Tue, Oct 17, 2017 - Page 8 News List

Geothermal holds huge promise

By Lu Shyi-min 呂錫民

In April, the Environmental Protection Administration announced that Taiwan’s first geothermal power plant would be built in the Lize Industrial Zone in Yilan County’s Wujie Township (五結). It is estimated that, after construction is completed in 2025, the plant’s electric power generation capacity could reach 11 megawatts (MW), so that it could supply 800 gigawatt-hours of electricity annually.

In so doing, it could bring about a reduction of 350,000 tonnes of carbon dioxide emissions per year compared with a thermal power station generating the same amount of electricity.

According to the plan, 11 geothermal wells are to be drilled in the industrial zone. The plant will use advanced geothermal power generation technology that extracts heat without extracting water. That is to say that water is injected deep into the earth, where it is heated to a high temperature before being circulated through a boiler, heating water in the boiler pipes to produce water vapor that drives a turbine to generate electricity.

This method avoids excessive consumption of geothermal resources, thus continuously sustaining the geothermal power plant’s operating efficiency.

Unlike solar energy and wind power, geothermal power is not affected by weather conditions, so it can generate a stable output of electricity and can therefore perform an important role in baseload power generation.

Notably, geothermal power plants occupy a small surface area, making it a green energy resource that countries around the world are eager to develop.

Geothermal heat is nowadays mostly used to generate electricity, which still costs more than electricity generated by conventional methods. However, hot water that remains following electricity generation can be further utilized for multiple functions, including recreational spas, heated swimming pools, greenhouse horticulture, high-end agriculture, cool and warm air conditioning and so on, thus extracting additional economic value from the process.

From a geological point of view, Taiwan is located on an orogenic (mountain-forming) collision belt between two tectonic plates — the Philippine Sea Plate and the Eurasian Plate — as a result of which the land often undergoes compression and collisions, and earthquakes occur very frequently.

It also means that rock formations are prone to faults and folds, so that rock strata are constantly being lifted up and broken. Since rock is a material that has low thermal conductivity, heat is not easily dissipated through it. The constant accumulation of geothermal heat in rock formations over a long period gives rise to a relatively steep geothermal gradient in the area of the Central Mountain Range.

Additionally, there has in the distant past been large-scale volcanic activity in northern Taiwan and islands off the east coast and, although volcanic activity has ceased for the time being, there are still reserves of hot magma under the dead or dormant volcanoes.

From a climatic point of view, Taiwan is located on the western rim of the Pacific Ocean. It undergoes a northeast monsoon in winter and a southwest monsoon and typhoons in summer, bringing an average annual rainfall of more than 2,500mm.

After rain hits the ground, some rainwater seeps into the Earth’s crust through fissures or broken rock and is heated as it passes along the geothermal gradient or when it comes into contact with hot magma. These features give rise to rich geothermal resources and they explain why hot springs are an important feature of geothermal systems.

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