Below, we list the potential pros and cons of geothermal energy.
This guide forms part of a series of guides we have put together outlining the benefits and disadvantages of different energy sources and energy generation methods.
Summary – Pros & Cons Of Geothermal Energy
Potential Pros
Geothermal Energy Has Several Potential Uses
Currently Used By A Range Of Countries
Is Considered A Renewable Energy Source
Might Have A Low Carbon Footprint
May Release Less Air Pollutants Than Fossil Fuel Energy Sources
Systems & Technology Exist To Manage Outputs & Waste From Geothermal Energy
Centralisation May Have Benefits
May Have A High Capacity Factor
May Be An Efficient Energy Source
May Deliver A Reasonably Consistent Power Output, & Be Reasonably Reliable
May Be Capable Of Providing Base Load Power
Doesn’t Require Refuelling Like Some Other Energy Sources Do
Can Be Used On Both Small, & Large Scales
Energy Potential Of Geothermal Energy May Be Significant
Recent Developments May Have Improved Geothermal Energy In Different Ways
Some Geothermal Systems Might Have Minimal To No Negative Environmental Impact
May Not Be As Costly/Expensive As Some Other Energy Sources
May Be One Of The Most Land Efficient Energy Sources According To Some Metrics
May Be One Of The Most Water Efficient Energy Sources According To Some Metrics
Potential Cons
Not Every Country Has The Resources, Conditions, Or Capabilities For Utility Scale Geothermal Energy Use & Electricity Generation
Geothermal Heat Pumps & Associated Geothermal Household Devices/Systems Can Be Costly, & Can Have A Longer Payback Period
Legal Framework Issues May Present Some Challenges
May Still Release Some Greenhouse Gases
Still Has A Water Footprint To Consider
May Have Other Potential Environmental Concerns To Consider
Can Produce A Toxic Waste By-Product
May Lead To Land Subsidence
Some Question Whether Geothermal Energy Contributes To The Incidence Rate Of Earthquakes Or Seismic Activity
General Summary
Geothermal has a range of uses across different sectors and industries across society.
It’s also used by some countries as a key part of their energy mix for electricity.
So, it’s an reasonably important source of energy globally.
Having said that, geothermal energy may have some key drawbacks or limitations too
A few examples are the number and positioning of geological hotspots, the cost of drilling, and the general cost of geothermal systems to install the home vs other heating and cooling systems.
Other renewable energy sources like solar, wind and hydro might have a greater % of energy share and use in many countries than geothermal energy.
Solar and wind in particular may continue to grow at a quicker rate than geothermal energy on a global scale in the future.
*Note
The pros and cons in this guide are broad generalisations.
Each energy project in each geographic location will have it’s own factors and variables to consider, so, each one will require a separate assessment of it’s individual pros and cons.
The development of technology, as well as other factors might change pros and cons in the future too.
What Is Geothermal Energy?
What ‘Geothermal’ Refers To
Geothermal gets it’s name from:
– Geo, referring to rocks
– Thermal, referring to heat
What Is Geothermal Energy?
Geothermal energy involves capturing and using heat energy (thermal energy) that comes from the Earth’s core, usually in the form of steam or water.
This energy has several potential uses.
The temperature of the steam or water might impact how that energy can be used though.
For example, electricity generation might require higher temperatures.
How Geothermal Energy Is Accessed
There might be two main ways energy is accessed:
1. Using hot water close to the Earth’s surface where hot molten rock is located
These spots are referred to as ‘geologic hot spots’
Sometimes power plants are constructed in these locations for electricity generation, and they are known as hydrothermal plants
2. Drilling deeper into the Earth’s surface to reach heat energy further down
This is called ‘hot dry rock geothermal’ (also known as ‘enhanced geothermal systems’)
Potential Pros Of Geothermal Energy
Geothermal Energy Has Several Potential Uses
Three of the main uses for geothermal energy are:
– Heating (space heating, water heating, etc.)
– Cooling
– Electricity generation
There’s various methods to make use of geothermal energy.
For example …
Heating and cooling of homes can be achieved via a geothermal heat pump
Heating of buildings and homes can also be achieved via geothermal district heating
Electricity generation happen on large scales with the use of a geothermal power plant.
