As part of assessing the best energy sources for the future, we are looking at the pros and cons of these different energy sources.
This is our guide on the Pros & Cons Of Geothermal Energy.
What Is Geothermal Energy
Geothermal energy is obtained from the ground around us.
Because the earth has a fairly constant temperature within the upper 10 feet of the Earth’s surface (between 50 and 60°F or 10 and 16°C), one can create a water pump system that pushes colder water down into the earth to return warmer in the winter months, or the opposite during the summer months.
The use of a heat exchanger will convert the temperature change into the air, similar to a air conditioner or a heater. On a larger scale, the drilling is done much deeper, or over a geothermal field.
Geothermal energy can be produced in larger amounts with geothermal power plants, and in smaller household applications with ground source heat pumps.
Geothermal Energy Pros
- Green Energy – geothermal energy does not produce greenhouse gases during energy generation
- Renewable – Geothermal reservoirs are naturally replenished and not finite like fossil fuels. But, they do have to be managed properly to stay sustainable and renewable.
- Large Potential For Power Capacity – upper estimates show a worldwide potential of 2 terawatts (TW). But, other estimates of geothermal power plants vary between 0.035 to 2 TW. Worldwide energy consumption – about 15 terawatts (TW) – is not anywhere near the amount of energy stored in earth.
- Is Reliable & Not Intermittent – can meet the base load energy demand unlike wind and solar.
- Flexibility & Versatility – can be used for larger and smaller scale energy generation. Can be used for small households and residential purposes. Is generally available in most places.
- Doesn’t Involves Fuels – means less cost fluctuations and stable electricity prices. Also means you don’t have to re-stock a power plant like you do with coal power plants.
- Doesn’t Take Up Lots Of Space – can be partially built underground and doesn’t require as much above ground real estate as solar and wind farms.
- Technological Advancements Are Progressing The Energy Source – recent technological advancements (e.g. enhanced geothermal systems) have made more resources exploitable and lowered costs.
- Good For Heating & Cooling – We need water temperatures of more than 150°C (about 300°F) or greater in order to effectively turn turbines and generate electricity with geothermal energy. Another approach is to use the (relatively small) temperature difference between the surface and a ground source. The earth is generally more resistant to seasonal temperature changes than air. Consequently, the ground only a couple of meters below the surface can act as a heat sink/source with a geothermal heat pump (much in the same way an electrical heat pump works). Geothermal is good for heating and cooling for homes.
Geothermal Energy Cons
- High Set Up Costs – heavy upfront costs associated with both geothermal power plants and geothermal heating/cooling systems. Total costs usually end up somewhere between $2 – 7 million for a geothermal power plant with a capacity of 1 megawatt (MW).
- Not Cost Effective Everywhere – some resources are profitably exploitable, and some aren’t. This limits practically where you can install geothermal plants. Current technology, level of subsidies and energy prices are issues. Geothermal power plants across the world currently deliver about 10,715 megawatts (MW) of electricity – far less than installed geothermal heating capacity (about 28,000 MW). For residential ground thermal pumps, ground source heat pumps typically costs $3,000 – $10,000 and have a payback time of 10 – 20 years.
- Not Practical Everywhere – Some countries have been blessed with great resources – Iceland and Philippines meets nearly one third of their electricity demand with geothermal energy. If geothermal energy is transported long distances by the means of hot water (not electricity), significant energy losses has to be taken into account.
- Minor Environmental Impact – there is some environmental impact with some land use, but nothing major. Also, they are associated with sulfur dioxide and silica emissions, and the reservoirs can contain traces of toxic heavy metals including mercury, arsenic and boron. But, this is nothing compared to fossil fuels.
- Can Cause Natural Events – in some very rare cases, they can cause earthquakes because they affect the stability of the land. Germany and New Zealand are examples where this has happened. Earthquakes can be triggered due to hydraulic fracturing, which is an intrinsic part of developing enhanced geothermal system (EGS) power plants.
Geothermal Energy Summary
- Geothermal has good long term potential as a sustainable, renewable energy source
- But, it is costly upfront, location dependent, and also depends on technological advancements, energy prices and politics (subsidies)
- These limitations mean renewable energy sources like solar, wind and hydro are probably better sustainable energy sources at the moment
- The World Bank currently estimates that around forty countries could meet most of their power demands using geothermal power.