Geothermal energy is sometimes seen as one of the sustainable alternatives to fossil fuels. However, not much is heard about it and it is not as widely used as solar or wind energies are.
So, why isn’t geothermal energy used today? Geothermal energy isn’t more used today mostly because of three reasons. First, the high costs it has compared to other energy sources. Second, the limited locations it can be installed in. And third, because of the risk of earthquakes its installation brings.
In the rest of the article, we will look a bit more into all the reasons geothermal energy is not used more often, and we will also explain what are the advantages of this technology and why it should still be a part of our energy creation system.
Challenges and Disadvantages of geothermal energy
There are some challenges and disadvantages associated with the production of geothermal energy, being this all the reasons why geothermal energy is not used more often.
1. Surface instability (earthquakes may occur)
When geothermal power plants are constructed, it is likely to make the land a bit unstable. In some parts of Germany, New Zealand, and Switzerland, geothermal power plants have led to the earth’s surface sinking. Earthquakes can be caused by hydraulic fracturing – an intrinsic process in developing enhanced geothermal system power plants.
A geothermal power plant constructed in Switzerland caused an earthquake in 2006. The magnitude of the earthquake on the Richter scale was 3.4.
2. Expensive
Constructing a commercial geothermal power plant is very costly. The total cost of installation is around $2.5 to 5 million for a geothermal power plant with 1 megawatt (MW) capacity. The drilling and exploration of new reservoirs play a major role in driving the costs up and account for about half of the total costs.
As I mentioned earlier, most geothermal resources cannot be used cost-effectively, not with the level of subsidies, current technology, and energy prices. Also, the pricing of geothermal cooling and heating systems for both commercial buildings and homes are steep.
With that said, these systems are likely to save money years down the line, and should therefore be regarded as a long-term investment. The cost of ground source heat pumps is about $12,000 to $30,000 for installation and mostly has a ten to twenty years payback time.
3. Location-specific
Most times, it is not easy to find good geothermal reservoirs. But a few countries have been blessed with many great resources. For example, in the Philippines and Iceland, one-third of the country’s electricity demand is met with geothermal energy. When geothermal energy is transported long distances by using hot water instead of electricity, it leads to the loss of a substantial amount of energy.
Even though the whole earth’s surface contains geothermal energy, not all of this energy can be harnessed. Only a small percentage of land lies above steam and water pockets suitable for heating homes or powering electrical plants. This limits the possibility of installing geothermal power plants in some regions.
However, most of the ideal places for generating substantial amounts of geothermal energy capable of being converted to electricity are usually located in very tectonically active regions. The constant risk of volcanic activity and earthquakes prevent corporations from installing large-scale electricity generating facilities.
4. Environmental issues
One of the most prominent disadvantages of geothermal energy is the environmental issues associated with it. There are many greenhouse gases underneath the earth’s surface. Using geothermal energy can cause the escape of some gases to the earth’s surface and the atmosphere. And these emissions are usually higher around geothermal power plants.
Geothermal power plants give off small amounts of silica and sulfur (IV) oxide and emissions. Also, reservoirs may contain some toxic heavy metals, such as arsenic, mercury, and boron. With that said, geothermal plants are not as polluted as many other energy sources.
Only a little fraction of what you normally see with fossil fuels and coal power. Besides, no water contamination cases have been reported from any geothermal site in the United States, according to the Union of Concerned Scientists.
5. Sustainability issues
Sustainability is another challenge associated with geothermal energy production. Over the years, rainwater seeps into the earth’s surface and get to geothermal reservoirs. Studies have shown that these reservoirs can get depleted when the fluid is removed faster than replaced. However, the fluid can be injected back into the geothermal reservoir once the thermal energy has been used (i.e., when the turbine has produced electricity).
Geothermal power can be sustained if reservoirs are managed properly. And this is not a case of residential geothermal cooling and heating, where geothermal energy is used in a different way than in geothermal power plants. Nonetheless, geothermal energy can be regarded as sustainable, environmentally friendly, and reliable.
And this makes it a no-brainer in certain locations, but high upfront costs can stop you from maximizing the full potential. The level of influence geothermal energy will have on our power systems in the future largely depends on energy prices, technological advancements, and politics (i.e., subsidies). You can’t really say what the situation will look like one or two decades down the line.
