Environmental Engineering Reference
In-Depth Information
4
Electrical Power Generation
and Conditioning
4.1 The Conversion of Renewable Energy into Electrical Form
Renewable energy is available in a variety of forms. Uniquely, biomass is available in the
form of combustible fuel and thus can play a similar role in generation as conventional fossil
fuels. To generate electricity, all other renewables require a number of conversion stages that
differ from those found in systems based on traditional fuels.
Wind energy is available in kinetic form. The function of a wind turbine is to extract energy
from the intercepted wind by slowing it down and to convert this energy into a mechanical
form that suits an electric generator. To improve the effi ciency of conversion and for other
operational reasons, the generator may be interfaced to the mains through a power elec-
tronic converter.
Water power in the form of tides (potential) or water fl ow (kinetic) requires a turbine to
transform this energy into rotational form for further conversion into electricity, again
through a generator.
The kinetic energy in water currents caused by tidal effects can alternatively be captured
through an underwater 'wind turbine' that uses the same technology as those on land.
Wave energy conversion requires specially designed devices that transform the low fre-
quency energy in the waves into (usually) pressure energy in oil, which in turn drives an
electrical generator. In other wave energy concepts the rise and fall of waves drives air
through a turbine coupled to an electrical generator.
Solar energy is available as radiation ranging from ultraviolet to infrared. Conversion
into electricity can be implemented thermally by solar furnaces that raise steam to
drive conventional turbines or through solid state photovoltaic devices that utilize the
radiation to separate charges in semiconductor junctions. The effi cient operation of PV
based systems depends on interfacing the PV array to the grid through a power electronic
converter.
