Verena Zipf, born 26th october in Heilbronn,
studied mechanical engineering at the Karlsruhe Institute of Technology (KIT). She finished her studies in april 2011 with distinction; since that time, she is working at the Fraunhofer Institute for solar energy systems in the section "solarthermal systems". From the beginning of her studies, she was highly interested in renewable energy technology and therefore she majored in "energy and environmental technology". In a term paper she worked on wave power plants. Thus she got fascinated in innovative technical developments and evolved the wish to implement a new and useful technology once by herself. After study stays in Sweden and in France she completed her studies with an external thesis at the Fraunhofer ISE. In her work "Application of a screw heat exchanger for a latent heat storage: methodic development of a prototype" she started the development of a innovative concept for the thermal storage of solarthermally generated steam.
"Development of a latent heat storage to increase the efficiency, dispatchability and profitability of solar energy production"
To increase the proportion of solar energy production,the decentralised production of combinded heat and power (CHP) with solarthermal collectors in small/middle scale power is investigated at the Fraunhofer ISE. Due to relatively small total investment needs, the distribution of CHP facilities is fairly easy. However, the specific investment is relatively high, therefore the efficiency of these facilites has to be increased to make them profitable. With a thermal storage the occupancy rate can be increased to after the sunshine hours, resulting in a better profitability of CHP facilities. Moreover, with a thermal storage the dispatchability of heat and power is improved. The development of a suitable storage technology is imperative.
Latent heat storage are exergetically optimal suited for the storage of the energy in two phase working fluids (e.g. steam). Up to now, there is no technical implementation of latent heat storages in this field of application due to technical challenges (e.g. very low heat conductivity of phase change materials(PCM)). The innovative two tank storage concept consists of a granules and a molten material storage. The phase changes occurs during the transport of the PCM from one storage tank to the other in a screw heat exchanger (SHE). The SHE is (dis)charged with steam/water. The phase change takes places during the transport of the PCM. Therefore a small heat exchanger area, high loading/unloading speeds and high storage capacity are present at the same time (in contrary to existing latent heat storage concepts). The three years work includes the development, built up and survey of prototypes of the storage. With the measurement results, a dynamic simulation modell of the storage will be vailidated. With a system simulation model, the use of the storage in different system designs will be investigated and judged.
