Environmental Engineering Reference
In-Depth Information
Cogeneration or CHP (combined heat and power) devices allow the simultaneous
production of electric and thermal energy in energy systems. They typically recov-
er and use waste heat from a thermal power plant burning coal.
These systems are widely used in Eastern Europe to distribute hot water (at tem-
peratures between 80 and 150°C) to houses and apartments, and even to whole dis-
tricts using heat generated in a central station. Thus, these systems are called “dis-
trict heating.” Heat at moderate temperatures can also be used in absorption chillers
for cooling. A plant producing electricity, heat, and gas is called a trigeneration or
polygeneration plant.
Eleven percent of the electricity generation in the European Union uses cogen-
eration, but there are large differences between member states ranging from 2 to
60%.
In Brazil, cogeneration is used widely in industrial installation using sugarcane
bagasse, which is produced after the cane juice has been extracted and converted
into either sugar or ethanol. The bagasse is solid biofuel that can be burned to pro-
duce all the heat and electricity needed in the industrial process of sugar or ethan-
ol production. In modern efficient installations surplus, bagasse is used to produce
electricity to be sold to the electricity grid.
There is a technological revolution currently under way in power generation, where
advanced systems are replacing steam turbine technologies. Natural gas- fired
combined cycle plants offer low cost, high efficiency, and low environmental im-
pact, and they are being utilized wherever natural gas is readily available. In some
countries they are even replacing new large hydropower projects. Cogeneration
(i.e., the combined delivery of heat and power or CHP) based on gas turbines and
combined cycles is more cost effective and can play a much larger role in the en-
ergy economy than cogeneration with steam turbines, because combined cycles
