Although the sun provides an unlimited amount of energy, night is and remains a problem. For almost half of the day, equipment dependent on solar energy has to be switched off or store extra energy. This process is especially disruptive for installations that rely on concentrated solar energy. German scientists therefore developed a solar reactor, known as CONTISOL, that also stores thermal energy. This allows the plant to keep running day or night.
Back to concentrating for a moment: photovoltaic systems derive energy from light; concentrated solar systems capture heat from the sun. This is usually done by putting up a series of mirrors that reflect sunlight to a 'receiver' in a central tower. This then uses the heat for a thermochemical reaction. This may involve turning water into steam to run a turbine or-in the case of CONTISOL-produce hydrogen by splitting water vapour.
This requires the reactor to reach temperatures between 800° C and 900° C. This works fine when the sun is shining, but in the darkness of the night, the system cools down and wastes time and heat because the reactor has to heat up every morning. The CONTISOL should solve this problem. During the day, sunlight heats two pairs of chambers filled with air from outside. When the air is heated, it is fed into the reactor where it starts a thermochemical reaction and hydrogen can be produced. In the other chamber, the energy can be easily stored. Once the sun goes down, the system can extract hot air from the 'storage chamber' and continue to use it in the reactor.
To test the system, a team of German team scientists set up a small-scale prototype. This continued to work successfully at a temperature of 850°C and a power of 5kW. These are not huge amounts of energy but prove the viability of the reactor. It can then be scaled up for commercial applications.
