Solar energy has great potential to be the energy source of the future, but it is unreliable. What happens when the sun goes down at night? Or when the sky is cloud covered all day? These questions are currently being addressed, as researchers are experimenting on ways to store the energy captured from the sun.
One current solution used in Spain in parabolic trough power plants, is to use solar energy to heat up a thermo oil, which in turn heats up liquid salt, and when the sun goes down, the heat of the liquid salt is used to power a steam turbine. However, liquid salt is very expensive and it is not allowed to cool down, or else it will congeal and destroy the container. Furthermore, liquid salt is not compatible with solar thermal power plants, thus different containment methods have to be developed for the varying power plants.
In a solar power plant In Jülich Germany, solar panels reflect the sunlight to a huge tower, which stores the heat. In this case we are dealing with heat in gas form, which makes a storage container of molten salt not feasible. Thus, in this situation ceramic is used, which is however also very expensive. Currently the researchers are working on an alternative solution that uses salt. The salt falls into a collecting container and in the process, the warm gas is blown onto the sand, transferring its warmth onto it.
The salt method is also not perfect, as it cannot be as easily pumped through pipes as liquids or gases. A final method is the chemical thermal storage, where, for example, calcium hydroxide would be split into Calcium and Water. Then the two elements would be brought back together and heat would be released. This way, the energy can be saved for a long period of time and released at whatever temperature necessary. However, this method has only been tested in the confines of scientific labs and would require the construction of a special chemical reactor.
There is a lot of potential for development in this area and experimentation with different materials and processes. If renewable energies are to replace current non-renewable sources, a process for their storage has to be developed, so that we will still have energy when the sun doesn’t shine or the wind dies down.
