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PV-enhanced solar thermal power

: Platzer, W.

Fulltext (PDF; )

Energy Procedia 57 (2014), pp.477-486
ISSN: 1876-6102
Solar World Congress (SWC) <2013, Cancun>
Journal Article, Conference Paper, Electronic Publication
Fraunhofer ISE ()

Solar electricity generation using concentrating solar thermal collectors faces the challenge of strongly decreased levelized electricity costs by photovoltaic power plants. One of the selling points favouring solar thermal power is the possibility to generate dispatchable power. Concepts discussed here are solar hybridization of conventional or biomass thermal power plants. Another option is the use of thermal energy storage (TES) charged with solar heat which allow to drive the generation of electricity by steam turbines also during hours with no or low solar irradiation. Usually the solar fields of solar thermal power plants utilizing storage with several hours capacity will be much larger than those of plants without storage. This contributes to much higher cost per installed capacity in the case of storage utilization. In this paper the question shall be tackled in a rather fundamental way whether the combination of solar thermal power with cheaper photovoltaic systems plus minimum solar thermal power with storage may give lower levelized electricity cost plus dispatchability than either photovoltaics alone or solar thermal power alone.
For the investigation of a combined PV-enhanced solar thermal power plant no specifically developed software was available. Therefore the simulation of the photovoltaic plant and the solar thermal power plant including TES was done individually. For the solar thermal power plant TES storage capacity and solar field area were varied. Solar field area ranged between solar multiple of two and below one. The latter choice would have been senseless without PV-enhancement. Hourly power generations profiles over a complete year were combined and matched in order to generate electricity according to a prescribed demand curve. Using dispatch prescriptions the scheduling of solar thermal power was controlled. With typical generic cost data and variations of those in a sensitivity study the combined levelized electricity cost were determined and analysed.
Photovoltaic generation and solar thermal power generation via thermal energy storage may produce high annual capacity factors above 50% due to dispatchable solar power from the thermal storage. Depending on the climatic conditions and on seasonal and daily load profiles the combinations of photovoltaic and solar thermal power may change. Many open questions have to be solved in order to proceed with the basic idea of PV-enhanced solar thermal power generation. Real cost data and optimization requires a specific project case. Then also the selection of the most promising photovoltaic technology and the different solar thermal technologies may be discussed in more detail.