Among the key renewable energy technologies, concentrated solar power (CSP) permits the use of relatively cheap thermal energy storage (TES) systems. For storing the collected energy, usually a suitable molten salt that is kept at high temperatures is used in conjunction with CSP. The EU-funded project ‘Optimization of a thermal energy storage system with integrated steam generator’ (OPTS) is studying an innovative TES system concept based on a single tank configuration. It is using a stratifying molten salt as heat storage medium along with an integrated steam generator. Scientists aim to demonstrate this technology for large-scale CSP plants (50-MWe electric power). To this end, the experimental concept should be verified in a relevant scale (at least 12.5-MWth thermal power).
Integration is realised in two different ways. Salt mixture stratification can either be determined by a steam generator that is positioned into the tank (pool-type) or with an external (loop-type) shell-and-tube once-through.
The first project period was dedicated to the investigation of thermophysical, material compatibility and heat transport properties of the employed molten salt. The research included modelling of thermocline and heat exchange behaviour. Work also started for studying the TES impact on CSP plant and the design of a test section plant; this campaign is going to be concluded during the second project period.
Besides the system employing an integrated steam generator, an alternative storage tank configuration has also been designed. In the latter case, different kinds of solid filling materials have been employed for storing thermal energy. Unfortunately, given the withdrawal of an industrial partner, it won’t be possible to complete the project by the construction of the test section. However, the obtained modelling results, experimental data and preliminary components cost analysis, all of which will be reported on in the final report, show that the technology proposed in OPTS is likely to be effective and competitive with regard to other CSP storage systems.
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