Geothermal energy has been used by ancient civilisations as far back as 300BCE[1]. Stored in the earth’s core is a massive amount of thermal energy (heat) and in some countries, such as Iceland, the energy is released at the earth’s surface in the form of geysers.
The core of the earth is about 6000° C which is about the temperature of the sun’s surface. There is approximately 50,000 times more energy in the earth’s core than the entirety of the world’s oil and natural gas resources.[2]
Geothermal energy uses deep wells to create a path for heat to flow from the hot source deep down upwards to the relatively cold earth’s surface. The temperature difference can be used to do useful work, such as generate steam that can drive turbines connected to an electrical generator. Similar to the flow of steam flying out of a whistling kettle, imagine that thousands of times greater and pushing a large fan that turns a generator.
Does Bermuda have geothermal energy?
Deep drills at the BIOS station in 1972 showed normal levels of heat production[3], but nothing above normal that would make geothermal a viable option. In 2003, while working at the Bermuda Biological Station, marine biologist Thomas Iliffe discovered that some Bermuda caves are warmer at the bottom than the top and suggested geothermal heating as a potential reason.[4] However this is only a matter of a few degrees across a cave and much more exploratory investigation is needed to determine if Bermuda has a geothermal resource.
Bermuda’s geology consists of a large volcanic cone capped with an icing of limestone. Normally geothermal reservoirs contain a large volume of porous rock, such as limestone, surrounded by an impervious layer of rock that acts as a barrier. Water is pumped into the porous rock where it is heated and removed as hot water or steam. In Bermuda’s case, the porous rock sits on top of the volcanic core, meaning we have no lid to our porous container and no energy dense heat source within the extinct volcano. If the region was volcanic and still a source of heat energy, then the challenge of tapping into that energy source many kilometres below the surface would be difficult.
Geothermal energy is also used at much smaller scales as heat pumps. Dual cycle heat pumps can take advantage of temperature differences between the air and the earth. When the earth is warmer than the air, it can use that energy difference to heat a house. Similarly, if the ground is cooler than the air, it can cool a house. [5]
While geothermal energy is a clean, renewable resource, Bermuda unfortunately doesn’t have the right geology and so it is unlikely it will ever be an option to include in our energy mix.
[1] What is Geothermal – International Geothermal Association (geothermal-energy.org)
[2] How Geothermal Energy Works | Union of Concerned Scientists (ucsusa.org)
[3] R. D. Hyndman, G. K. Muecke, and F. Aumento. Deep Drill 1972. Heat Flow and Heat Production in Bermuda. Canadian Journal of Earth Sciences. 11(6): 809-818. https://doi.org/10.1139/e74-081
[4] Iliffe, T.M., Hart, C.W., Manning, R.B., 1983. Biography and the caves of Bermuda, Nature, 302, 141 – 142.