All of you know that: Imagine you are on the beach during a sunny summer day. No clouds, no wind, just sun. Suddenly you decide to walk without shoes on your feet. Possible? Impossible because rocky road is too hot for your skin on feet. Actually, the rock can be good absorbent of enormous heat and it can deliver it quite quickly to all things in close contact with it.

Quality of rock is the same on Earth’s surface as well as underground. This principle uses geothermal approach called „Hot Dry Rock“. In previous article we wrote that if there are no natural hot water streams or natural hot water reservoirs, we can establish closed water loop and inject it down the well under high pressure. This water is warmed by „hot dry rock“ underground. In other words, in each area under the Earth’s surface there is geological layer composed of rock. It is close to hot magma and it is of a very hot temperature. If we drill enough deep and make water to circulate through rock pores, after it is heated we can pump it above and use it as a source of energy in geothermal power plant. In order to bring rock permeability as close to ideal as possible, we can fracture this rock manually, through controlled detonation. Altogether, this process uses so called Enhanced Geothermal Systems.

There are more types of geothermal classification. One of them defines so called „hydrothermal“ and „petrothermal“ types of energy. „Hydro“ means that we drill and exploit presence of natural hot water. On the other hand,  „petro“ refers to drilling in order to establish closed water loop circulating through „hot dry rock“. Surely, in each area there are some natural underground water sources and at the same time, not all water injected down the well is able to be pumped back, so „petrothermal“ represents just ideal concept. In reality, all geothermal energy installations are combination between hydrothermal and petrothermal (based more or less on concrete type). But in general, „Hot Dry Rock“ is usually linked to „petrothermal“.

Well, this was just a brief explanation of what „Hot Dry Rock“ means. All is sketched on picture by civil engineer Mr. Geoff Sims on picture at the bottom. We also reccommend 10 minutes video explanation below: