Guide to Renewables

Brief Introduction to Renewable Technology

Wind Turbines

Wind turbines convert kinetic energy (from the wind) into mechanical energy. This mechanical energy drives a generator that converts the energy into electricity. Small scale turbines are particularly suited to mobile, off grid and combined wind and photovoltaic applications.

0.6kW-50kW turbines can be used to provide electricity generation for individual houses and businesses.

Solar Water Heating

This technology uses the sun’s radiation to heat water in a panel that is often sited on the roof of a property. This heat can then be supplied either as hot water, or to a central heating system. If correctly sized, 40-60% of an annual domestic hot water demand can be supplied, reducing CO2 emissions by up to 400kg per year.

Photovoltaics (electricity from the sun)

Photovoltaic (PV) cells use light to generate electricity. There are a number of different PV panel technologies and they can be arranged on the roof or wall of a building, usually feeding electricity directly into the building. They are particularly appropriate where grid connection is difficult. A combination of wind technology and PV is popular as there is usually more wind than sun in the winter and the opposite is true in the summer, providing all year round generation.

Biomass

Biomass normally refers to organic material such as wood or crops grown specifically to be burnt to generate heat and/or power (Combined Heat and Power (CHP)). It is said to be a carbon neutral technology, because the carbon released during burning is balanced by the carbon absorbed during photosynthesis when the biomass is growing. Wood is the most popular form of biomass for domestic situations and can be used for water and/or space heating.

Bio-fuels & Bio-Gas

This usually refers to fuels such as bio-methane, bio-ethanol and bio-diesel. They can be derived from biomass, domestic or agricultural waste and sewage, using technology such as anaerobic digestion. Fuels can be burnt to produce heat and power (CHP), power fuel cells or run vehicles. All existing petrol vehicles can run on up to 5% bio-ethanol. Flexible fuel vehicles are able to use up to 85% bio-ethanol.

 Hydroelectric

Hydroelectric schemes use falling water to generate electricity. It is very site specific as a flow of water and a head of water is needed to give the latent power required. A turbine supplier will normally be able to advise on the potential of locations, and, given the right location, hydro power is a renewable, low maintenance source of energy. Small hydro schemes can be a practical and economic method of supplying electricity to communities or small residences.

Heat Pumps

Heat pumps use the same technology as a domestic fridge, moving heat from one area to another at an elevated temperature. Heat can be transferred from the ground, air or a water source. In the case of ground source heat pumps, heat is removed from the ground using a transfer fluid (refrigerant) in a buried pipe, to be used elsewhere. The important thing with heat pumps of any type is the ratio of the heat output compared to the electrical power used to run the pump, or the electrical input. When the output temperature is low (such as in under floor heating) the system is at its most efficient, but when the temperature is higher (as for radiators or hot water supply) the running costs increase and the environmental benefits are reduced. There is the option of using wind energy or solar PV to power the pump, thus reducing environmental impact.

It is important to address energy efficiency issues (e.g. insulation, glazing, low energy light bulbs) to reduce consumption, either before or at the same time as considering renewable technology.

There are many good sources of general information available, including further information on renewable technology, energy efficiency, grant schemes and other related issues which can be found at  http://www.TheRenewableEnergyCentre.co.uk