Wind Turbines

• Wind farms have been springing up in many countries as these countries attempt to reduce their reliance on fossil fuels or nuclear energy. The turbines, which can be sited onshore or offshore, are making a bigger impact as their numbers increase, but they remain controversial, with critics claiming they are inefficient because the wind is both unpredictable and inconsistent. One of the drawbacks to wind turbines is that they do not turn if there is either too little or too much wind.
  
  

Wave Power

• The seas are proving to be a valuable source of energy, with waves and tides offering substantial potential for power generation. The advantages of wave power are that it requires no fuel, produces no greenhouse gases and is cheap to harness. Indeed, the energy is free once a wave plant is up and running. However, like wind, it is unpredictable with spells of very low output, and it has to be able to harness energy from different sea conditions.
  
  

Tidal Power

• Tides, on the other hand, are reliable and constant and also provide clean energy that requires no fuel. There are different ways to harness the tides, using either barrages or vertical-axis turbines. Tidal power is also free once generators are operational and construction is complete. However, while vertical-axis turbines are cheaper, the more effective barrages are expensive to construct, require suitable estuary sites and can change estuary habitats for wildlife.
  
  

Hydro Power

• Possibly the best form of renewable energy is that deriving from hydroelectric plants. It is the most reliable and can produce a constant supply of power because it uses stored water from a dam or other reservoir. In addition, it produces no waste and very little pollution. However, hydro plants are very expensive to construct and, because the dams often flood large areas, there is a direct impact on local wildlife habitats.
  
  

Solar Energy

• Solar power comes directly from the sun and is, therefore, free and results in neither waste nor pollution. In the hottest locations, it is reliable and excellent for minor uses such as home electricity generation. It has drawbacks, however, including the fact that it does not work at night, is only of any realistic use for low-demand applications and can be expensive to harness. Technology, though, is improving and reducing the costs involved.