By Technology Topic

Condenser-Air Pre-Cooling

Alleviating System Demand by Pre-Cooling the Supply Air

In hot dry climates there are huge opportunities to improve air conditioner efficiency using evaporative technologies that reduce air temperatures at the condenser. As outdoor air temperature increases, air conditioner efficiency falls quickly; and therefore, uses more energy to deliver the same amount of cooling to a space. This is compounded by the fact that during hotter periods the cooling needs for a space increases. More»

Indirect Evaporative Cooling

All of The Benefits of Evaporative Cooling Without Adding Moisture to The Air

Indirect evaporative cooling operates by the same fundamental concept as evaporative cooling (evaporating water to cool the air), except that cooling is achieved without adding moisture to the supply air stream. Various formats are available for indirect evaporative coolers, many of which are capable of cooling well beyond the wet bulb temperature—the temperature one feels when one’s skin is wet and is exposed to moving air. More»

Energy Recovery

Transfer Waste Energy Into Something Useful

Many energy consuming systems today, including HVAC systems, either convert one form of energy to another or transfer energy from one system to another. In an HVAC system, electricity is converted into a cooled air flow from the condenser and fan. In a vapor compression cycle on a typical HVAC unit, the condenser’s heat is rejected into the atmosphere and away from the air stream. This rejected heat could be used in many applications that already require energy-to-heat generation including de-humidification/desiccant systems or water heaters and swimming pools.More»

Radiant Cooling

Cooling A Space with Circulating Water

A typical home air conditioning system will have a number of sources of wasted energy: air leaks out of the ducts, wasting the energy used to cool it, and the fan used to circulate the air round the house not only uses a lot of energy, but adds that energy to the air it is circulating. A radiant cooling system works by circulating chilled water through pipes embedded behind the ceiling, walls, or floor of the house. This keeps the surfaces of the room cool, so excess heat in the room can be absorbed by them and removed. Because of the high heat capacity of water compared to air, less of it needs to be pumped round thereby saving energy. Because water will not leak out of the pipes the way air leaks from the ducts, less energy is wasted. More»

Thermal Energy Storage

Storing Thermal Energy to Reduce Peak Demand Loads

Hot afternoons cause real problems for both users and suppliers of electricity. The efficiency of a standard air conditioning system depends inversely on the difference between the indoor and outdoor temperatures, so the hotter the day the less efficiently the system runs, pushing up the cost of cooling for the user. More»

Water Management for Evaporative Systems

Finding Solutions to Increase the Reliability and Efficiency of Evaporative Systems.

Though evaporative systems are gaining ground in the field of energy efficient cooling, the efficiency boost provided by evaporation creates other implications. When water evaporates off a surface the solids are left behind. These solids can form bonds to the metal surfaces (aka: scale) that diminish the heat transfer properties of that surface, and potentially reduce the airflow allowed through. More»

Advanced Control Devices

Using Adaptive Occupancy Sensors and Intuitive User Interfaces to Increase Efficiency

Recent Energy efficiency research has shown that deep retrofits in commercial buildings can achieve 30-50% energy savings. Complete renovations of HVAC units are generally fairly expensive, but significant, cost effective improvements can be made to existing systems with appropriate maintenance and sophisticated controls.More»

Efficient HVAC Control Strategies

How System Control Strategies Can Save Energy and Reduce Peak Demand

Rooftop packaged units provide heating and cooling for roughly 60% of the commercial floor area in California, and with split systems and other unitary equipment included, it’s likely that 90% is controlled with relatively simple strategies. A thermostatic control in the building calls for heating and cooling when the room temperature is above or below the setpoint. More»

Cool Roofs & Duct Coatings

Reduce Solar Heat Gains on Ducts by Up to 80%

Many buildings today have a portion of their ductwork either exposed to the outdoors or improperly insulated. The radiant heat from direct sunlight onto these exposed ducts significantly increases the ambient temperature within the ductwork. This trapped heat forces the air conditioning system to first cool the ductwork down before it can properly cool any room in the building. Unwanted duct heat gains can be minimized through the use of high-reflectivity/high-emissivity “cool duct” coatings, which have the potential to reduce the solar heat gains by ~80%. Properly insulated ducts can help further reduce heat gains from warm attics. More»

Efficient Heat Pump Systems

Using Less Heat to Create More Warmth

Heat pump air conditioners can supply heating to a space by reversing the flow of refrigerant. An automatic advantage of using heat pumps for heating is that these systems produce more heat than the energy used to operate them, whereas typical heating systems that use fossil fuels or electric resistance cannot. Heat pumps are ideal for systems that exchange heat with a source or sink that is more or less constant throughout the year, and at a temperature close to room temperatures.More»

Phase-Change Materials

Increase Heat Carrying Capacity With The Same Volume of Liquid

The purpose of heating or air conditioning is to deliver or remove heat.  Traditionally air, cold water, or refrigerant is piped into an area to be conditioned. Energy is used to pump the fluid, and in the case of forced air systems some supply air is lost to leakage.  Using water or refrigerant is preferable to forced air because water or refrigerants have a better ability to carry heat. To reduce the energy required to pump, the fluid should carry as much heat as possible. More»

Retrofits for Rooftop Package Air Conditioners & Air Handlers

Increase the energy efficiency of existing RTU equipment

Rooftop air conditioning units (RTUs) are self contained units that are typically installed on the roof but may be installed at ground level. Around 80% of individual systems in California are RTUs, and around half of all commercial floor space in the United States is cooled by RTUs. Most of these systems are older RTU models that are not as efficient as the models being made today. Installation of new RTUs is costly, which can discourage building owners from upgrading. More»

Interactions of Behavior and Technology

Understanding the implications and providing solutions for how we interact with HVAC technology

Has it ever occurred to you that air conditioners would work much more efficiently if it weren’t for the people involved? Always twiddling with the thermostat, or installing things incorrectly, or choosing the wrong technology for the application or failing to maintain things as manufacturers specify. If this thought has occurred to you, then you may have an appreciation for WCEC’s HVAC Behavioral Research Initiative (HBRI)… More»

Water-Energy Nexus

Understanding the relationship between energy and water-use.

The energy sector may be the largest water consumer among all industrial sectors. As long as there is a surplus of both water and energy we overlook the close relationship between them. When either water or energy are limited it becomes necessary for us to consider their interdependence. Most of us realize intuitively that all water operations will require energy…. More»

Air Tightness for Buildings

Building envelope tightness has a profound impact on energy efficiency

Using a high efficiency HVAC unit can reduce energy use, but it is entirely dependent on how tight or leak-free the conditioned space is. Imagine using an ice chest cooler with many holes in it to keep your picnic food cold… it wouldn’t stay at the desired temperature long enough without the continual addition of ice because the conditioned air would be leaving through the holes and, undesired, non-conditioned air would infiltrate the cooler. A building’s envelope works in much the same way…More»