system design with large thermal energy storage because it has the potential to greatly reduce GHG emissions,” Vernon said. “It can help stabilize the grid by using energy when renewable generation is high and reducing energy consumption when renewable generation is low.”
To meet California’s climate goals requires large increases in renewable energy generation, energy storage, and load shifting technologies. District energy systems with large thermal energy storage have the potential to be an effective energy storage and load shifting strategy. The WCEC mission is to advance design, monitoring, and objective reporting of the performance of these types of technologies to inform policy and economic decisionmakers.
Energy modeling and analysis
The heating, ventilation, and air conditioning (HVAC) manufacturer Trane completed energy models of the proposed baseline and district energy system designs and provided the hourly energy consumption results. The WCEC researchers then used these hourly energy consumption results to calculate Time Dependent Valuation—a metric that incorporates the social and environmental impacts of energy used to evaluate energy efficiency, total energy consumption, and GHG emissions of the designs.
“Our analysis shows that district energy systems offer significant opportunities to reduce energy consumption and GHG emissions compared to more common HVAC designs,” said Vernon. “It is important to note that our results are on the conservative side, and implementation of this design could result in even larger GHG savings.”
This study was funded by Ramco Enterprises, Inc. and the Buzz Oates Group of Companies.
Media Resources
- David Vernon, UC Davis Western Cooling Efficiency Center, dvernon@ucdavis.edu
- Ali Loge, UC Davis Energy and Efficiency Institute, 530-204-8865, asloge@ucdavis.edu
Market Transformation Research Group Publishes Study on Human Factors and Indoor Air Quality in Schools
Classrooms 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’ perceptions and practices that may also have important implications for achieving a safe classroom environment.
We report on a (pre- pandemic) survey of 84 teachers across 11 California schools, exploring their perceptions of environmental quality in relation to monitored indoor environmental quality (IEQ) data from their classrooms. Teachers were not educated regarding mechanical ventilation. Errors in HVAC system installation and programming contributed to misunderstandings (because mechanical ventilation was often not performing as it should) and even occasionally made it possible for teachers to turn off the HVAC fan (to reduce noise).
Teachers did not accurately perceive (in)sufficient ventilation; in fact, those in classrooms with poorer ventilation were more satisfied with IEQ, likely due to more temperature fluctuations when ventilation rates were higher combined with occupants’ tendency to conflate perceptions of air quality and temperature. We conclude that classroom CO2 monitoring and teacher education are vital to ensure that teachers feel safe in the classroom and empowered to protect the health of themselves and their students.
WCEC Newly Published Journal Article on Greenhouse Gas Emission Forecasts for Residential Heat Pumps
This 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. The study accounted for long-run marginal emissions from electricity generation, emissions from natural gas combustion in homes, and fugitive methane and refrigerant emissions from leaks.
The population weighted US average results show emission reductions for a heat pump over furnace to be 38–53% for carbon dioxide, 53–67% for 20-Year global warming potential (GWP), and 44–60% for 100-Year GWP, with reductions increasing over time. The impact of fugitive emissions from the furnace is significantly higher than that of the heat pump. While more energy efficient construction reduces overall emissions for both heating types, the forecasted percent emission reduction for replacement of a gas furnace with heat pump was not impacted by changes in home construction parameters.
R-466A Refrigerant Demonstration and Performance
Refrigerants 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 safety, performance, and GWP.
The California Air Resources Board (CARB) has approved a new regulation requiring refrigerants used in all new stationary residential air conditioning systems to have a 100-year GWP value of 750 or less. For reference, the most common refrigerant currently used in unitary air conditioning equipment is R-410A, which has a 100-year GWP of 2,088.
A number of refrigerant solutions have been developed to meet the CARB GWP requirement, but the majority of these refrigerants have a low level of flammability (A2L). While there are strategies for mitigating the risk of using flammable refrigerants, finding a non-flammable solution presents the easiest path to market and would not require additional safety controls and updates to codes and standards.
Student-Built Air Purifiers Tackle Wildfire Smoke and Covid-19
Schools are facing many challenges this fall, including minimizing risks to students and staff from Covid-19 and wildfire smoke exposure. Air purifiers are one tool that can help.
Researchers from the UC Davis Energy and Efficiency Institute (EEI) partnered with science teachers at Rio Tierra Junior High School in Sacramento to teach a two-day lesson on air quality and build 30 portable air cleaners with approximately 150 8th grade students. The portable air cleaners will be distributed to every classroom on campus.
Knowledge to action
“It is really important to empower students and help them understand indoor and outdoor pollution sources, and how to measure and improve indoor air quality,” explained UC Davis researcher and project lead Theresa Pistochini. The lesson culminated with groups of 4-5 students constructing do-it-yourself (DIY) portable air cleaners using a Corsi-Rosenthal cube design, which uses a box fan and four filters with a MERV 13 rating. The materials for each air cleaner cost $75. Each air cleaner is expected to provide about the same amount of air cleaning effectiveness as small commercially available portable air cleaners that cost about $200.
Science teachers Amber Mitchell and Kathryn Graf planned the visit with UC Davis researchers Theresa Pistochini and Robert McMurry. “I love having outside speakers come in. Air quality is such a relevant topic that we are able to teach the kids about,” Mitchell said. “We are always trying to relate science to current events and student’s lives. There’s not much more relatable right now than making air purifiers to help our school.”
