Geothermal energy is a desirable alternative to traditional, “dirty” energy technologies based on non-renewable raw materials. In forecasted gas and oil shortages it creates potential for economic stability.
Unfortunately, obtaining it is not easy and involves some environmental losses. So, how ecological is geothermal energy, and what does its future look like in the Philippines?
The history of the use of geothermal energy is long and dates back to the Paleolithic times, when people discovered the benefits of bathing in thermal springs.
Ancient Romans in Great Britain used hot streams from underground to heat their baths, and in France in the 15th century, the first heating system based on the hottest Chaudes-Aiges springs in Europe existed and powered households. However, only at the beginning of the 20th century did interest in geothermal energy acquire an industrial dimension.
What is geothermal energy?
Geothermal energy, in short, is heat from the Earth’s interior. The temperature inside the core of our planet is up to 5,200 °C and, although it is slowly decreasing, it will remain high for billions of years. It is powered by radioactive isotopes such as potassium -40 and thorium-232, which decay to generate heat.
However, because the Earth’s crust is much colder, there is a constant energy transfer process from inside to outside. The red-hot rocks melt and create magma, which in some places pushes higher and higher towards the land surface, heating underwater streams.
As a result, rocks and water within the earth’s crust (reaching 40 km deep) reach temperatures of up to 370°C. It is, therefore, a natural source of heat that spontaneously escapes onto land in the form of volcanic lava, geysers, or the already mentioned hot springs.
The idea of geothermal energy is to reach deep into the planet and use the energy hidden there for economic purposes, both heating and electricity production.
How is geothermal energy obtained?
Geothermal potential varies in different places on Earth. In Iceland, many hot springs are reaching the land surface, and their geothermal energy is effortless to use.
In other locations, you must drill several kilometers deep to reach the optimal temperature level. Therefore, obtaining energy from the Earth’s interior depends primarily on its availability in a given area.
In the simplest scheme, low-temperature geothermal energy (approx. 150°C) is obtained directly from wells and used to heat greenhouses, breeding ponds, or houses.
More advanced technology includes heat pumps placed in boreholes at a level of up to 100 meters. The pump is connected to the surface by a pipe in which water or glycerol circulates, which transfers heat from underground to receiving devices.
In summer, the same system can act as a cooling system. Heat pumps already heat millions of homes and public facilities around the world.
High-temperature thermal waters at a depth of 3 km are used in balneology and heating plants. However, heating is not the only purpose of geothermal energy.
Energy from the depths of the Earth can also be converted into electricity, which in today’s reality is never enough. For this purpose, drillings are up to 6 km long and use high temperatures of dry rocks (approx. 200°C). It is processed in geothermal power plants operating on the principle of:
1. Dry steam
Dry steam at approximately 200°C is obtained from deep wells, which is directed to the turbine and condensed there.
2. Wet steam
Steam from the liquid bed is first recovered in the expander and then directed to the generating turbine.
3. Binary
Using an intermediary medium called a heat exchanger and a second cycle with the working medium. This is where the so-called ORC (Organic Rankine Cycle) cycle involves using an organic substance to generate steam at a lower temperature.
Binary geothermal power plants also collect heat through wells, but it is transferred to a cycle in which a low-boiling energy carrier, such as ammonia or carbon dioxide, circulates.
There, steam is produced at temperatures of up to 80°C, which further drives the turbine. Although quite complicated, this technology allows you to generate electricity even from geothermal sources with lower temperatures.
It is also worth mentioning the EGS (Enhanced Geothermal Systems) technology, which allows the use of Earth’s energy even in locations where no liquid medium can conduct heat. In this variant, water is pumped under high pressure into wells 1-5 km deep into the earth’s crust.
As a result, the rocks crack and dissolve, creating a well in which the temperature of the rocks heats the water. It can then be pumped to the surface and used in a power plant.
Interesting fact: Energy is also obtained from hot water, which is a by-product in the process of exploiting gas and oil deposits. Recovering heat from such waters is particularly important in poor, industrialized regions of the world.
Advantages of geothermal energy
Geothermal energy has many advantages, including:
1. Geothermal energy is considered a renewable energy source ( RES ). Heat in the core of our planet is created continuously and will continue to be created for the next millions of years, perhaps even more.
2. A geothermal power plant can operate continuously, regardless of the weather conditions, time of day, or season. It operates 24 hours a day, seven days a week, which makes it as reliable as a fossil fuel power plant.
3. Thermal energy can be easily used for heating but also to produce electricity depending on needs, which makes it a universal energy.
