Pros & Cons Of Geothermal Energy

In this guide, 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 – Geothermal Energy Pros & Cons

Pros

Is used by a range of countries

Renewable, unlike fossil fuels which are finite

Generally has a lower carbon footprint compared to other energy sources 

Lower air pollution compared to coal plants

Technology exists to manage air pollutants

Systems and technology exist to manage other forms of pollution and contamination too

Is reliable and not an intermittent/variable source of energy

Doesn’t need refuelling like some other energy sources (like coal for example)

Different types of geothermal set ups exists for different geological conditions

Can be used on either a small or large scale – for either individual households, or larger populations

Good for a range of uses – heating and cooling, drying and electricity generation

Potential for significant power capacity

The land used is usually in remote areas

Has made technological progressions throughout time

Some geothermal set ups have no environmental effects

 

Cons

Can still release some greenhouse gases

Not every country has the geologic conditions/resources for it

Some countries have various barriers relating to viability of geothermal energy

Legal framework can be a barrier

Not cost effective everywhere

Not practical or available everywhere

Can produce a toxic sludge waste by-product

Has a water footprint, and has potential to impact water quality

Some environmental impacts to consider

Can be one contributing cause of natural events like earthquakes

Can have other issues such as land subsidence

 

General Summary

Geothermal energy has some benefits, and is used by some countries as a key part of their energy mix for electricity.

Having said that, geothermal energy can be limited on larger scale by factors such as geographic suitability, as well as challenges relating to financial viability for some countries.

Drilling made geothermal energy theoretically more widely available, but the cost of drilling and associated set up costs doesn’t always make geothermal energy profitable.

These limitations mean that renewable energy sources like solar, wind and hydro are used more widely than geothermal, and in the case of solar and wind, will probably grow at a more significant rate.

 

*Note – the above pros and cons are broad generalisations.

Obviously there are different variables to each specific energy project that impact the final pros and cons (like new technology that reduces emissions for coal power plants just as one of many examples).

Each energy project and situation (in different countries and cities) should be analysed individually.

Having said that, some broad principles and patterns about the pros and cons of different energy sources tend to stay consistent too.

 

What Is Geothermal Energy?

Geothermal gets it’s name from geo, referring to rocks, and thermal, referring to heat.

Geothermal energy is heat energy (thermal energy) that comes from the Earth’s core, usually in the form of steam or water.

The temperature of the steam or water can play a role in determining how heat or energy can be used or converted.

For example, for electricity generation, higher temperatures may be required.

 

What Is Geothermal Energy Used For?

The energy can be used for space heating, electricity generation, and drying.

Households can use geothermal heat directly to heat their water (via pumps).

On larger scales, geothermal power plants are set up that can generate electricity.

 

Main Types Of Geothermal Energy Production, & How They Work

There can be various ways to classify geothermal energy.

 

The first (as outlined by irena.org) might involve:

1. Direct uses (district heating, geothermal heat pumps, etc)

2. Electricity generation from hydrothermal reservoirs via geothermal power plants

 

Another way to classify geothermal energy on larger scales might be in two categories:

1. Harnessing hot water close to the Earth’s surface where hot molten rock is located (referred to as geologic hot spots). Power plants in these locations are known as hydrothermal plants

2. Drilling deeper into the Earth’s surface to reach heat energy further down. This system is called hot dry rock geothermal – also known as enhanced geothermal systems 

Different geothermal energy sites used different technology or methods for energy to electricity conversion, and also for cooling.

 

Geothermal Energy Pros

Is Used By A Range Of Countries

For both electricity and heating.

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’

Some sources indicate that geothermal power plants across the world currently deliver about a third of the electricity that geothermal power plants do for heating.

 

According to wikipedia.org, as of 2010, the United States and Philippines had the highest total installed geothermal electric capacity

 

Renewable

Geothermal reservoirs can be replenished in a reasonably sustainable way compared to say fossil fuels – usually water is re-injected back into the reservoir, so access to water resources ar required.

When geothermal energy is used directly via a water heat pump for example, it’s still reasonably sustainable and renewable

 

Generally Has A Lower Carbon Footprint Compared To Other Energy Sources

Several sets of data show that geothermal energy tends to have a lower carbon footprint compared to other energy sources like fossil fuels, dedicated biomass, and others

eia.gov mentions that ‘Geothermal power plants emit … 99% less carbon dioxide than fossil fuel power plants of similar size’

Additionally, closed loop systems can help inject carbon dioxide and methane as greenhouse gases back into the ground before they get out into the atmosphere

 

Lower air pollution compared to coal plants and other fossil fuel plants

[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’

 

Technology Exists To Manage Air Pollutants

Air pollutants from geothermal plants can be managed with scrubbers, and also mercury filters

Additionally, closed loop systems can help inject air pollutants back into the ground without being exposed to the atmosphere

 

Systems & technology exists to manage other forms of pollution too

In particular closed loop systems can prevent pollution and contamination of different types.

Closed loop systems can help in pumping water that might contain salt, sulfur and other minerals back underground into reservoirs, and this can help prevent water contamination and pollution

 

Is Reliable, & Not A Variable Form Of Energy 

Geothermal isn’t reliant on weather conditions like solar or wind, and this makes it non variable, and reliable

According to irena.org, geothermal has high capacity factors, and is capable of ‘supplying baseload electricity, as well as providing ancillary services’

 

Doesn’t Require Refuelling Like Other Forms Of Energy Do

A coal power plant for example needs to have coal purchased, and needs refuelling.

Apart from perhaps needing to re-fill water reservoirs, geothermal power plants don’t need refuelling like a coal power plant does.

This may als mean less cost fluctuations and stable electricity prices.

