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Why is it important? Small scale hydro power can provide clean, safe energy. Hydro power produces no pollution in operation and does not produce carbon dioxide so it does not contribute to climate change. Large scale hydro-electric dams can provide very large quantities of energy but generally have serious environmental consequences such as flooding large areas of land and displacing populations. Small hydro power systems, with an output of 5 Mega Watts (MW) or less, are seen as cleaner and a safer alternative. How does it work? Hydro power works by using falling water to drive a turbine, which generates electricity. The amount of energy produced by a hydro power scheme depends on how far the water is falling and the flow rate (i.e. how much water is flowing past each second). Small hydro power systems usually have a water intake above a weir or dam. Some of the water flowing along a river is redirected into the intake which leads into a channel or pipe to one or more turbines. The water passes through the turbines, generating electricity and is returned to the river afterwards. Hydro power provides a fairly steady reliable renewable energy source as its output is only affected by seasonal changes in the river's flow rate. The turbine and the majority of the machinery for small hydro power stations can be hidden in a small building by the side of the river. This may be designed in a traditional style to blend in with the surroundings. |
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How much energy can it generate? Small hydro power systems are those with a capacity of up to 5MW. A 5MW system might produce enough electricity for a small town or village of several thousand homes. Much smaller systems are also available. The smallest systems can supply electricity to a single house. How much will it cost? The initial capital cost of a scheme is quite high (2-3 thousand pounds per kW capacity for the smaller systems). However, once the plant is in place, it could generate free electricity (apart from maintenance costs) for decades. Only the turbine itself would need to be replaced every 15-50 years. In general, higher output hydro sites tend to have a lower cost per kW capacity. |
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Environmental effects Small hydro schemes produce electricity without releasing carbon dioxide, which contributes to climate change. They also so not pollute the air, land or sea during operation. Hydro power schemes usually involve some construction work to install the pipes to and from the turbine. As noted earlier, careful design can conceal the hydroplant and pipes. The environmental impacts associated with construction and possible alterations to the river environment should be minimal for a small hydro power project if the scheme is well designed. Nevertheless, sites should be chosen carefully. Water used to run the turbine is returned to the river and is aerated by passing through the turbine. This means that the turbine can actually improve water quality. Fish screens are fitted to the water inlet for the hydro power turbine to avoid injuring aquatic life. |
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Where should it be sited? As noted earlier the key criteria determining the output of a hydro project are a high flow rate and a large drop in water level (or "head" as it is known). However, hydro power can also be produced at "low-head sites" where the drop is less than 3 meters. Environmental criteria are also very important in deciding whether a site is suitable for hydro power. The following permissions are usually needed to run a hydro power project:
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Further information:
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