This group brings together the best thinkers on energy and climate. Join us for smart, insightful posts and conversations about where the energy industry is and where it is going.

Post

The Possibilities and Limitations of Geothermal Energy

image credit: https://pixabay.com/photos/power-plant-geothermal-67538/

You’d think that in today’s world, the average Joe doesn’t need much more convincing that renewables are the future of energy. It’s no secret that the fossil fuels we currently use to fuel our modern lifestyles are largely contributing to climate change, through increased exponentially increased emissions. What’s more, fossil fuels aren’t an unlimited source of energy and can easily run out as the demand for energy rises. Turning to alternative and renewable sources of energy is one way to secure the stability of our planet, while also fulfilling human energy needs. 

In this regard, geothermal energy is one of many alternative sources of energy that harnesses the pockets of steam, hot water, and rock beneath the Earth’s surface to generate electricity and power heating/cooling systems. As with most things, geothermal energy has its own set of benefits and limitations. Here, we take a look at some of its duplicities: 

Pros

The most obvious, surface-level advantages of geothermal energy include its constant availability, environmental friendliness, and its relatively low cost. When compared to other sources of renewable energy, like wind and solar power, geothermal energy makes for the most reliable option.  Wind doesn’t blow every day, and the sun isn’t always shining — but the heat under the Earth’s surface is available virtually anytime. Since it can be extracted without burning fossil fuels, geothermal energy is also more eco-friendly, resulting in lower emissions. According to the U.S. Energy Information Administration, geothermal power plants emit produce, “97% less acid rain-causing sulfur compounds and about 99% less carbon dioxide than fossil fuel power plants of similar size. 

In terms of expenditure, direct use of geothermal energy can save as much as 80%when compared to fossil fuels. In fact, geothermal energy is recognized as the world’s greenest heating/cooling system, with geothermal heat pumps providing a much more efficient and cost-effective alternative than conventional residential systems. Today, research shows that “up to 95% of geothermal system owners would recommend installing such a system in the home.”

Much like the nature of geothermal energy, its advantages go a bit deeper. Not only is geothermal energy already established as a source of sustainable power, but it also has benefits in terms of job creation. Only workers with adequate training can properly harness the power of geothermal energy. Renewable energy engineers are thus in great demand, ranging from the need for more chemical and electrical engineers to mechanical and industrial engineers. 

Cons

Even though it would be ideal if geothermal energy came with no strings attached, this isn’t the case. One major concern around geothermal energy, as articulated by GreenMatch, is in regards to its extraction — often, the extraction of geothermal energy “leads to a release of greenhouse gases like hydrogen sulfide, carbon dioxide, methane and ammonia.” While this shouldn’t be ignored, it is worth noting that the amount of emissions from geothermal energy extraction is still significantly lower than that of fossil fuels. 

Scientists have acknowledged this and taken steps to find a viable solution in the form of a binary plant — a geothermal plant that passes hot water by a secondary fluid with a much lower boiling point, This causes the secondary fluid to turn to vapor and turn the turbines for extraction, resulting in virtually no emissions through the process. The Office of Energy Efficiency and Renewable Energy predicts that a massive chunk of geothermal electricity in the future will come from binary plants.

Another limitation of geothermal energy is the initial cost required for geothermal exploration. While geothermal energy has the potential to save money in the long run, the initial capital needed to build a plant and harness it can be quite prohibiting in nature. This, paired with the lack of government buy-in makes for a pretty big hurdle to overcome. For instance, both Texas (USA) and Chile have been identified as potential areas in which geothermal energy would be very advantageous, but these opportunities have not been capitalized upon due to the aforementioned obstacles. 

However, as illustrated by Greenmatch, if governments were to buy into geothermal energy as is with the case of Iceland — where almost the entire country runs on it - this obstacle could be overcome. The US government has recently chosen to take a page out of Iceland’s book, by agreeing to set aside a significant amount of funding towards geothermal exploratory research. This is a small step, but definitely one in the right direction. 

