What is Geothermal Energy?
Geothermal energy, in a narrow sense, refers to the energy contained within the Earth, originating from the sun. Broadly, geothermal energy refers to renewable thermal energy that comes from the Earth’s molten magma and the decay of radioactive materials. The English term for this is geothermal energy.
Categories of Geothermal Energy
Geothermal resources can be categorized by temperature:
- High-Temperature Geothermal: Above 150°C
- Medium-Temperature Geothermal: Between 90°C and 150°C
- Low-Temperature Geothermal: Below 90°C
In terms of total resources, medium and low-temperature geothermal resources are most prevalent in China. Based on storage forms, geothermal resources can be classified into steam type, hot water type, ground pressure type, lava type, and dry hot rock type.
Advantages and Disadvantages of Geothermal Energy
Advantages:
- Renewable
- Widely distributed
- Abundant reserves
- Low unit cost
- Short construction time for geothermal plants
Disadvantages:
- High capital investment
- Geographically limited
- Low thermal efficiency (only 30% of geothermal energy is used to drive the turbine generator)
- Outgoing hot water contains high mineral content
- Some toxic gases released with the heat can cause air pollution
Current Utilization of Geothermal Energy
20°C – 50°C:
- Bathing
- Aquaculture
- Raising livestock
- Soil heating
- Dehydration processing
50°C – 100°C:
- Greenhouse heating
- Domestic hot water
- Industrial drying
100°C – 150°C:
- Heating
- Cooling
- Dual-cycle power generation
- Canned food production
- Dehydration processing
- Salt recovery
100°C – 200°C:
- Dual-cycle power generation
- Refrigeration
- Industrial drying
- Industrial thermal processing
200°C – 400°C:
- Direct electricity generation
Comprehensive Utilization of Geothermal Energy
Direct use of geothermal energy includes heating, hot water supply, and hot spring health preservation. This method is the second most common utilization of geothermal energy after geothermal power generation.
A ground source heat pump is a high-efficiency and energy-saving air conditioning system that uses shallow underground geothermal resources for both heating and cooling. It transfers heat energy from low to high temperatures by inputting a small amount of high-grade energy.