Environmental Engineering Reference
In-Depth Information
Picture 11.3
Combined heat and power plant in Malženice, Slovenia. The plant has an efficiency of
58 percent and supplies energy to 900,000 households.
© Siemens AG, Munich/Berlin.
lower, and because electricity is produced on site, the reliability increases and losses during
electricity distribution are eliminated.
The core of a CHP system is the prime mover that can be a diesel engine, a natural gas
engine, a gas turbine, a microturbine, a steam turbine, or a fuel cell. Mechanical energy
produced by the prime mover can be converted into electricity by a generator or used to drive
rotating equipment such as compressors, pumps, and fans. The heat released by the prime
mover can be use in direct processes (e.g., drying) or indirectly to produce steam, hot water,
or chilled water for process cooling via an absorption chiller (EPA, 2008). The way heat is
captured is by routing the exhaust gas from the prime mover (or low-pressure steam in the
case of a steam turbine) to a heat exchanger where heat is transferred to air, water, or a
thermal fluid.
Ideally a CHP system should be run on renewable resources such as biogas, landfill gas,
or biomass. However, even if the system uses fossil fuels there is still a net benefit to it because
of the higher efficiency of the CHP system.
