Good news on a technology that could revolutionize geothermal energy made waves at the American Geophysical Union meeting last week. Anyone who understands that the world's hunger for energy will push our planet beyond the point of no return without technological solutions will welcome the idea of CO2 plume geothermal power or CPG.
CPG benefits include sequestering CO2; making geothermal energy accessible in geographic regions where it has not been economically feasible to use this natural heat source for generating power; and storing energy from solar or wind farms. CPG could produce ten times more geothermal energy than traditional geothermal approaches currently yield, offering an important new source of renewable energy while simultaneously contributing to the reduction of CO2 entering the atmosphere due to fossil fuel burning.
The idea starts with the liquid carbon dioxide which is increasingly envisioned as a solution to global climate change. The CO2 is captured at the source from fossil fuel burning electrical generation facilities. For efficient storage, the CO2 is compressed into a liquid, which can be pumped deep into the earth, to be trapped in the same porous rock beds which once provided oily reservoirs.
But instead of just storing the CO2 underground, the COS would feed what is described as a "cross between a typical geothermal power plant and the Large Hadron Collider." Liquid CO2 would be pumped into horizontal wells set up in concentric rings deep in the earth.
Carbon dioxide flows through the porous rock bed deep in the earth more quickly than water, collecting as much heat more easily. More importantly, the CO2 expands more than water when heated, so the pressure differential between the CO2 pumped into the ground and the heated CO2 is much greater than the pressure differential of the water making the same loop.
The amount of energy that can be generated depends on this pressure differential -- and is therefore substantially greater in CPG than in traditional geothermal plants. The CO2 expands so much that the pressure alone can carry the heated CO2 back to the surface, an effect referred to as a "thermo-siphon". The thermo-siphon makes the use of pumps for recovering the hot CO2 unnecessary, reducing the energy costs required to generate the geothermal electricity for a higher overall efficiency.
Traditional geothermal technology uses warmth from deep in the earth to generate electricity. Currently, geothermal plants rely on locations where hot water is trapped under the surface, pumping the hot water out to collect that deep-earth heat. This technology limits the locations where geothermal energy recovery can occur.
In contrast, CPG could be used in many locations that do not have the correct underground reservoirs, expanding the geopgraphic range of geothermal power generation.
CPG offers an interesting bonus as well: electricity generated from the sun or the wind often gets wasted as demand does not meet the supply. This excess energy from renewable sources could be used to provide the energy needed to compress the CO2 sequestered from fossil fuel power plants, storing the waste renewable energy to be later recovered as geothermal energy.
In addition to announcing the new technology, the scientists behind the CPG project have pioneered cooperation with communication experts to "explore new ways for scientists, engineers, economists and artists to work together." This collaboration resulted in a video explaining the CPG concept.
We wish we could say the video will go viral, setting new standards for communicating science, but in fact it is rather dry and much too long to keep the ever-shortening attention span of the people who need to know about these technologies. But it is worth a look, especially starting around 8:40 into the video where the carbon dioxide plume concept is described.