Today in Cleantech

Geothermal Coming on Strong

Geothermal power is energy generated by heat stored in the earth.  Geothermal power generation refers to the collection of absorbed heat derived from underground resources.  Geothermal resources range from shallow ground to hot water and rock several miles below the Earth's surface, and even further down to the extremely hot molten rock. Wells over a mile deep can be drilled into underground reservoirs to tap steam and very hot water that can be brought to the surface for use in a variety of applications. As of 2008, geothermal power supplies less than 1% of the world's energy.

The United Stated has the greatest amount of geothermal production in the world.  Its largest group of power plants is located in The Geysers, a geothermal field in California. This plant is recharged by injecting treated sewage effluent from the City of Santa Rosa and the Lake County sewage treatment plant, which used to be dumped into rivers and streams.

Geothermal steam and hot springs have been used for centuries for bathing and heating, but it was not until the 20th century that geothermal power started being used to make electricity.  The first geothermal power generator was tested on July 4th, 1904 in Italy.

Twenty-four countries generated a total of 56,786 GWh (204 PJ) of electricity from geothermal power in 2005, accounting for 0.3% of worldwide electricity consumption. This output is growing by 3% annually, thanks to a growing number of plants as well as improvements in their capacity factors.

Because a geothermal power station does not rely on transient sources of energy, unlike, for example, wind turbines or solar panels, its capacity factor can be quite large.  In fact, a capacity factor of up to 90% has been demonstrated. The global average was 73% in 2005. The global capacity was 10 GW in 2007.

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Editorial

Hydropower: Is it Really 'Green'

Hydropower is the production of power through the use of the gravitational force of water. In traditional Hydropower, the force of water flowing downhill is used to power the station's turbines.

as of 2006, hydroelectric power supplied about 715,000 megawatts or 19% of world electricity. Large dams are still being designed. The world's largest is the Three Gorges Dam on the third longest river in the world, the Yangtze River. Apart from a few countries with an abundance of hydro power, this energy source is normally applied to peak load demand, because it is readily stopped and started. It also provides a high-capacity, low-cost means of energy storage, known as "pumped storage".

Hydropower produces essentially no carbon dioxide or other harmful emissions, in contrast to burning fossil fuels, and is not a significant contributor to global warming through CO₂.

Hydroelectric power can be far less expensive than electricity generated from fossil fuels or nuclear energy. Areas with abundant hydroelectric power attract industry. Environmental concerns about the effects of reservoirs may prohibit development of economic hydropower sources.

The chief advantage of hydroelectric dams is their ability to handle seasonal (as well as daily) high peak loads. When the electricity demands drop, the dam simply stores more water (which provides more flow when it releases). Some electricity generators use water dams to store excess energy (often during the night), by using the electricity to pump water up into a basin. Electricity can be generated when demand increases. In practice the utilization of stored water in river dams is sometimes complicated by demands for irrigation which may occur out of phase with peak electrical demands.

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