adminHYDROGEN ENERGY NOW AND THE FUTURE
Hydrogen is the most abundant known element in the universe, making up about 90% of all matter. Its atomic structure is the simplest and it consists of one outer electron and one proton and neutron in its nucleus. In its normal state that is at standard temperature and pressure hydrogen is gaseous, odorless, tasteless, colorless and non-toxic. Hydrogen when exposed to oxygen burns readily releasing a considerable amount of heat energy and water as the product of the chemical reaction.
Hydrogen is a carrier and not a source of energy. Primary sources of energy such as coal, oil, and natural gas store energy. They can be burned directly to release energy for use for heating or they can be transformed into secondary energy sources for final consumption. Energy transformation allows energy to be transported or delivered in more convenient or useable form. Electricity is the most common secondary source of energy. Hydrogen is also a secondary source, as it can be produced using a hydrogen rich source. It can be converted to energy (heat) either through combustion or through an electrochemical reaction to generate heat and electricity. Secondary sources are also known as energy carriers.
Almost all the hydrogen in the world today is produced by steam reforming of fossil fuels using nickel as catalyst. In most cases, natural gas (methane) is the raw material. The methane first reacts with steam to produce carbon monoxide and hydrogen. The carbon monoxide, passed over a hot iron oxide or cobalt oxide catalyst, then reacts with steam to produce carbon dioxide and additional amount of hydrogen.
Natural gas is usually the cheapest feedstock for producing hydrogen in steam reforming. Even so, producing hydrogen from natural gas costs about two or three times, more than producing gasoline from crude oil.
Another proven method uses partial oxidation of methane to produce hydrogen. The process involves mixing the methane with oxygen in a chemical reaction to produce hydrogen and carbon monoxide which is then reacted with water to produce more hydrogen and carbon dioxide. Overall conversion efficiency is generally lower than for steam reforming. Which is why the latter technique is preferred in the commercial production of hydrogen.
Gasification of coal is the oldest technique for making hydrogen. The coal is heated until it turns into a gaseous state, and is then mixed with steam in the presence of a catalyst to produce a mixture of hydrogen (around 60%), carbon monoxide, carbon dioxide and oxides of sulphur and nitrogen. This synthesis gas may then be steam reformed to extract the hydrogen or simply burned to generate electricity.
Hydrogen can also be produced from biomass, such as crop residues, wood and dung using pyrolysis process and gasification (thermochemical) techniques. These processes produce a carbon rich synthesis gas that can be reformed into hydrogen in the same way as natural gas or coal based synthesis gas. The advantage of biomass over fossil fuels is that it produces no net emission of carbon dioxide, since the carbon released into the atmosphere was previously absorbed by the plants through photosynthesis.
Hydrogen production using water electrolysis is minimal today because it requires large amount of electricity which is expensive. To be economical the electricity used for electrolysis would need to be cheap. The environmental benefit of electrolysis based hydrogen energy depends on how the electricity is produced. If it is generated from nuclear or renewable energy sources such as wind, solar and biomass electrolysis will produce carbon free hydrogen. But large reduction in the cost of renewable based electricity and nuclear power are needed to enable hydrogen produced by electrolysis to compete with conventional sources of energy on a large scale.
Hydrogen is the main fuel of the sun and the universe. The sun energy comes from the fusion of hydrogen atoms to form a helium atom with tremendous amount of heat generated during the process. Hence if man wants to solve completely his energy needs, he has to mimic or copy the sun. Moreover water the raw material for this process exists in abundance on earth. So how can we go wrong if we adopt the hydrogen technology and economy for our future energy security?
However, in this quest there are obvious drawback and limitations. Nuclear fusion technology is farfetched and may gain traction in another hundred years, but the recourse is here. Fuel cell technology is that recourse; it is a technology that produces electricity with hydrogen and air as the raw material producing water and heat as exhaust. This technology is already proven technically and commercially.
The other attraction to hydrogen as fuel is the potential advantage it has over fossil fuels that it burns without producing harmful emissions like carbon dioxide and associated pollutant to the air. Thus hydrogen holds the potential to provide energy services to all section of the economy, including transportation, building and the industry. The use of hydrogen the fuel of choice in the aerospace industry is founded not only on its lightness but also on it excellent energy storage capacity. Also the use of hydrogen to produce green steel and green ammonia is well known in industry. In addition the poor countries of the world can exploit their biomass potential to produce hydrogen, then using the hydrogen for domestic heating and as raw material for industrial energy production using fuel cell technology, thus simulating economic, technological and industrial growth.
Sources;
- Hoffman P.(2001), Tomorrow’s energy hydrogen, fuel cells and the prospect for a cleaner planet. MIT press Massachusetts.
- European commission (2003), Hydrogen Energy and Fuel cells; A Vision of our future. DGTREN Brussels.
- United Nations Environmental Program (2006) THE HYDROGEN ECONOMY: UNEP.
- IEA (2004) Hydrogen and fuel cells: OECD/IEA.
- EG&G Technical services, Inc. (2004) : fuel cell handbook.US Dept. of energy.
