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Showing posts with label combustion. Show all posts
Showing posts with label combustion. Show all posts

Friday, February 24, 2012

Renewable Hydrogen-Future source of clean energy

I use the word ‘renewable Hydrogen’ for the Hydrogen derived from water using renewable energy sources such as solar, wind, geothermal, wave energy, ocean thermal energy conversion systems and biological processes. Hydrogen is clearly the energy source of the future because it has got the highest energy content, compared to any other fossil fuels such a diesel, gasoline, or Butane. The energy content is more than three times that of natural gas, which is currently considered as the cleanest commercial fuel available in the market. The heating value of Hydrogen is 61,100Btu/lb compared to 23,879 Btu/lb of natural gas. Moreover, only Hydrogen can guarantee a complete reduction of Carbon dioxide from the atmosphere. The problem with renewable Hydrogen is the cost, at current situation. The DOE (department of energy, USA) has targeted a cost for Hydrogen production at $10to $15 per mmBtu, which is comparable with current Natural gas cost. Currently bulk of the Hydrogen is commercially produced by steam reforming natural gas. However; this process will emit carbon dioxide at the rate of 11,888gms per Kg of Hydrogen produced. Though the cost of Hydrogen by this route is cheaper, mitigation of carbon dioxide is clearly an environmental issue. However it is an important route during the transition process from fossil fuel to a full- fledged Hydrogen economy of the future. Natural gas is increasingly in demand and the price of natural gas keeps increasing as the supply demand gap widens. Large natural gas liquefaction plants are already in operation in many parts of the world and number of new plants are under implementation or under planning stages. Japan, South Korea, Taiwan are three largest importers of LNG (liquefied natural gas) from Australia in Pacific region. There are many coal seam methane gas facilities already in operation in Australia and many are under planning. Due to the disaster at Fukashima nuclear plant, Japan has stepped up its import of LNG. India and China, which have been traditionally using coal as a major fuel, have started importing LNG for their power plants. This has pushed the prices of LNG in the international market significantly. Though LNG is relatively a cleaner fuel, it is very expensive to build import terminals. Moreover countries like India and China do not have a good distribution network by pipelines.The economy of scale also favor only large capacity LNG plants and terminals. However it is not a sustainable solution in the long run considering the fact that supply of natural gas also keeps dwindling steadily. Despite all these obstacles, Governments around the world are looking only for short term solutions like LNG, simply because it is an easy fix. Biogas can be generated from organic waste and waste waters by anaerobic digestion. Many sewage treatment plants around the world have started generating biogas to generate power and use captively and to export the surplus power to the grid. Similarly municipalities are also implementing projects to convert ‘waste garbage’ to ‘energy’. However, the scale of operation favors only large capacity plants in larger cities. However these biogas plants will still emit carbon dioxide because biogas will be combusted using conventional engines, micro turbines and Fuelcells.This is once again a temporary solution only. We need to look beyond all these technologies to really reduce the greenhouse emissions. The only option is by Renewable Hydrogen and we need to take steps to make it a commercial reality. Biohydrogen is another potential technology. However the technology is still in a nascent stage but it is promising. Renewable Hydrogen using renewable energy sources are our best bet. Countries have already started investing in renewable energy infrastructures such as solar and wind. They can as well plan for renewable Hydrogen so that they can be certain about three things. One, they can generate and use uninterrupted power supply without importing oil or gas. Secondly they can be certain that greenhouse emissions can be reduced to pre-industrialization level. Thirdly they can be certain about the final cost of energy and its stability in the long run. These are three important factors every citizen of a country is looking for. It requires political will, determination and swift action on the part of individual Governments.

Monday, February 20, 2012

Fuel Cell- a new concept in power generation

Power generation using fossil fuels is a well established technology dating back to 1839, when Michael Faraday invented the principle of Electro-magnetism. There was not much of a change in this technology all these years. But recently greenhouse emission and global warming has become an issue; and the world started looking for an alternative source of energy and method of power generation. However it is not an easy task to develop completely a different technology as well as a fuel in a short span of time, while an unabated man-made greenhouse gas emission continues. Scientists are now warning catastrophic consequences if the greenhouse gas emission is not curtailed with great urgency.Untill now the world was able to avert some of the potentially catastrophic events happening, like ozone layer depletion, pandemic bird flu etc.But global warming is a new thereat that demands an entirely a new solution and a swift action. But majority of countries in the world are not is a position to curtail greenhouse emission gas, simply because there is no alternative fuel known, except fossil fuels. Renewable energy is relatively a new concept. Though solar and wind energy sources were known long time back, they were not persuaded seriously because they could not compete with conventional fossil fuels. But the time has come for new emerging technologies that can not only compete with fossil fuels but also eliminate greenhouse emissions. The world has invested massively on fossil fuel infrastructures and still investing heavily on oil and gas explorations. Obviously there is no end in sight as far as fossil fuels are concerned and the world is carrying on business as usual. Meanwhile a new technology based on fuel cell is emerging as an alternative for power generation. Fuel cell is a known concept and it has been successfully deployed in ‘Apollo space programme in space shuttle. This old version of alkaline fuel cells was replaced with PEM (proton exchange membrane) fuel cell or (PEMF) Polymer electrode membrane fuel cell. This new version was used in Gemini’s space programme in sixties. Fuel cell is an electro chemical devise that uses Hydrogen gas as a fuel and it operates at ambient temperature. It is like a battery cell. The difference between fuel cell and batteries is the Fuel cell will keep generating power as long as fuel is supplied unlike a battery, where energy is stored in the form of chemical energy and converted into electrical energy when used by connecting through a conductor. Battery needs recharging but Fuel cell requires refueling. The fuel used in Fuel cell is invariably Hydrogen. Conventional power generation involves combustion of fossil fuel (heat energy) which drives a turbine (mechanical energy) to run an alternator to generate power (electrical energy).In fuel cell; Hydrogen gas reacts with oxygen from the atmosphere (electrochemically) to generate power. It produces water as by-product. The efficiency of Fuel cell is about 50-60% compared to 35-40% by steam or gas turbine. In regenerative fuel cell, water can be split into Hydrogen and oxygen using same proton exchange membrane elecrolyzer.The resulting Hydrogen can be used as a Fuel to the PEM Fuel cell to generate power, thus recovering water. It is a closed circuit system. There are no mechanical moving parts, no combustion, no smoke or no noise. It is a quiet and clean operation. It is a very promising technology that can revolutionize the way we produce fuel and generate power. The Hydrogen and fuel cell combination is used in cars. Honda FCX (fuel cell model) cars work on the same principle and they are already on roads! One problem with Hydrogen generation is it requires more power to split water, into Hydrogen and oxygen, than the power generated by resulting hydrogen, using Fuel cell. However, this technology will change the future of power generation by eliminating greenhouse emission completely. But how long it will take to become a commercial reality is something to be seen! If political leaders and Governments around the world recognize the potential of this technology and take bold decisions coupled with swift actions, probably our future generation can breathe a clean air.