4. Geothermal energy can be accessed virtually anywhere on the planet. If there are no surface forms of geothermal energy in a given place (e.g. geysers), we will always find it under the surface.
5. The amount of thermal energy that is generated in the interior of our planet is enormous. It is estimated that we have only used less than 7% of the world’s geothermal energy potential, which means that it can provide us with a lot of heat and electricity in the future.
Disadvantages of geothermal energy
Geothermal energy is not perfect and also has disadvantages:
1. Despite access to geothermal energy worldwide, good conditions for its use exist only in certain places. The most profitable areas are those with more than twice the average geothermal gradient.
2. Even though geothermal energy is low-emission, it is still possible to emit carbon dioxide, hydrogen sulfide, and methane into the atmosphere – although this is a small percentage compared to power plants powered by fossil fuels.
3. The technology for obtaining geothermal energy is quite expensive, which makes the initial cost of the plant and the required infrastructure high.
4. Possible triggering of seismic activity in the region. There is a well-known case from Switzerland where, after earthquakes occurred, it was decided to close the local geothermal power plant.
5. Although in theory, the source of heat deep underground is infinite, too fast and excessive exploitation in one place may slow down the source.
Difference between Solar and Geothermal Energy
Solar and geothermal energy are two types of clean and renewable energy. Both have in common that they use a heat source as an energy source to generate electricity. But they also have significant differences, such as installation.
Solar energy: Characteristics
Solar energy is one of the world’s most useful and used types of clean energy. Energy is obtained directly from the impact of the sun and its electromagnetic radiation. Therefore, the energy source is inexhaustible, persistent, and non-polluting.
Its production depends on how many hours of direct sun the solar panels installed have. In the Philippines, the country has perfect climatic conditions for producing solar energy due to the very high number of hours of sunshine we have per year. There are several types of solar energy:
1. Photovoltaic solar energy: obtaining electricity directly from solar radiation using solar panels.
2. Solar thermal energy: it draws on the sun’s heat to produce energy for electricity consumption. Solar panels or collectors are designed to transform solar radiation into thermal energy.
3. Passive solar energy: it is not a type of energy as such. The orientation of buildings to have more luminosity and the impact of the sun is a form of energy since it reduces heating and lighting expenses.
Relationship of solar energy with other energy sources
Solar energy intervenes directly with other energies. Wind energy, for example, works thanks to the wind and air currents. This wind is formed when the sun heats large masses of air.
It is also part of the fossil fuel production since most plants carried out photosynthesis. The sun is also essential in hydraulic energy since without its radiation, the water cycle would not exist.
In 2021, the share of energy production through renewable sources increased by 2.7% compared to the previous year, rising to 46.7% of the total.
Geothermal energy: what is it and how does it work?
Geothermal energy is obtained by taking advantage of the heat from the planet’s interior. The energy production system is underground in areas of very high temperatures to convert that heat into energy. Earth’s soil, rocks, and seabed can store much heat.
This is an enormously usable resource because it is also inexhaustible, and although it is irregular and inconsistent, it is tremendously influential and powerful. Its production is divided according to the temperature of the resources found:
1. High-temperature resources above 150 degrees. Used to transform water vapor into electrical energy
2. Average temperature between 90 and 100 degrees. It is used for electricity production
3. Low temperature between 30 and 90 degrees. It can produce thermal energy to heat buildings and some factories.
4. Very low temperature with resources of less than 30 degrees. They are helpful for air conditioning and hot water. Its use is purely domestic or agricultural.
Comparison between solar and geothermal energy
Solar energy and geothermal energy have advantages and disadvantages that are common, and that help to make a comparison between the two at the level of development, price and generation.
Advantages of solar and geothermal energy
| Solar Energy | Geothermal Energy |
| Clean and inexhaustible | Clean and inexhaustible |
| Minimal impact | Low and cheap maintenance |
| Does not affect the environment | Safe and controllable |
| Storable, usable and accessible | Storable |
| Sustainable development | Oblivious to energy prices |
| Fossil fuel reduction | Fossil fuel reduction |
Disadvantages of solar and geothermal energy
| Solar Energy | Geothermal Energy |
| Low efficiency: 25% convertible | Very specific and complex location |
| High cost in installation | Very complicated and expensive installation |
| Minor activity for a few months | Impossibility of transporting energy |
| Pollution in large cities influences | Possibility of contamination of aquifers |
What is the most significant difference between solar and geothermal energy?
The most significant difficulty between solar and geothermal energy is the form of extraction. Solar is done using the heat produced by the Sun’s rays, while geothermal energy is done with the heat of the Earth.