U.S. Department of Energy - Energy Efficiency and Renewable Energy
Distributed Energy Program
— Thermally Activated Technologies
Over the past two decades, the U.S. Department of Energy (DOE) has worked with industry to develop on-site energy conversion technologies, often classified as thermally activated technologies (TAT), for energy and economic purposes.
TAT optimize energy delivery systems by using nonelectric devices to displace electric devices when the electric distribution system is at peak demand. Because air conditioning and refrigeration drive U.S. electric peak demand, TAT such as absorption cooling/refrigeration and desiccant dehumidification can reduce this demand peak.
TAT can also improve the efficiency of distributed generation systems. For example, if a distributed generator produces electricity for $0.07/kWh when operating alone, the same distributed generator in cooling, heating, and power (CHP) mode will, by recycling thermal energy, yield a system production cost of $0.057/kWh.
DOE has partnered with industry to establish absorption and desiccant technologies for CHP systems to provide high-efficiency space-conditioning systems that can also address indoor air quality problems.
Power interruptions across the United States in recent years have increased the need for near-term solutions for localized electric grid support systems and demand reduction. Long-term economic growth requires a reliable power supply, and CHP systems dependent on TAT equipment can fill this need.
Recycling Thermal Energy
In the year 2020, 5% of all energy consumed in the United States will be recycled thermal energy.
- Thermal energy recycling is the largest opportunity for reducing energy consumption. American industry needs to accelerate the development of TAT to meet the energy and economic challenges of the future.
- TAT are critical to ensuring indoor environmental security and reducing air pollution. American industry needs to accelerate the development of desiccant ventilation air technologies as a health and protection measure.
- Direct fuel-based and recycled energy-based TAT are the focus of a new public-private partnership roadmap. Leapfrog materials, design, and control technologies are essential elements of this accelerated research, testing, and verification roadmap.
Thermally Activated Technologies
TAT are a diverse portfolio of equipment that transforms heat for useful purposes such as heating, cooling, humidity control, thermal storage, and shaft/electrical power. CHP systems are recognized as energy-efficient devices that will supplement central-station electric power generation using discrete, economical, reliable, and secure distributed power generation. TAT are essential for CHP-integrated systems that maximize energy savings and economic return. TAT systems also enable customers to reduce seasonal peak electric demand and future electric and gas grids to operate with more level loads.
Absorption Chillers
The use of absorption chiller technology, popular in the 1960s, faded from the American scene during the energy crisis of the 1970s because of gas curtailments. The technology was developed in Asia to reduce summer electric peaks that slowed Asian economies in the late 1980s and 1990s. Absorption chillers today are important energy tools in Japan, Korea, and China, but they are just being recognized in the United States as an important and immediate grid-support tool.
Commercial-sized lithium bromide-water absorption equipment—greater than 100 refrigeration tons (RT)—has advanced to a point that industry can develop viable and competitive products. In other industries (such as the automotive industry), leapfrog materials, design, and control technologies hold great promise for equipment that is half the size, one-eighth the weight, and 25% more efficient than the current state of the art.
Advanced ammonia-water absorption equipment (for residential and small commercial applications and typically less than 15 RT) has been developed with DOE and industry support. This technology is moving out of the laboratory and into prototype development and field testing. Ammonia-water absorption technology can provide below-freezing refrigeration temperatures, which allows additional applications such as refrigeration and freezing.
Absorption equipment can be optimized to recycle thermal energy from power generation equipment. This combination offers significant opportunities for maximizing fuel efficiency. Distributed power generation sites can benefit from integration with absorption chillers, especially for gas turbine inlet cooling, process cooling, and air-conditioning in buildings.
Desiccant Dehumidifiers
Desiccant equipment is useful for the mitigation of indoor environmental quality and security problems and for humidity control in buildings. Commercial desiccant technologies have not been designed for integration into CHP systems. Advanced ventilation air conditioning designs using recovered energy are the key to efficiently controlling buildings' indoor humidity, environmental quality, and safety.
The TAT program works with the desiccant-based ventilation air conditioning industry to accelerate the development of components, systems, and overall ventilation air conditioning design. This is essential for the building industry's compliance with American Society of Heating, Refrigerating, and Air-Conditioning Engineers' Standard 62, "Ventilation for Acceptable Indoor Air Quality." Liquid desiccant technologies, in particular, with air washing and biocidal capabilities, are viewed as a critical path toward ensuring indoor environmental security under extraordinary circumstances and reducing indoor air pollution in general.
Standalone desiccant technology in the commercial sector is a young technology with a premium price. It needs additional component, system, and application research to reach economic viability. Recycled thermal energy is an important path forward for many distributed generation technologies and fits well with desiccant systems.
American industry needs to accelerate the development of desiccant ventilation air technologies as a health and protection measure. DOE's role is to partner with industry to speed the development of lower-cost solid desiccant wheels, liquid desiccant systems, and desiccant-based indoor environmental quality and security and CHP systems.
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