CHP TECHNOLOGY AND APPLICATIONS

The Department of Energy's Distributed Energy Program has been working with industry to develop combined heat and power (CHP) technologies for some time. The primary fuel for many CHP systems can be natural gas, clean oil, coal, biomass, solar concentrators, and hydrogen. CHP applications range from industrial, district energy, institutional, Government, commercial, and residential-in virtually any stationary application that can utilize waste heat from onsite power for cooling or heating. View the CHP Market Studies for further information.

• Prime Movers including reciprocating enginges, microturbines, industrial turbines, and fuel cells
• Thermally Activated Technologies using Cooling technologies including absorption chillers and Dehumidification technologies including solid and liquid desiccant dehumidifiers.
• CHP Technological Advances including Packaged Systems and other Advanced Technologies

The California Energy Commission has an online DER equipment guide including commercially available equipment as well as emerging technologies. Detailed information is included for microturbines, combustion turbines, reciprocating engines, stirling engines, fuel cells, energy Storage / UPS, photovoltaic systems, wind systems, hybrid systems, and combined heat and power.

Prime Movers

Prime mover, or power generation technologies, include reciprocating engines, microturbines, industrial turbines, and fuel cells. (Click on any image to enlarge.) Natural gas is the cleanest and most common fuel; propane is less common but also relatively clean. There is a growing trend toward dual-fuel systems that can combust either natural gas or diesel.

Reciprocating engines (5 kW-7 MW)
Combustion turbines (500 kW-25 MW)
Microturbines (25-500 kW)
Backpressure Steam Turbine (50 kW and up)
Fuel cells (1 kW-10 MW)

CHP systems should always be able to exceed the total fuel efficiency of even the best central power plants, dividing the energy content of the fuel inputs into the delivered energy content of the total useful output, and taking average transmission and distribution line losses into account. A state-of-the-art central plant (a combined cycle combustion turbine using natural gas) offers a maximum system fuel efficiency for delivered power in the range of 55-60%. At this efficiency level, CHP systems will effectively double the central electric system's average delivered fuel-use efficiency of about 30%. However, under common circumstances, CHP systems will achieve efficiencies exceeding 70%. CHP systems achieving efficiencies exceeding 80% are frequent, and some systems have been shown to reach levels in excess of 90%.

For these reasons, while USCHPA seeks policies to recognize and provide incentive for any CHP systems that can reduce energy waste compared to the current central system power production, USCHPA is willing to accept a requirement that CHP systems qualify for incentives only when they can demonstrate efficiency exceeding the best of the central-station power plants on a delivered power basis; i.e., achieve a useful energy output representing at least 60% of the gross energy input into the CHP system's prime mover.

A Resource Dynamics Corporation report for DOE, Integrated Energy Systems (IES) for Buildings: A Market Assessment, August 2002, gives the following costs and performance data for CHP prime mover technologies. Backpressure steam turbine information was compiled by USCHPA member Turbosteam:

	Reciprocating Engine	Turbine and Microturbine
Size	30kW-8MW	30kW-20MW+
Installed cost ($/kW)*	300-1500	350-1500
Electrical efficiency (LHV)	28-42%	14-40%
Overall efficiency**	~80-85%	~85-90%
Variable O&M costs ($/kWh)	0.0075-0.02	0.004-0.01
Footprint (m2/kW)	0.02-0.03	0.01-0.03
Emissions (g/kWh unless otherwise noted)	Diesel: NOx: 9.9-11, CO: 0.45-0.9 Natural gas: NOx: 0.07-1.7, CO: 1.8-2.7	NOx: 3-50ppm CO: 3-50ppm
Fuels	Diesel, natural gas, gasoline, digester gas, biomass and landfill gas; larger units can use dual fuel (gas/diesel) or heavy fuels	Natural gas, diesel, kerosene, naphtha, methanol, ethanol, alcohol, flare gas, digester gas, biomass and landfill gas
*Cost varies significantly based on siting and interconnection requirements, as well as unit size and configuration. **Assuming CHP.

	Fuel Cell	Backpressure Steam Turbine
Size	100-3000kW	50 kW and up
Installed cost ($/kW)*	2000-5000	300-2000
Electrical efficiency (LHV)	40-57%	>70% (marginal basis)
Overall efficiency**	~80-85%	>80%
Variable O&M costs ($/kWh)	0.002-0.05	<0.01
Footprint (m2/kW)	0.08	0.004 - 0.03
Emissions (g/kWh unless otherwise noted)	NOx:<0.02 CO: <0.01	Depends on boiler fuel. However, no need to obtain permits for back-pressure units
Fuels	Natural gas, propane, digester gas, biomass and landfill gas (potentially)	All
*Cost varies significantly based on siting and interconnection requirements, as well as unit size and configuration. **Assuming CHP.