Renewable Energy
Biofuels
Biofuels are fuels made from organic matter that can be replenished easily. In recent years, the term "biofuel" has come to mean biodiesel and bio-ethanol, made from crops including corn, sugarcane and rapeseed. Bio-ethanol, an alcohol, is usually mixed with petrol, while biodiesel is used either on its own or in a mixture. Brazil leads the world in production and use, generating around 16 billion litres of ethanol each year from its sugarcane industry.
Biofuels are considered to be more renewable and sustainable than fossil fuels. The best types of biofuels are those that generate considerably more energy than the amount needed to produce them. For example, the ethanol produced from sugar cane in Brazil can generate 10 times more energy than is required to make the ethanol.
Biofuels are considered to be more renewable and sustainable than fossil fuels. The best types of biofuels are those that generate considerably more energy than the amount needed to produce them. For example, the ethanol produced from sugar cane in Brazil can generate 10 times more energy than is required to make the ethanol.
Sixty percent of new cars can run on a fuel mix including 85% ethanol. One litre of biodiesel costs around 90p, but only a limited number of stations stock it. However, there is a growing market for home-made biodiesel. The fuel costs between 15 and 80p per litre to produce, mainly dependent upon the price of the crop. Since July 2007, production of under 2,500 litres per year for own use is duty-free, which equates to around 25,000 miles in a conventional vehicle for what could be as little as £375 a year.
The European Union’s target for 2010 is for 5.75% of transport fuels to come from biological sources, but this target is unlikely to be met. The British government's Renewable Transport Fuel Obligation requires 5% of fuel sold at pumps to be biofuel by 2010. In the US, the Renewable Fuels Standard aims to double the use of biofuels in transport by 2012.
In theory, biofuels are much better for the environment than conventional fossil fuels because the plants grown for biofuel production absorb carbon. However, the energy required to farm and process the crops can result in the biofuels polluting the environment as much as petrol-based fuels. There is also concern that producing large amounts of one crop will mean that there is a decrease in biodiversity when areas are cleared and replaced with a single crop. In addition, large chunks of forests have been cut down to allow for biofuel production, thus releasing large amounts of greenhouse gases.
Food shortages are on the rise in poorer countries, as farmland traditionally used for food and animal feed has been turned over to grow crops suitable for biofuels. The increase in demand for crops, such as rice, corn or soya, which can be used as both food and biofuels, has pushed the cost up, thus pricing out those living in poorer countries. In Mexico last year, there were riots after the price of maize quadrupled, as a result of an increased demand for biofuels.
Currently, biofuel production is limited as only certain parts of the plant can be used. There is now increased interest in second generation biofuels as these can be sourced from a larger range of plants and animal waste. Rather than only using one part of the plant, the whole crop can be used.
Wind energy
Wind energy is harvested by turbines that operate like old-fashioned windmills. When the blades are spinning, they drive a shaft connected to an electrical generator by a gearbox. Most wind turbines produce electricity when the wind is blowing at 10-30mph. One 1.8mW wind turbine produces enough electricity for 1,000 households every year.
Turbines tend to be built in groups, as "windfarms", to produce more electricity in places that have strong, steady winds. Windfarms can be onshore - on ridgelines, at the tops of rounded hills, open plains and gaps in mountains; near shore - on land within 3km of a shoreline; or offshore - generally 10km or more from land. Offshore farms cost more to build but produce more electricity because they usually stand in open, windier spots. There is opposition to on-shore wind farms and it is difficult to obtain planning permission to build them.
The UK is a very attractive destination for wind farms with some of the best winds in Europe. There is enough wind to power the country several times over. However, the major problem with wind power is that it can only be used to generate electricity when the wind is blowing with suitable force. Good sites for wind turbines are often quite remote, either offshore or on mountainsides, far from the cities where the energy is most needed.
For more information on wind energy click here
Solar Power
Solar power is created by photovoltaic cells (PV’s) converting sunlight directly into electricity. Photovoltaic cells (PV's) can be used as roof tiles. They cover the roof of a house and take advantage of the light coming from the sun. This is trapped by the cells and turned into electricity. Solar power can also be used for heating water which is then stored in an insulated hot water tank. In the UK thin water pipes are painted black and put in a 'greenhouse' type insulator to heat our water supply.
Another way to take advantage of the energy from the sun is to design buildings so they can collect the heat. Buildings must be designed facing a specific direction in order to capture maximum heat from the sun. Some power stations are now also using solar dishes to boil the water required to make electricity.
As solar energy can be created on rooftops it means that no extra land is needed and it can also be generated in urban spaces. The technology used today is about 90% cheaper than it was in the 1970s. Houses with solar roof tiles can in fact generate more electricity than is required at certain times in the day, and can sell this back to local electricity companies through electricity grids.
The UK is behind many other countries in Europe and the rest of the world when it comes to using solar power technologies. In Japan and the USA, billions has been spent on developing PV over a number of years. More recently, a consortium of German companies has pledged to supply Europe with 15% of its electricity needs by 2050, from solar plants in the Sahara desert, that will carry electricity across the Mediterranean sea on power lines.
Nuclear power
Nuclear power is produced from controlled (ie, non-explosive) nuclear reactions. Commercial plants use nuclear fission reactions. Electric utility reactors heat water to produce steam, which is then used to generate electricity. To make sure the power plant does not overheat, control rods made of a material that absorbs neutrons are lowered into the reactor. The whole reactor is encased in a thick concrete shield, which prevents radiation escaping into the environment. In 2007, 14% of the world's electricity came from nuclear power. In Britain, nuclear power stations provide 19% of our electricity and account for 3.5% of our total energy use. In November 2009 the government announced plans for ten new generation nuclear power plants.
Nuclear power plants do not release greenhouse gases, which cause coal and gas-fired power plants to contribute to global warming. It also uses a comparatively small amount of energy for the amount of fuel it produces. However, nuclear power is very dangerous and if radioactive waste leaks it can cause a major disaster. There are groups that oppose nuclear power because of this, and believe money should be invested in cleaner renewable sources of energy as opposed to power plants.
Hydropower
Hydropower technology turns the potential or kinetic energy of the water into energy by means of a turbine. Turbines either use water "dropped" from behind a dam or from natural "run of the river" with no water storage reservoir. The world's largest hydro-electric dam is the Three Gorges Dam on the third longest river in the world, the Yangtze River. Hydroelectric power can be far less expensive than electricity generated from fossil fuels or nuclear energy, and areas with abundant hydroelectric power attract industry.
The chief advantage of hydroelectric dams is their ability to handle seasonal demands. When the electricity demands drop, the dam simply stores more water. Electricity can be generated when demand increases. Tidal power can also be harnessed in bags or estuaries. The trapped water turns turbines when the tide moves. The disadvantage is that whilst tidal power is predictable, it is not able to adapt to changing electricity demands as it is dependent on tidal changes.
Small scale hydro or micro-hydro power has been increasingly used as renewable energy source, especially in remote areas where other power sources are not viable. Small scale hydro power systems can be installed in small rivers or streams with little or no discernible environmental effect on things such as fish migration. Most small scale hydro power systems make no use of a dam or major water diversion, but rather use water wheels.
Hydropower produces essentially no carbon dioxide or other harmful emissions, in contrast to burning fossil fuels, and is not a significant contributor to global warming through CO2. Environmental concerns about the effects of reservoirs may prohibit development of economic hydropower sources.
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