Top five UK renewable electricity technologies

Renewable energy may make up only a small proportion of the UK's overall electricity supply, but it is growing. According to the government's own figures, renewable energy made up 4.55 per cent of all electricity generated in the UK in 2006, which is 0.32 per cent higher than in 2005, and nearly a whole percentage point ahead of the 2004 figure. 

That 4.55 per cent makes up 18,133 gigawatt hours (GWh) of electricity generated, an increase of 7.5 per cent compared to 2005. It may sound like a lot, but greater London alone consumed around 41,436GWh of electricity in 2005. And the big guns are still coal (which produces 33 per cent of the UK's electricity), nuclear (20 per cent) and gas (a whopping 40 per cent).

Renewable energy is measured in megawatt-electrical (MWe), the amount of electrical power a plant has the capacity to produce. For renewables, of course, power capacity doesn't always equate to how much power is actually produced -- wind turbines, for example, only produce power when there is wind. Nevertheless, the UK's current renewables capacity is 5,659MWe. The UK's entire electricity power capacity -- including coal, gas and nuclear power stations -- is 83,045MWe.

The UK still lags well behind other countries in renewable energy generation. In Spain over a weekend in March, according to the AEE (Spanish Wind Energy Association), wind power accounted for an average of 28 per cent of Spain's entire power demand. But renewables are growing and will continue to do so, as necessity dictates. To shed some light on the use of renewable technologies for electricity production, we've looked at the UK's top five renewables -- in no particular order -- in terms of total installed capacity and future potential.

1: Wind
Wind power has massive potential in the UK with offshore wind farms alone apparently able to meet all of the UK's current electricity needs, according to the government's figures. Onshore facilities, however, are easier to build and 327 wind farms currently make up 1,842MWe of the UK's electrical power capacity, according to statistics from the RESTATS database. Wind turbines are more difficult and expensive to install at sea and such make up a more modest 394MWe, but offshore wind farms have fewer planning issues and 90MWe of new capacity has become operational since January 2007. There are currently seven operational offshore wind farms in the UK with a further five under construction.

2: Hydroelectric
These plants can be divided into large (producing over 5MWe) and small (below 5MWe) hydroelectric plants. Most of the large plants are concentrated in Scotland and Wales and draw their water from high-level reservoirs with their own natural catchment areas, and make up 1,369MWe of energy capacity. Opportunities to grow large hydro capacity are very limited as most of the potential sites are already in use. Smaller-scale plants are growing in popularity and are typically used for domestic or small business purposes and make up 156MWe. Watermills, for example, are increasingly being refurbished and brought back into use.

3: Biofuels
There are many different kinds of biofuels in use for electricity generation, such as the oats-powered plant used by Quaker Oats. Landfill gas is one of the fastest-growing areas -- it is the methane-rich biogas formed by the decomposition of organic matter in landfill and can be used to fuel electricity turbines or directly in boilers. RESTAT estimates that this makes up some 875MWe of electricity capacity. Another growing area is sewage sludge digestion, which uses the gas produced to maintain the temperature necessary for the process. This makes up 122MWe with the excess energy being sold off onto the grid. The final growth area is municipal solid waste, which is produced in incinerators and makes up 327MWe of energy capacity. At the end of 2006, there were 24 such plants in operation burning municipal solid waste (MSW), refuse derived fuel (RDF) and general industrial waste (GIW). Other biomass generation projects include Lockerbie's plant powered mainly by forestry waste, and a straw-fired power station near Ely, Cambridgeshire.

4: Wave and tidal stream
Being an island at the edge of the Atlantic Ocean makes the UK well-suited for wave and tidal power, but the difficulty in harnessing this means that it so far contributes just 0.5MWe of total energy capacity. The Limpet oscillating water column is the only wave device in the UK. It is located off the isle of Islay in Scotland and is operated by Wavegen. Tidal energy is estimated to have the potential to produce up to 22,000GWh per year, but current deployments are still only prototypes. The government has launched a couple of schemes to encourage wave and tidal plants, but these are not expected to amount to more than around 25MWe of capacity in total, the majority of which will come on stream after 2010.

5: Photovoltaic
The final major renewable energy technology in the UK is photovoltaics (PV), which currently contribute 12MWe of the UK total electricity capacity. Many installations are on schools and office buildings, but some are being offered directly to consumers by house builders, as with the St James Homes in Reading. Photovoltaics are growing rapidly, with 2.4MWe of this capacity having become operational since January 2007. Much of that growth was driven by a government funding programme that is now complete, which offered grants for small, medium and large-scale implementations. Whether this growth will continue is a moot point as the government's successor programme has been criticised by Friends of the Earth for failing to offer consumers enough funding.

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