Our star, the Sun, will supply us with enough energy for at least another 4 billion years. Credit: NASA
The daily amount of solar irradiation on the Earth’s surface is about 165 Watt per square metre. The resultant energy keeps the Earth’s atmosphere moving, makes the weather – wind and rain – and is used by plants and algae to produce biomass. A small proportion of the energy has been conserved for millions of years – as coal, oil and gas. However, over the last 200 years, we have used up a large part of our supply of fossilised fuels. If we continue at this rate, we will need the resources of three Earths by 2050. Yet the solar energy that reaches Earth would be more than adequate to supply the energy we need: About 5000 times the amount of energy that all humans require per day reaches the Earth’s surface. The problem is collecting and storing the energy.
How can we store energy?
A simple experiment to investigate the conversion of energy in the DLR_School_Lab Cologne (left to right: solar panel, electrolyser, fuel cell, appliance). Credit: DLR (CC-BY 3.0)
For millennia, people have used wind and water energy, which also incorporate solar energy. Appliances that produce electricity using solar energy are also well-known to us. But is technology like this really economically viable in our climes? How can we store energy? What use is a car that slows down every time a cloud passes or that cannot be driven at night? Rechargeable batteries and chemical energy carriers are currently being tested and improved.
Hydrogen could be the chemical energy carrier of the future. It is environmentally friendly, as it is produced during the dissociation of water and when burned it converts back into water without any residues. This can be done in a hot flame or in a “cold” fuel cell that produces electricity. In principle, fuels cells have been in use since 1838. During the 1960s they were developed further for use in aerospace technologies. The Apollo capsule used fuel cells as energy sources for the lunar missions – though this did lead to a very critical situation during the Apollo 13 mission.
The time has come!
True, we have cars and busses that run on hydrogen. The power glider Antares - developed by the DLR - is the first aeroplane able to take off using its own motors that is powered by a fuel cell. But a lot of research will be necessary in order for hydrogen technology to be implemented in many other fields. Out experiment will show you some of the obstacles that need to be tackled. And time is running out: The Earth’s energy supply has to be based on renewable energies within your lifetime.