We like to say that life on Earth could not survive without the sun, but that isn't actually true. Without the sun the surface of the planet would freeze down to a certain depth, but the amount of energy contained in the molten planetary core could provide ample heat and electric power to maintain human civilisation for hundreds of thousands of years or longer.
From the western US to Australia (Queensland and Victoria), Indonesia, the Phillipines, Kamchatka, Alaska, and New Zealand, the Pacific Ring of Fire makes thermal energy available to much of the world's population. Similar "rings of fire" over the rest of the Earth extends this ample fund of energy to Europe, western and central Asia, and parts of Africa.
Jefferson Tester: The figure for the whole world is on the order of 100 million exojoules or quads [a quad is one quadrillion BTUs]. This is the part that would be useable. We now use worldwide just over 400 exojoules per year. So you do the math, and you know you've got a very big source of energy.
How much of that massive resource base could we usefully extract? Imagine that only a fraction of a percent comes out. It's still big. A tenth of a percent is 100,000 quads. You have access to a tremendous amount of stored energy. And assessment studies have shown that this is thousands of times in excess of the amount of energy we consume per-year in the country. The trick is to get it out of the ground economically and efficiently and to do it in an environmentally sustainable manner. That's what a lot of the field efforts have focused on. _TechReview
If you drill far enough down into the Earth, you will find hot rock. Circulating a heat exchange fluid into the rock allows you to utilise the heat to drive a heat engine to generate electric power. Using both the heat and the electricity obtained from below ground, life on planet Earth could be maintained under large domes for millions of years, even without the sun. Add the energy you can get from nuclear fission and fusion, and human civilisation could go on even longer.
Since the sun is likely to go on for another billion years or longer, what we are talking about is two things: 1. geothermal energy as supplementary, baseload energy for parts of the world where nuclear power is not practical or safe, and 2. human settlements on molten-core planets which are too far away from a star for conventional star-powered photosynthetic life cycles and atmospheric heating.
Geothermal is expensive, and is a low-grade form of energy. But it is 24 hour a day baseload energy which can also be load-following power. Enhanced geothermal requires deep drilling and regular maintenance. And there is the fear of earthquakes:
Using EGS, producers drill deeply into hot rocks and pump surface water to them. The heat is transferred to the water and it is pumped back to the surface with geothermal energy that is used in a standard geothermal power plant. Much heralded until recently, EGS began to garner controversy when its deep fracturing of geologic structures seemed to be associated with increased seismic activity, first in Basel, Switzerland, and later in California.
..."The thing is, you've got to address it," Gawell said. "If you've got major slip faults in the area, you don't do a project there. You simply stay away. When somebody permits a geothermal project in Basel, Switzerland, the site of the biggest earthquake in European history, you have to wonder whether they did any screening or thinking" beforehand. _GreentechMedia
But think about it: Earthquakes come from faultlines where plates are pushing and sliding against each other. The best way to prevent a large earthquake is to trigger multiple small earthquakes to relieve the pressure that is building over time.
The hysteria over EGS-caused mini-quakes is misplaced. The danger comes from not relieving the pressure.
And so massive quantities of baseload energy goes untapped, because for now it is cheaper to use other forms of energy -- such as coal, gas, oil, hydro. How does geothermal compare to wind?
According to Tantoco, the company may spend as much as $3.5 million to produce a megawatt of geothermal power through its greenfield facilities, and about $2.5 million per megawatt for its wind power project. [EDC Philippines] _BusinessInquirer
But geothermal is 24 hour baseload and potentially load-following power. Wind power is intermittent, with a capacity factor of 0.3 or less -- and essentially unpredictable! Wind machines often break down within 5 to 10 years, whereas geothermal can last for several decades or longer.
No one is saying that geothermal is better than small modular nuclear reactors in terms of portability, versatility, efficiency, or affordability. But for demographic reasons, some parts of the world are simply not safe places to put nuclear plants -- even SMRs. If geothermal energy is available, it represents a better alternative, for those particular places.
By. Al Fin