Harnessing direct solar energy – a progress report
Box 5 | Chemical fuels from the sun
Putting the sun’s energy into a light and portable form is the only way to allow all sectors of modern society to run entirely on solar energy.
Solar energy can help to produce energy in a portable form
In Australia, the CSIRO Division of Energy Technology is using high temperatures from concentrated solar energy to convert methane and water to a gas mixture containing hydrogen and carbon monoxide. This energy-rich gas mixture can be stored and transported. The gas can then be burnt as a fuel or the stored solar energy can be released by allowing the mixture to separate back into methane and water.
Advantages of hydrogen as a fuel
For many in the field, it’s clear that the ultimate fuel is hydrogen – the lightest substance in the universe. We can produce hydrogen from water, but need energy to do so. Once we have the hydrogen gas, it can be safely stored and transported. Hydrogen is currently only used to power rockets and some demonstration vehicles, but with some modifications it could power all our transport and electricity generators. When burnt, hydrogen releases energy and combines with oxygen in the air to form water – a product with no pollution potential! At the same time, the water that was used to produce the hydrogen is regenerated – so the cycle can continue until the sun burns out.
Ways to generate hydrogen
Hydrogen can be generated from water by using an electric current; this is called electrolysis. The electricity can be derived from sunlight. Another possibility would be to simply use very high temperatures from concentrated sunlight, which can literally tear apart the molecules of water into its hydrogen and oxygen atoms. Ideally the gases would then be separated.
But there are much more sophisticated ways of splitting water using sunlight. The secret lies in plants. When exposed to light, green plants continually split water – releasing the oxygen into the air for us to breathe, and combining the hydrogen with carbon dioxide to form sugars. If we could duplicate this process, we would be well on the way to becoming a truly solar society. Research continues.
The future of hydrogen as an energy source
Australia’s Sir Mark Oliphant, the distinguished physicist, is one of several experts who have considered that the move to a solar-powered ‘hydrogen’ society would eventually come. Under such a scenario, desert areas could be used for intensive solar collection and the production of liquid fuels would power our world, in much the same way that modern agriculture, with its huge area of wheatfields, continually converts sunlight into solid chemical energy for us to eat.
Boxes
Box 1. Eliminating the zeroes
Box 2. Driving on a sunbeam
Box 3. Light to electricity
Box 4. The Big Dish
Related Nova topics
The quest to make hydrogen the fuel of the future
Which way ahead for hydrogen cars?
Fuelling the 21st century
Page updated November 2009.