Geothermal has become established as a reliable and environmentally benign source of energy and one of the key resources in a sustainable energy future. Only a small fraction of the world's geothermal potential has been developed so far, which leaves enough room for growth and development in both electricity and direct use sectors. Geothermal energy has many advantages, especially when compared to conventional sources of energy. A few of these advantages are briefly described below [1], [2].
Renewable energy source
Geothermal resources consist of thermal energy from the Earth's interior stored in both rock and trapped steam or water. With appropriate resource management, the tapped heat from an active reservoir is continuously restored by natural heat production, and the extracted geothermal fluids are replenished by natural recharge and by injection of the depleted fluids.
Low emission of CO2 and local air pollutants
Geothermal technologies are environmentally advantageous compared to conventional combustion technologies using fossil fuels, such as oil, gas, coal, etc., because the only direct emissions come from the underground fluids in the reservoir. Emissions from direct use applications and EGS systems that are under development are negligible. Although the environmental benefits is a common feature of practically all renewable energy technologies there are several advantages that distinguish geothermal energy from other renewable energies.
Low requirement for land
Geothermal power plants require less land compared to hydropower with storage or coal power plants. Their land requirements also compare favorably with those of grid-connected wind or solar power. Due to directional drilling techniques and appropriate design of pipeline routes, the land area above geothermal resources that is not covered by surface installations can still be used for other purposes such as farming, horticulture and forestry.
Independent of fuel prices
Without fuel costs, operating costs for geothermal plants are predictable in comparison to combustion-based power plants that are subject to market fluctuations in fuel prices. This contributes to energy security.
Stable base-load energy
Geothermal power is ideally suited to operating around the clock as a stable source of base-load power, regardless of weather and other climatic phenomena. Such a resource helps utilities more accurately plan and schedule power generation to meet their load demand, usually for several decades.
Relatively low cost energy
Despite its relatively high investment costs, geothermal power has under favorable geological conditions a fairly competitive cost per unit of electricity produced as a result of its high availability factor and the absence of combustible fuel costs. Over the long life of a geothermal plant, these two factors compensate for the high upfront investment costs.
Mature technology
Geothermal power generation has been around for more than a century and presents few technological unknowns. To produce electricity, conventional steam cycle turbine generation is usually employed. The operational risks and maintenance requirements are well known and manageable. Technologies for different direct uses are also mature.
Scalable to utility size without taking up much land/space
Geothermal power plants are scalable to utility size (over 50 MW) without taking up much land or space. This is a valuable feature for a power system as it allows economies of scale to be achieved. From an environmental standpoint, this is also a plus if geothermal plants are located in areas of high scenic value, as they often are.