Monday, April 2, 2012
Can we duplicate Nature’s photosynthesis for Hydrogen production?
One of the wonders of Mother Nature is her ability to sustain life on earth with sun light, water and Carbon dioxide from the atmosphere producing food. No toxic chemicals, no polluting gas emissions and no noise. We can only admire the majesty and power of Nature with our fragile knowledge of science and try to duplicate Nature in order to satisfy our growing energy needs. Nature produces Carbohydrates C6H12O6 using sun’s light, Carbon dioxide from atmosphere and water by a chemical reaction as shown below: 6H2O + 6 CO2 ----------- C6H12O6 + 6O2 The same Carbon dioxide from the atmosphere is now threatening the globe with warming. Can’t we grow more trees so that all the carbon dioxide emissions from our power plants and cars can be converted into more carbohydrates? It sounds very simple and logical but is it feasible? The carbon dioxide in the atmosphere before industrialization was about 280ppm but it has now increased to 392ppm which is almost double. It has grown roughly 2.2% exponentially in the last decade. It is the highest in the past 800 years and likely higher than in the past 20 million years. (Ref: Wikipeadia). Couple of things happened during this period. The industrial and population growth increased rapidly building up carbon dioxide level in the atmosphere and at the same time displacing tropical and rain forests with people and industries; it resulted in the buildup of greenhouse gases to a level, which scientists say are unsustainable. We don’t have enough forest to absorb so much of carbon dioxide. Alternatively, scientists are now trying to interfere with Nature’s photosynthesis process using micro algae called chlamydomonas reinhardtii that will support the production of Hydrogen instead of Oxygen in a normal photosynthesis reaction. This was based on the discovery that if an algae growing culture medium is deprived of Sulfur; it will generate Hydrogen instead of Oxygen. They also found out that such an algae can thrive in a Carbon source such as Carbon dioxide or even in Acetic acid medium. They tested the process using a pilot Photo bioreactor and concluded that the cost of producing Hydrogen by this route will be about $ 42/kg.The cost is high compared to the target cost of Hydrogen by DEO (Department of Energy,USA) at $2.80/kg which is fifteen times lower. However scientists are still working to reduce the cost. Meanwhile scientists are also working on Hydrogen production using Photoelectrolysis.The water electrolysis using Direct current is a known process but the cost of energy in this process is still high. The high cost is due to several stages involved. In the first stage, one has to generate power using PV cells. In the second stage the PV generated electricity will be used to split water electrolyticlly.But scientists are now trying to substitute both the above steps with a single step of utilizing direct sun light to split water into Hydrogen and Oxygen.Thie requires a catalyst known as Photocatalyst which will use light energy instead of electrical energy to split water into elements. Using TIO2 (Titanium dioxide coated electrode) and ultraviolet rays of the sun they believe that a 20m2 PV solar panel can generate about 5m3 of Hydrogen ad 2.5m3 of Oxygen in 24 hours, equival to a power generation capacity of 15kwhrs or roughly about 2.01 gallons of Gasoline from 4 liters of pure water. Scientist are now hoping that light energy, more precisely ultraviolet rays from the sun will come to the rescue of human beings in solving one of the greatest energy crisis in the history of mankind. At last we can hope to see some ‘light’ at the end of the tunnel.