Last edited 11 Jul 2017

Microgeneration for buildings

Microgeneration (or micro-generation) is the local production of electricity or heat on a very small scale in comparison to the typical output of a power station. Generating locally to demand provides an alternative to the traditional method of centralised generation distributed by the national grid. Typically, this is more efficient as distribution and transmission losses are greatly reduced.

Typically, microgeneration has an output of under 45kW for heat and under 50kW for electricity. Microgeneration systems include:

Air source heat pumps – absorb heat from the external air and use it to warm buildings and water. Three to four units of heat are produced for every one unit of electricity required to drive the pump.
Ground source heat pumps – heat from the ground is transferred and used to heat buildings and water. Similar to air source pumps they provide three to four units of heat for every one unit of electricity needed to run the pump.
Bio-energy – this form of renewable energy is produced from biomass and organic materials. The carbon it emits is offset by the amount it absorbs, hence it is often regarded as carbon neutral. A few examples of suitable biomass fuels frequently used in community schemes and households are wood chips, logs and pellets.
Solar photo-voltaic panels – create electricity by using energy from the sun. Compared with other renewable energy technologies, it can be expensive to install a PV system but they need very little maintenance.
Solar thermal panels – use the heat from the sun to heat water. Heating water accounts for about a quarter of typical energy usage, so installing a solar thermal water system can reduce bills and a buildings carbon footprint.
Small scale hydro-electric – a turbine is turned by the flow of water which uses the energy from moving water to create electricity. Hydro-electric systems below 100kW are sometimes considered to constitute microgeneration.
Wind turbines – the wind flow turns a generator to make electricity. The UK has around 40% of Europe’s total wind energy.
Micro-CHP – combined heat and power, sometimes referred to as ‘cogeneration’, a process in which the heat that is created as a by-product of power generation is captured and used rather than simply being wasted.
Fuel cells.

Some microgeneration systems are considered to be ‘green’ as they use renewable fuels rather than fossil-fuels. The use of local and secure renewable resources means there is less dependence on non-renewable energy and a decrease in the production of carbon dioxide and other green house gases.

On 1 April 2010 the Government’s Department for Energy and Climate Change (DECC) introduced Feed-in Tariffs (FIT’s). Consumers who generate their own electricity from a renewable or low-carbon source can qualify for a payment (‘Feed-in Tariff’ (FIT)) for each unit of electricity generated. Consumers can also qualify for an ‘export tariff’ by selling surplus electricity back to their supplier.

Allowable technologies are:

Solar photovoltaic panels.
Wind turbines.
Water turbines.
Anaerobic digestion (biogas energy).
Micro combined heat and power (micro-CHP).

This has lead to a sharp increase in microgeneration. The Government views microgeneration as a significant part of the power and energy strategy for the UK in the years ahead. By far the most installations registered under the Government’s FIT scheme are solar photovoltaics.

NB: The building regulations define microgeneration as:

...the use for the generation of electricity or the production of heat or cooling of any plant (which for this purpose includes any equipment, apparatus or appliance) which, in generating electricity or (as the case may be) producing heat or cooling, relies wholly or mainly on a source of energy or a technology mentioned in section 26(2) of the Climate Change and Sustainable Energy Act 2006