Christian Odenthal

Development of the CellFlux Storage Concept for Sensible Heat

Two tank storage systems using molten salt represent todays state of the art in energy storage for concentrating solar power (CSP) plants. This concept shows a limited potential for further cost reductions, since the capital costs are dominated by the expenses for the salt inventory. The application of solid storage materials represents a promising approach to reduce capital costs. While this approach avoids also the risk of freezing and lessens corrosion problems, the efficiency of the heat transfer between the heat transfer fluid (HTF) and the solid storage medium is crucial. This paper introduces the CellFlux concept, which uses an intermediate closed air loop to transfer energy between the HTF and the solid storage material. A modular concept is chosen to optimize the size of the air flow channels. An initial project will provide the fundamentals needed to design a CellFlux storage unit. The feasibility will be proven by a 100 kW/500 kWh pilot storage module.

Modelling and Operation Strategies of DLR's Large Scale Thermocline Test Facility (TESIS)

In this work an overview of the TESIS:store thermocline test facility and its current construction status will be given. Based on this, the TESIS:store facility using sensible solid filler material is modelled with a fully transient model, implemented in MATLAB®. Results in terms of the impact of filler site and operation strategies will be presented. While low porosity and small particle diameters for the filler material are beneficial, operation strategy is one key element with potential for optimization. It is shown that plant operators have to ponder between utilization and exergetic efficiency. Different durations of the charging and discharging period enable further potential for optimizations.

Proof-of-concept and advancement of the CellFlux concept

The CellFlux storage system is a new concept for reducing the costs of medium to high temperature thermal energy storage. Initially designed for solar thermal power plants, the concept is suitable for industrial processes and power to heat applications as well. This paper gives first results of a new pilot scale plant set up at DLR in Stuttgart as a proof of concept. Experimental results are used for the validation of a simplified model. The model is apllied to calculate pareto optimal storage configurations in terms of necessary storage mass and exergetic efficiency, suitable for two types of solar thermal power plants. Particularly for applications having larger temperature differences, high exergetic efficiencies at low costs for the storage material can be achieved.