Eco-Electricity from Geothermal Energy
The core of the earth can generate electricity for the whole planet and the magma of the earth’s core produces more energy than all the nuclear power plants on the entire planet.
The magma continually produces heat from the natural decay of radioactive materials such as uranium and potassium. This heat naturally flows to the surface by conduction at a rate of 44.2 Tera watts (TW) / hour and is restocked by radioactive decay at a rate of 30TW/hour, which is more than double the world’s entire energy consumption.
As of 2015, the global geothermal-power capacity amounts to 12.8 gigawatts (GW) and only 6.5% of the total global potential has been used so far, but more projects are on their way to reach 17GW by the year 2020.
In the UK and in some areas in the USA, the mean annual ground temperature at 15 meters deep is from 9°C to 13°C and hence is colder than the air in summer and warmer in winter. So, if we can live underground or in a basement without the need to heat or cool our living space, we do not need to spend money on electricity.
The simplest, shallow geothermal energy is gained by digging 5 to 10 meters into the earth, where the temperature is consistently between 10°C and 16°C in some areas and there is no need to generate electricity. Shallow geothermal energy can be used for warming the house floors and to keep the gardens’ raised soil beds at a steady temperature all year around. The French built underground cellars to keep their wine at a constant temperature all year round without having to invest in an expensive air-conditioning system.
However, for the substantial conversion of geothermal energy, digging deeper for a hotter temperature becomes necessary to convert pumped water or steam to electricity by using it to propel turbines that drive motors. The cost of power production depends on the geothermal activity of the geographical locations. In volcanic areas such as Iceland, New Zealand, North Italy and other such countries, it is easier and less expensive to use geothermal energy. In Iceland, most electricity and heating supplies are from a geothermal renewable energy source and not from fossil fuel.
Technically, there are three basic designs for geothermal power plants that pull hot water and steam from the ground. The depth required for generating cost-effective electricity depends on the geology and energy requirements.
The most straightforward design is dry steam that goes directly through the turbine to rotate a motor, then into a condenser to convert it into water. The second method is to de-pressurize the hot water or ‘flash’ it into steam, which can then drive the turbine. The third approach is called a binary cycle system. The hot water is passed through a heat exchanger, where it heats an isobutene liquid in a closed loop. The isobutene liquid boils at a temperature lower than water and converts into steam to run the turbine.
The geothermal gradient has an average value of 26°C per kilometer, so the deeper we dig, the higher the temperature we get till we reach the core of the earth at seven million °C. However, in practical terms, for some areas, to reach 76°C a depth of 1.8 kilometers would have to be dug to produce 23MW of heat and 24.1MW of electricity.
Commercial companies inject pressurized, toxic fluids to fracture the rocks to extract shale gases and that might cause seismic activity in the form of unpredictable earthquakes. The process releases harmful gases and if they are not captured and re-injected into the earth, they become harmful to the living beings on this planet.
The control standards for deep geothermal energy should put the greenhouse effect before profits and commercialism, where long-term safety comes first at any cost and not the other way around. Rooted geothermal-energy plants and shale-gas extraction are not recommended to be built-in the Eco-city’s housing areas to avoid the possible geological disturbance of the earth’s surface and earthquakes in extreme cases. Therefore, the geothermal power plants should be constructed outside the Eco-city or in the energy sustenance area if proven to be safe.
The advantages of geothermal power are the use of smaller areas of land and 20 liters of freshwater per MW/h verses over 1,000 liters per MW/h for nuclear, coal or oil power stations and has almost no harmful impact on the environment.