Hydrogen 'ideal' as fuel for the future
by Timmy Ramirez Cuesta
09 June 2011
Hyrdogen is an excellent candidate as the ideal clean fuel for the future – but storage is proving an elusive target, writes Timmy Ramirez Cuesta
Meeting the world's ever increasing energy needs in an efficient, safe and sustainable way is one of the most demanding challenges we currently face.
Supplying such energy requires fuels – materials in which large amounts of energy can be stored. Fossil fuels like oil and gas are made up of ancient plants and algae which captured solar energy. This energy was then trapped when various geochemical processes converted the plant matter into energy-rich substances that we use today.
Unfortunately, this energy is non-renewable, and the combustion of these fossil fuels releases pollution and greenhouse gases. To produce a truly sustainable fuel, the original energy must come from a renewable source such as the wind or the sun. Creating a perfect fuel, one that is cheap, safe, efficient, and stores renewable energy, is a tough challenge for scientists.
Hydrogen is an excellent candidate for this ideal fuel, as it can be used to produce a great deal of energy. It can also be obtained very easily – though at an energy cost – by splitting water molecules. It can be used either to store energy like that from the sun, or burnt in an internal combustion engine, which releases the energy directly from the hydrogen. The by-product of the process is just water vapour, making this energy production process one of the most environmentally friendly that we know.
As hydrogen is a gas at ambient temperatures and pressures, its volumetric energy capacity is very low – you need a large volume of hydrogen gas to create a small amount of energy. Hydrogen can be stored as a gas at high pressures, 350 to 700 atm, or as a liquid at temperatures of -252°C. But both of these are energy-intensive processes and impractical for domestic use. This is the major roadblock to a hydrogen economy.
One option is to use lightweight porous materials which adsorb hydrogen molecules into their tiny pores, acting like a sponge. But these materials still need to be kept at low temperatures of -196°C and moderately high pressures.
Research facilities such as the world leading ISIS neutron source – based at the Rutherford Appleton Laboratory in the UK – are also investigating the potential for storing hydrogen in chemical compounds, such as metal hydrides. These can store a large amount of hydrogen per volume, some as much as twice the volumetric density of liquid hydrogen. However, metal hydrides are too heavy to be of practical use and there are problems with the hydrogen extraction and re-insertion in all existing compounds investigated – a practical issue for refuelling a hydrogen powered car.
Hydrogen storage is proving to be an elusive target but large experimental facilities such as ISIS, which uses neutrons to examine the atomic structure of possible hydrogen storage materials, are critical. As more applications of hydrogen start to make an appearance in the consumer market, the need for safer and more efficient hydrogen stores will become more urgent, and a renewed effort into basic materials research will undoubtedly provide the required breakthrough that will make the widespread use of hydrogen a reality.
Timmy Ramirez Cuesta is an instrument scientist working on the ISIS neutron source. ISIS is operated by the Science and Technology Facilities Council
Meeting the world's ever increasing energy needs in an efficient, safe and sustainable way is one of the most demanding challenges we currently face.
Supplying such energy requires fuels – materials in which large amounts of energy can be stored. Fossil fuels like oil and gas are made up of ancient plants and algae which captured solar energy. This energy was then trapped when various geochemical processes converted the plant matter into energy-rich substances that we use today.
Unfortunately, this energy is non-renewable, and the combustion of these fossil fuels releases pollution and greenhouse gases. To produce a truly sustainable fuel, the original energy must come from a renewable source such as the wind or the sun. Creating a perfect fuel, one that is cheap, safe, efficient, and stores renewable energy, is a tough challenge for scientists.
Hydrogen is an excellent candidate for this ideal fuel, as it can be used to produce a great deal of energy. It can also be obtained very easily – though at an energy cost – by splitting water molecules. It can be used either to store energy like that from the sun, or burnt in an internal combustion engine, which releases the energy directly from the hydrogen. The by-product of the process is just water vapour, making this energy production process one of the most environmentally friendly that we know.
As hydrogen is a gas at ambient temperatures and pressures, its volumetric energy capacity is very low – you need a large volume of hydrogen gas to create a small amount of energy. Hydrogen can be stored as a gas at high pressures, 350 to 700 atm, or as a liquid at temperatures of -252°C. But both of these are energy-intensive processes and impractical for domestic use. This is the major roadblock to a hydrogen economy.
One option is to use lightweight porous materials which adsorb hydrogen molecules into their tiny pores, acting like a sponge. But these materials still need to be kept at low temperatures of -196°C and moderately high pressures.
Research facilities such as the world leading ISIS neutron source – based at the Rutherford Appleton Laboratory in the UK – are also investigating the potential for storing hydrogen in chemical compounds, such as metal hydrides. These can store a large amount of hydrogen per volume, some as much as twice the volumetric density of liquid hydrogen. However, metal hydrides are too heavy to be of practical use and there are problems with the hydrogen extraction and re-insertion in all existing compounds investigated – a practical issue for refuelling a hydrogen powered car.
Hydrogen storage is proving to be an elusive target but large experimental facilities such as ISIS, which uses neutrons to examine the atomic structure of possible hydrogen storage materials, are critical. As more applications of hydrogen start to make an appearance in the consumer market, the need for safer and more efficient hydrogen stores will become more urgent, and a renewed effort into basic materials research will undoubtedly provide the required breakthrough that will make the widespread use of hydrogen a reality.
Timmy Ramirez Cuesta is an instrument scientist working on the ISIS neutron source. ISIS is operated by the Science and Technology Facilities Council
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