Geothermal energy refers to heat energy stored under the ground for millions of years through the earth formation. Geothermal energy comes from various heat sources as described below.
- Low-temperatureground-basedheat sources are located directly under your feet but cannot be directly used for space heat or hot water production. Such sources use an electrical driven “heat-pump” to in effect add additional energy to the heat source by using an electrical compressor. This type of geothermal source is normally used to produce hot water that can be used for space heat and domestic or hot water production is domestic or in the building. Since the overall extraction efficiency is dependent on the temperature of the geothermal source that at your disposal, the efficiency of the heat pumpand the economics of the system will depend on various site-specificparameters that will need assessment before the decision is made to invest in the geothermal option.
- Medium temperature ground-based heat sources in the region of (50-150°C) are sometimes available) and can be used for various direct uses such as district heating and even industrial processing activities that require either hot water or even low-pressure steam that can be produced using special heat pumps design to raise the heat source temperature to over 100°C.
- Higher temperature geothermal heat sources in the region of (150°C+) are sometimesavailable that use naturally occurring hot springs and other sources that may be deeper in the earth and these sources can be used for both space heating and even power generation.
- The hot water or steam generated using a can be used to create cold water using special chemical and desiccant chillers. This cold water can be used for process cooling in industry or space cooing in buildings.
Large scale applications of geothermal energy
Dry-steam power stations
Basically, dry steam stations utilize the steam that flows out of geo-deposits to heat a secondary fluid that turns turbines to generate electricity. The steam emerges at a temperature of up to 150 degrees, hot enough to expand the fluid in the geothermal plant. This is one of the oldest techniques of geothermal electricity.
The expansion of the secondary fluid then produces mechanical energy needed for turning the turbines to generate electricity.
Flash steam power stations
Water in wells under high pressure is drawn to a region of lower pressure. This pressure shift vaporizes the water emitting steam at high temperature. This steam is separated from the water and used to heat up the fluid that turns the turbines in the generator. At this pressure, the gas is at a very high temperature.