Submitted by: Agung Pambudi

Fulfilling of the world energy needs which are focused on fossil fuel such as oil, coal and natural gas will face a serious problem in energy security because its consumption and existence. High consumptions of energy contradict to decreasing of fossil fuel resources. In basic economic theory, this condition will affect increasing of price which is definitely consequent in industrialization expansion and will outcome in economic growth. According to Jess, [Energy Policy. 38 (2010), pp. 4663-4678] that the total energy demands increased sharply since 1965 with 3.8 billion toe to 11.3 billion toe in 2008.

Saxena et al [Renewable and Sustainable Energy Reviews. 13 (2009), pp. 167178] also reported that the world’s crude oil reserved, is estimated to get depleted in 2050. The other crucial problem that exists in fossil energy usage is relating with green house gas emission which causes global warming.

To prevent the negative impact on energy security as well as environmental damage by green house gas emissions, renewable energy clearly shows the solution offering a sustainable energy and low emission. Geothermal is a form of renewable energy derived from deep heat in ground which is utilized to electricity production by geothermal power plants and has high availability because the source is not dependent on weather conditions Ramazon [Renewable and Sustainable Energy Reviews. 11 (2007),pp. 497-511.] .

[youtube]http://www.youtube.com/watch?v=ctlkLn8L5Vw[/youtube]

The resource of heat comes from molten rock called magma, located at deep earth core below the geothermal resources layer. The water layer which contained geothermal layer, collected in water reservoir comes from the rainwater seeps through ground crack over thousand of years ago. It is heated by magma radiation and formed superheated fluid. To reach the superheated fluid in deep ground, production wells is made with drilling the ground in the depth around 5000 10000 feet from ground surface. The production wells will transport superheated fluid to either geothermal power plant or direct heating system with different purpose.

Geothermal power plant is needed to utilize superheated fluids in surface through turbine equipment which transforms geothermal energy into mechanical energy. Pressured steam is created from superheated fluid carries a force and energy, hit the blades and spin the turbine. Generator is connected by shaft with turbine and produces electricity.

There are three main types of geothermal power plants: dry steam, flash steam, and binary or two cycle power plant. In dry steam geothermal plant, steam flows directly into the turbine and spin generator. The used steam from turbine output is then cooled and injected back into the ground. Currently, the dry steam power plant is less common because it needs geothermal field which produce steam. The second type of geothermal power plant is flash steam which employs flash container. The superheated fluid comes from production wells consists water and steam, flows into flash container which works to separate steam and water. Pressure of the superheated fluid should be decreased at constant enthalpy occurring in flash container Mortaza [Yari Renewable Energy. 35 (2010), pp. 112-121].

There are two products from flash container: unflashed fluid and high pressure steam. High pressure steam flows into turbine while unlflashed fluid flows into second flash container and produces again medium pressure steam and unflashed fluid. The remaining unflashed fluid is again flows into flash separator and produces the low-pressure steam. All the pressure steam is delivered to turbine and spins the generator while all unflashed fluid injected back into reservoir wells. The binary or two-cycle power plants are more popular and technically advance in geothermal power plant technology. The hot water from production wells flows to heat exchanger while the other working fluids, called binary liquid, working in other side of heat exchanger. Isobutane is usually the choice of cycle for liquid-dominated geothermal resources Mehmet [Kanoglua et al International Journal of Hydrogen Energy. 35 (2010), pp.8783-8791]. The two of substance in heat exchanger never mix but the heat energy from hot water transport to the working fluids.

About the Author: Nugroho Agung Pambudi has joined Lab. Energy Eng.& Enviro. Protection, Aalto Uni. Finland. Now he working as PhD student. His special interest lies in the field of bioenergy. He likes bloging and manage three blog :

teamburma.orgcamerastall.com

and http:www.nextscholarship.info

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