Promoting best practice in Combined Heat & Power in Ireland
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Promoting best practice in Combined Heat & Power in Ireland |
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and Power Applications |
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CHP Applications
In essence combined heat and power allows a customer to generate their own electricity (reducing their payments to the electricity utility) and then make good use of the substantial quantities of heat created as a by-product of electricity production. In a normal gas-fired CHP scheme the waste heat is recovered and distributed to where it is needed in the form of hot water or steam.
Large Scale CHP
The choice of prime mover is based on a number of factors and even with similar energy requirements, no two sites are the same. For more detail on the various types of prime movers for CHP solution the CHP Technology section below.
Small Scale CHPSmall Scale CHP schemes have tended to have a reciprocating engine as prime mover whereas the large schemes tend to be turbine-based. Recent developments in turbine technology have led to the introduction of ‘microturbines’ for small scale CHP systems. Small Scale CHP is particularly suitable for applications such as hotels, hospitals and leisure centres, where there is a steady demand for heat and power throughout the year. Large Scale CHP Systems are suitable for use in larger industrial and commercial processes such as chemistry/ pharmaceutical plants, breweries, airports, universities and food processing plants. In small scale schemes the CHP unit consists of a reciprocating engine or microturbine, which is mounted in an acoustic enclosure. Heat exchangers recover heat from the engine exhaust gases and cooling system to produce hot water, which can be integrated into the site services. The unit is normally designed to meet the site’s base heat and electrical power requirements. Peak heating demand can be supplied using high efficiency modular gas boilers to provide hot water, with additional electricity being imported from the national grid. A control system will allow the automatic operation of the unit to meet the heat and power demands of the site.
Micro-CHPMicro-CHP Micro-CHP (mCHP) is a mass produced small scale CHP unit that is suitable for domestic and small business applications. mCHP units vary in size up to 100kWe and use a number of different technologies: internal combustion engines; external combustion engines; micro-turbines; and fuel cells (although these are still at the development and demonstration stage).
District HeatingDistrict heating (DH) is heat distributed from a central boiler or CHP plant. The preferred distribution medium is water and district heating has been around for over a century in the US and Europe. District heating has not had the same penetration in Ireland for a number of reasons. Ireland’s relatively mild climate does not help the economics of installing DH on a large scale. Low density of housing even in cities makes it impractical to pump warm water over long distances. It has also a poor public perception and is sometimes seen as ‘poor man’s heat’. A report by Sustainable Energy Ireland in 2001 quantified the potential for district heating in Ireland as 100MW was ‘technically’ feasible and 50MW was feasible against ‘economic’ criteria. The report identified a potential for between 5-10 ‘economic’ schemes. District heating has had some recent success in the UK with a successful scheme introduced in Southampton and a large city-wide scheme in Leicester. In 2003 there was around 43MW thermal of district heating in Ireland and the majority of this was the Ballymun scheme which is not being replaced during the current regeneration project. The economics are such that retrofitting a house for DH can cost in the region of €2,500 per house whereas new houses can be connected to a DH scheme for as little as €150 per unit.
CHP in Hotels
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| Questions/Comments? | Irish CHP Association Contact Information | Links © Irish CHP Association. Last Updated: Fri 13 May 2005. |
The
prime mover in large scale CHP can be a gas turbine or spark ignition
gas engine. This drives a generator, which produces the electricity,
the exhaust gases then pass through a recovery unit which provides the
heat in the form required by the site (e.g. steam). Additional steam
or hot water, can be produced using a technique called afterfiring,
this involves burning more gas in the oxygen rich gases prior to the
waste heat boiler. This increases the heat output with the facility
to modulate heat production without affecting electricity generation.
As with small scale CHP, electricity may be imported from, or exported
to, the national grid as site demand varies (known as top-up and spill).
CHP
has proved a popular solution for many hotels in Ireland, particularly
the larger ones. Now that natural gas is becoming available to more
and more parts of the country and the smaller-scale CHP units are becoming
increasingly economic the opportunity exists for many more of Ireland's
hundreds of hotels to make the switch to cleaner lower cost energy.
PRIME MOVERS >>