Currently Used By A Range Of Countries
There’s a range of countries worldwide that use geothermal energy for both electricity and heating.
Some of these countries get majority of their energy for these uses from geothermal too.
irena.org outlines that ‘Geothermal energy provides … a significant share of electricity demand in countries like Iceland, El Salvador, New Zealand, Kenya, and Philippines and more than 90% of heating demand in Iceland’
According to wikipedia.org (paraphrased), as of 2010, the United States and Philippines had the highest total installed geothermal electric capacity
Globally, geothermal power plants are widespread. The US has the largest installed geothermal power plant right now – The Geysers, located north of San Francisco. Italy, Mexico, the Philippines and Iceland also have some large geothermal power plants (wikipedia.org, and worldatlas.com)
Is Considered A Renewable Energy Source
The heat available from geothermal reservoirs is continually replenished from the Earth’s interior
Additionally, there are techniques such as water reinjection for water reservoirs, that can help with things such as maintaining reservoir pressure and maintaining the productivity of the well
At the rate we consume geothermal energy, this might make make geothermal energy a renewable energy source
This is in comparison to fossil fuels which are generally considered to be non renewable
Might Have A Low Carbon Footprint
– General Carbon Footprint
Several sets of data show that geothermal energy has a low carbon footprint – lower than fossil fuels, and also dedicated biomass
eia.gov mentions that ‘Geothermal power plants emit … 99% less carbon dioxide than fossil fuel power plants of similar size’
– Methane Leak
Several reports indicate that methane can leak from geothermal systems.
However, some of these reports also indicate that:
These emissions are natural emissions, and the emissions tend to be minimal
Additionally, closed loop systems might be used to help inject carbon dioxide and methane as greenhouse gases back into the ground before they get out into the atmosphere
May Release Less Air Pollutants Than Fossil Fuel Energy Sources
Geothermal energy may release less air pollutants, such as sulfur compounds, compared to a fossil fuel energy source like coal.
Additionally, technology and devices exist to help manage air pollutants before they get into the air.
[Some data shows that SO2 emissions from geothermal plants is 30x lower than from coal plants] (ucsusa.org)
eia.gov also outlines that ‘Geothermal power plants emit 97% less acid rain-causing sulfur compounds … than fossil fuel power plants of similar size’
Systems & Technology Exist To Manage Outputs & Waste From Geothermal Energy
In particular, closed loop systems might be used to help manage potential forms of waste and pollution.
As one example, closed loop systems might be used to pump water that contains salt, sulfur and other minerals back underground into reservoirs
This can may help prevent water contamination.
Centralisation May Have Benefits
Geothermal power plants can be centralized in some countries or regions
One of the benefits of this centralisation might be that it’s easier to make improvements to things like sustainability and environmental impact
May Have A High Capacity Factor
According to irena.org: ‘… geothermal has high capacity factors …’
May Be An Efficient Energy Source
One study found that geothermal energy has one of the highest efficiency rates when measuring the rate at which different energy sources convert their original energy to electricity
May Deliver A Reasonably Consistent Power Output, & Be Reasonably Reliable
Geothermal is not considered a variable energy source like solar energy or wind energy might be (both solar and wind rely on external weather conditions, whereas geothermal doesn’t)
Geothermal instead might deliver a reasonably consistent and predictable power output
This might make geothermal energy a reasonably reliable energy source too
May Be Capable Of Providing Base Load Power
Typically, fossil fuels and nuclear plants might be used for providing base load power for a power grid.
But, several reports indicate that geothermal and hydro energy are currently the only two ‘renewable’ energy sources capable of delivering base load power.
From irena.org: ‘… geothermal … is capable of ‘supplying baseload electricity, as well as providing ancillary services”
Doesn’t Require Refuelling Like Some Other Energy Sources Do
Coal power plants (coal) and nuclear reactors (uranium) require refuelling.
Apart from perhaps needing to re-fill water reservoirs, geothermal power plants don’t need refuelling.
Can Be Used On Both Small, & Large Scales
Geothermal energy can be used on the single household level, making use of a geothermal heat pump or heat exchanger.
However, it can also be used on a much larger utility scale, whereby geothermal power plants deliver electricity to cities or towns.
