Pros & Cons Of Geothermal Energy

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

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

 

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

 

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.

 

May Have A High Capacity Factor

One study found that geothermal energy has the second highest capacity factor behind nuclear energy when comparing a range of different energy sources.

 

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

Some reports indicate that geothermal is one of the most land efficient energy sources when measuring median land use intensity

 

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

Geothermal energy, hydroelectric energy, and other renewables might be some of the most water efficient energy sources when comparing water use to energy generation

 

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:

Silica can precipitate out of geothermal fluid as it cools

Reservoirs can contain traces of toxic heavy metals (such as mercury, arsenic and boron), and may contribute to water contamination in some instances (but closed loop systems might prevent this)

 

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

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.

 

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] 

 

 

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

1 thought on “Pros & Cons Of Geothermal Energy”

  1. 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.

    Reply

Leave a Comment