It is well known that renewable energies like wind and solar radiation are by far not as concentrated as coal or uranium. In addition, these renewable energies fluctuate on a short term within minutes as well as within days and months on a long term. These features cause large problems for the reliable use of renewable energies as an alternative for nuclear or fossil power plants. The first disadvantage results in the need for a high conversion efficiency to reduce costs. One means for this purpose is the use of concentrated solar power. The second disadvantage leads to the need of large storage systems to overcome at least fluctuations up to a time of a day.
For commercial purposes, it will be necessary to combine several measures. One of the possibilities that might be used is outlined in the lower part of the figure below. Concentrated solar power can be transferred to sodium as a transport or a storage medium. In this way, either solar power may be used directly in a conventional thermal power station, or solar energy may be stored in a tank. When the facility is sized appropriately, the thermal power plant runs day and night without interruption and hence contributes to base load. The great advantage of such a layout is the continuous operation of the turbine, increasing its life time substantially: the transients during the start and stop that are harmful to a turbine are avoided due to the storage tank. If a direct conversion system is added, peak load demand may also be satisfied, and excess energy supply may likewise be stored in the tank. In such a configuration, the facility may also be used for load balancing in the distribution grid.