How does geothermal energy work?

What is Geothermal Energy?

A turbine of a certain size is required to achieve Geothermal Power Capture. It is the spinning of the turbine that delivers the energy from the Earth's hot fluids. This creates steam. Sometimes, the expansion of secondary working fluids is caused by the heat from underground, to give rotational and mechanical energy to turbine blades. By using electromagnetic induction heat can be converted into electricity.

Electrical power can be generated by converting the energy in the soil. After that, electricity has to reach the powerlines. For this to occur, a power transformer will be installed somewhere downstream from the generator. Often, it is outside the plant.

Geothermal powerplants are not like other types of plants

Main difference: additional heat does not need to be added. A natural process, called hydrothermal evaporation, occurs when geothermal water reservoirs in the ground heat up and warm down underground. It is not necessary to use boilers or fuel for heating. Extracted water ranges between 220degF to 600degF. Also, plants have rock catchers. Other substances can also surge upwards, including hot fluids. Rocks reaching the steam generators could cause serious damage, rendering the facility inoperable. In order to prevent this, they install filters.

Use of different geothermal plant types

• Dried Steam: Water-vapor reservoirs are located beneath the plant. A turbine is fed steam that has a temperature of 300degF or more from the production wells. This is not only the most rare type of power plant but also the oldest. A plant was built by Italians in 1904. California hosts the U.S.'s current plant.
• Flaming Steam: Within the flash tanks, water as hot as 360degF will instantly be vaporized. The pressure is lowered and the turbines are moved. In 1958, New Zealand built the world's first flash-steam plant. Today, it is one of the most common types of geothermal plants.
• Binary Cycle: Using water temperatures as low at 135 degrees Fahrenheit, binary cycle systems use binary fluids that turn to steam as soon as they come into contact with the thermal energy of reservoir water. Fluids do not mix. Heat exchangers are used instead to allow the exchange of thermal energy. Injecting the ground water into the ground will recoup the thermal energy. This variation is growing in popularity as geothermal resources are available with more moderate water temperature.

Geothermal Energy and Cogeneration

The geothermal plant efficiency rate is generally very low. They never exceed 23 percent and are sometimes even lower than 10 percent. As long as fuel isn't used, it doesn't affect the operation of a plant. Plus, the use of byproducts that contain thermal energy, like warm water from exhaust, or heat generated during combustion, can increase overall efficiency.

The use of heat pumps that are based on the ground is another option. Over the course of a year, the temperature is around 50degF not too far beneath the ground surface. The air or antifreeze can then be circulated back through buildings by pumping it into pipes. Buildings can lose heat in the summer while bringing it in during winter.

Preparing Water for Re-Injection

Three main methods are used to cool the water down after use. Water cooling is the best way to handle super-heated Steam. The fluid may contain minerals or solids that must be filtered. If not, it will put more stress on the heat-exchanger and require additional maintenance. A condensing device consists a of hot wells, tubes sheets, flanges along with a water supply and outlet. Heat exchange systems convert steam or vapor from turbines back to water.

A larger space is required for air cooling compared with water cooling. But it's often the better option in cases where there's not enough available water. The air-to liquid heat exchanger is powered by ambient air. Meanwhile, a fan boosts the air flow. Like a car's radiator, it works. Condensers that are air-cooled require only the power to run the fan.

When the plant is operating in a climate with a relative dry and cool temperature, hybrid cooling is possible if some form of cooling water is readily available. To remove the heat, evaporative coolers use air and/or water. It uses less water. The cooling towers are designed to allow the air to pass over the water. In this way, the water in the cooling tower evaporates. Meanwhile the steam coming out of the turbine will condense into liquid. In order to replace the water lost through evaporation (which is less than five percent), extra water must be added.

Geothermal Energy Available Where?

It is only possible to operate geothermal energy plants in areas where heat exists below the surface. It's usually in seismically-active areas where there is a steady supply of heat, from the ground up to thousands feet deep. Most of the geothermal heating in America occurs along the western edge of the Rocky Mountains. Plants which use milder heating for direct heat draw their resources closer to the ground and do not necessarily have to be close to volcanoes or geysers.

Enhanced Geothermal Systems, which are not the same as traditional geothermal, can extract energy from a broader range of rock types. They are, however, still in a developmental phase. In 2013 demonstrations in Australia and America generated electricity. The U.S. National Renewable Energy Laboratory Study noted the high-potential of hydrothermal conventional sources. Research also showed that hot dry rock can be used to supply more electricity than is currently needed in the country.

Sources:go-green-solar-energy.com, energyinformative.org, Energy.gov, Open EI, USC USA