Combined Unit

Combined Units

What is it?
Combined heat and power (CHP), is the generation of heat and power (usually electricity) at the same time.

How does it work?
In its simplest form a CHP system comprises a gas turbine, engine or steam turbine to drive an alternator. The resulting electricity is used primarily on-site. The waste heat, in the form of steam or hot water, is collected and can be used to provide heat for industrial processes, for community heating and for space heating. It can also provide cooling using advanced absorption cooling technology. Systems vary considerable in size, from micro turbines (<50 kW) to many MW of electrical output.
Not only does CHP enable the conversion of a high proportion of otherwise waste heat to usable heat, but it is very efficient because power is generated close to where it is being used (and thus electricity transmission losses are minimised). The predominant fuel used for CHP schemes is natural gas (62% in
2000). Other fuels include oil, coal or even renewables (such as municipal and industrial waste, sewage gases, biogases, from anaerobic digestion, biodiesel, gasification etc and wood).

The market
There is a large potential for small-scale CHP in the UK with substantial political and financial support for its use by the Government. Greater competition, lower payback times and reduced regulation are all encouraging the uptake of CHP in a range of settings and using a variety of fuels. The cost of CHP plants depends on the site, requirements and the machine installed.

Benefits
• CHP typically leads to a 25-35% reduction in primary energy use – and associated cost saving.
• CHP can be 80% efficient, compared to 58% in conventional systems
• CO2 emissions and associated climate change impacts are reduced, particularly where renewable fuels are used
• CHP generates less harmful gases such as sulphur dioxide (SO2), nitrogen oxides (NOx) and particulates

Who is it suitable for?
CHP can be used throughout the commercial, industrial and public sectors at present; however with current advances is technology CHP systems will be making their way into the domestic market soon.


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