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Tag Archives: Photoelectrolysis

Photovoltaic  solar energy  is becoming popular as a source of clean energy and an alternative to fossil fuels to combat climate change. Though the initial cost is expensive people have started realizing the potential of PV solar as  a real alternative to grid power, especially when they can export surplus power to the grid and earn some revenue. It is  a source of income for potential investors as the energy cost keeps rising steadily. The cost of solar panels, batteries and inverters are slowly coming down as the systems get more popular and more competition is created in the market. However, during cloudy days or when the solar hours are less, the power generation by solar panels is considerably low. Moreover, the ‘power in tariff ‘ system is not available in many countries especially in developing countries. Therefore, energy storage becomes an issue. Lead acid batteries serve as storage devices for smaller applications but it becomes expensive for lager systems. Operation and maintenance, replacement and waste disposal are some of the issues with battery storage.

Generating Hydrogen on site using solar power and storing Hydrogen under pressure in a tank is the best method of storing solar energy. The stored Hydrogen can be used to generate power using a Fuel cell as and when we need power. However, the amount of energy required to convert water into Hydrogen using Alkaline Electrolyzer or Solid Polymer Electrolyzer is still high, averaging 5-7 kwhrs/m3.When you calculate the economics of  Hydrogen storage versus battery storage using a computer modeling for a stand alone system, it is clear that Hydrogen storage is more economical and also guarantees an uninterrupted power supply using a Fuel cell.

One US company has developed a Carbon doped Titanium oxide nanopowder visible light photo catalyst to  generates Hydrogen using sun’s light energy. The company claims that it consumes only one-third of the power consumed by PEM Electrolyzer or half of an Alkaline Electrolyzer.It can be easily installed at roof tops and it can generate Hydrogen even at one-third of sunlight because it can effectively use short UV light and blue wave length of suns light because these energetic wavelengths penetrate cloud cover more effectively than the rest of sunlight. A 2mm modular solar panel can be installed on roof top or installed in multi-acre field installations. Even during the absence of sunlight the company claims it can use grid power to generate Hydrogen using its hybrid integral (MMO) Mixed metal oxide Titanium anode as efficiently as PEM Electrolyzer.

While a PEM electrolyzer generates about 1.3kg Hydrogen from a power input of 100Kwhrs, this model can generate about 2.5kg Hydrogen using MMO + TiO2 anode and about 3.8kg using TiO2 alone. (Based on higher heating value of Hydrogen at 39.4 kwhrs/kg).The panel consuming 26.7kwhr power at 1.0Volt DC current at Anode can generate 1.25kg Hydrogen with Electrolysis electrical efficiency at 148%.  This will make Hydrogen fuel a commercial reality because it will consume only 21.36 kwhrs of Dc power to generate 1 Kg Hydrogen. The generated Hydrogen can generate about 15 Kw power using a Fuel cell. This is an elegant solution to generate and store power using sun’s light than Photovoltaic power.

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 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: Wikipedia). 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 cut 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, equal to a power generation capacity of 15kwhrs or roughly about  2.01 gallons of Gasoline from 4 liters of pure water.

Scientists 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.

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