Hydro-electric power
Hydroelectric power or hydroelectricity is electrical power which is generated through the energy of falling water. Hydro electric power systems work by converting potential energy stored in water held at height into kinetic energy to turn a turbine in order to produce electricity. This is a mature technology with water mills already extensively used by the time of the industrial revolution.
Pumped storage: Reusing water for peak electricity demand
Demand for electricity is not constant. Demand goes up and down during the day, and overnight there is less need for electricity in homes, businesses, and other facilities. For example, during the day on a hot August weekday in Australia the demand for electricity to run air-conditioning will be high but during the night the demand will be lower. Hydroelectric plants are more efficient at providing for peak power demands during short periods than are fossil-fuel and nuclear power plants, and one way of doing that is by using "pumped storage", which reuses the same water more than once.
Pumped storage is a method of keeping water in reserve for peak period power demands by pumping water that has already flowed through the turbines back up a storage pool above the powerplant at a time when customer demand for energy is low, such as during the middle of the night. The water is then allowed to flow back through the turbine-generators at times when demand is high and a heavy load is placed on the system.

Advantages: * Once a dam is constructed, electricity can be produced at a constant rate. * If electricity is not needed, the sluice gates can be shut, stopping electricity generation. The water can be saved for use another time when electricity demand is high. The build up of water in the lake means that energy can be stored until needed, when the water is released to produce electricity. * Dams are designed to last many decades and so can contribute to the generation of electricity for many years / decades. * The lake that forms behind the dam can be used for water sports and leisure / pleasure activities. Often large dams become tourist attractions in their own right. * Hydropower is a fuelled by water, so it's a clean fuel source. Hydropower doesn't pollute the air like power plants that burn fossil fuels, such as coal, oil or natural gas. * Hydropower can cost less than a penny per kWh (Kilowatt Hour) compared to fossil fuel power plants at around 2 to 3 cents per kWh. That may not seem like a big difference, but when factored out over a year and the millions of kW hours Americans burn, it adds up to a huge savings.

Disadvantages: * Dams are extremely expensive to build and must be built to a very high standard. * The high cost of dam construction means that they must operate for many decades to become profitable. * The flooding of large areas of land means that the natural environment is destroyed. * People living in villages and towns that are in the valley to be flooded, must move out. This means that they lose their farms and businesses. In some countries, people are forcibly removed so that hydro-power schemes can go ahead. * The building of large dams can cause serious geological damage. For example, the building of the Hoover Dam in the USA triggered a number of earth quakes and has depressed the earth's surface at its location. * Hydro power dams can damage the surrounding environment and alter the quality of the water by creating low dissolved oxygen levels, which impacts fish and the surrounding ecosystems. They also take up a great deal of space and can impose on animal, plant, and even human environments. * Fish populations can be impacted if fish cannot migrate upstream past impoundment dams to spawning grounds or if they cannot migrate downstream to the ocean. Upstream fish passage can be aided using fish ladders or elevators, or by trapping and hauling the fish upstream by truck. Downstream fish passage is aided by diverting fish from turbine intakes using screens or racks or even underwater lights and sounds, and by maintaining a minimum spill flow past the turbine. * Hydro power plants can be impacted by drought. When water is not available, the hydro power plants can't produce electricity. * By 2020, it is projected that the percentage of power obtained from hydro power dams will decrease to around four percent because no new plants are in the works, and because more money is being invested in other alternative energy sources such as solar power and wind power.
The Lower Granite Dam on the Snake River in Washington state is a "run-of-the-river" hydroelectric dam operated by the U.S. Army Corps of Engineers. The Bonneville Power Administration, a federal agency located in the Pacific Northwest, markets wholesale electricity and transmission from Lower Granite and twenty-nine other federal dams. From left to right is the dam's earthen embankment; locks; the spillway; and the powerhouse.

