How Does Geothermal Energy Work?
There is a power source underneath the earth’s surface that is not usually talked about – geothermal energy. Geothermal is a pool of water heated by molten rocks that are commonly known as magma. Geothermal energy is great at producing electricity or heating and cooling the home. But how does geothermal energy really work? Read on to find out more. Also, check out our illustrations for better visualization.
More than 80 countries have keyed into this energy, and according to the Geothermal Energy Association, the United States is the leading country of these countries. Following the US on the list of the leading countries in geothermal plants are Turkey, Indonesia, and Kenya. Other countries are also making efforts to venture into geothermal plants, having seen its efficiency.
This is to show how beneficial geothermal energy is. Now, let’s get into answering the question: how does geothermal energy work?
How Does Geothermal Energy Work?
How this system works depends on the type. Geothermal energy plants are of three types based on how they generate power. Though they are similar, there are slight differences between how each system generates power.
Geothermal Dry Steam Power Plant
These are more common than other geothermal plants, as they account for more than half of the total number of installed geothermal plants. The system generates power by piping hot steam into the turbines.
This steam is generated from the geothermal reservoir located deep below the ground. The steam is needed to power the turbine and condenses to water after performing this function. The water is directed back to the earth through an injection well.
Geothermal Flash Steam Power Plant
While the dry steam system works by pumping hot steam from the geothermal reservoir, the flash steam system pumps hot water to the surface. This pumping takes place at high pressure, and the flash tank converts the water into steam.
The steam powers the turbine and is later condensed back to water. Similarly to the dry steam system, the water is sent back to the ground through an injection well.
Geothermal Binary Cycle Power Plant
While the other two types of geothermal systems work by powering the turbine directly by the steam from the ground, the binary system works by heating another liquid (in the exchanger). Isobutane is the most commonly used liquid for this purpose, as it boils at a lower temperature than water.
When heated by the hot water from the ground, the Isobutane liquid converts into steam to power the turbines. Once the hot water from the ground is through heating the Isobutane liquid, it is condensed and sent back into the ground through the injection well. The Isobutane liquid is sent back into the exchanger, recycled, and reused for another cycle.
Geothermal Heat Pumps
To answer the question of how does geothermal energy work, it is important to discuss geothermal heat pumps as well.
A geothermal heat pump comprises different sections through which heat can be transferred from underground to the building or the other way round. Geothermal heat pumps make it possible to utilize the hot temperature under the ground to power homes and businesses. While the temperatures above the earth’s surface fluctuate, temperatures below the earth’s surface are comparatively stable throughout the year, fluctuating only between 50˚F – 60˚F (10˚C – 16˚C).
Geothermal heating pumps are mainly classified into two categories: closed-loop and open-loop. Which one is best for a home or business depends on the available type of soil, climate conditions, and land.
Also Read: How Does a Heat Pump Work?
Closed Loop Geothermal Heat Pumps: Horizontal and Vertical
The closed-loop horizontal system consumes more land than the closed-loop vertical system. Hence, while the closed-loop horizontal system might be a great choice for residential buildings for its low cost, the closed-loop vertical system is more chosen for commercial buildings as they consume less land. One means to reduce the cost of a close loop system is to construct it under a pond or lake.
A closed-loop system works by circulating an antifreeze mixture through a piping system located underground or under a body of water. Since the temperature underneath the earth’s surface is always warmer than the temperature above the earth’s surface in the winter, this antifreeze is heated and circulated in the building through ducts.
In the summer, the system circulates an antifreeze mixture in the building through a heat exchanger. This lets the liquid absorb heat from the building into the water or earth. This means the system can function as a heater or AC, depending on the season of the year.
Open Loop Geothermal Heat Pumps
While the closed-loop systems circulates an antifreeze mixture to transfer heat, the open-loop system circulates water directly from a source.
This means that an open-loop system pumps water from a water source through the piping system. The water is later directed to the same source or another water source. The water circulating in the system performs the function of transferring heat from one end to the other.
An open-loop system is considered cheaper compared to its counterpart closed-loop system. However, an open-loop system requires a constant supply of water to function.
All geothermal heating systems generally work on the temperature differences between the earth’s surface and the underground. However, they have different efficiency levels and costs of installation.