Energy Potential Of Geothermal Energy May Be Significant
Different estimates indicate that geothermal energy could have a potential global energy output of around 0.035 to 2 TW.
This is lower than the worldwide energy consumption figure of about 15 terawatts (TW), but, it’s still a significant amount of potential energy to tap into
Putting the entire world’s energy demand aside, geothermal energy might at least be able to meet majority of the energy needs of some individual countries
Various reports indicate that:
… around forty countries could meet most of their power demands using geothermal power …
But, only a certain amount of all geothermal energy is extractable in an economically feasible way – so, this should be taken into account from a practical or economic point of view.
Recent Developments May Have Improved Geothermal Energy In Different Ways
Recent technological advancements like enhanced geothermal systems may have made more geothermal resources exploitable (i.e. drilling made geothermal energy more widely accessible), and may have also lowered costs.
Although, there might be claims that ‘enhanced geothermal systems’ (drilling) also has drawbacks to consider.
Some Geothermal Systems Might Have Minimal To No Negative Environmental Impact
eia.gov outlines that:
‘… direct use applications and geothermal heat pumps have almost no negative effects on the environment’
May Not Be As Costly/Expensive As Some Other Energy Sources
In terms of the cost of geothermal energy compared to other energy sources, it might rate:
Somewhere in the middle for capital costs
Somewhere between the middle and being one of the cheaper energy sources on a LCOE/per MWh of electricity generated basis
May Be One Of The Most Land Efficient Energy Sources According To Some Metrics
What might also be worth mentioning about geothermal energy’s land use is that land used for utility scale geothermal power plants might not have another land use that is as valuable as using the land for geothermal electricity generation.
This might especially be true if the land is further out from urban areas.
May Be One Of The Most Water Efficient Energy Sources According To Some Metrics
Potential Cons Of Geothermal Energy
Not Every Country Has The Resources, Conditions, Or Capabilities For Utility Scale Geothermal Energy Use & Electricity Generation
There might be several reasons for this:
– Requirement For ‘Geologic Hot Spots’
One way to be able to use geothermal energy at utility scale is by having ‘geologic hot spots’
Not every region might have access to adequate hot spots because of geography (they might be limited to places near tectonic plate boundaries)
– Drilling May Be Too Costly
Drilling has made geothermal energy more widely accessible to countries that don’t necessarily have ‘geologic hot spots’ nearby
Drilling enables thermal energy below the Earth’s surface to be accessed
However, not every country can carry out drilling because of the cost, which also impacts how profitable geothermal energy can be.
Some geothermal resources are profitable, and some aren’t – this ultimately impacts where geothermal power plants can be built.
– High Temperatures Are Required For Electricity Generation
Additionally, electricity generation from geothermal energy generally needs higher temperatures to be effective.
energyinformative.org outlines ‘… water temperatures of more than 150°C (about 300°F) or greater [are required] in order to effectively turn turbines and generate electricity with geothermal energy’
– Geothermal Resources May Be Too Far Away From Where The Energy Will Eventually Be Used, & There Might Be Issues Transporting This Energy
Transporting geothermal energy longer distances by the means of hot water (not electricity), might lead to significant energy losses
– Other Factors
arena.gov.au indicates that a country like Australia could have good geothermal potential, but barriers like finding suitable resources, producing hot fluid at a high enough rate, and adequate finances, all stand in the way of financial viability of the geothermal as an energy source.
Geothermal Heat Pumps & Associated Geothermal Household Devices/Systems Can Be Costly, & Can Have A Longer Payback Period
Geothermal heat pumps for household use can cost in the thousands of dollars, up to the tens of thousands of dollars
That may also be without considering underfloor heating systems
Not only can geothermal heat pumps be costly, but the payback period can be significant in some instances
Some reports indicate that the payback period in some cases can be decades (10 to 20 years)
This of course depends on different local variables too though – the payback period might be shorter in some instances
Potential Legal Framework Issues May Present Some Challenges
wikipedia.org outlines that (paraphrased) legal framework issues might present some challenges for geothermal energy relating to ownership, permits, royalties, and so on
May Still Release Some Greenhouse Gases
As mentioned above, methane and carbon dioxide can leak from geothermal energy setups.
