Geothermal Energy: Myth Versus Reality Of Sustainability

Geothermal energy is thermal energy generated and stored in the Earth. It is a clean, renewable energy source that utilizes heat from the Earth’s core to produce steam to drive turbines and generate electricity.

Despite its advantages, there are some common myths and misconceptions around the sustainability of geothermal energy. This article examines some of the top sustainability myths about geothermal energy and provides facts to dispel them. We will look at claims around earthquakes, depletion, costs, and global potential.

Myth: Geothermal Causes Earthquakes

There is a common perception that geothermal energy production can lead to increased seismic activity and earthquakes. Some fear that injecting water deep underground during geothermal drilling and operations could lubricate fault lines and trigger earthquakes.

However, research shows that the risk of induced seismicity from geothermal energy is extremely low compared to other energy sources. Geothermal reservoirs are typically not located near major fault lines. Additionally, geothermal drilling takes place at much shallower depths than fracking or wastewater injection.

Strict regulations also require monitoring seismic activity during geothermal drilling and operations. Any measured seismic events are minor and comparable to natural background seismicity. A 2019 study found only 17 cases of felt earthquakes attributed to geothermal operations worldwide since the 1960s, all minor events of magnitude 3 or less.

While no energy source is completely risk-free, multiple studies confirm geothermal carries an extremely low risk of earthquakes compared to other energy technologies. With careful siting and monitoring, geothermal energy can provide reliable base-load power without meaningfully contributing to seismic activity.

Reality: Low Seismic Risk

While geothermal projects can induce small seismic events, studies show the risks are low compared to other energy sources. Proper siting and operation can mitigate seismic effects.

Research by MIT found only a 0.0006% chance of geothermal causing earthquakes above 3.0 magnitude in the US. Coal mining and oil/gas extraction have much higher induced seismicity. With careful reservoir management, geothermal seismic risk is near zero.

Operators can adjust fluid injection rates and install early warning systems. New enhanced geothermal systems (EGS) use advanced imaging to avoid fault lines. Projects are designed according to strict seismic guidelines and closely monitored.

In over 50 years, rare induced seismic events above 4.0 magnitude have occurred. But with safety measures, geothermal causes less detectable ground movement than trucks driving by. While small tremors may occur, risks are insignificant.

Myth: Geothermal Depletes with Use

A common misconception about geothermal energy is that it is a finite resource that will eventually deplete if overused. Some believe that extracting heat from the earth’s crust will “use up” the available thermal energy over time. However, this is a myth stemming from a misunderstanding of geothermal processes.

In reality, geothermal energy derives from the Earth’s internal heat, which flows continuously from the hot core to the cooler surface. This heat flow occurs through conduction and convection currents in the mantle and crust. The rate of heat flow is immense—approximately 44 terawatts—and has remained fairly constant over billions of years. This is because the earth constantly produces heat from radioactive decay deep within its core.

While geothermal reservoirs can be depleted locally if extracted at an unsustainable rate, the earth’s overall heat flow remains undiminished. With proper site management and sustainable extraction rates, geothermal energy can be harnessed indefinitely, making it a renewable resource. Most geothermal power plants are designed to extract heat at a rate lower than the natural heat recharge rate of the reservoir, ensuring its long-term viability.

Therefore, fears of geothermal energy being finite or non-renewable are largely unfounded. The earth’s vast internal heat resource far exceeds what humanity could plausibly utilize. With thoughtful usage, geothermal provides sustainable energy for generations to come.

Reality: Sustainable Usage

While it’s true that geothermal resources can be depleted if over-extracted, sustainable usage practices allow for continual replenishment of geothermal reservoirs. The key is to limit extraction to no more than 20-30% of the estimated usable heat content over a 30 year period. This prevents over-depletion and allows time for the geothermal brines to be re-heated by the Earth’s internal heat sources.

Additionally, extracted geothermal fluids are often re-injected back into the reservoir once the heat has been captured for energy production. This circulation and re-injection of geothermal brines allows the subsurface heat reservoirs to recharge over time. Thermal equilibrium models indicate that with proper reservoir management, geothermal systems can be sustained for hundreds to thousands of years.

Furthermore, newer enhanced geothermal systems (EGS) can create artificial geothermal reservoirs in hot dry rock through hydraulic fracturing. This expands potential geothermal resources exponentially, as EGS is not limited to natural hydrothermal sites. With prudent resource management and emerging technologies like EGS, geothermal has the potential to provide sustainable renewable energy worldwide.

