Northeast Clean Energy Application Center


What is CHP?

Energy is the most significant driving force of our economy. All buildings need electric power for lighting and operating equipment and appliances. One of the major consumers of energy in buildings is the equipment for space conditioning. Most commercial and institutional buildings for businesses, education, and healthcare require space conditioning for cooling, heating, and/or humidity control.

Two-thirds of all the fuel used to make electricity in the U.S. is generally wasted by venting unused thermal energy, from power generation equipment, into the air or discharging into water streams. While there have been impressive energy efficiency gains in other sectors of the economy since the oil price shocks of the 1970’s, the average efficiency of power generation within the U.S. has remained around 33% since 1960. The average overall efficiency of generating electricity and heat by conventional systems is around 51 percent.

CHP diagram

A 1 MW natural gas reciprocating engine in a combined heat and power application produces 35 units of electricity and 50 units of heat with only 100 units of fuel. Losses amount to 15 units of energy. With conventional generation, the losses are more substantial: 165 units of fuel are needed to produce the same amount of useful electricity and heat, with total losses of 80 units of energy.

Combined heat and power (CHP) or cogeneration is the production of two forms of useful energy from a single fuel source. In most CHP applications, energy from a fuel source such as natural gas or oil is converted to both mechanical and thermal energy. The mechanical energy is used to generate electricity, while the thermal energy or heat is used to produce steam, hot water, or hot air. Depending on the application, CHP is referred to by various names including Building Cooling, Heating, and Power (BCHP); Cooling, Heating, and Power for Buildings (CHPB); Combined Cooling, Heating, and Power (CCHP); Integrated Energy Systems (IES), or Distributed Energy Resources (DER).

Integrated combined heat and power (CHP) systems significantly increase efficiency of energy utilization, up to 85%, by using thermal energy from power generation equipment for cooling, heating and humidity control systems. These systems are located at or near the building using power and space conditioning, and can save about 40% of the input energy required by conventional systems. In other words, conventional systems require 65% more energy than the integrated systems, as shown in the above diagram.

Commercial buildings, college campuses, hospital complexes, and government facilities are good candidates for benefiting from integrated CHP systems. The CHP systems can be economically attractive for many types of buildings, including, but not limited to the following:

Educational facilities
Office buildings
Data centers
Nursing homes
Refrigerated warehouses
Retail stores
Ice arenas