Carbon Dioxide emissions are on a rise all over the world. Not only does it contribute to the Greenhouse Effect and Global Warming, it also adversely affects the health of people who are unlucky enough to breathe it. Many researchers are looking for viable options to do away with this excess carbon in our atmosphere.
A group of scientists from Berkeley Lab, California, have come up with a new method that stores Carbon Dioxide, uses the earth's heat to increase its temperature, and produces energy from it. This project has received funding worth USD 5 million by the United States Department of Energy, and is presently in the initial stages of development. In this method, Carbon Dioxide is pumped into a layer of the crust 3km below the surface, where the temperature is above 120 degrees Celsius. A closer look at the phase diagram of CO2 can lend us an insight into its behavior at high temperatures and pressures:
A group of scientists from Berkeley Lab, California, have come up with a new method that stores Carbon Dioxide, uses the earth's heat to increase its temperature, and produces energy from it. This project has received funding worth USD 5 million by the United States Department of Energy, and is presently in the initial stages of development. In this method, Carbon Dioxide is pumped into a layer of the crust 3km below the surface, where the temperature is above 120 degrees Celsius. A closer look at the phase diagram of CO2 can lend us an insight into its behavior at high temperatures and pressures:
At temperatures above 32 degrees C, and pressures above 73 atm, Carbon dioxide enters into a super-critical state. This means that distinct solid and liquid phases do not exist. This fluid has very low viscosity, high diffusivity and (most importantly) a high value of enthalpy (stored energy) per unit mass. If the CO2 pumped into the earth's crust were allowed to reach a super-critical state and then released, it would reach the surface with enormous amounts of energy - energy which could be used to produce electricity. Basically, CO2 is being provided the earth's own energy, and that very energy is later converted to electricity.
This will offer a very interesting solution to our CO2 crisis - Carbon dioxide generating companies could pump the gas underground and let it reach critical state, after which it can be used to produce electricity at the surface. The spent gas can be recycled, and more gas will be added over course of time to compensate for losses due to absorption onto the crust.
There are two main drawbacks to this scheme:
- Carbon storage / recovery is costly.
- Pumping carbon into the crust may have an adverse effect on underground life, and may affect water reservoirs as well.
A more detailed study is required before this innovative idea can be implemented on a large scale.
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