The Way Forward

There’s no doubt that geothermal energy shows a lot of promise for our common future. Yes, it does come with limitations, but so far, these are outweighed by its benefits. While geothermal energy isn’t flawless, it must be recognized that it makes for a much better alternative to the fossil fuel-supported course we currently find ourselves on.

Indiana  Lee's picture

Thank Indiana for the Post!

Energy Central contributors share their experience and insights for the benefit of other Members (like you). Please show them your appreciation by leaving a comment, 'liking' this post, or following this Member.

Discussions

Matt Chester's picture
Matt Chester on Feb 19, 2020 1:08 pm GMT

This, paired with the lack of government buy-in makes for a pretty big hurdle to overcome.

Seems like a shortsighted failure to buy-in; even with the challenges you outline, the long-term outlook of geothermal plants in areas where the resource is plentiful is hard to deny. 

Roger Arnold's picture
Roger Arnold on Feb 19, 2020 9:07 pm GMT

Indiana, you should be aware that there are many different forms and sources of geothermal energy, and many different ways of using it. The technical and economic considerations vary widely over different cases. One thing I think we would agree on, however, is that geothermal is a clean energy resource that is not presently being utilized at its potential.

.. In fact, geothermal energy is recognized as the world’s greenest heating/cooling system, with geothermal heat pumps providing a much more efficient and cost-effective alternative than conventional residential systems.

The kind of geothermal energy you're referring to there is quite different than what people usually think of when they hear "geothermal energy". It really has nothing to do with pockets of hot rock and steam beneath the surface of the earth. It's just ordinary dirt or rock being used to provide thermal ballast for a heat pump. The efficiency of heat pumps is sensitive to the temperature difference between heat source and heat sink across which the pump is moving thermal energy. Having a large thermal ballast at moderate temperature from which heat can be drawn (for winter heating) or injected (for summer cooling) does indeed allow a heat pump to operate with high efficiency. The issue is the initial system cost.

For the kind of geothermal energy that people think of for power production, there's still a range of resource types, with different considerations that apply to each. That's a bit much to get into here, but I certainly do agree with your conclusion:

While geothermal energy isn’t flawless, it must be recognized that it makes for a much better alternative to the fossil fuel-supported course we currently find ourselves on.

 

Indiana  Lee's picture
Indiana Lee on Feb 25, 2020 6:04 pm GMT

Thank you for your input Roger, I have been reading yours input, Matt's and Gary's as well. This discussion is great and I second what Matt stated that your details on what actually makes geothermal energy viable in the areas it is prevelent are very wide factors!

Gary Hilberg's picture
Gary Hilberg on Feb 21, 2020 3:58 pm GMT

Indiana - I was fortunate to be part of a company, TAS Energy that developed a very (relative to other solutions) efficient super critical ORC solution for heat to power applications - we did sucessfully install over 100 MW of facilities in the US & Turkey, most of which are still running well.  The challenge for ORC is the very low conversion efficiency of heat to power, the efficiency gets much lower as temperatures decrease - so even the best US ORC resources are around 10-15% efficient and the low hot water temperatures outside of the traditional geothermal development areas are as low as 6%.  Also the costs/risks of drilling and production are high (vs. wind & solar - well known) - so most US geothermal plants need long term PPA's of over 10 cents per KWH - vs. Solar and Wind at 5 cents +- AND the facilities take many more years to develop and build.  The comparison to Iceland is not good, as Iceland has very high temperature geothermal resources so their conversion efficiency is 20+ % - thus very competitive costs.  In addition, their renewalbe alternatives (other than hydro) are not as good as ours.  Direct heating is a great option but the heat user needs to be ontop of the geothermal resource - so opportunities are less here in the US - while Iceland need more heat and resources are closer.  It would be great for geothermal to work in the US - but unlikely due to better alternatives - even ones which are not base load like geothermal.  

Matt Chester's picture
Matt Chester on Feb 21, 2020 4:47 pm GMT

 It would be great for geothermal to work in the US - but unlikely due to better alternatives - even ones which are not base load like geothermal.  

