Northeast Clean Energy Application Center

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CHP Thermal Technologies

Each of the CHP prime mover technologies described in the previous page produce excess heat that is recycled for another thermal energy need, such as space heating, domestic hot water, air conditioning, humidity control, process steam for industrial steam loads, product frying, greenhouses, or nearly any other thermal energy need. The end result is significantly more efficient than generating power, heating, and cooling separately. Below are descriptions of some of the technologies that run on the recycled thermal energy. Which one you employ obviously depends on what output you need and on the temperature and quantity of the excess heat available. It is often possible to employ more than one of these, either at the same time (i.e. air conditioning and humidity control) or seasonally (i.e. cooling in the summer and heating in the winter).

Efficient capture and effective use of thermal energy is essential for maximizing the energy savings and economic return of CHP. Cooling is often an especially useful add-on, as it allows customers to reduce seasonal peak electric demand and allows future electric and gas grids to operate with more level loads.

In most topping cycle CHP applications, the exhaust gas from the electric generation equipment is ducted to a heat exchanger to recover the thermal energy in the gas. Generally, these heat exchangers are air-to-water heat exchangers, where the exhaust gas flows over some form of tube and fin heat exchange surface and the heat from the exhaust gas is transferred to make hot water or steam. In the majority of installations, a flapper damper or "diverter" is employed to vary flow across the heat transfer surfaces of the heat exchanger to maintain a specific design temperature of the hot water or steam generation rate. The hot water or steam is then used to provide hot water or steam heating and/or to operate thermally activated equipment, such as an absorption chiller for cooling or a desiccant dehumidifier for dehumidification.

The next frontier in thermally-activated technologies for CHP — especially absorption chillers and desiccant dehumidifiers — is to factory design pre-engineered, integrated, packaged systems using standard, modular equipment, as opposed to using custom-designed and custom-engineered systems for each particular site. Some companies are making strides in smaller-scale integrated systems (small, medium and large commercial sites or small industrial sites); larger sites will still require custom work.

Next: Fuels for CHP >

(Page 5 of 7)

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