What is Geothermal Energy?
The interior of the Earth is hot – really hot. 99% of our planet’s volume is hotter than 1000˚ C. The Earth’s core is hotter than the surface of the sun. The rate at which the temperature increases with depth within the Earth is called the “geothermal gradient.” In the Earth’s upper – crust, i.e. the parts accessible to modern drilling technology, the average geothermal gradient is ~30˚ C per km. Near volcanoes or tectonic plate boundaries, this gradient is much higher. For example, in the United States’ Yellowstone National Park, water in excess of 100˚ C is boiling right up at the Earth’s surface. Taken cumulatively, the amount of thermal energy contained only in the upper 10 km of the Earth’s could provide a practically inexhaustible source of power for human activities.
Geothermal production systems fundamentally consist of at least one production and one injection well (aka a ‘doublet’). These wells are designed and operated such that hot fluids can be continuously circulated from the Earth’s interior to the surface and back again. One doublet can produce anywhere from 1 – 20 MWe, depending on temperatures and flow rates. Large geothermal fields employ many wells to achieve power production of 100s of MWe.
In high – temperature geothermal systems (i.e. ≥ 200˚ C), produced steam is directly used to drive a turbine and generator combination, as is the case in most fossil – fueled power plants. Medium temperature geothermal systems (i.e. 90˚ – 200˚ C) employ ‘binary’ electricity production systems. In these designs, the heat content of the geothermal fluid brought to the surface in the production well is transferred to a low – boiling point fluid, whose vapor is used to drive a the turbine and generator. Organic Rankine (ORC) and Kalina cycle engines are commonly employed in binary geothermal plants.
Residual thermal energy from geothermal electricity plants can be captured before the geothermal fluid is reinjected and used directly for heating residential spaces or industrial processes (i.e. direct – use geothermics). Low temperature geothermal resources (40˚ – 90˚ C) may also be used for this purpose. In these systems, the geothermal fluid’s heat content is transferred to a working fluid that is pumped throughout the space to be heated. With the addition of a heat pump, the cycle can be reversed to cool a space and store heat back in the reservoir during warm months. Common direct use geothermal energy applications include district space conditioning, greenhouse heating, timber drying, industrial process heat, snow melting and balneology (spas).
(Vs Solar and other renewables)
- Baseload and dispatchable
- Cost competitive with wind and solar on a per kWh basis
- Large resource base within the Western Canadian Sedimentary Basin
Geothermal and the Environment
- Smallest land footprint of any power source (including fossil fuels)
- Increased efficiency in Northern latitudes
- Opportunity for repurposing oil and gas infrastructure
Future Energy Systems develops energy technologies for the future.
Future Energy Systems develops the energy technologies of the near future, examines their integration into current infrastructure, and considers their social, economic, and environmental impacts. We also contribute to the development of solutions for challenges presented by current energy systems.
Future Energy Systems research is being undertaken thanks in part to a $75 million investment from the Canada First Research Excellence Fund (CFREF), which helps competitively selected Canadian postsecondary institutions turn their key strengths into world-leading capabilities. CFREF is a tri-agency initiative of the Social Sciences and Humanities Research Council, the Natural Sciences and Engineering Research Council and the Canadian Institutes of Health Research.
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