Why We Should Be Discussing Geothermal Energy for a Net Zero Future
By Jane Marsh
The 21st century has seen a rise in renewable energy initiatives worldwide. Fueled by growing awareness of climate change issues and the dependence on fossil fuels, many countries prioritize finding ways to use sustainable power.
While solar, wind and water power are the biggest renewable energy resources, there’s another option underneath the ground, waiting to be tapped further: geothermal. It has the potential to help the world reach net zero emissions.
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What Is Geothermal Energy?
Geothermal energy uses the Earth’s heat as a renewable energy source. The planet’s core reaches temperatures of 9,000 degrees Fahrenheit. This heat is distributed throughout the mantle of the Earth and gets trapped in rock formations. Harnessing these pockets of warmth is the basis of using geothermal as a renewable energy source.
Like solar and wind power, the act of using geothermal energy produces no harmful emissions. In addition, geothermal energy can be used by residential and commercial buildings with specialized installations.
How Much Geothermal Energy Is the World Using?
Geothermal energy usage worldwide has been steadily increasing — reaching 15.6 gigawatts of power in 2021. The countries leading in geothermal energy usage are the U.S., Indonesia and the Philippines. These nations have the most significant power plants installed and produce the most power globally.
Those numbers might seem impressive, but other studies show that the U.S. has tapped less than 0.7% of geothermal energy resources, although it’s one of the leaders in usage.
This implies that geothermal resources are much vaster than they appear. In the same study, the U.S. Department of Energy states that there are enough geothermal resources to power 10% of the U.S. electrical capacity — 40 times more than currently installed.
How to Harness Geothermal Energy
Harnessing geothermal power requires finding energy sources by either drilling into the ground or using existing openings such as geysers and hot steam vents.
The typical geothermal power plant is designed to use heat to turn water into steam. This steam is pressurized and travels through several pipes to power turbines, producing electricity. There are three types of geothermal power plants currently in operation.
Flash Steam Plants
Flash steam power plants are the most common types of geothermal plants. They harvest underground pockets of water heated to temperatures over 360 degrees Fahrenheit. The hot water is sucked into pipes, becoming highly pressurized, and turned to steam.
This newly formed steam travels through the plant’s turbines, producing electricity. Afterward, the steam is looped back through another series of pipes until it turns into water. The water is returned to the reservoir to cycle through the system again. The speed at which this process happens is called flash steam.
Dry Steam Plants
Instead of using pockets of superheated water, dry steam plants utilize underground steam caverns. These plants pipe the steam from the source to power turbines like flash steam plants.
However, large pockets of underground steam are extremely rare. There are only two known sources in the U.S.: The Geysers in Northern California and Old Faithful at Yellowstone National Park. However, Old Faithful is preserved as a national landmark, so The Geysers is the only one available.
Binary Steam Plants
Binary steam plants are the newest generation of geothermal energy production. They operate using underground water sources at temperatures below 360 degrees Fahrenheit. Rather than turning the water into steam, these plants use it to fuel a heat exchanger system.
Hot water is piped up from the reservoir to boil a working fluid. This fluid has a low boiling point, quickly turning into vapor. This vapor is then sent through another pipe system, pressuring and sending it through a turbine.
The main benefit of using this type of configuration is that it is much more flexible regarding location. While finding the right resources to power dry and flash steam plants can be challenging, binary steam plants can use lower-temperature resources to produce the same amount of electricity.
This means less time finding steam or water at the right temperature and less drilling, which can destroy the surrounding environment.
Residential Geothermal Systems
Geothermal energy can also be used in heating and cooling systems for residential buildings. This is not a new process — people have been using it as far back as 10,000 years ago. A ground source heat pump can be installed in buildings on top of a geothermal energy source.
The geothermal HVAC system will store refrigerant underground in winter, where it becomes warm. When the inside of the building gets too cold, the refrigerant travels through the system, pressurizing it into gas. This gas powers a condenser, which heats the building’s interior.
In hotter seasons, the system works to cool buildings instead. When the interior gets too hot, the refrigerant travels through the condenser, which cools the air. The refrigerant is cycled back underground to cool off. The difference is that the liquid is not pressurized and remains cool.
Using residential geothermal systems has a wide range of benefits. They significantly reduce the harmful emissions a home can emit and are also an excellent way to save money on heating and electric bills.
Geothermal Energy for a Net Zero Future
Geothermal is becoming a big player in the race to find more renewable energy sources. It’s more difficult to harvest due to the need to drill and build specialized plants, but it’s one of the few sustainable resources unaffected by outside factors such as weather. As technology improves, people will find more efficient ways of utilizing geothermal energy.