Combined solar thermal and photovoltaic power plants – An approach to 24h solar electricity?

Abstract

Solar thermal power plants have the advantage of being able to provide dispatchable renewable electricity even when the sun is not shining. Using thermal energy strorage (TES) they may increase the capacity factor (CF) considerably. However in order to increase the operating hours one has to increase both, thermal storage capacity and solar field size, because the additional solar field is needed to charge the storage. This increases investment cost, although levelised electricity cost (LEC) may decrease due to the higher generation. Photovoltaics as a fluctuating source on the other side has arrived at very low generation costs well below 10 ct/kWh even for Central Europe. Aiming at a capacity factor above 70% and at producing dispatchable power it is shown that by a suitable combination of CSP and PV we can arrive at lower costs than by increasing storage and solar field size in CSP plants alone. Although a complete baseload power plant with more than 90% full load hours may not be the most economic choice, power plants approaching a full 24h service in most days of the year seem to be possible at reasonably low tariffs.