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Research project

StorEx – Theoretical and experimental investigations on the stratification efficiency of heat storages

The stratification efficiency of heat storages has a decisive impact on the energetic efficiency of solar thermal systems as well as of heat pumps. In this project, a representative key figure for stratification efficiency and a cost-efficient test procedure for its determination are developed for combi-storages that provide space heat and domestic hot water. The procedure is applied to combi-storages of different manufacturers, and the results are compared with each other. In addition to this, CFD simulations are carried out for the determination of the impact of direct horizontal storage inlets on the stratification of the storage. Selected stratification experiments are also validated with measurements the laboratory. At the end of the project, recommendations are given for the geometry and maximum volume flow rate at which direct horizontal inlets can be used without disturbing an already existing stratification in the storage.


This project receives funding from the Swiss Federal Office of Energy SFOE.

Final report (PDF, German)

Duration: 01.06.2013 - 31.05.2015