What is combined heat & electrical power?
The concept of cogeneration is all about combined heat and electrical power (CHP). Unlike a classic power station, where heat produced when making electricity, is wasted into the environment – CHP units collect all this waste heat and use it for something. This saves fuel which would otherwise need to be used in boilers for producing that heat.
How does a cogeneration unit work?
Electricity in all power stations originates by using and engine of some form to spin an electrical generator. The engine is often a steam turbine. The heat necessary for the production of steam to drive the turbine, mainly comes from the burning of fossil fuels. Together with electricity production, large amounts of heat are generated. However, most of this heat is wasted by release into the atmosphere. On average, power plants therefore operate at only around 32% efficiency, which means that the rest of energy (70%) is wasted. Unfortunately, your energy bill is based on the fuel that the power station consumes, and includes no credits for energy they waste.
In CHP units, the electricity is generated in the same way as in other power stations, but the heat is utilised. Another advantage of CHP is decentralisation. This is where energy is produced close to the point of consumption. This saves further losses of power which occur transporting electricity through the national grid. The overall effect of this is the efficiency of CHP units can be as high as 95.5%. New designs are also emerging with exhaust gas condensers, promising efficiencies of over 98%.