Alternative Energy

Hydropower

Hydropower is produced by constructing a dam wall across a river to create a reservoir. The stored water is then released through turbines built into the dam wall, generating electricity. Although the generation of hydroelectricity does not produce any climate-changing emissions, the construction of large dams does cause significant environmental and social problems. When completed in 2009, the Three Gorges Dam in China will be the world's largest hydroelectricity scheme and able to generate 18,200 megawatts of power. However, the project will create a reservoir that is 412 miles (159 kilometers) long and will inundate 13 cities, submerge ancient archaeological and tourist sites, and make up to 1.2 million people homeless.

At an environmental level, a hydro-dam drastically changes the landscape and local hydrological processes. A dam hinders the movement of fish upstream, preventing them from spawning; downstream, less silt moves through the river system, starving the land of valuable nutrients. In heavily degraded landscapes, this loss of silt can be beneficial in reducing the need for dredging river estuaries. Another environmental impact of hydro technology is cold water pollution, in which the water in the deeper parts of the reservoir, normally at the dam wall, is significantly colder than at the surface. This temperature change has caused fish kills.

Wind Power

Wind power is generated by the force of the wind, which spins rotor blades attached to a turbine.

The clean, efficient nature of wind energy has seen a rapid expansion in the development of wind farms.

Modern wind turbines can be up to 305 feet (93 meters) tall with rotor diameters larger than the wingspan of a jumbo jet (210 feet [64 meters]), and which at full power can generate enough energy to power more than 500 homes. It is a very clean and efficient method of generating power, producing zero emissions of climate-changing gases, and it competes relatively well on price with other sources of traditional sources of power.

The clean, efficient nature of wind energy has seen a rapid expansion in the development of wind farms. Energy generated by wind grew by 28 percent in 2004, and is the second-fastest growing source of alternative energy in the world. Consequently, major companies including General Electric and Siemens are now investing in the wind industry, ensuring that the cost of production becomes even more competitive with traditional forms of energy.

Wind energy is not without its critics. Due to the many social and political issues raised by the prospect of wind farming, including the availability of suitable sites, visual impacts, competing land pressures, and noise pollution fears, wind farms are increasingly being built offshore. Energy outputs can also be 50 percent higher offshore than onshore.

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