Nuclear Power

Nuclear power is generated using Uranium, which is a metal mined in various parts of the world. The first large-scale nuclear power station opened at Calder Hall in Cumbria, England, in 1956. Some military ships and submarines have nuclear power plants for engines. Nuclear power produces around 11% of the world's energy needs, and produces huge amounts of energy from small amounts of fuel, without the pollution that you'd get from burning fossil fuels.
Nuclear power stations work in pretty much the same way as fossil fuel-burning stations, except that a "chain reaction" inside a nuclear reactor makes the heat instead.
The reactor uses Uranium rods as fuel, and the heat is generated by nuclear fission: neutrons smash into the nucleus of the uranium atoms, which split roughly in half and release energy in the form of heat. Carbon dioxide gas or water is pumped through the reactor to take the heat away, this then heats water to make steam. The steam drives turbines which drive generators. Modern nuclear power stations use the same type of turbines and generators as conventional power stations.
In Britain, nuclear power stations are often built on the coast, and use sea water for cooling the steam ready to be pumped round again. This means that they don't have the huge "cooling towers" seen at other power stations. The reactor is controlled with "control rods", made of boron, which absorb neutrons. When the rods are lowered into the reactor, they absorb more neutrons and the fission process slows down. To generate more power, the rods are raised and more neutrons can crash into uranium atoms.
Advantages
* Nuclear power costs about the same as coal, so it's not expensive to make. * Does not produce smoke or carbon dioxide, so it does not contribute to the greenhouse effect. * Produces huge amounts of energy from small amounts of fuel. * Produces small amounts of waste. Nuclear power is reliable.
Disadvantages
* Although not much waste is produced, it is very, very dangerous. * It must be sealed up and buried for many thousands of years to allow the radioactivity to die away. * For all that time it must be kept safe from earthquakes, flooding, terrorists and everything else. This is difficult. * Nuclear power is reliable, but a lot of money has to be spent on safety - if it does go wrong, a nuclear accident can be a major disaster. * People are increasingly concerned about this - in the 1990's nuclear power was the fastest-growing source of power in much of the world. In 2005 it was the second slowest-growing.

Nuclear power in Japan
The Onagawa Nuclear Power Plant, a 3-unit BWR site typical of Japan's nuclear plants.
Since 1973, nuclear energy has been a national strategic priority in Japan, as the nation is heavily dependent on imported fuel, with fuel imports accounting for 61% of energy production. There has been concern about the ability of Japan's nuclear plants to withstand seismic activity. The Kashiwazaki-Kariwa Nuclear Power Plant was completely shut down for 21 months following an earthquake in 2007.
Following an earthquake, tsunami, and the failure of cooling systems at the Fukushima I Nuclear Power Plant on March 11, 2011, a nuclear emergency was declared. This was the first time a nuclear emergency had been declared in Japan, and 140,000 residents within 20 km of the plant were evacuated. The amount of radiation released is unclear, as the crisis is ongoing.

Energy Conservation
Energy conservation is the action of saving energy to reduce the impact on the environment and to reduce costs. It attempts to limit energy use so that the growth in overall global energy use is slowed.
Energy conservation can result in increased financial capital, environmental quality, national security, personal security, and human comfort. Individuals and organizations that are direct consumers of energy choose to conserve energy to reduce energy costs and promote economic security. Industrial and commercial users can increase energy use efficiency to maximize profit.
Energy conservation in India
Petroleum Conservation Research Association (PCRA) www.pcra.org is an Indian government body created in 1977 and engaged in promoting energy efficiency and conservation in every walk of life. In the recent past PCRA has done mass media campaigns in television, radio & print media. An impact assessment survey by a third party revealed that due to these mega campaigns by PCRA, overall awareness level have gone up leading to saving of fossil fuels worth crores of rupees besides reducing pollution.
Bureau of Energy Efficiency is an Indian governmental organization created in 2001 responsible for promoting energy efficiency and conservation.

By Azyba Ellis 9H