Frequently Asked Questions
A. CHP delivers a range of economic, environmental and benefits - some of these accrue to its users, some to operators of the electricity grid and yet others to the wider community:
Cost savings - CHP’s high efficiency leads to a reduction in the use of primary energy. Precious fuels are used much more efficiently, so less is used. And less fuel used means significantly lower energy costs to the end user. Savings vary, but can be between 15% and 40% compared to imported electricity and on-site boilers.
Lower emissions - less fuel burnt means reduced emissions of carbon dioxide (the main greenhouse gas) and other products of combustion. Indeed CHP could provide the largest single contribution to reducing carbon dioxide emissions. Host organisations that wish to reduce their environmental footprint benefit - as does the environment.
Increased security and power quality - CHP systems can be designed to continue to operate and serve essential loads during an interruption to mains power supplies, increasing security of energy supplies. CHP can also supply higher-quality power than that from the grid - this can be important for computer data centres etc.
Grid reinforcement - siting an on-site CHP unit within the electricity grid can strengthen the network and remove the need for network operators to upgrade the system there
A. CHP is a family of energy conversion processes, rather than a single technology, so it can be used to provide energy to anything from a single home to a large industrial plant, or even a whole city. Unlike conventional power plants, CHP units are sited close to where their energy output is to be used.
The main design criterion is that, to make the investment worthwhile, there must be a need for both the heat and electricity produced by the CHP unit.
In the home, a micro CHP unit resembling a gas-fired boiler will provide both heat for space and water heating, as does a boiler, but also electricity to power domestic lights and appliances. Micro CHP units are a very new technology only recently appearing in the UK market, but the potential for them is as large as the number of homes in the country.
For commercial buildings and small industrial spaces, a factory-assembled, ‘packaged’ CHP system is appropriate. Here, an electricity generator, heat exchanger, controls and either an engine or a turbine is packaged together into a CHP unit that can be connected to the heating and electricity systems of the building.
Some building types, particularly those that need a lot of energy, or operate around the clock, are particularly suitable for CHP - leisure centres, hotels, hospitals and many others. CHP systems can, with the addition of a chiller, supply cooling for air conditioning systems as well as heating - such an arrangement is often called a ‘tri-generation’ system.
Homes and buildings fitted with CHP are usually also connected to the mains electricity grid, and may also retain back-up boilers, so that they are never short of an energy supply, during maintenance of the CHP plant, for example, or during periods of unusually-high energy loads.
Industrial CHP plants tend to be designed and built individually to fit the industrial process they serve. These CHP plants are based on gas turbines, steam turbines or engines, together with electricity generators and control systems. The very largest CHP plants rival traditional power-only plants in size and deliver huge quantities of energy - but at a much higher efficiency
Some industrial processes are particularly well-suited to CHP, those that use lots of heat and operate around the clock - the manufacture of paper, chemicals, food and drink products, as well as refineries, are among those that can benefit most from CHP.
Community heating systems serve whole towns, areas of cities or, in a few cases, whole cities. Here, one or more CHP plants supply heating to a grid of insulated hot water pipes that carry heat to a range of buildings, including public and private sector flats. As well as CHP plants, boilers and other sources of heat may feed heat into the grid. Buildings that take heat from the community heating system do not need their own boilers. Meanwhile, the electricity generated is used to help run the community heating plant, and within the customer buildings, or is exported to the electricity grid.
Community energy systems supply cooling, as well as heating and electricity, to buildings.
A. In recognition of the significant carbon saving potential of CHP, following the first Earth Summit negotiations in 1992, the then Conservative Government, established in 1993, the first target for CHP of 4 GW (4,000MW) by 2000. With the rapid development of schemes at this time, this target was raised the following year to 5 GW as part of the Government’s Climate Change Programme.
The present Government increased this once again in 2000, establishing the current target of 10,000 MW by 2010, which remains a key element of the Government’s revised Climate Change Programme, issued in March 2006.
The latest Government statistics (up to 31 December 2005) show that 5,792MW of CHP capacity is operating in the UK. (Further information detailed in CHP Statistics).
A. Defra published the Government's Strategy for Combined Heat and Power to 2010 in April 2004. This, along with a number of other Government reports on CHP can be downloaded from Defra’s CHP webpage.
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