Emissions may come naturally from reservoirs, but, also during the drilling process
This might especially be the case when open loop systems are used for geothermal energy.
Still Has A Water Footprint To Consider
Geothermal projects and power plants still use water for:
Cooling (at power plants)
Water lost as steam
And, also water that is reinjected back into the reservoir being used (water is reinjected to prevent land subsidence, and also to maintain the volume of water in the reservoir)
May Have Other Potential Environmental Concerns To Consider
Such as:
– Air Pollution
Air and water pollution are two leading environmental issues associated with geothermal energy technologies [and sometimes these pollutants can be concentrated] (fws.gov)
Hydrogen sulfide may be one of the pollutants/gases emitted from geothermal energy
– Water Pollution
Different types of waste from geothermal energy projects may contribute to water contamination in some instances, and this may impact aquatic wild life too
However, closed loop systems might prevent or reduce this
From fws.gov: ‘Open-loop systems expel waste steam and gases into the atmosphere and generally result in greater environmental impacts than closed-loop systems’
Another form of ‘water pollution’ from some geothermal power plants might be thermal water pollution, whereby heated/increased temperature water is discharged to lakes or freshwater bodies
– Waste Pollution
Silica can precipitate out of geothermal fluid as it cools
Also, reservoirs can contain traces of toxic heavy metals (such as mercury, arsenic and boron)
– Other Notes
Environmental impact can also be affected by the energy to electricity conversion method used, and also the cooling method used
Can Produce A Toxic Waste By-Product
When scrubbers or other devices are used to capture air pollutants, a toxic sludge (from the captured pollutants and chemicals) can be produced as a waste by-product
This sludge might be hazardous waste, and might need the proper hazardous waste management
May Lead To Land Subsidence
Land subsidence is effectively when land sinks due the the groundwater beneath it being withdrawn or decreasing in volume.
Some reports indicate that this can happen when underground water reservoirs are used for geothermal energy purposes.
However, other reports indicate that this problem can be addressed with water reinjection (whereby water is injected back into these reservoirs)
Some Question Whether Geothermal Energy Contributes To The Incidence Rate Of Earthquakes Or Seismic Activity
Some reports question whether geothermal energy contributes to earthquakes in the instances that they involve hydraulic fracturing (for enhanced geothermal system (EGS) power plants).
This fracturing may affect the stability of the land, and trigger an earthquake.
There might be things that can be done to address this risk though.
In a hot dry rock geothermal plant, water under high pressure is pumped through a specially drilled well into a deep body of hot compact rock, causing its hydraulic fracturing (fws.gov)
From energyinformative.org:
Germany and New Zealand are examples [of places where land instability might have been an issue from geothermal energy]
From ussusa.org:
… there is some evidence that hydrothermal plants can lead to greater earthquake frequency.
[And …] enhanced geothermal systems might increase the risk of small earthquakes [however, there are things that can be done to minimize this risk]
Additionally, wikipedia.org mentions that (paraphrased) where geothermal energy involves removal of groundwater and accelerated cooling of rock formations, there may be links to this activity resulting in greater probability of earth tremors and seismic activity ma
Sources
1. http://efficientgreenpower.com/geothermal-energy
2. http://energyinformative.org/geothermal-energy-pros-and-cons/
3. https://www.renewableresourcescoalition.org/alternative-energy-sources/
4. https://www.ucsusa.org/resources/environmental-impacts-geothermal-energy
5. https://www.eia.gov/energyexplained/geothermal/geothermal-energy-and-the-environment.php
6. https://arena.gov.au/renewable-energy/geothermal/
7. https://www.irena.org/geothermal
8. https://en.wikipedia.org/wiki/Geothermal_energy
9. https://en.wikipedia.org/wiki/List_of_geothermal_power_stations
10. https://www.worldatlas.com/articles/largest-geothermal-power-plants-in-the-world.html
11. https://en.wikipedia.org/wiki/Environmental_impact_of_electricity_generation
12. https://www.fws.gov/ecological-services/energy-development/geothermal.html
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So the greens don`t like fracking for gas which supposedly cause a 0.8 tremor in Lancashire but accept a 5.4 earthquake caused by enhanced geothermal in South Korea and similar sized quakes in Germany, odd that.