1. Scope

Thermal power stations are facilities in which the energy content of an energy carrier, i.e., a fuel, can be converted into either electricity or electricity and heat. The type of power plant employed depends on the source of energy and the type of energy being produced.

Possible energy sources include:

– fossil fuels such as coal, petroleum products and natural gas
– residual and waste materials such as domestic and industrial refuse and fuel made from recovered oil
– fissionable material

Thermal power plants can be designed for different fuel sectors in the interest of greater fueling flexibility and/or higher efficiency - one example being a combination power plant with a gas turbine running on natural gas and an oil- or coal-fired steam generator feeding a steam turbine.

Renewable sources of energy such as wood and other forms of biomass are not dealt with here, as they are the subject of a separate environmental brief. Nuclear thermal power plants have also been omitted from this catalogue. The frame of reference concentrates extensively on fossil-fueled power plants, in particular types using coal and petroleum products, the present and near-future use of which is of eminent importance in most developing countries. With regard to hydropower, the reader is referred to the environmental brief Large-scale Hydraulic Engineering.

As far as the form of energy being generated is concerned, there are three main types of thermal power stations:

– condensing power plants used exclusively for generating electricity
– steam- or hot-water producing heating stations for domestic or industrial purposes
– district heating power stations, or cogenerating plants, for the simultaneous generation of electricity and available heat.

It is important to note that, for economic reasons, process heat and heat for heating purposes should only be generated in close proximity to the users. For thermal outputs ranging from 50 to 100 MW, the distance between the power plant and the user should not exceed 2 to 5 km. Conversely, electricity can be economically transmitted over very substantial distances; cf. environmental brief Power Transmission and Distribution.

The unit power ratings of fossil-fueled thermal power plants range from a few hundred kW (diesel stations) to more than 1000 MW (oil- and coal-fired stations). In many countries, preference is given to unit ratings of 200 - 300 MWel with deference to power system stability. The better the boundary conditions, the higher the achievable capacities.