One of the main costs when harvesting geothermal energy is the digging itself. Just like oil wells, geothermal wells have to be several kilometers deep, because temperature rises along by 50 degrees Celsius with every kilometer. This is where abandoned oil wells could help generate clean electricity.
A team of researchers from the Chinese Academy of Sciences in Guangzho, led by Xianbiao Bu, have devised a method to get the heat specific to the depths of old oil and gas wells and transform it into electricity.
They studied a “pipe-within-a-pipe” approach, meaning cold water would go down through one pipe inside the earth’s crust and then return through the other pipe as hot and under pressure. A turbine would harvest its pressure and generate some 54 kilowatts of electricity.
Taking into account the huge number of abandoned oil and gas wells worldwide, this technique will add up to the sources of renewable energy.
It’s also a known fact that drilling for geothermal resources sometimes disturbs the equilibrium of the tectonic plates and creates earthquakes. By using oil wells that had already been used and that were once filled with petroleum or gas, the risks of causing tectonic instability are greatly diminished.