6. Infrastructure
Aside from the lack of adequate resources, geothermal electricity is not widely used in the United States because of a lack of infrastructure. Naturally, a geothermal energy source can only generate the baseline power for an electrical grid, which can cause issues. Also, the equipment needed for setting up power plants and drilling wells is extremely expensive. Also, people need to be trained to staff the geothermal power plant – a costly and time-consuming process.
Also, there is a restriction on where to use geothermal energy. Once the energy is gotten from the underground wells, it cannot be moved to another facility whose grid needs it more. The energy must be used once it is extracted.
7. Renewable Does Not Mean Unlimited
Most people believe that the water and steam that is extracted from the earth are boundless. But this is not true as every well has only so much water that can be used to generate power without any reinjection of used water back into the wells. The pressure is always not enough to propel the water and steam upwards. When the pressure gradient is not properly reestablished, there is a tendency that the energy source will dwindle. Also, there is the possibility of more geological impacts, such as the creation of sinkholes.
Advantages of geothermal energy
There are many advantages associated with the production of geothermal energy. And I have listed them below.
1. Environmentally friendly
One good thing about geothermal energy is that it is environmentally friendly. Geothermal power has a very small carbon footprint. According to the EIA, the average geothermal power plant gives off 99% less carbon (IV) oxide for every megawatt per hour (MWh) of electricity it generates.
There are some polluting processes involved in harnessing geothermal energy, but these are minimal compared to the pollution that comes from conventional fossil fuel sources like natural gas and coal. If our geothermal resources are properly developed, it can be helpful in the battle against global warming.
2. Renewable and sustainable
Another advantage of geothermal energy is that its reservoirs are from natural resources meaning that they are naturally replenished. So, one can say that geothermal energy is a renewable energy source. Most renewable sources of energy are sustainable, and so is geothermal energy. This means that geothermal energy is a resource that can sustain its consumption rate – an ability that is not seen in conventional energy sources like fossil fuels and coal. According to scientists, geothermal reservoirs contain enough energy that will last billions of years.
3. Massive potential
The energy consumption worldwide is about 17 terawatts (TW) of power from all fossil and renewable sources. This might sound like a lot, but there are many times more energy than stored inside the earth. The issue is that most geothermal energy is either unprofitable to access or difficult (sometimes both). The potential of geothermal power plants has been estimated to vary between 0.035 to 2 TW.
In recent times, geothermal power plants worldwide deliver about 12.7 gigawatts (GW) of electricity. The installed geothermal heating capacity is a bit higher at 28 GW. Therefore, there is much scope for more geothermal energy generation.
4. Stable
Another good thing about geothermal energy is that it is a reliable energy source. The power output of any geothermal power plant can be predicted with accuracy. But this is not the case with wind and solar, where the weather plays a major role in power production. Therefore, geothermal power plants are great for meeting the baseload energy requirements.
Furthermore, geothermal power plants possess a high capacity factor. Their actual power output is super close to the total installed capacity. The global average power output in 2017 was above 80 percent (capacity factor) of total installed capacity, but 96% was realized.
5. Great for heating and cooling
This is another advantage of geothermal energy. In the process of generating electricity with geothermal energy, high water temperatures are needed. The water must have a temperature of 150°C (300°F) or above. If the temperature is less than 150°C, it will not effectively turn the power-generating turbines. Another easier method of utilizing geothermal energy is by using it for cooling and heating. In this approach, the relatively small temperature gradient between the surface and a ground source is utilized.
The earth is usually more resistant to seasonal temperature variations than air. As a result, the ground a few feet below the surface can function as a heat sink or source with the geothermal heat pump in a similar way an electrical heat pump utilizes the heat in the air.
In recent times, there has been a huge increase in the number of homeowners that use geothermal cooling or heating.
Environmental Impact of Geothermal Energy
Geothermal energy is considered one of the cleanest forms of energy there is. There are no emissions involved apart from the electricity needed to power the heat pump. However, these emissions can be minimized by using solar panels as the heat pump’s power source. Air emissions are also controlled using standard practices to reduce sulfur (IV) oxide to about 4% and carbon (IV) oxide to 0.1 – 0.2%. Nitrogen oxides are not emitted.
