Jan 04, 2012— read in full
Hydrogen and sustainable energy
For environmental scientists, hydrogen is the best thing since sliced bread when it comes to sustainable energies, but why?
- It is the most abundant element in the universe
- It can be found in many different materials, including water, natural gas and biomass
- It is non-polluting: when you burn hydrogen the only by-product is water
When is hydrogen not sustainable?
Although hydrogen is abundant and free, capturing this element can be tricky.
Hydrogen tends to bond easily with other elements and has to be extracted. As a result there isn't much pure hydrogen around.
To make hydrogen fuel, hydrogen must be separated from whatever it's attached to, a process that requires energy. For this reason, hydrogen is often called an "energy carrier" rather than an energy source.
To get hydrogen, you first have to put energy in. For example, making a kilogram of hydrogen from water through electrolysis requires 45-70 kWh of electricity, depending on the technology. This amount of electricity could power the average home for roughly two to three days.
Because of this whilst many hail hydrogen as a green source of energy, it’s only sustainable if it’s produced using renewable energy.
How is it produced?
Common ways of producing hydrogen include:
- Reshaping the structure of natural gas (CH4). This is done by steam methane reforming, a process by which high-temperature steam (700 degrees Celsius to 1000 degrees Celsius) extracts hydrogen from the natural gas.
- Electrolyzing water. This is when an electric current is passed through a water to separate the hydrogen atoms from the oxygen atom.
This can be achieved without the use of natural gas through the use of nuclear reactors to operating at around 950-1000°C.
- Burning organic waste at high temperatures to produce gases that can be refined to make hydrogen.
What can hydrogen be used for?
Hydrogen can be used directly as a fuel to drive a vehicle, to heat water or indirectly to produce electricity for industrial, transport and domestic use.
It is the least polluting fuel when used for transport and yields more energy than conventional fuels.
It has been the fuel used to provide electricity for the space shuttle for the last two decades via on-board fuel cells that combine hydrogen and oxygen to generate electricity; the exhaust from the fuel cell – pure water – is used by the crew as drinking water.