Energy Crisis

Periodic crises in the supply and price of fossil fuels have drawn attention to the fact that renewable energy sources are the only long-term solution to the energy requirements of the world’s population. Molecular hydrogen is a future energy source/carrier that is being actively investigated as an alternative to fossil fuels. It reacts with oxygen, forming only water; hence, it is a clean renewable energy source. It has a high calorific value, and can be transported for domestic consumption through conventional pipelines. Contrary to a widely held belief (the ‘Hindenburg disaster syndrome’), hydrogen gas is safer to handle than domestic natural gas.
When fossil fuels are no longer abundant, or their use is curtailed because of concerns over changes in the atmosphere, the way in which we use energy will be fundamentally changed. For example, the present methods of generating electricity are a compromise between the efficiency of large power stations and the losses in transmission over long distances. It is more efficient to transmit H2 gas through pipelines, than electricity through power lines. Electricity could be produced locally, even domestically, from H2 and air, in fuel cells. The risks of using H2 are offset by the use of lower electric voltages. The switch to a hydrogen economy could be a gradual transition. Hydrogen can be mixed with methane in domestic gas supplies with minimal change to the equipment. But the greatest benefits for H2 will come when exploiting the thermodynamic advantage of fuel cells, converting chemical energy directly to electricity.
A great deal of research is being applied to the use of hydrogen as a fuel in transportation, for cars and airplanes. The goal here is the promise of near-zero emissions.
H2 is also being considered as an alternative to batteries for electronic equipment.
For transport, the difficulties are concerned with finding a compact storage for the low-density fuel; and the expense of the catalysts. Various approaches are being used for storage. One is to store it as a higher-density liquid such as methanol, and reform it to H2 as required. This is somewhat analogous to the biological approach, though it leads to the release of CO2. Other options are to compress the H2, store it as liquid hydrogen at very low temperatures, or combine it with metals to form hydrides from which the gas can be released at will. Another method, which again resembles the biological solution, is to store the H2 in carbon nanotubes, which offer high-density and lightweight storage.
At present most of the H2 is produced industrially by conversion of fossil fuels, either directly or indirectly. This leads inevitably to the net production of the greenhouse gas CO2. New methods will have to involve recycling of organic matter, or direct production of H2 from water using energy sources such as sunlight. This can be achieved either directly in photochemical fuel cells, or by using photovoltaic cells, which use solar radiation to electric current for electrolysis of water into H2 and O2. A great deal of effort has gone into the development of silicon solar cells (photovoltaic) for production of energy from sunlight, which have become less expensive and improved in efficiency.
The costs of production of H2 from the electricity produced are decreasing steadily, but they still involve noble-metal catalysts.