Myth: High Upfront Costs

One common myth about geothermal energy is that it requires very high upfront capital costs to build geothermal power plants. This misconception comes from the fact that geothermal power plants do require substantial initial investments for resource exploration, drilling wells, building power generation facilities, and installing transmission lines.

However, once built, geothermal power plants have very low operating costs compared to fossil fuel plants. Geothermal plants use steam from the earth as their “fuel”, so they do not incur ongoing fuel purchase or transportation costs. The facilities also require less maintenance over decades of operation. While the upfront cost seems high, geothermal plants offer a better return on investment in the long run.

Additionally, as geothermal technology improves and project development costs decrease over time, the initial capital costs are becoming more competitive with other energy sources. Geothermal power can provide reliable baseload renewable energy for decades once built, offsetting the initial investment.

Reality: Long-Term Savings

While the upfront costs of building a geothermal power plant are significant, the long-term savings make geothermal energy cost-competitive. Once built, the “fuel” to operate a geothermal plant is free and results in low operational costs for decades. This contrasts with fossil fuel plants that require continually purchasing coal, natural gas, or oil.

According to a study by the US Department of Energy, geothermal power costs about $0.05 per kWh, comparable to coal and natural gas. But more importantly, geothermal offers predictable pricing not susceptible to fuel price volatility. The study estimates geothermal energy saves consumers $5 billion per year compared to conventional sources.

In addition to lower fuel costs, geothermal plants have a high capacity factor over 90%, meaning they reliably generate electricity 24/7 with minimal downtime. The plants have long operating lifespans of over 20 years. Overall, geothermal offers affordable, consistent power generation over decades, resulting in tremendous lifetime savings.

Myth: Limited Global Potential

One of the most prevalent myths surrounding geothermal energy is that its potential capacity is very limited globally. Many critics argue that geothermal can only be harnessed in select locations near tectonic plate boundaries or hot spots, restricting the total amount of energy that can be generated to a tiny fraction of global energy demand.

This myth stems from the fact that high-temperature geothermal resources, which are suitable for traditional geothermal power plants, are indeed limited to certain geologic settings like active volcanic areas. However, this view overlooks the enormous potential of lower-temperature geothermal resources to provide heating, cooling and hot water across a much wider geography.

With advances in technology like binary power plants and heat pumps to take advantage of lower temperature geothermal, experts estimate there are over 100 gigawatts of electricity generation potential and 100 exajoules of heat energy accessible globally. That’s enough to meet a substantial portion of the world’s energy needs sustainably. While high-temperature hydrothermal sources are geographically constrained, low-temperature geothermal can be utilized almost anywhere.

So while the locations where traditional geothermal plants can operate are limited, the total global potential for geothermal energy as a whole is enormous when considering advances in technology that increase accessibility.

Reality: Vast Global Resources

Geothermal energy has enormous global potential with over 300,000 megawatts of proven resources worldwide. The estimated potential capacity is over 2 million megawatts, providing abundant opportunity for expansion. According to studies, over 40 countries could meet 100% of their energy needs through geothermal power alone.

The countries with the largest geothermal capacity include the United States, Indonesia, Philippines, Mexico, Italy, New Zealand, Iceland, Turkey, Kenya, and Japan. However, many other countries have untapped potential reserves waiting to be harnessed. For example, estimates show East Africa’s Rift Valley alone could produce over 15,000 megawatts of geothermal capacity.

With vast global resources still unutilized, geothermal energy has significant room for growth as an alternative energy source. The potential capacity could meet a substantial portion of the world’s electricity demands. With further exploration and technology improvements, geothermal will play a major role in the global renewable energy mix.

Conclusion

In summary, many of the myths surrounding geothermal energy are unfounded when examined closely. The low risk of induced seismicity, sustainable usage of geothermal reservoirs over time, long-term cost savings, and vast global potential all point to geothermal being a highly sustainable energy source.

While geothermal does have some limitations in terms of suitable locations, the technology is constantly improving to access resources in more areas. With the ability to provide continuous base load power and zero emissions, geothermal can play a major role in the global transition to renewable energy.

The evidence clearly shows that geothermal energy is far more sustainable than negative perceptions would suggest. Policymakers and the public should base decisions on the proven sustainability benefits of geothermal rather than myths not grounded in facts.