What Is Geothermal Energy

Wondering what is geothermal energy?

Geothermal energy is heat energy created from the centre of the Earth. In turn, geothermal electricity uses heat from the Earth’s core to generate electricity.

This form of energy is considered a sustainable and renewable source of energy because the amount of heat extracted from within the Earth in the process is actually only a small fraction of the heat content of the Earth’s core.

In geothermal industry terms, low temperatures refer to temperatures of 149 °C or less.


What is geothermal energy created from

The earth is designed with a layer, known as magma, lying directly beneath the crust of the earth. The magma comprises of hot molten on which the earth’s crust floats. If the magma penetrates the crust, breaking through to the surface of the earth, it forms what we call molten lava.

The temperature of the magma varies depending on how deeply you penetrate below the earth’s crust. The temperature rises just over five degrees Fahrenheit for approximately every 300 feet deep.

This heat that is trapped beneath the earth’s crust is released to the surface of the earth when the lava or underground water penetrates the earth’s crust and emerges on the earth’s surface. This heat energy is known as geothermal energy.


What is geothermal energy – history

Who discovered what is geothermal energy?

Most people may not realize, geothermal heat has been used for thousands of years in hot baths and space heating since pre-historic and ancient Roman times. The underground water heated by the magma beneath the earth’s crust often manifests as steam as it emerges to the surface, creating what is often referred to as a hot spring.

But it was only in the beginning of the 20th century that geothermal energy started to be used for the generation of electricity.

It began in 1904, when Prince Piero Ginori Conti did his first tests on a geothermal power generator which managed to light up 4 light bulbs. Seven years later, the world’s first geothermal power plant was built. This geothermal power plant was the only geothermal power plant in the world until 1958, when a second one was built in New Zealand. The first geothermal power plant in the United States was built in 1960 at The Geysers in California and was operated by Pacific Gas and Electric.

Several technological innovations have been making geothermal energy more and more competitive as an alternative source of energy.

For example, at the beginning, geothermal power plants were only built over high-temperature geothermal sites. But innovations in drilling and extraction technology, and the development of binary cycle power plants now allow geothermal power plants to be built on much cooler sites.


What is geothermal energy -- Types of geothermal power plants

There are three types of geothermal power stations -- dry steam power plants, flash steam power plants and binary cycle power plants.

Dry steam power plants make use of the steam (heated water) that comes out of the earth to drive turbines and generate electricity. Such power plants require steam of at least 150º C to turn the turbines, which are connected to generators that produce electricity.

In flash steam power plants, water heated up by geothermal rocks is pumped to the earth’s surface at high pressures. Upon reaching the earth’s surface or entering a collection tank, the pressure on the hot water is greatly reduced, as such allowing some of the water to change to steam. This steam moves the turbines in the power plant, generating electricity. This process requires temperatures of at least 180º C. As the steam cools and condenses back into water, the cooled water is returned to the geothermal rocks for reheating.

The third type of geothermal power station is the binary cycle power plants, which uses binary cycle technology that allows these plants to operate at temperatures as low as 57º C. This system creates steam by passing the heated geothermal water through another fluid with a much lower boiling point. The latter fluid turns into steam when it comes into contact with the geothermal water, and the steam moves the plant turbines to generate electricity.


What is geothermal energy - Uses in today’s world

What is geothermal energy used for in today’s world?

Other than the generation of electricity, geothermal energy is often also used in the heating and cooling system for homes, buildings and even green houses. Though the heat pump was invented in 1852, it was not until the 1946 that the heat pump was successfully used with geothermal energy, allowing it to provide heat and cooling to buildings.

With heating systems, water heated underground is circulated through heat pumps. Heat is extracted from the heated water, and the energy is used to heat up homes and buildings. Although electricity is needed in the heat extraction process, the energy produced at the end of the process highly outweighs the energy used.