 

Different types of geothermal set ups exists for different geological conditions

As outlined above, geothermal energy can run on two main types of set ups when used at scale:

1. Hydrothermal set ups where hot water closer to the Earth’s surface can be utilized for heating or energy

2. Hot dry rock geothermal set ups (enhanced geothermal systems) that involve drilling deeper into the Earth to access heat or energy

 

Can be used on a large scale or small scale

Geothermal energy can be utilized by single households, or by large populations.

efficientgreenpower.com outlines that water pump systems (ground source heat pumps) and heat exchangers can be used by households directly

On a larger scale, geothermal power plants can be used for mass electricity or heating

 

Good For A Range Of Uses

Such as heating, electricity generation, and drying.

 

Large Potential For Power Capacity

One estimate from renewableresourcescoalition.org is:

Upper estimates show a worldwide potential of 2 terawatts (TW).

But, other estimates of geothermal power plants vary between 0.035 to 2 TW.

Worldwide energy consumption – about 15 terawatts (TW) – is not anywhere near the amount of energy stored in earth.

In other estimations … currently … around forty countries could meet most of their power demands using geothermal power [which illustrates the potential in geothermal energy]

 

As mentioned elsewhere in this guide though – only a certain % of this energy potential is economically exploitable in a profitable way.

 

The land used is usually in remote areas

Land use for geothermal energy can be a little or a lot.

But, the land use is usually in more remote areas where land use might not be as much of an issue.

 

Technological Advancements Are Progressing The Energy Source

Recent technological advancements like enhanced geothermal systems have made more resources exploitable, and have lowered costs.

 

Some geothermal set ups have no environmental effects

eia.gov outlines that ‘direct use applications and geothermal heat pumps have almost no negative effects on the environment’

 

Geothermal Energy Cons

Can still release some greenhouse gases

When open loop systems are used, carbon dioxide and methane can be released

Additionally, there’s also a carbon footprint for the construction and infrastructure of a geothermal plant

 

Not Every Country Has The Geologic Conditions/Resource For It

If drilling isn’t undertaken, geothermal energy at scale requires the right ‘geologic hot spots’.

These hot spots aren’t distributed equally across each country or even regions within a country in the world, so, not every country or region will have suitable geologic conditions for geothermal energy production.

So, it might be limited to places near tectonic plate boundaries.

Even since the introduction of drilling which made geothermal energy more widely available, the cost of drilling still limits the countries and regions where geothermal energy can profitable be set up and operated.

Additionally, electricity generation generally needs higher temperatures to be effective.

energyinformative.org outlines ‘We need water temperatures of more than 150°C (about 300°F) or greater in order to effectively turn turbines and generate electricity with geothermal energy’

 

Some countries have various barriers relating to practicality or viability of geothermal energy

These barriers might include suitable geothermal resources, being able to scale geothermal production, and financial barriers.

Current technology, levels of subsidies and energy prices can also be other issues.

 

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.

 

More on costs for some context:

… the costs associated with both geothermal power plants and geothermal heating/cooling systems … might end up somewhere between $2 – 7 million for a geothermal power plant with a capacity of 1 megawatt (MW)

[Drilling for geothermal energy can also be expensive]

 

On profitability:

Some resources are profitably exploitable, and some aren’t [and] this limits the practically of where you can install geothermal plants.

 

On payback time for residents installing geothermal pumps:

For residential ground thermal pumps, ground source heat pumps typically costs $3,000 – $10,000 and have a payback time of 10 – 20 years.

 

On practicality of transporting energy:

If geothermal energy is transported long distances by the means of hot water (not electricity), significant energy losses has to be taken into account.

 

Legal Framework Can Be A Barrier

As wikipedia.org outlines, there can be a number of legal framework issues relating to geothermal energy, such as issues or questions over ownership, permits, royalties, and so on

 

Can produce a toxic sludge waste by-product

When scrubbers are used to capture air pollutants, a toxic sludge full of the captured pollutants and chemicals is produced, and this sludge is generally hazardous and must be managed safely and properly at hazardous waste sites

 

Has A Water Footprint, & Has Potential To Impact Water Quality

Geothermal energy plants need water – mainly for cooling.

This water can be geothermal fluid or fresh water – the larger the amount of external fresh water needed, the higher the fresh water resource footprint is.

Water is also needed for reinjecting back into the reservoir being used (to prevent land subsidence, and also to maintain the volume of water in the reservoir), and water can also be lost as steam.

The principle is the same here – the more fresh water used (or lost), the higher the fresh water resource impact.

Geothermal plants also have potential to impact water quality via water contamination, but closed loop systems generally prevent this.

 

Some Potential Environmental Concerns

Also, they are associated with sulfur dioxide and silica emissions, and the reservoirs can contain traces of toxic heavy metals including mercury, arsenic and boron.

But, there is not as much environment impact compared to fossil fuels.

Environmental impacts can also be dependent on the energy to electricity conversion technology/method, and the cooling technology/method used 

 

Can Cause Or Contribute To The Incidence Of Natural Events

In some very rare cases, geothermal energy cause earthquakes because they affect the stability of the land.

Germany and New Zealand are examples where this thought to have happened.

Earthquakes can be triggered due to hydraulic fracturing, which is an intrinsic part of developing enhanced geothermal system (EGS) power plants.

– energyinformative.org

 

Additionally, 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] (ussusa.org)

 

Can involve other issues such as land subsidence

Using underground water reservoirs can lead to the volume of water in the reservoirs decreasing, which can lead to the land sinking – known as land subsidence.

However, land subsidence can be minimized or prevented by injecting water back into the reservoirs as part of the geothermal energy process.

 

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

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