How Geothermal Energy Works

If only we could harness the sheer power of the Earth itself to power our human societies! In a clean, healthy and renewable way, of course. 

From wind energy to hydrogen fuel cells to solar power, lithium energy and more, scientists and engineers all over the world are brainstorming ways to generate electricity from renewable and naturally-occurring energy sources. 

One of those ways is to use the same kind of energy that caused Mount Vesuvius to annihilate Pompeii, Mount St. Helens to halve its height and, eventually, Yellowstone to erupt and possibly end the world as we know it. 

Geothermal energy.

The Earth has been generating heat deep underground for as long as our little ball of rock has been orbiting the sun, and all that intense pressure and heat has the ability to do anything from creating the Hawaiian islands to forming the Rocky Mountains to making the diamond on your engagement ring — and, more recently, powering your home!

Here’s how humans are harnessing the power of the Earth to generate a type of clean, renewable energy that may one day provide power to your city!

All you need to know about geothermal energy

Types of geothermal energy production 

Conventional geothermal energy

This type of energy production uses steam or hot water that is naturally found underground. There are three main kinds of processes that draw these hot fluids from underground: dry steam, flash steam and binary cycle processes. All of them follow a similar system.

First, a well is drilled deep underground (as in, a few miles deep!) to access the water or steam. The water and/or steam is brought up to the surface, where the steam is used to turn blades in a turbine. The blades are attached to a rotating shaft (a rotor) which has a ring of magnets attached to it. This rotor spins around within a copper coil housed in the generator and, as the magnets spin around, an electric current is created between the stationary coils and the rotating magnets. 

That electric current heads down to a transformer that converts the current into a more transmissible current, and from there it heads out to a power station or other location on a power grid!

You may recognize this process from the one used in generating wind energy — and that’s because it is! Rather than using wind to turn the turbines, hot steam is the driving force behind the movement.

Enhanced geothermal systems

This other major type of geothermal process is a little more complex in how the heat is extracted from the ground. 

An enhanced geothermal system (or EGS, as it’s called) is used when there is no source of underground hot water or steam, but there are still pockets of heat that are accessible.

First, two holes are drilled into the ground not too far from each other. Once the holes are drilled, engineers use hydraulic fracturing to create cracks in the rocks between the two holes. Water is injected into the first hole and, as it descends further into the hot pocket, it starts to warm up and get hot. A suction pump attached to the second hole draws the water through the cracks between the two holes and brings it back up to the surface, by which point the water has picked up plenty of heat from the hot rocks. 

Once on the surface, the same process used in conventional drilling is used to convert the hot water and steam into electricity.

Easy peasy, huh?

Where are geothermal wells located?

Ideal environments for drilling geothermal energy wells are those with high heat flow from the Earth's interior. These environments are typically found near tectonic plate boundaries, where the Earth's crust is fractured and allows heat to escape.

Some of the ideal environments for drilling geothermal energy wells include:

Volcanic areas: Volcanic areas are ideal for geothermal energy production because they are associated with high heat flow from the Earth's interior. 

Geothermal fields: Geothermal fields are areas where hot water or steam is naturally found underground. 

Hot springs: Hot springs are areas where hot water flows naturally to the surface.

Places like these exist all over the world, but not all of them are necessarily great for establishing a geothermal energy well. There’s a lot of other factors that may make these theoretically-ideal locations practically impossible.

First is the depth of the well. If drills can’t make it to the heat source or the terrain is too difficult to drill at all, then the well can’t work. There’s also the permeability of the rock itself, since certain types of basalt, granite, limestone and gneiss are too hard or too impure to drill through at all. This is especially tricky, since most areas of volcanic activity have high quantities of such rocks. 

Finally, there’s the temperature of the geothermal resource. If the pocket of heat isn’t strong enough, then drilling an energy well there could be using more energy than it’s getting in return.

Don’t let that discourage you, though! Scientists and geothermal engineers are able to find ideal spots for drilling geothermal wells in locations all over the world! The United States leads the pack with geothermal wells concentrated all over Utah, Nevada and California. There are also wells in Indonesia, the Philippines, Iceland and New Zealand, all of which use the energy generated from these wells to heat buildings and generate clean electricity!

Fun fact: Iceland is 100% powered by renewable energy, 30% of which is geothermal power!

Pros and cons of geothermal energy

As with any kind of energy source, both clean and dirty, there are pros and cons — and all of them will impact the environment negatively in some way (just take a peek at what lithium mining does, for example!).

The benefits of geothermal energy are vast. It’s renewable (there will always be heat deep underground), it’s reliable (the heat source can be used 24/7), it’s low cost (geothermal heat is free) and it’s a great resource for domestic energy markets. It’s also able to generate large amounts of energy from a relatively small footprint, and the different production methods mean the process isn’t limited to a specific geographical profile.

Plus, steam doesn’t release greenhouse gasses, so there are fewer pollutants generated as a result!

Of course, there’s also the cost of the equipment and drilling procedures to take into account, both of which are expensive and costly to install and repair. There are also concerns with collecting the water used in enhanced geothermal system energy production, as using water from the surrounding area can negatively impact the local environment. 

And finally, while geothermal heat occurs naturally all over the world, some locations just don’t have the right conditions to mine for geothermal energy. All this doesn't mean geothermal energy plants are bad, it just means that it’s not equally accessible or realistic across the globe. 

All in all

Geothermal energy is another answer to humanity’s problem of dwindling energy sources. It may not be the only answer, it may not be the right answer and it may not be the most sustainable answer — but right now, it’s helping power millions of homes around the world using just the heat from deep in the Earth’s crust.

And that’s just really pretty neat, isn’t it?

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Featured photo courtesy Pixabay/WikiImages