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Waste Heat Recycling: Onsite and National Energy Impact Analysis
NREL combines modeling, field-testing, and analysis studies incorporating the latest technologies to identify optimal configurations and predict opportunities for leapfrog ideas in research. NREL particularly focuses on the concept of combined heat and power (CHP) to promote an efficient distributed energy resources model.
CHP, which is also referred to as cooling, heating, and power, or cogeneration, is the implementation of integrated energy systems (IES) that facilitate on-site or near-site power generation and utilization of the resulting heat for thermally activated equipment. For on-site power generation, the wide spectrum of potential prime movers includes microturbines, gas turbines, internal combustion engines, fuel cells, and hybrid systems. Included in the portfolio for thermally activated technologies are absorption cooling (single-, double-, and triple-effect), solid and liquid desiccant dehumidification, space heating, and service hot water production. In the context of CHP, thermally activated technologies not only facilitate effective and efficient means for indoor air quality control, but they can also lend themselves to industrial applications. Technological diversities along with the variations in the electrical and thermal load characteristics of various applications contribute to the complexities in optimum design of CHP systems.
 Onsite power generation makes recoverable thermal energy available to meet end-use loads. |
A CHP system can be interconnected with an electric grid or can be grid-independent. The efficient use of distributed primary energy sources is a distinguishing attribute that renders the CHP concept a promising alternative to centralized power plants. The current central power generation and distribution system offers an average efficiency of about 33%, leading to a loss of 67% of the primary energy input (largely in the form of recoverable thermal energy).
In contrast, well-designed CHP systems offer primary utilization efficiencies in excess of 70% as a result of recycling of the thermal energy exhausted by the prime movers and reduction of electrical transmission losses. This also translates into a major reduction in emissions that is of a great significance from an environmental point of view. Energy reliability and security are also significantly enhanced with implementation of the concept. Remote rural areas, particularly in developing countries, can greatly benefit from CHP as well.
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