Combined Heat and Power (CHP)

Combined heat and power is the simultaneous production of electricity and heat from a single fuel source.
Electricity produced in a conventional way (fossil fuel burning) has an efficiency of about 40%. This is due to the second law of thermodynamics, which states that, in the Lord Kelvin formulation,

"It is impossible to convert heat completely into work in a cyclic process."

This means that there are no processes with an efficiency of 100% because losses in the form of heat are always occurring and heat cannot be completely converted into work.
So, to try to use the energy we produce in a more efficient way, why not use the heat instead of letting it slip to the atmosphere?
In order to do so, there are some changes required in the production process, for example, installing a heat recovery unit or using a steam turbine. Steam turbines normally generate electricity as a byproduct of heat (steam) generation.
Currently, CHP processes are used for example in district energy systems (district heating).
Advantages and disadvantages will be discussed later.