|
|
|
Hydrogen: the optimum future fuel
ENERGY is an essential component for all economic activities and is required for the production of all goods and the provision of all services. Sustainable economic growth needs to be fuelled by energy systems that are increasingly more efficient, less expensive and cleaner.
In order to sustain economic growth, energy systems must increase economic productivity and competitiveness, put more people to work and must, in the short term, limit, and in the long term, reduce environmental degradation.
The present day energy systems can be categorized into three main branches, fossil fuel, renewables and nuclear power. Historically, fossil fuels have been the main source of energy supply and have served human energy needs for thousands of years.
Fossil fuels have traditionally been used in their solid phase i.e. wood and coal. Wood and coal have been serving society to meet energy needs for a long time. In the beginning, this energy source was very stable and sustainable. Forests and coal resources were in abundance and were sufficient to meet energy demands.
However, as human demand exceeded expectations, particularly with the advent of industrial revolution in nineteenth century, a more efficient energy technology was needed. The world moved from wood and coal fuels to oil and then to natural gas. This energy transition from wood to coal to oil to natural gas has been the different phases of traditional fossil fuels. All these forms of fossil fuels got their respective cycle of domination, then depletion phase.
Renewable energy systems, that use indigenous resources, include biomass, solar, wind, geothermal, wave, and hydropower.
Renewable energy sources have also been important for humans since the beginning of civilization. Biomass, for example has been used for heating, cooking and steam production __ and hydropower and wind energy, for transport and later for electricity production.
In developed countries, by the middle of last century, mass application of existing renewable technologies was in practice, i.e. hydel power systems and windmills, but also invention of new technologies such as Photovoltaic (solar), wave and tidal energy systems. Fossil fuels and renewables were accompanied by a new energy system, nuclear power. This however, with a few exceptions, has been the domain of developed/western countries.
At present, fossil fuels are still the primary source of the world’s energy supply.
Fossil fuels depletion, however, is a cause for concern. Fossil fuels reserves, presently meeting 80 per cent of the global energy demands, are diminishing rapidly across the world.
Stress on existing reserves is increasing day by day due to increased demand. It was reported in year 2003, that reserve to production ratio of fossil fuels for North America, Europe and Eurasia, and Asia Pacific were 10, 57 and 40 years respectively while the world’s resource to production ratio is projected to be 62 years.
Research conducted at the University of Uppsala in Sweden claims that oil supplies will peak soon after 2010, and gas supplies not long afterwards, making the price of petrol and other fuels rocket with potentially disastrous economic consequences unless people have moved to alternatives.
Renewables have the potential to provide energy services with zero or almost zero emissions of both air pollutants and greenhouse gases. They have now been acknowledged as a vital and plentiful source of energy that can indeed meet the entire world’s energy demand.
It is interesting to note that way back in 1923 Haldane prophesied the production of hydrogen in UK by renewable energy means. He writes thus, “The country will be covered with rows of metallic windmills working electric motors which in their turn supply current at a very high voltage to great electric mains. At suitable distances, there will be great power stations where during windy weather the surplus power will be used for the electrolytic decomposition of water into oxygen and hydrogen.
These gases will be liquefied, and stored in vast vacuum jacketed reservoirs, probably sunk in the ground. In times of calm, the gasses will be recombined in explosion motors working dynamos which produce electrical energy once more, or more probably in oxidation cells.”
Renewable energy sector at present is meeting 13.5 per cent of the global energy demand. This sector is now growing faster than the growth in overall energy market. Some long-term scenarios postulate a rapidly increasing share of renewable technologies (made up of solar, wind, geothermal, modern biomass, as well as the more traditional hydro).
Under these scenarios, renewables could reach up to 50 per cent of the total share by mid-21st century with appropriate policies and new technology developments.
In present energy chain, collected or extracted primary energy is, in one or several steps, converted into energy carriers, such as diesel oil or gas that are suitable for end uses. In future, it is expected that hydrogen will take over the role of energy carrier. Hydrogen in the capacity of energy vector will be the optimum solution for intermittency and storage of energy produced by renewables.
Hydrogen can be primarily produced through reformation of natural gas, electrolysis of water, or partial oxidation of heavy fossil fuels such as diesel. In a renewable energy scenario, solar PV energy will be utilized to carry out electrolysis of water to yield hydrogen.
The transition of world energy system to hydrogen — the simplest and most abundant element in the universe — as a fuel is quite logical and becomes clearer when one takes a look at historical energy production sequence. Each successive transition from one source to another — from wood to coal, from coal to oil — has entailed a shift to fuels that were not only harnessed and transported more economically, but also had a lower carbon content and higher hydrogen content. It is also evident that at each step greater energy density is being achieved.
