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STEP 1

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Geothermal Energy

What is it?

  • Geothermal energy is energy created and stored in the Earth. The thermal energy originates from two sources, heat from when the planet was formed, and radioactive decay.
    • There is a continuous conduction of thermal energy from the core of the Earth to the surface. Near tectonic plate boundaries, the thermal energy is more easily accessible, however newer technologies make it accessible in other areas as well.
    • This is not the same type of geothermal as heat pump driven thermodynamic exchange.
  • Geothermal heat can be used directly for heating or can be converted to electricity. With more recent advances in technology, electricity can be generated at temperatures as low as 57°C. In general, though, a ground source of approximately 150°C and less than 7km below the earth’s surface is required to generate the steam.

How does it work?

  • Open Loop System
    • Traditional geothermal energy taps into reservoirs of hot water or steam in the ground, drawing it to the surface through a wellhead. The hot water or steam then drives a turbine to produce electricity. Wastewater, after passing through a condenser is reinjected back into the ground through a second wellhead, prolonging the useful life of the system. This is commonly referred to as an “open loop” system.
  • Not to be confused with heat pump energy use.

Size considerations

  • True geothermal for electricity generation is generally restricted to commercial size due to high input costs and restrictions on location.

Applications

  • Geothermal can be applied directly as thermal energy for such things as district heating, greenhouses, and fisheries. Used in this way, it is actually much more efficient that generating electricity.
  • Generating electricity from geothermal energy is generally an on-grid, large scale process and does not really have viable small scale applications.

Is it right for you?

  • Geographic location and cost are currently the largest barriers to geothermal. Access to technological expertise also needs to be considered.

Positives of Geothermal Energy

  • Supply of energy is constant, not intermittent as in wind and Solar PV
  • Potential supply of power is essentially limitless
  • Technological expertise from the oil and gas industry (drilling) can be applied
  • Can produce emissions of greenhouse gases and other toxic gases which escape from the Earth, however far less than with fossil fuel use

Issues with Geothermal Energy

  • Due to input costs and geographic restrictions, size is generally limited to commercial, on-grid applications
  • Can release greenhouse gases and heavy metals
  • Can destabilize the land where drilling occurs, earthquakes and other problems have occurred at some sites
  • Large scale projects can be expensive
  • Local depletion of energy can occur and therefore energy extraction must be monitored
  • Requires technological expertise