- The main 3 disadvantages of geothermal energy are:
- What is geothermal energy?
- How does geothermal energy work?
- What are the negative effects of geothermal energy?
- What are the advantages of geothermal energy?
- Uses of geothermal energy
- Is geothermal energy renewable or non-renewable?
- How does geothermal energy work in a house?
- Is geothermal energy expensive?
- Does geothermal energy cause pollution?
- How practical is geothermal energy?
The main 3 disadvantages of geothermal energy are:
- It is location-specific and depends on favorable drilling conditions
- Capital cost is high, both for drilling and for energy conversion machinery
- Can be destabilizing for rock strata and release greenhouse gases
Other disadvantages include the possibility of triggering earthquakes and depleting aquifers (in the case of direct drawing of geothermically heated undeground water reservoirs).
All energy sources have pros and cons and must be managed in order to minimize the drawbacks while enhancing the positive aspects.
What is geothermal energy?
Simply defined, ‘geothermal refers’ to heat generated inside the Earth. If you drill down into our planet’s crust, the temperature increases in a mostly linear fashion until the heat would eventually melt the drill bit!
The center of the Earth is actually a ball of white hot iron, which should be molten but is at such tremendous pressure that it is probably solid at a temperature of around 5430°C (9806°F)! Luckily, we don’t have to drill down very far to find heat mankind can use.
How does geothermal energy work?
Geothermal energy is the amount of heat available underground for extraction and conversion. Sometimes the heat can be used directly, as in space heating for buildings, and sometimes it can be converted into electricity.
Depending on the intended use of the energy, different types of machines and plants are needed to extract and convert the heat.
What are the negative effects of geothermal energy?
Negative effects of energy resources are mostly defined in the way their use affects the environment i.e. does it pollute or not?
In the case of geothermal the main focus is on air and water pollution. Whatever type of plant used, a lot of water is moving around so there is potential for contamination, particularly as some plants re-inject water back into underground reservoirs to maintain the resource.
Toxic gases, as well as greenhouse gases, can be released in various quantities. In brief, it’s essential that geothermal plants are managed responsibly to manage these negative effects.
What are the advantages of geothermal energy?
No energy source is perfect in every way – they all have benefits and drawbacks to various degrees. Some of the biggest advantages of drawing heat from inside the planet revolve around the fact that it’s always there.
You don’t have to wonder if it will be available today. The other two popular renewable energy sources, wind and solar, depend on the constant winds and no clouds for maximum efficiency. The energy output of solar power drops to about 10% on a very cloudy day.
- Always available
- Temperature gradient vs depth known and reliable
- Low carbon footprint
- Very low environmental impact
- Renewable and sustainable
What is the biggest advantage of geothermal power?
The main advantage is that this type of energy is truly renewable. The reserves of available heat inside the Earth are huge and will never go away. After all, it is the pressure of the mass of the planet acting under gravity that causes the heat, so it can never disappear.
Uses of geothermal energy
How it is used depends on the depth of the extraction, and hence temperature, and in what form it is extracted:
- Some plants draw super-hot water from deep within the Earth which converts to steam as the pressure reduces. This steam can be used to drive electric generators directly or piped into buildings for heating.
- Water can also be circulated around dry hot rock strata before bringing the captured heat back to the surface for heating or generating purposes.
- Water at lower temperatures can be used for heating greenhouses used for food production
- Pipes laid just 2 meters deep can be used with heat-pump technology to heat individual homes
Is geothermal energy renewable or non-renewable?
What does renewable and nonrenewable mean?
A definition of ‘renewable’ should include:
- the resource should replace itself by natural processes
- renewal should be short term and be replaced faster than we use it
Why is geothermal energy considered renewable energy?
A non-renewable resource is not replaced at all, or at least so slowly that it’s no use to mankind in the short term. Oil and coal, for example, took millions of years to form out of ancient vegetation.
Geothermal energy is the perfect example of a renewable resource as the heat deep underground is always being generated by the planet itself.
What are examples of renewable and non-renewable?
We normally think of a renewable or non-renewable resource as something we convert into energy, but many other things come under these classifications.
Non-renewables include food, sand and soil, for example. Ideally, food is renewable. If it wasn’t, none of us would be here! However, the planet’s population is growing so fast that the sustainability and availability of food is coming under question.
