Welcome to a deep dive into one of the world’s most intriguing sources of renewable energy – geothermal! The name itself might give you a hint: ‘geo’ meaning earth, and ‘thermal’ meaning heat. Yes, you got it right! It’s the heat from the earth’s core that we are talking about when we speak of geothermal energy.
This abundant and clean source of energy has been used throughout history in various forms. However, as with every other form of energy, harnessing geothermal power plant using it efficiently and effectively is key. But before we delve into how geothermal energy is harnessed, let’s understand what exactly geothermal energy is and how it forms.
Introduction
Geothermal energy is the heat that comes from the sub-surface of the earth. It is contained in the rocks and fluids beneath the earth’s crust and can be found deep down to the earth’s hot molten core. This heat energy originated from the formation of the planet around 4.5 billion years ago and from radioactive decay of materials. The amount of geothermal heat pumps within 10,000 meters (about 33,000 feet) of Earth’s surface contains 50,000 times more energy than all the oil and natural gas resources in the world!
Understanding Geothermal Energy
While the concept of geothermal energy might seem complex at first glance, it’s quite straightforward once you get the hang of it. Basically, our planet is a massive ball of heat! In fact, the further below the surface you go, the hotter it oil and gas wells it gets. This heat is always there, making geothermal energy a constant and reliable source of power. Unlike other sources of renewable energy such as wind or solar, geothermal energy doesn’t depend on weather conditions or daylight hours, making it a dependable source of energy round the clock, all year long.
As of 2021, the global geothermal power capacity was approximately 15.4 gigawatts (GW), with around 88 countries utilizing geothermal energy for electricity generation.
The Science Behind Geothermal Energy
Now that we’ve established what geothermal energy is, let’s delve deeper into geothermal power and the science behind it. It’s all about the heat from the earth’s core, but how does this heat reach the surface? And, more importantly, how do we harness it?
What Makes Geothermal Energy Possible
The earth’s core is like a giant ball of heat, with temperatures reaching up to 9,000 degrees Fahrenheit. This heat is continuously conducted from the core to the surrounding rock. Some of the heat also reaches the earth’s surface as thermal energy. This thermal energy can be harnessed and converted into electricity, providing us with a sustainable and environmentally friendly energy source full of power.
Geothermal power plants generated about 106.3 terawatt-hours (TWh) of electricity globally in 2020, providing a consistent and reliable source of energy.
The Earth’s Internal Heat Source
The primary source of geothermal energy is the earth’s core. The core consists of two parts: a solid inner core with temperatures of up to 9,000 degrees Fahrenheit and a molten outer core. The heat from the core is transferred to the mantle, which is the layer of the earth just above the core. This heat transfer leads to movements in the mantle, causing earthquakes and volcanic activity. The areas where these activities occur are hotspots for geothermal energy.
How Heat Transfers To The Surface
This thermal energy travels through the mantle and reaches the earth’s crust. At the crust, there are various geological formations like faults, fractures, and porous rocks that allow the thermal energy to seep upward. When water comes into contact with these rocks, it gets heated and rises to the surface, creating geysers, hot springs, and fumaroles. It’s this naturally heated water (or steam) that we use to harness geothermal energy.
Binary cycle geothermal power plants can achieve thermal efficiency levels of around 10% to 13%. This technology utilizes lower-temperature geothermal resources, making it suitable for a wider range of locations.
Harnessing Geothermal Energy
Now that we’ve understood the science behind geothermal energy, let’s explore how we tap into this underground reservoir of heat. The process of geothermal electricity typically involves drilling deep wells into the earth’s crust, pumping cold water into the wells, and bringing the heated water or steam back to the surface.
An Overview Of The Harnessing Process
The geothermal electricity generation process begins by identifying suitable sites for drilling. These are usually areas with high seismic activities, like the western United States, Alaska, and Hawaii. Once a site has been identified, a well is drilled into the earth’s crust. Cold water is then pumped into the well.
As the water travels down the well, it gets heated by the hot rocks. The heated water (or steam) is brought back up to the surface through a different set of pipes. This hot water or steam then powers a turbine connected to a generator, converting the geothermal energy into electrical energy.
Flash steam geothermal power plants, which use high-pressure hot water to produce steam for turbines, can achieve thermal efficiency rates of approximately 15% to 17%.
Types Of Geothermal Energy Systems
There are three main types of geothermal energy systems: Direct Use Geothermal Systems, Geothermal Heat Pump Systems, and Electric geothermal Power Generation Systems.
1. Direct Use Geothermal Systems
These systems use the thermal energy directly from the source. The hot water is pumped from the ground and is used to heat buildings, grow plants in greenhouses, dry crops, for electricity generation heat water at fish farms, and for several industrial processes.
Dry steam geothermal power plants, which use steam directly from underground reservoirs, can achieve the highest thermal efficiency, typically around 20% to 30%.
2. Geothermal Heat Pump Systems
Also known as ground-source heat pumps, these heating systems use stable ground or water temperatures near the earth’s surface to control building temperatures above ground. During winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air delivery system. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger, cooling the building.
3. Electric Power Generation Systems
These systems generate electricity by using the steam or hot water from a geothermal reservoir to power a turbine, which drives a generator. There are three types of electric power generation systems: dry steam power plants, full power plant, flash steam power plants, and binary cycle power plants. Each of these uses a different method to extract the heat from the earth and convert it into electrical energy.
Geothermal heat pumps, used for heating and cooling purposes, are known for their high energy efficiency. They can achieve efficiency levels of 300% to 600%, meaning they can provide 3 to 6 units of heating or cooling for every unit of electricity consumed.
The Future Of Geothermal Energy
With the growing focus on renewable sources of energy, the future of geothermal energy looks promising. Despite its current contribution of just 0.4% of U.S. electricity generation, its potential is vast. With technological advancements and increased funding for geothermal plants, we can expect to see a significant rise in the use of geothermal energy in the coming years.
Geothermal wells can reach depths of anywhere from 1,500 to 10,000 feet or more, depending on the temperature and pressure of the geothermal resource. The deeper the well, the higher the temperature of the resource.
Final Thoughts
Geothermal energy is a fascinating and powerful form of energy that’s available right beneath our feet. Not only is it a reliable and constant source of power, but it’s also environmentally friendly and sustainable. By understanding how geothermal power plants how it works and harnessing it efficiently, we can make significant strides towards a greener and more sustainable future. As with any form of energy, there are challenges to overcome, but with continued research and technological advancements, the full potential of geothermal energy can be unlocked.
Last Updated on September 25, 2023 by Priyanshi Sharma
