Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%). Though this energy is promising, there are still disadvantages from it use for electrical generation.
Geothermal energy is one of the largest sources of electrical power in the world. The USA, Philippines and Indonesia are the three largest producers of geothermal electricity. The science behind this technology is simple – we use the heat beneath the ground either by extracting the steam produced underground or by pumping water into the heat source, thereby steam and bringing it up to be used. Inside the plant, the steam conveyed through the pipes is used to turn generator which eventually produces electricity.
This type of energy is renewable as the heat underground does not get exhausted. It sounds promising, but there are certain disadvantages with its use. Here are the ten major drawbacks of geothermal energy:
1. Location. Geothermal systems are site specific. Though hot rock reserves are found all over the world, the technology is very much applicable only to places located near the Pacific Ring of Fire, volcanic areas, or spots near tectonic plate boundaries. Hot rock reserves in these places are shallower and hence, easier to access than other sites.
2. Reachable reserves. Aside from their depth with respect to ground surface, the type of rock above the reserve is also important. It must be a type that can be easily drilled through.
3. Capital. Plant construction requires large investment costs. The building, facilities and pipes systems must be strong and durable enough to withstand constant exposure to gas and liquid at very high and low temperatures.
4. Maintenance. Similarly, geothermal plants require high maintenance cost and efforts to keep it on full operation.
5. Increased soil salinity. Brine can salinize soil if the water is not injected back into the reserve after the heat is extracted. Water underground is not pure; it contains certain salts and minerals which are not ideal to be amended or mixed with the soil. It can affect the salinity or alkalinity of the soil which consequently becomes not suitable for crop production. Hence, the water extracted must be pumped back to the heat source to avoid deposition of salts in the ground surface.
6. Land stability. Even during construction, geothermal plant can already cause inconvenience to the nearby community as it can affect land stability. Enhanced and continued geothermal systems can trigger earthquakes as a result of hydraulic fracturing.
7. Potential land subsidence. Continued extraction of large amounts of water can cause land subsidence. This can lead to an increase in seismic activity and even produce sinkholes. To prevent this from happening, the cooled water must be injected back to the reserve to maintain the water pressure constant underground.
8. Gas emission. Construction of production and injection wells can release gases trapped beneath the ground. Likewise, if geothermal plants do not inject the cooled water back underground, hydrogen sulfide (H2S) or the “rotten” gas is released. This gas can cause problems if large quantities escape since inhaling too much of this gas is fatal.
Geothermal plants also free carbon dioxide. The emission intensity of existing geothermal electric plants is on average 122 kg of CO2 per megawatt-hour (MW•h) of electricity.
Other gases that can be released are methane and ammonia. These pollutants contribute to global warming and acid rain.
9. Noise pollution. One must drill through hard layers of rocks deep underground in order to fully utilize geothermal energy. The activity can cause tremendous noise pollution.
10. Potential water pollution. Minerals extracted underground may leach through water reservoirs and cause water pollution. Among them are traces of toxic chemicals like mercury, arsenic, boron and antimony.
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