What Is Geothermal Energy and What Is Its Future?

What Is Geothermal Energy? With improvements in enhanced geothermal systems technology the earth’s heat could become a major electricity generator. Flickr/xavierbt

Geothermal means, literally, “earth heat”. The temperature of the earth increases as we drill deeper towards its core. We can use that heat for energy by circulating water through hot subterranean reservoirs, bringing the hot water or steam to the surface. We can then convert the energy in the hot fluid to mechanical and electrical power at the surface using a heat engine.

The private investment in Australian geothermal power development slowed down after a very fast start ten years ago. This should pick up again as new developments bring commercial viability to enhanced geothermal systems. These have the potential to grow exponentially, promising abundant power for the world.

Conventional geothermal systems

In 2010, the world generated 20 terawatt hours (TWh) of geothermal electricity. All of this came from conventional resources. These are naturally occurring hot water or steam flows heated by magma and circulating through permeable rock. They are associated with volcanic systems and limited to regions with active or young volcanoes.

The use of conventional resources is not new. In 1904, a plant was built in Larderello, Italy, to generate electricity from geothermal steam. Since then, geothermal power installations have spread at a steady rate but have been limited to resources that are relatively easy to access.

Enhanced geothermal systems

There is another form of geothermal heat that is abundant and generally available around the globe. It is produced by the radioactive decay of potassium, uranium, and thorium isotopes found in some granite types.

In granites in the Cooper Basin, in South Australia, there are isotope concentrations at trace level. Heat is generated at a very low rate. At such a low rate, it would take almost one million years for a mass of granite to increase its temperature by 100°C. Through that time the rock has to remain well-insulated at great depth.

To access this deep heat, at least two wells must be drilled. Cold water is injected from one well, it is heated by the rock and is extracted from the other well. The two wells are typically 800 to 1000m apart. In such a system, the water will travel from one well to the other only if the rock between the wells is sufficiently permeable.

Natural rock permeability is not high enough but can be enhanced by well-established oil and gas engineering techniques. These systems are called Enhanced Geothermal Systems (EGS).

Commercial EGS development

Electricity from enhanced geothermal systems is not cost-competitive now because deep wells are expensive. To generate enough electricity to pay for the wells and for the surface equipment, the hot water has to be brought to the surface at rates close to 100kg/s. One of the best EGS flow rates in the world was achieved by the Australian company Geodynamics, and it was only a third of this target. Although this is a significant achievement, it is not enough to make EGS electricity commercially competitive.

It’s possible to compensate for these low flow rates if you can improve the efficiency of converting the energy into power. But improvements in this area have yet to see electricity production become cost-competitive.

EGS flow rates must be tripled before EGS electricity is commercially feasible. It was reported last December that a promising technique for geothermal wells might have been developed by the US company AltaRock. If the reported results are substantiated by further testing, it will provide new breath for the EGS geothermal development around the world and in Australia.

Other Australian geothermal resources

The division between conventional and enhanced geothermal systems is artificial and the actual global geothermal resource covers a continuous spectrum extending from naturally occurring hot springs to enhanced geothermal systems.

Recent results show that although Australia is not a volcanic country, it has areas where magma gets close to the surface to produce hot water in sedimentary rock. The Australian geothermal industry calls these hot sedimentary aquifers. They are expected to have natural permeabilities higher than EGS but maybe not as high as conventional geothermal systems.

Around the world, there has not been much work in this type of resource but there are new developments in Australia as well as other places like Turkey and South America directed at such resources.

Environmental impacts

In accessing geothermal energy, the technologies involved can have slight effects on the immediate environment. As seen by the Paralana experience, slight tremors may be felt on the surface but these do not constitute a significant risk. Geothermal energy does not use any more water than other renewable thermal power energy applications. Also the fracture stimulation used in the EGS projects does not pose a risk for surface aquifers because EGS reservoirs are very deep and the wells are sealed in steel casings.

In some volcanically-sourced conventional geothermal resources, the dissolved gases released to the atmosphere may affect the immediate environment. This is probably the most serious hazard associated with geothermal energy but it is limited only to some conventional resources (not relevant to Australia) and is easy to control.

The future for geothermal

The fundamentals for geothermal energy are strong. It is abundant – the resource underneath the Great Artesian basin is estimated to be large enough to deliver the current Australian annual energy consumption for 6000 years. It is one of the few renewable power sources that can completely replace coal as a baseload electricity generator. It also has a very low environmental impact.

The failure to achieve sufficient flow was hindering its commercial development but this problem may be solved in the near future. If that happens, geothermal power could become one of the leading renewable power technologies for the 2020s.The Conversation

About the Author

Hal Gurgenci, Professor of Mechanical Engineering, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Related Books

Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming

by Paul Hawken and Tom Steyer
9780143130444In the face of widespread fear and apathy, an international coalition of researchers, professionals, and scientists have come together to offer a set of realistic and bold solutions to climate change. One hundred techniques and practices are described here—some are well known; some you may have never heard of. They range from clean energy to educating girls in lower-income countries to land use practices that pull carbon out of the air. The solutions exist, are economically viable, and communities throughout the world are currently enacting them with skill and determination. Available On Amazon

Designing Climate Solutions: A Policy Guide for Low-Carbon Energy

by Hal Harvey, Robbie Orvis, Jeffrey Rissman
1610919564With the effects of climate change already upon us, the need to cut global greenhouse gas emissions is nothing less than urgent. It’s a daunting challenge, but the technologies and strategies to meet it exist today. A small set of energy policies, designed and implemented well, can put us on the path to a low carbon future. Energy systems are large and complex, so energy policy must be focused and cost-effective. One-size-fits-all approaches simply won’t get the job done. Policymakers need a clear, comprehensive resource that outlines the energy policies that will have the biggest impact on our climate future, and describes how to design these policies well. Available On Amazon

