Renewable energy
Renewable electricity from sources such as wind, wave and solar energy is crucial in helping cut harmful carbon dioxide emissions – the 'greenhouse gases' which can contribute to global warming.
The Government’s Climate Change Programme and Energy White Paper mean that by 2010, renewable energy should be contributing 10% of the UK's electricity supply.
This contribution should be doubled by 2020 - helping the country reach its ambitious target of UK carbon emission reductions. Less than four per cent of our electricity supply currently comes from renewable sources.
The main sources of renewable energy being considered are biomass, geo-energy, hydro-electric, hydrogen, solar, tidal, wave and wind.
Biomass
Also known as biofuels or bioenergy - is obtained from organic matter either directly from plants or indirectly from industrial, commercial, domestic or agricultural products.
The use of biomass is classed as a 'carbon neutral' process because the carbon dioxide released during the generation of energy from biomass is balanced by that absorbed by plants during their growth.
It can be converted into heat and electricity in a number of ways including: burning, pyrolysis (the decomposition or transformation of a compound caused by heat), gasification, anaerobic digestion or fermentation.
Geo-energy
Uses different grades of thermal energy stored within the earth and, i n geologically suitable areas, heat from deep within the planet’s interior can rise up to the surface. Such heat is referred to as geothermal energy.
H eated water can be trapped below the earth's surface as a geothermal reservoir - reaching temperatures of 400°C - and can be accessed by drilling to depths of over two miles.
Ground source heat is extracted from the low temperature heat (around 10-20 oC) found at relatively shallow depths. Heat pumps can provide a more useful output temperature of around 40-50 oC - ideal for low temperature heating like under floor systems and radiant panels.
Hydroelectric
Hydroelectric power is energy derived from flowing water in rivers or where water flows from a high reservoir down through a tunnel to drive electricity-producing turbines and generators.
Hydrogen
Hydrogen fuel cells can produce energy and work like a conventional battery, except that it does not run down or require charging. They can produce energy in the form of heat and fuel.
Solar
Solar energy captures energy from the sun. There are three main ways of doing this:
Passive solar design makes sure a building's form and fabric captures as much of the sun's energy as possible - reducing the need for artificial light and heating.
- Active solar water heating converts solar radiation into heat which can be used directly or stored.
- Photovoltaic (PV) solar panels convert sunlight into electricity.
Tidal
Tidal energy uses the natural ebb and flow of coastal waters, as the level fluctuates twice daily, alternatively filling and emptying natural basins along the shoreline. The currents flowing in and out of these basins can be used to turn mechanical devices to produce electricity.
Tidal stream technology uses fast sea currents created by the tides to drive electricity-producing devices.
Waves can provide an unlimited source of renewable energy, as energy can be extracted and converted into electricity by wave power machines. These can be deployed either on the shoreline or in the deeper waters offshore.
There are three main types of wave power machine, some which sit on the shoreline and others free floating.
An oscillating water column is a part-submerged, hollow structure installed in the ocean. Waves cause the column to rise and fall, which causes trapped air to drive a turbine.
A buoyant moored device floats on or just below the surface of the water and is moored to the sea floor. Wave motion drives machinery inside the device, which generates electricity.
A hinged contour device uses wave motion to push hydraulic fluid through pumps to generate electricity.
Wind
Wind energy involves harnessing the power contained in moving air and is a vast source of energy, which man has harnessed for hundreds of years.
The UK has the largest potential wind energy resource in Europe and wind is regarded as one of our most promising renewable energy technologies. It already provides electricity for over 390,000 households or 940,000 people - preventing the annual emission of over 1.46 million tonnes of carbon dioxide.
This page was last updated on 28 November 2007