HKNIC - Renewable energy
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renewable energy
Renewable energy
Renewable energy includes hydropower, wind energy, solar photovoltaic energy, tide and ocean current energy, biomass and geothermal energy. The energy supply is naturally replenished in a relatively short period of time. However, the supply of many types of renewable energies is seasonal or intermittent, and some of them are not in widespread use or proven on a commercial scale. Because the source of most of these energies is not intensive, except in the case of hydropower we would need to use several hundred square kilometres of land or sea surface to harvest enough renewable energy to supply a city such as Hong Kong.
renewable energy
renewable energy
renewable energy
renewable energy
renewable energy
renewable energy
renewable energy
Hydropower is energy extracted when river water descends a certain height from a dam, propelling water turbines to produce electricity. Smaller turbines can be used in what is known as a “run-of-the-river” system, where they are driven by running water in a river. A hydro-electric generating unit has a typical capacity of up to several hundred MW.
Wind energy is extracted when wind blows over a wind-mill or a wind turbine to provide electricity. A single large wind turbine has a capacity of between 1 - 5 MW and large numbers of such turbines are often grouped together in a “wind farm” spanning over many square kilometres.
Solar photo-voltaic energy is extracted when sunlight, or solar radiation, strikes a photo-voltaic panel to produce electricity. A solar panel has a typical capacity of several hundred Watts per square metre.
Tide energy makes use of the difference in sea levels between tides to drive water turbines.
Ocean current energy uses turbines immersed in an ocean current to extract energy.
Biomass energy is the a collective grouping for energy extracted from the organic material in plants and animals, including wood, crops and manure. Firewood and manure have been used traditionally as fuel and are still in widespread use in many parts of the world today. On a commercial scale, crops can be grown for fermentation to produce alcohol for transportation or for combustion. Crops can also be burnt directly as fuel in a conventional power station to produce electricity. Methane gas can be collected from sewage or landfill sites for commercial use.
Geothermal energy is heat extracted from the ground in volcanic regions and used to raise steam to produce electricity.