Artists impression of a Solar Tower
In a CO2 collecting tower an amine solution would be pumped up to the top of the tower and allowed to fall from the top to be collected at the bottom. As the rising air stream passes over the falling amine stream, CO2 is absorbed from the air by the solution which is then collected at the bottom, heated to release the CO2 and then pumped up to the top of tower again. As this process occurs after the air passes through the wind turbines the Solar Tower would generate most of the electricity needed for the integrated plant. As it does not interfere with the power generation capabilities of the tower it is possible that CO2 absorbers could be retro-fitted to existing Power Towers. This could reduce the cost of implementing Solar Methane by using existing structures.
Currently there are plans to capture CO2 from fossil fuel power station and sequester it underground. If this CO2 is shipped to the Solar Methane plant instead this can supplement the CO2 stream from the Solar Tower. This means that the CO2 from the fossil fuel plant is at least used twice thereby decreasing the net impact of the CO2 released
Converting Hydrogen to Methane
I first became of aware of the Sabatier reaction form reading a book “The Case For Mars” by Robert Zubrin. He envisioned that a mission to Mars would make it’s return fuel from the Martian atmosphere, which consists of 99% CO2, and hydrogen carried aboard. This way a small amount of hydrogen could be multiplied to become enough methane and oxygen, from reacting with CO2, to make such a mission viable. The Sabatier reaction is a well known reaction where H2 and CO2 react in the presence of a catalyst to form CH4 and H2O. This is the reaction
4H2 + CO2 = CH4 + 2H2O
While this reaction will work there is another called the Reverse Water Gas Shift (RWGS) reaction. Its main product is CO and H2 in this reaction
CO2 + H2 = CO + H2O
The product of this reaction is called a synthesis gas and can be fed to a reactor to produce methanol. This would giv