In 1997, Kyoto Protocol : Signatory countries commit to reducing greenhouse gas emissions, changing the climate. First, the control of energies, then renewable energies, such as solar, wind or biomass, but there is another renewable source, less publicized, although extremely effective, is geothermal.

From the Greek “geo” (earth) and “thermos” (hot), the term “geothermal” covers both the science that studies the earth’s internal phenomena and the industrial processes that seek to exploit it to generate electricity and/or heat.

Well, it comes from deep beneath the surface of the earth and it’s called geothermal energy and we can use it to generate clean renewable electricity. Ok, here’s how geothermal works.

Have you ever thought where all this heat comes from?

Heat from the earth’s crust warms water that has seeped into undergound reservoirs.

When the water becomes hot enough, it can penetrate the surface of the earth in the form of steam or hot water. This usually occurs when the Earth’s crust or “plates” meet and move.

Previously, the use of geothermal energy was limited to areas where hot water flowed near the surface. But as geothermal technologies progress, we can take advantage of these natural renewable energy sources even more.

Engineers have developed different ways to generate electricity from geothermal wells drilled into the ground.

The environnemental benefits of this clean, round-the-clock renewable energy source are substantial : low emissions, small physical footprint, and minimal environmental impact. The few by products that can come up are often re-injected underground.

Geothermal energy can also help recycle wastewater.

Geothermal energy is the exploitation of the heat of my Earth. The planet Earth, inside, is extremely hot, we have temperatures under a few tens of kilometers that reach 1200 degrees. That’s the temperature of the mantle. The deeper you dig in the earth, the higher the temperature increases, depending on the thickness of the earth’s crust.

For example, under Paris we reach temperatures of 70 degrees, around 1800m.

To exploit the hot water, two holes are drilled. The first one draws the fluid at a temperature of about 70 degrees. The other to re-inject it into the basement after extracting heat. This is the principle of the geothermal doublet, to which a heat exchanger is associated. You don’t send the heat directly into the radiators because the geothermal water, in fact, is often loaded with salts. However, heat is exchanged with a surface heat exchanger with the residential heat distribution network.

Under Paris we have this formation of the Dogger, it is a floor of the Jurassic, a limestone floor, which allows to heat directly because one reaches temperatures of 70 to 80 degrees, to heat directly housing complexes.

Home heating accounts for about ¼ of CO2 emissions into the atmosphere.

Heating is, precisely, the most natural application of geothermal energy. It is a heat exchange without chemical production.

The geothermal installations in Ile de France prevent an annual release of 340,000 tonnes of CO2. 1st renewable energy in the region.

Sources : ADEME_French_Know-how-Geothermal-Energy / www.egec.org