Alternative Energy

Renewable EnergyAlternative energy refers to energy sources that have no undesired consequences such for example fossil fuels or nuclear energy. 

Read More...

 

 

ELECTRICITY PRODUCTION USING GEOTHERMAL ENERGY 

By: Gestur Gislason, senior geochemist at Reykjavik Geothermal &
      Snorri Gudbrandsson PhD geochemist at Reykjavik Geothermal
 
Emera Caribbean Inc. and Reykjavik Geothermal, in association with the Government of St. Vincent and the Grenadines, are planning a 10MW geothermal power plant at the foot of La Soufriere on the northern part of St. Vincent.
 
Geothermal steam has been used for over 100 years to produce electricity. The first power plant was built in Italy in 1904. Since then, more and more geothermal resources have been harnessed for power production.
 
With over a century-long history and world-wide distribution, geothermal power is a well-known and thoroughly tested technology. The USA has the world ́s highest installed capacity at 3,450 MW, mostly in the Geyser fields and Salton Sea, CA. The Philippines has the second highest installed capacity with 1,870 MW, followed by Indonesia at 1,340 MW.
 
Today, there are geothermal power plants in 25 countries with a total 12,635 MW installed capacity and an annual production of 73,549 GWh. For comparison, the annual production of VINLEC is about 140 GWh. The planned 10 MW geothermal power plant will potentially serve about 60% of the electricity needs of the island.
 
Geothermal energy has proven to be a reliable energy source, ideal as a firm power source not subject to weather conditions, oil prices, etc.
 
Geothermal systems
 
Sourcing of geothermal resources suitable for power production are closely related to the Earth’s plate tectonics and volcanism. Most commonly the resources are located on or near plate boundaries, both where rifting occurs, such as in Iceland and Kenya, and on subductions boundaries, as is the case in the Philippines and Indonesia. With its complex tectonics, with both subduction and transverse faults the Caribbean Gulf and Central America is a promising area for geothermal energy for electricity production.
 
geo picThe heat source of geothermal systems is magma that indirectly heats deep-flowing water which seeps through permeable bedrock at great depths. The magma transfers heat to shallower levels in the crust. As the magma cools, it conducts heats through the surrounding rock formations as wells as the overlying rock towards the surface. The heat transfer can elevate the rock temperatures to as high as 250 – 500 °C at 1-5 km depth, forming ideal conditions for a geothermal reservoir. At this depth, the rock is still permeable enough to allow surface water (either fresh rainwater or seawater) to percolate through the reservoir rock. As the water heats up, it starts to rise back towards the surface due to lowered density of the hot water. With time, the system will develop into a convectional system where the hot fluid will rise above the heat source to shallower levels where it cools and starts to sink away from the main up- flow zone. The circular motion is driven by the continuous heat being brought to the system fromthe deep-seated magma. The elevated water temperature will alter the reservoir rock and form the so-called cap rock, sealing the geothermal system from the surrounding colder environment. Leakages in the cap rock will enable some of the geothermal fluid to escape to the surface, forming surface manifestations such as hot springs, mud pools and steam vents. 
 
The Soufriere volcano on St. Vincent is an example of a geothermal system as described above, with manifestations of geothermal steam in the crater area and the warm springs of Trinity Falls in the upper reaches of the Wallibou River.