microgeneration technologies

There are several micro-generation technologies. Some produce heat and others power. Combined heat and power systems (CHP) generate both.

Small scale wind
Wind power is a clean, renewable source of energy which produces no carbon dioxide emissions or waste products. Wind turbines use the wind's lift forces to rotate aerodynamic blades that turn a rotor which creates electricity. Small scale wind typically generates between 1kilowatt and 50kilowatts of power and, subject to average wind speed in a given area, is ideal for large domestic properties, farms and commercial applications.

Solar PV
Solar photovoltaics or PV generates electricity from sunlight. Small-scale PV modules are available as roof mounted panels or roof tiles. Larger scale panels can be integrated into building cladding or mounted in arrays on roofs or the ground. 1-3 kW is a typical power output for a domestic installation although this depends on the number of PV modules installed. A PV system generates no greenhouse gases and saves 8 tonnes over its lifetime.

Solar water heating
Solar water heating systems use heat from the sun to work alongside heaters. There are three main components for hot water systems: Solar panels, a heat transfer system, and a hot water cylinder. The solar panels, or collectors, are usually fitted to a roof and collect heat from the sun’s radiation. This heat is used to raise the temperature of the water and is delivered by the heat transfer system which takes the heated water to the hot water cylinder for storage until use. The average domestic system reduces carbon dioxide by around 350kg per year, depending on the fuel replaced.

Small scale hydro electric
Hydro power systems use running water to turn a turbine to produce electricity. For buildings with no mains connection, a good hydro system can generate a steady, reliable electricity supply. The performance and size of micro-hydro schemes is site specific with plant ranging from a few hundred watts to 100kW, with the higher range used for commercial schemes.

Ground source heat pumps
In the UK, the earth keeps a constant temperature of about 11-12°C throughout the year. The ground has a high thermal mass which allows it to store heat from the sun during the summer. Ground source heat pumps tap the heat within the ground and convert it into energy. The heat pump operates under similar principles to a refrigerator. The heat is captured from within the ground by either pipes laid into trenches or down a borehole and is eventually distributed within the building through radiators or under-floor heating. Where cooling is required, the reverse happens and heat is removed and discharged into air, water, soil or rock.

Biomass
Biomass heating usually involves the use of commercial energy crops in the form of fast-growing trees, such as willow or poplar, for woodchips or waste wood products such as sawdust, pallets or untreated recycled wood for pellets. These fuels are burned in either pellet stoves or larger scale boilers to provide heating and/or water heating.

Air source heat pumps
Air source heat pumps absorb heat from the outside to heat buildings. There are two types of air source heating systems. Air-to-air systems provide warm air, which is circulated to heat the building. Air-to-water systems heat water to provide heating to a building through radiators or an under floor system.

Combined heat and power
CHP is the co-generation of heat and electricity, in which the "spare" heat produced, is used for hot water or building heating. The principle is that a natural gas or bio-diesel fuelled engine drives a generator that produces electricity. The heat from the engine and exhaust which would normally be wasted is used for heating.