Posted by Andrew Bone Tuesday, 20th September 2016
Thank you for your question. Yes, geothermal energy is a realistic alternative to dirty fossil fuel for generating electricity. Unfortunately, there are not many places around the world with such large geothermal resources such as Iceland enjoys: the USA, China, the Philippines, Mexico, Japan, New Zealand and Italy are some of the other major exploiters of geothermal energy.
Electricity is made by a generator: this is basically a large number of powerful magnets and a moving coil (or you can have a static coil and moving magnets - your choice). When a coil moves relative to a magnetic field, there is a force, called the electromotive force, on all the electrons in the wire of the coil. These get 'pushed' down the wire, and that is electrical current.
To turn the shaft the coil is on, any form of energy can be used: fossil fuel evaporates water, which drives through a turbine (a complex set of fans on a shaft), to turn the rotor of the electrical generator. In a hydropower plant, water rushes out of a pipe at the base of a dam, and drives the turbine by physical pressure.
There needs to be a temperature differential in order for the water to have the energy to turn to steam and drive the generator shaft. By passing cool water through hot rocks beneath the Earth's surface, the expansion to steam loads it with sufficient kinetic energy to generate electricity, just like steam from a fossil fuel boiler. But in the case of geothermal energy, there are no carbon dioxide, sulphur dioxide or nitrous oxide emssions, all of which are seriously bad news for the environment.