Extraordinary energy :: Geothermal UK?

For a multimedia version of this blog entry click here

All energy on Earth, whether fossil fuel, wind energy, solar thermal, biomass or photo voltaic comes from the sun, right? Wrong! Well, in a way. What about all that energy within the Earth, geothermal and nuclear? Well, actually they come from the same source as the energy and matter as our Sun and the rest of the solar system.

As the swirling cloud of gas matter condensed to form our solar system- 4.3 billion years ago the nuclear material and, heat were trapped and insulated by the crust of the planet. We have to remember that each planet was pulled together by gravitational force from many molten blobs of magma type material. The lighter parts floated to the top and formed the crust which cooled, solidified, and began to act as a duvet that insulates the hotter, denser magma below.  Difficult to think of rock as a light floating duvet, isn’t it? But it is in comparison to the denser material below. 

There are groups of extraordinary people who’ve used this potential energy source to make the arctic habitat habitable-they even heat their roads with it!- and get oodles of energy (electric) – nearly free, once the system is installed.

Watch this short vid: For a multimedia version of this blog entry click here

The idea is simple, drill two holes close together in the Earth’s crust, to a depth that the surrounding rock is super hot. Pump water down one, and hey presto- steam comes up the other, which you can use to drive a turbine to move electricity, or use directly to heat your home, roads, or whatever you need. The Icelanders `are lucky though. Their icy land is formed of solidified magma from a mid-ocean ridge, meaning they don’t have to dig deep at all to get the energy they need. This means drilling costs are lower than in areas where the hot rocks deeper. 

In other places around the world modern technology is increasing the technical feasibility of geothermal power plants in less accessible locations. Geodynamics, an Australian company based in Queenland is piloting geothermal drilling technology in the Cooper Basin. There they have drilled to a depth of around 4,300m, where temperatures are up to 250 degrees C.

So what potential is there in the UK for this relatively clean green energy source? Can we follow the lead of the Icelanders and the Australians? We have geothermal springs, the hot spring in Bath is about 47 degrees C, which means that the hot rocks are certainly down there. The British Geological Survey say that our geothermal gradient is 25-35 degrees per Km of depth. 

This means we’d need to drill some 7.5Km before we reached temperatures similar to those found by Geodynamics in Australia. Although this is not yet technically feasible, there may come a time in the future when when we are both technically and economically able to drill to such depths.  However, in the meantime, there are ways of using lower temperature heat available at shallower depths, not to produce electricity, but to heat our homes and offices. Ground source heat pumps allow concentration of lower energy heat for space heating purposes and are becoming widely available. For more information click here

Toby Roscoe (EcoHub | Sustainability Solutions)