This Changes Everything: Capitalism vs. The Climate

by Naomi Klein
1451697392In This Changes Everything Naomi Klein argues that climate change isn’t just another issue to be neatly filed between taxes and health care. It’s an alarm that calls us to fix an economic system that is already failing us in many ways. Klein meticulously builds the case for how massively reducing our greenhouse emissions is our best chance to simultaneously reduce gaping inequalities, re-imagine our broken democracies, and rebuild our gutted local economies. She exposes the ideological desperation of the climate-change deniers, the messianic delusions of the would-be geoengineers, and the tragic defeatism of too many mainstream green initiatives. And she demonstrates precisely why the market has not—and cannot—fix the climate crisis but will instead make things worse, with ever more extreme and ecologically damaging extraction methods, accompanied by rampant disaster capitalism. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook-icontwitter-iconrss-icon

 Get The Latest By Email

{emailcloak=off}

LATEST VIDEOS

Methane Emissions Hit Record Breaking Levels
Methane Emissions Hit Record Breaking Levels
by Josie Garthwaite
Global emissions of methane have reached the highest levels on record, research shows.
kelp forrest 7 12
How The Forests Of The World’s Oceans Contribute To Alleviating The Climate Crisis
by Emma Bryce
Researchers are looking to kelp for help storing carbon dioxide far beneath the surface of the sea.
Tiny Plankton Drive Processes In The Ocean That Capture Twice As Much Carbon As Scientists Thought
Tiny Plankton Drive Processes In The Ocean That Capture Twice As Much Carbon As Scientists Thought
by Ken Buesseler
The ocean plays a major role in the global carbon cycle. The driving force comes from tiny plankton that produce…
Climate Change Threatens Drinking Water Quality Across The Great Lakes
Climate Change Threatens Drinking Water Quality Across The Great Lakes
by Gabriel Filippelli and Joseph D. Ortiz
“Do Not Drink/Do Not Boil” is not what anyone wants to hear about their city’s tap water. But the combined effects of…
Talking About Energy Change Could Break The Climate impasse
Talking About Energy Change Could Break The Climate Impasse
by InnerSelf Staff
Everyone has energy stories, whether they’re about a relative working on an oil rig, a parent teaching a child to turn…
Crops Could Face Double Trouble From Insects And A Warming Climate
Crops Could Face Double Trouble From Insects And A Warming Climate
by Gregg Howe and Nathan Havko
For millennia, insects and the plants they feed on have been engaged in a co-evolutionary battle: to eat or not be…
To Reach Zero Emissions Government Must Address Hurdles Putting People Off Electric Cars
To Reach Zero Emissions Government Must Address Hurdles Putting People Off Electric Cars
by Swapnesh Masrani
Ambitious targets have been set by the UK and Scottish governments to become net-zero carbon economies by 2050 and 2045…
Spring Is Arriving Earlier Across The US, And That's Not Always Good News
Spring Is Arriving Earlier Across The US, And That's Not Always Good News
by Theresa Crimmins
Across much of the United States, a warming climate has advanced the arrival of spring. This year is no exception.

LATEST ARTICLES

Two-thirds Of Glacier Ice In The Himalayas Could Be Lost By 2100
Two-thirds Of Glacier Ice In The Himalayas Could Be Lost By 2100
by Ann Rowan
In the world of glaciology, the year 2007 would go down in history. It was the year a seemingly small error in a major…
Rising Temps Could Kill Millions A Year By Century’s End
Rising Temps Could Kill Millions A Year By Century’s End
by Edward Lempinen
By the end of this century, tens of millions of people could die each year worldwide as a result of temperatures rising…
New Zealand Wants To Build A 100% Renewable Electricity Grid, But Massive Infrastructure Is Not The Best Option
New Zealand Wants To Build A 100% Renewable Electricity Grid, But Massive Infrastructure Is Not The Best Option
by Janet Stephenson
A proposed multibillion-dollar project to build a pumped hydro storage plant could make New Zealand’s electricity grid…
Wind Farms Built On Carbon-rich Peat Bogs Lose Their Ability To Fight Climate Change
Wind Farms Built On Carbon-rich Peat Bogs Lose Their Ability To Fight Climate Change
by Guaduneth Chico et al
Wind power in the UK now accounts for nearly 30% of all electricity production. Land-based wind turbines now produce…
Climate Denial Hasn't Gone Away – Here's How To Spot Arguments For Delaying Climate Action
Climate Denial Hasn't Gone Away – Here's How To Spot Arguments For Delaying Climate Action
by Stuart Capstick
In new research, we have identified what we call 12 “discourses of delay”. These are ways of speaking and writing about…
Routine Gas Flaring Is Wasteful, Polluting And Undermeasured
Routine Gas Flaring Is Wasteful, Polluting And Undermeasured
by Gunnar W. Schade
If you’ve driven through an area where companies extract oil and gas from shale formations, you’ve probably seen flames…
Flight Shaming: How To Spread The Campaign That Made Swedes Give Up Flying For Good
Flight Shaming: How To Spread The Campaign That Made Swedes Give Up Flying For Good
by Avit K Bhowmik
Europe’s major airlines are likely to see their turnover drop by 50% in 2020 as a result of the COVID-19 pandemic,…
Will The Climate Warm As Much As Feared By Some?
Will The Climate Warm As Much As Feared By Some?
by Steven Sherwood et al
We know the climate changes as greenhouse gas concentrations rise, but the exact amount of expected warming remains…