Interesting, Gary-- so you're saying it's not just a lack of the favorable geography across the U.S. that keeps geothermal more limited, but even in areas of the country where the natural availability of geothermal exists under the surface, it still might not be the best option in those places? I had always figured geothermal was uniformly advantageous for those who could take advantage, but it's interesting to hear that even in those places there can still be better alternatives (depending on how you weigh various factors like price, carbon intensity, etc.)

Roger Arnold's picture
Roger Arnold on Feb 21, 2020 11:33 pm GMT

The specific problem with low thermal efficiency for power production is that it translates to high capital cost for the facility per megawatt of power output. The cost of capital renders new facilities uneconomical. Uneconomical, that is, in relation to competing resources that are available. On the other hand, once a facility has been built, its cost of construction is "sunk"; if construction costs can be written off, the O&M costs for the facility are low enough that the facility can deliver low cost clean energy for many years...

But not indefinitely. The heat reservoirs that a geothermal well taps do deplete. If operations are suspended for a decade or so, the reservoir will usually renew itself. But the renewal mechanism is heat flow from surrounding rocks. That's a slow process. More commonly, new wells are drilled to tap new portions of the heat reservoir. But if the heat reservoir is in a deep bedrock formation, new drilling can be very expensive.

As energy resources just for power production, there are few known geothermal fields -- on land -- that are worth the cost of developing. The really good ones close to the surface tend to advertize their presence with steaming hot springs and gysers. For the most part, those that aren't in protected areas (think Yellowstone) have already been found and tapped.  There are extensive regions where the geology dictates that large heat reservoirs should be present at accessible depths, but detailed surveys to identify fields that might be economically exploited have not been conducted. The incentive to search is small, because any field that isn't near enough to the surface to advertise its presence will at best be marginally profitable to develop.

The situation changes if one is looking for more than just power production.  There is substantial new geothermal development planned near the Salton Sea. Even though the region hosts a very high quality geothermal resource, power production is only half of the economic case for development. The geothermal resource in this case resides in brine-saturated sedimentary deposits. The brine is rich in mineral content, including lithium salts. So alongside power production, the wells will be used for lithium production. Waste heat from power production will be used to concentrate the brine for mineral extraction and limited production of fresh water. It's all about synergies.

Matt Chester's picture
Matt Chester on Feb 24, 2020 12:49 pm GMT

Even though the region hosts a very high quality geothermal resource, power production is only half of the economic case for development. The geothermal resource in this case resides in brine-saturated sedimentary deposits. The brine is rich in mineral content, including lithium salts. So alongside power production, the wells will be used for lithium production. Waste heat from power production will be used to concentrate the brine for mineral extraction and limited production of fresh water. It's all about synergies.

This is fascinating-- thanks for sharing, Roger. While it sounds extremely valuable and obvious for this specific scenario, it certainly goes further to show how not-scalable that is to other areas that almost certainly don't have the same benefits. 

Gary Hilberg's picture
Gary Hilberg on Feb 24, 2020 7:18 pm GMT

There are companies looking to "mine" the geothermal water.  This material adds value but also makes the heat removal very difficult due to contamination from the minerals so it will always be small scale.  Matt - actual where the geothermal resource is good - the best US resource is actually North of San Francisco - it can make sense to export it.  These plants were actually running out of water, not heat, until they started injecting grey water around the field and production returned pretty well.  Roger is right, the best resources tend to display on the surface.  Japan, Indonesia, East Africa, Turkey and Iceland have active developments.  

Get Published - Build a Following

The Energy Central Power Industry Network is based on one core idea - power industry professionals helping each other and advancing the industry by sharing and learning from each other.

If you have an experience or insight to share or have learned something from a conference or seminar, your peers and colleagues on Energy Central want to hear about it. It's also easy to share a link to an article you've liked or an industry resource that you think would be helpful.

                 Learn more about posting on Energy Central »