Block heat and power plant

Block heat and power plants (BHPPs) are modular facilities or installations that generate both electrical energy and heat for local heat requirements. They may also feed heat for distribution into local heat networks. Their underlying principle is called cogeneration.

As prime movers for the generators, BHPPs may use internal combustion engines such as Diesel, plant oil and gas engines, but also gas turbines, stirling engines or even generate electricity directly with fuel cells.

Since BHPPs make use of the waste heat from the electricity generation, they achieve better capacity factors than the conventional combination of local heating and centralized power stations. Depending on size, BHPPs with combustion engines achieve an energy conversion efficiency of 25% to 44% of the fuel's total heat of combustion). BHPPs using fuel cells may achieve an electrical efficiency of 55% to 60%. If the waste heat is used locally and to the greatest possible extent, it is possible to reach 80 to 90% total efficiency relative to the primary energy content. While condensing boilers are almost 100% efficient, they do not generate any electricity. (Also note different efficiency definitions are used for condensing boilers.)

Common BHPP modules are available with electrical power outputs between one kilowatt (kW) and tens of megawatts (MW). Units below 50 kW are also called mini cogeneration plants, and installations up to 10 kW are known as micro cogeneration. Devices under 2.5 kW may be called nano BHPPs. Mini and micro BHPP are used to supply residential areas and business centers, hospitals, water parks and apartment buildings, but also small factories and housing developments. The nano class is even suitable for individual family homes. Cogeneration is also used by large central plants, typically with several hundred MW of electrical power.