Topsoil is essential for growing food and this too is becoming scarce, either by blowing away, washing away or being degraded by chemicals and pollution. Sand is used in massive quantities for building and is fast being used up.
The most common renewables on the energy front are solar, wind, wave-power and geothermal. The table below lists the most used renewable and non-renewable resources:
YES - but how use?
YES - if well-managed
How does geothermal energy work in a house?
Home-heating using underground heat is made possible using heat-pump technology. A heat-pump acts like a refrigerator in reverse, pushing cold outside and pumping heat into the home.
Large-scale industrial projects may drill down many hundreds of meters into the Earth, as greater depth means higher temperature, which in turn means a higher conversion efficiency. However, you don’t have to go too far down to take advantage of the temperature gradient between the surface and underground.
Geothermal home heating can be done in three ways:
- drilling a single borehole at a depth of up to 100 meters (closed loop system)
- drilling two boreholes to tap an existing underground water source (open-loop system)
- laying coils of pipes horizontally at a depth of about 2 meters
The temperature increases about 30°C for each km in ‘normal’ ground, that is, if not in a region with surface hot springs or other anomaly. The temperature 2 meters underground is a constant 10 to 12°C, so it should be around 15C at 100 meters.
The temperature difference between the surface and 2 meters underground is enough to use for home heating, by amplifying the difference using a heat-pump. Heat pumps typically output 400% more energy than the electrical energy used to run them.
Horizontal pipe systems make use of this low temperature gradient by using a big area of land for laying the pipe coils. If land isn’t available, then the pipes can be inserted vertically to a greater depth, making use of the higher temperature.
Is geothermal energy expensive?
Large-scale geothermal power plants carry a big installation cost, often in the range of $3 million to $6 million, depending on conditions and location. Once installed, however, they run very efficiently, often over 90%. Running costs are around $0.02 per kWh for geothermal generating stations.
This is a great option for home heating using a heat-pump. The installation cost for the average size home is a little expensive (between $15000 and $30000) depending on location and geological conditions, but running costs help payback the investment in several years.
Heat pumps in general output 3 to 4 times the input energy, so a unit with a 2kW electrical rating can generate up to 8kW of useful heat.
Is geothermal energy reliable?
Geothermal energy is a very reliable resource. It’s basically always available and unchanging. One proviso is that if water is drawn form heated aquifers, it should be injected back into the reservoir in a continuous cycle, or risk depleting the amount of water available.
Does geothermal energy cause pollution?
Geothermal does cause some pollution but nothing like as much as non-renewable processes. Small-scale systems, such as those used to heat individual homes, cause negligible amounts of pollution, but large-scale systems can release gases.
The biggest culprit is carbon dioxide (CO2), which is a greenhouse gas rather than a pollutant. Whenever we drill into the Earth there is always a chance that small quantities of hydrogen sulfide will be released, along with other gases classed as toxic.
Although geothermal is renewable, the machines used to drill the Earth and extract heat from underground have a carbon footprint. Invariably, the energy from non-renewable fossil fuels have been used to create the machines, and in most cases, to power them.
This carbon footprint causes various amounts of pollution that should be attributed to geothermal heat extraction.
Infographic – Main disadvantages of geothermal energy
How practical is geothermal energy?
It’s versatility makes it a practical option for large and small scale use. Although the efficiencies claimed are very high, the fact is that the thermal efficiency of a geothermal power plant is quite low at 17% to 20%.
At the other end of the spectrum, a heat pump used in home heating is very efficient, with a heat energy output 3 or 4 times higher than the electrical energy used to run the pump.
Initial cost is a big stumbling block to practicality, but once installed the plants are long-lived, run efficiently and provided relatively clean energy.
Why is geothermal not widely used?
There’s a couple of reasons geothermal isn’t used as widely as solar, say. It’s expensive to install, has a relatively long payback period and depends on location to some extent.
Why we should use geothermal energy?
We need to actively move over to renewables like geothermal if the planet is to survive, it’s as simple as that! The time when mankind could use as much of the planet’s resources as it likes is long past.
In the not-too-distant-future we just won’t have any coal, oil or gas to use anyway, so we better start changing over to clean, green energy now, before it’s too late!