The third wave of decarbonization is now at its threshold, with natural gas use growing fastest, in terms of use, among the fossil fuels. The fourth wave, the production and use of pure hydrogen, is certainly on the horizon.
Its major drivers are technological advances, renewed concern about the security and price of oil and gasoline, and growing pressure to address local air pollution and climate change.
Hydrogen is the simplest and one of the most plentiful elements in the universe. Despite this, hydrogen does not occur naturally as a gas on Earth, i.e., it always combines with other elements. Hydrogen’s potential use in fuel and energy applications includes powering vehicles, running turbines or fuel cells to produce electricity and generating heat and electricity for buildings.
Hydrogen is a unique fuel with unmatched properties, one of them being its ability to produce electricity electrochemically in fuel cells with high efficiencies. It is not subject to the limitations of the second law of thermodynamics, which is the case with present day thermal power plants, whether they burn fossil fuels or nuclear fuels.
In addition to having high (75-80 per cent) efficiencies, hydrogen fuel cells are much cleaner (the only by-product being water) and quiet (i.e. no moving parts). They are versatile, as they can be used for large-scale power generation in central power plants, as well as for small-scale electricity production in the distributed mode. As such, there is no doubt that hydrogen fuel cell generation capacity will grow rapidly.
Around the globe, there are a large number of hydrogen-based national and international programs that may be quoted here as examples of activity on this front. Owing to its unique properties, hydrogen has become a suitable fuel for motive power and has gained the attention of many leading automobile companies.
Hydrogen-fuelled vehicles are being produced by BMW, Ford, General Motors, Honda, Toyota, Mazda, Nissan and many others. Its low weight and excellent combustion have paved its way into naval applications, aerospace and aeroplanes.
There are demonstration projects for hydrogen-hydride air conditioning, refrigeration and heat pumps. They do not need chlorofluorocarbons, and as such, they will not damage the ozone layer. Conversion to hydrogen-hydride air conditioning and refrigeration systems will greatly reduce ozone layer depletion.
The writer
The race for a new energy source
‘ENERGY independence’ sounds good but will not be easy to achieve: the United States consumes a quarter of the world’s oil but sits on only 3% of its proven reserves. In spite of the difficulties, however, no one should underestimate the innovative powers of American industry, nor its ability to divert enormous resources to developing a new technology if it looks like being a winner.
Whatever the politicians may say, America’s overthrow of Saddam Hussein -- and its ambition to install a pro-American regime in Baghdad — were driven in large part by the looming world oil shortage. World oil supplies are expected to peak between 2010 and 2020, and would then be unable to meet the exploding world demand for oil. The major powers, with the US in the lead, are engaged in a scramble for remaining oil stocks – to fill the supply gap before an alternative energy source becomes widely available, probably in the second half of this century.
According to Wolfgang Reitzle quoted above, hydrogen is the most viable replacement. ‘Every dollar spent on hydrogen,’ he says, will save us many more when the final rush for oil begins.’ But hydrogen — which as a constituent of water is all around us — is not easy to harness. In theory, switching from fossil fuels to hydrogen is extremely tempting: it would end dependence on oil, reduce air pollution in cities and check the build-up of greenhouse gases that are already being held responsible for severe climate change. But, in spite of billions of dollars now being spent on research, no one has yet found a simple, safe and cheap way to produce hydrogen.
Hydrogen atoms are bound to other elements in molecules, such as water. To work in fuel cells, hydrogen atoms must be split off from these molecules. At present, this is a costly process. Storing hydrogen on board a car is also a problem, which has not yet been solved satisfactorily. The hydrogen would need to be compressed or liquefied, but this in turn would require it to be chilled to just a few degrees above zero, a process consuming large amounts of energy. Since hydrogen gas is highly flammable, safety is another concern for which no adequate solution has yet been found.
For the cars of the future to be powered by hydrogen fuel cells would require the creation of a massive new hydrogen infrastructure. Mass-market hydrogen cars would need the new fuel to be available at filling stations. Where is to be produced? Is it to be produced in centralised plants and then trucked or piped to filling stations? Or could it be produced on site?
Experts say that huge problems will need to be resolved in producing and storing hydrogen, in converting it to electricity, in supplying it to consumers, and in overcoming safety concerns. Nevertheless, car and energy companies are pumping billions of dollars into building prototypes of vehicles and filling stations, while governments are pursuing hydrogen as a potential replacement for car fuel.
Change is coming and the higher the oil price the faster it will come. — Patrick Seale
|
|
|
|
