Solar thermal power is the process by which solar energy is transformed into electricity in two stages: the energy from the sun in the form of light radiation is first converted into thermal energy by means of a special collector and the latter is then converted into electricity through a thermodynamic cycle. The temperatures required to generate high-pressure steam can be reached only by a high concentration, hundreds or even a thousand times the intensity of the solar radiation incident on the Earth's surface.
The light concentration process needed for solar thermal power, acts only on the direct solar radiation. As a result, even small fogging of the sky can lead to high power drops delivered by the system. Furthermore, direct light fluctuations not only affect the electric power generated but can induce high mechanical stress on plant components due to extremely rapid temperature variations. For this reason it is useful in many cases that the concentration systems are equipped with heat accumulators or in any case with sophisticated control systems that help to diminish temperature variations.
The yields of these plants are still small, between 15 and 20%, but may increase with technology developments. In the context of small generators that produce electricity by using the thermodynamic concentration of solar radiation, a new dish-Stirling solar generator, EuroDish type, was created, tested and put into operation in the Distributed Generation Test Facility at RSE. The plant has been the subject of several experimental activities over the years. The activity, which is still in progress, is aimed at investigating the issue concerning the loss of working fluid (He) during downtime. The short duration of the current dynamic seals is a crucial issue in the operation of the system and strongly penalizes its reliability. Different materials and different technological solutions are therefore being studied to increase the life of these components.