10 Dec 2013

Solar CO2 Scrubber

We have extensively harmed our planet by following a careless and profligate lifestyle. But the Rubicon has not yet been crossed. If we act swiftly and boldly, we can still avert disaster. Among several other solutions, carbon dioxide scrubbing could help us move towards a greener and brighter future.

Carbon sequestration or carbon capture and storage are effective processes of extracting carbon dioxide gas from the atmosphere or from large point sources such as fossil fuel power plants, and storing it in underground reservoirs.

Although a brilliant concept, the present technology is still very expensive and not perfectly sound. So here's the concept of a solar powered carbon scrubber that could be the key in bringing down CO2 levels in the atmosphere.

Application
This solar-powered appliance can be installed anywhere, preferably in locations with high CO2 levels such as traffic congested areas or industrial areas. This infamous gas which is harmful to the environment, has also its positive side.

The carbon dioxide that is extracted from the atmosphere through thermosiphon can then be recycled and used in chemical processes like making soda water or in fire extinguishers. It can also be pumped into a greenhouse and help in the growth of plants.

The best part is that this CO2 scrubber can be easily built by modifying a solar water heater.

The working principle of a solar water heater
 
Process
Here's how the solar carbon dioxide scrubber works:
 
Inlet
By exploiting the passive heat exchange based on the thermosiphon principle,  we let ambient air rise up the sloped glass case and bubble into a water container.
 
Absorption
Next, by exploiting the varied solubility of gases, we separate carbon dioxide from the rest of the gases that constitute air. At 40C and at normal pressure conditions, about 600ml of carbon dioxide can dissolve in 1L of water while the solubility of nitrogen and oxygen is a mere 10ml and 20ml respectively. Refer here for details on solubility and here for calculations on the fluid dynamics.
 
So when air is bubbled into water, CO2 will dissolve in water while the rest of the air just bubbles out. 
 
Outlet
The CO2 rich water then trickles back down the sloped glass tubes where it is heated by the sun and rises up again. In this heating process, the solubility of CO2 drops drastically and the gas bubbles out. At this point it can be tapped and used.
  


Further Improvement
Ingenious, right! Well, there's a snag...
 
Due to the poor concentration of carbon dioxide in the air, this process may not be as effective as it sounds. Probably this concept needs to be combined with other regular thermochemical processes such as reacting CO2 with calcium oxide or sodium hydroxide.
 
This energy independent concept of cleaning up the atmosphere through CO2 scrubbing needs considerable improvement but has a promising future.
 

1 comment:

Herman Shim said...

Why not mix Calcium Hydroxide in the water? I will try this.

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