In fact, the U.S. Environmental Protection Agency (EPA) considers such geothermal heat pumps to be most eco-friendly, cost and energy efficient space conditioning systems, especially if the electricity used in heat extraction process comes from renewable energy sources. And according to the United States Department of Energy, geothermal heat pumps can help consumers save hundreds of dollars in energy costs each year. Though expensive, these systems pay for themselves in a few years. Today, it is estimated that more than 600,000 American homes and buildings have heating supplied by geothermal heat pumps.

Geothermal energy is frequently used in Iceland. The western states within the United States, including Alaska and California also use geothermal energy. In fact, California has had the largest amount of geothermal capacity in the United States, since the state is located on tectonic plate conjunctions. Read more about alternative energy companies.

The use of geothermal energy from the northern California area started since the early 1960s. From 1981, California has had a program directly supporting geothermal energy. The project includes financial assistance for any businesses or projects in support of geothermal energy research or development. California is now responsible for nearly two thirds of the geothermal energy used in the United States. In the year 2007, California produced 13,000 GWh worth of electricity from the 43 geothermal plants which it operated.

Today, geothermal energy use is spreading all over the world. In 2010 geothermal energy generated 67,246 GWh (gigawatts hour) of energy, an increase of 20% when compared to 2005. According to the International Geothermal Association, there is a global 10,715 MW (megawatts) capacity spread over 24 countries today, and by 2015 this capacity is expected to reach 18,500 MW, in view of several projects under consideration.


What is geothermal energy – Advantages

What is geothermal energy good for?

As mentioned above, geothermal energy is a renewable energy source. The heat that is found in the centre of the earth occurs naturally, produced through natural processes that took place way before our time. This means that the energy source is free (we do not need to make it happen), and whether we use it or not, geothermal energy will always be produced.

Because the earth’s heat content is lots of times greater than the heat that reaches the earth’s surface, theoretically, the Earth’s geothermal supply would be more than sufficient to meet man’s needs for energy.

Although geothermal wells release green house gasses trapped in the Earth’s cores, the amount of these gases emitted are much lower per energy unit as compared to that when fossil fuels are used. Hence, geothermal energy is potentially an important energy alternative to fossil fuels, especially in our fight against global warming and climate change.


What is geothermal energy – Disadvantages

What is geothermal energy disadvantaged by?

The capital costs for harnessing geothermal energy are significant. Half of the costs arise from the drilling efforts. For example, according to Wikipedia, a plant using extraction and injection wells in Nevada that has the capacity of 4.5 MW can cost about $10 million to drill. Nonetheless, the cost of setting up different geothermal plants differs with the type of technology used. In a 2011 article in The Financial Express on Anglo MGH Energy’s efforts to build the first geothermal plant in Bangladesh, it indicated that a 200 MW gas-fired power plant can cost $150-200 million dollars, while a geothermal power plant with similar capacity can be set up at one third of that cost.

The explorataion for deep geothermal resources can involve significant risks. And this risk to lives continues even as the geothermal plants are being set up.

Conventionally, geothermal plants are located near techtonic plate boundaries where geothermal heat from the centre of the earth is able to rise to the earth’s surface. In turn, these regions near the techtonic fault lines are more prone to events like earthquakes and volcanic eruptions. Moreover, the drilling processes involved to create geothermal wells for the energy plants can also potentially trigger earthquakes through hydraulic fracturing.

Although geothermal wells can theoretically last for as long as the earth exists, care need to be taken in geothermal extraction to make sure that local depletion of geothermal energy does not take place. Over time, the geothermal heat content in the area around the well could be greatly reduced, unless time is given for the heat to be replenished.


What is geothermal energy research about?

Geothermal energy research today continues to work on improving the cost-efficiency of geothermal energy plants, as well as mitigating any adverse effects that geothermal energy plants might have on the environment. The final goal is to continually reduce the cost – financial or environmental – of harnessing geothermal energy.

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