This pure form of energy is being used in the United States. It displaces 80,000 tons of nitrogen oxides, 200,000 tons of sulfur (IV) oxide, 22 million tons of carbon (IV) oxide, and 110,000 tons of particulate matter compared with emissions given off by the same amount of electricity generated by fossil fuel plants.
The ground source heat pumps used in geothermal energy production need electricity to operate. And the source of this electricity might not be so eco-friendly. The transmission efficiency of most electric power plants is about 15%. These power plants also need to burn fuel to generate electricity. However, when you power the heat pump with a green energy source, they will practically be emissions-free, like solar panels.
Fluids from the earth always contain a mixture of gases, such as methane, carbon dioxide, hydrogen sulfide, and ammonia. These pollutants can cause acid rain, global warming, and noxious smells when released. Geothermal energy plants emit an average of 122 kilograms of CO2 per megawatt-hour of electricity – a little fraction when compared to the emission produced by conventional fossil fuel plants. Any plant with high volatile chemicals and acids is always equipped with emission-control systems to lower exhaust.
Also, hot water from geothermal sources may hold in solution trace amounts of toxic elements like boron, mercury, arsenic, and antimony. Such chemicals precipitate when the water cools and can cause harm to the environment when released. However, injecting cooled geothermal fluids back to the earth for the production of energy has the benefit of decreasing environmental risks.
Geothermal heating systems include compressors and pumps, which can consume energy from a polluting source. And this parasitic load is a fraction of the heat output. Therefore it is less polluting than electric heating. Furthermore, if the electricity is from burning fossil fuels, the net emissions of geothermal heating could directly burn the fuel for heat.
For example, an electrically powered geothermal heat pump from a combined-cycle natural gas plant can produce the same amount of pollution as a same-sized natural gas condensing furnace. So, the environmental value of geothermal heating applications is mostly dependent on the emission intensity of the next electric grid.
Plant construction can negatively affect land stability. Earthquakes have happened in the Wairakei field in New Zealand. Also, an uplift has occurred in Staufen im Breisgau, Germany, tectonic because of an isolated anhydrite layer mixed with water and formed into gypsum, doubling its volume. Advanced geothermal systems can cause earthquakes as part of hydraulic fracturing. A project in Basel, Switzerland, was stopped because of more than ten thousand seismic occurrences with a magnitude of 3.4 on the Richter Scale occurred over the first six days of water injection.
An important thing that should not be overlooked while operating a geothermal system is balancing the cooling and heating loads. This is very important because if the loads are not balanced properly, the result will decrease or increase in the earth’s temperature. And this is likely to affect the local environment.
What Types of Geothermal Systems Are There?
There are several geothermal systems out there. The system to choose depends on a lot of factors like climate, local installation costs on-site, soil conditions, and available land. There are two ground loop systems. These systems are further divided into several subgroups:
Open Geothermal Loop System
- Pond
- Standing well
Closed Geothermal Loop System
- Horizontal
- Vertical
- Pond
These systems differ in the pipes’ installation, depending on the size and structure of the land available.
How Much Does it Cost to Get a Geothermal Energy System Running?
After all this information on geothermal energy, one good question is: how much do you have to invest in order to get your geothermal system up and running in your own home? The total costs for installing a geothermal energy system usually end up somewhere between $2.5 to 5 million for a geothermal power plant with 1 megawatt (MW) capacity.
A geothermal ground source heat pump costs about $12,000 to $30,000 for installation, and an air source heat pump costs around $9,000 to $15,000. Even though geothermal systems are more costly than other heating or cooling systems, they have much lower operating costs and deliver more energy per unit.
Conclusion
Geothermal energy harnesses the earth’s heat and uses it for the production of electricity. This clean energy is sustainable, economically friendly, and reliable. Although this energy source has positive impacts on our environment, it is not widely used because of the risk of earthquakes, its high costs, and the small number of locations where it is available.
It is worth knowing that geothermal energy is one of the cleanest among the numerous energy sources out there.
