What are Disadvantages About Geothermal Energy?

Are there disadvantages about geothermal energy that we need to know?  Most of the facts clearly show advantages of this energy production method. Geothermal energy is a process that utilizes a naturally occurring and renewable energy source. It does not require high land use or use much fresh water in the process and those are both qualities to recommend geothermal energy.

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Photo: Joy of Seth

The disadvantages about geothermal energy are not insignificant. A nuclear power plant can be built wherever permission (and public opinion) allows it. Coal plants are often located fairly close to mining areas and oil powered plants are more cost effective if located either near oil fields or where docking of tankers is found. But coal and oil do not require being located close to the source of the fuel as both fuels can be transported by ships or by railcars.

Location May be a Disadvantage about Geothermal Energy
When producing electricity using geothermal energy the power plant must be located in a geothermal reservoir. The highly temperature reservoirs and hot rocks deep in the earth do occur around the world but only in areas where they are close enough to the surface to access can that geothermal energy be tapped.

The Ring of Fire is an area filled with geothermal reservoirs. This band around the Pacific Ocean is also an area known for the fault lines and seismic activity caused by the movement of tectonic plates of rock under the surface of the earth.

The porous nature of these rock formations and the fractured physical aspect allow water deep beneath the ground to flow through the hot rocks and provides areas where reservoirs naturally form.

To access the geothermal properties, it is necessary to drill multiple very deep wells miles into the earth. Year of study by geologists goes into the planning of geothermal power plant in order to locate the plant and wells safely. Seismology (the science of earthquakes) has come a long way in the past hundred years but there is much we don’t know about the movement of tectonic plates. Though there are times when seismic activity can be predicted, it’s not possible yet to predict the level or timing of a seismic event.

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One of the great disadvantages about geothermal energy is the potential for stimulating seismic activity that can result from the deep well drilling necessary to capture geothermal energy. Both northern and southern California are home to several geothermal power plants that have been in operation for many years. Even though studies are carefully done prior to drilling the first test wells, constant monitoring is necessary as drilling proceeds. If an increase in earthquakes or tremors is detected in the area, drilling will be topped until further evaluation can be made. In some cases, geothermal plant construction has been permanently halted due to great increases in seismic activity in the region that may be a direct result of drilling into a fault line.

Economic Reality
Once a geothermal plant is in operation, no fuel is required except for that needed to run pumps. A geothermal energy production plant is not affected by wide fluctuations in fuel costs. However, the capital costs to build this type of power producing plant are very high. More than half of the cost is for the drilling needed. Drilling is costly, time consuming and carries significant risks both to workers and of increased earthquake activity.

The failure rate for wells drilled is a full 20% and the cost of drilling one well is more than $10 million. Multiple wells are required as some are for extraction while other wells are injection wells where used water and substances are returned to the earth. Costs vary widely as geothermal energy is easily scaled to meet demands and a geothermal facility may be designed to power or heat a small village or to provide power to a huge city’s grid.

There is no disadvantage about geothermal energy when it comes to sustainability. Any amount of heat extracted is a tiny portion of the amount of heat produced in the earth’s core. About 20% of the heat referred to as residual heat while the remainder is thought to be caused by high radioactive decay rates in the distant past. The earth is slowly cooling as natural heat produced is not in balance but the amount of heat tapped by geothermal energy utilization is not enough to tip that balance or accelerate heat loss.

There is a disadvantage about geothermal energy in the potential to avoid depleting local geothermal sources. Wells reduce local temperatures and water levels as less water is returned than is mined. The water returned has been cooled in the geothermal energy production facility. This disadvantage of geothermal energy has been noted at The Geysers and two other older production facilities.

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Photo: musical photo man

These power plants have reduced output due to local depletion as heat and water were removed from the earth faster than natural flows could replace them. Scientists believe reducing the amount of power produced by these plants may theoretically help the reservoirs recover and re-balance. This is referred to as mitigation strategies and is being practice in a few older geothermal energy plants.

We do know that there is no disadvantage or question about geothermal energy production as a power source. In Italy, the Lardarello field has been in operation since 1913 and the Wairakei field in New Zealand has been producing power since 1958. In California, the Geysers power plants have been working hard since 1960. The standard procedure in the past has been to simply drill more deep wells when current wells began to produce less geothermal heated water and steam. In some areas, this is a potential cure but the current theories are that production levels should be reduced to allow the earth to recover its geothermal balance.

In California, the active fault lines make it difficult to drill additional deep wells. Each well drilled increases the chance that the drilling will disturb the position of the plates along the large fault lines so additional well drilling is approached with great caution.

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