The ancient Roman baths are perhaps one of the most famous uses in history of geothermal energy, where the hot water that heated the baths from underground geysers were said to have healing properties. But geothermal energy has been used for centuries before the Romans, with the oldest known use by humans dating back almost 10,000 years ago to the Paleo-Indians, who used the hot springs for cooking, warmth, and bathing.
Since then, geothermal energy has had a rich history. From the early days where settlers stumbled upon geysers and believed they had found the very gates of hell to the first residential use of the hot water as a heating system to the very first geothermal plant constructed.
That very first geothermal plant was built in the United States in 1960 by the Pacific Gas and Electric Company in California. The site is called The Geysers, and is still in production today as the largest geothermal development in the world 1. See the picture to the right.
What Is Geothermal Energy?
Geothermal literally means “earth’s heat,” and is used to describe the heat that comes from the earth’s interior. This heat is generated in the earth’s very core, 4,000 miles below the earth’s surface and seeps up through faults and cracks in the earth’s surface.
Once it reaches the surface, the heat is released naturally in the form of volcanoes, hot springs, and geysers. Depending on the geology, we can access this heat by drilling into the earth’s surface or tapping into the hot springs.
The most active site of geothermal energy is in the Pacific Ocean in a place called The Ring of Fire. In the United States, geothermal activity can be found mostly in the western states, including Alaska and Hawaii, with California leading the world in geothermal energy production 2.
How Do We Get Electricity from Geothermal Energy
Geothermal energy is converted into energy at geothermal power plants. These power plants are built above geothermal reservoirs. There are three main types of geothermal power plants.
The first type of geothermal power plant is called a Dry Steam Power Plant. This reservoir produces a dry steam that forces the turbines of the generator to spin. The largest dry steam power plant is in California.
A hot water reservoir produces hot water at a Flash Power Plant where water is between 300 and 700 degrees F. This water is brought to the surface and then produces a flash steam that powers the turbines.
The third and final geothermal reservoir is called a Binary Power Plant. This is where water that is not hot enough to create steam, somewhere between 250 and 360 degrees F is transferred into another liquid that allows it to boil at a lower temperature than just water. This liquid produces a vapor that powers the turbines 3.
Advantages to Geothermal Energy
There are many advantages to using the natural, renewable power of geothermal energy. The first and foremost is that this power source provides clean reusable energy. There are no fossil fuels that are burned and so the emission levels are extremely low, less than 1 percent of the carbon dioxide emissions of a plant that burns fossil fuels and 97 percent less hydrogen sulfide, the key culprit of acid rain.
Geothermal plants are also extremely reliable sources of power unlike other renewable energy sources. Unlike solar that depend on the weather and the time of year and day, geothermal power is available 24 hours a day, 7 days a week. As long as the earth continues to produce heat, we will have access to this potent energy source.
They also have a minimum impact on the land as well, not requiring river dams or the harvesting of limited resources. There are no waste heaps or oil spills and they have a smaller impact on the land than almost any other conventional power plant.
Additional Applications of Geothermal Energy
While harvesting geothermal power for electricity is one way to tap into this resource, there are other more direct applications that can be used almost anywhere, since the temperature just a few feet below the earth’s surface tends to be between 50 to 60 degrees F.
Since the early 1900s, hot water from hot springs has been piped into homes to provide natural heating. Space heating used to heat homes and even whole distracts pumps geothermal water directly into the buildings providing a natural source of heat. The largest and most prominent of these geothermal district heating systems is in Reykjavik, Iceland, now one of the cleanest cities in the world thanks to geothermal energy. It supplies the city with heat to more than 95% of the buildings 4.
In Klamath Falls, Oregon, they even pipe hot water under roads and sidewalks to keep them from icing over in the winter. Geothermal heat pumps are the most energy-efficient, cost-effective, and environmentally clean systems for temperature control according to the EPA.
Geothermal energy is also used in agriculture where hot water is piped under soil where flowers and vegetables are growing. This hot water ensures that the ground doesn’t freeze and thereby protects the crops from sudden temperature changes and gives the farmers a longer growing season.
How Geothermal Energy Measures up
While geothermal energy has been a proven source of clean energy, how cost-effective is it really? A recent article in Scientific America says that geothermal power is now cheaper than any other resource including coal in terms of cost per kilowatt-hour 5!
Also, because it is a renewable resource, it’s not susceptible to price fluctuations like oil and natural gas. The primary costs involved is in the exploration and drilling of the reservoirs, since our technology as of yet, cannot locate where these pockets are hidden under the earth’s surface.
Worldwide usage has increased of geothermal energy, with the United States leading the pack in geothermal energy production, followed by the Philippines, Indonesia, Mexico, Italy, and Japan. More than 70 countries in all produce some form of geothermal power 6.
With this source of clean energy literally sitting underneath us, waiting for us to tap into its valuable resources, geothermal energy is a renewable energy source that requires further funding and exploration to truly fulfill its maximum potential.