Modelling and optimization of transient processes in parabolic trough power plants with single-phase heat transfer medium (Motivation)

Kurzfassung

The Federal Government in Germany adopted a long term “Energy Concept” with the goal to significantly reduce CO¬2 emissions by 2050. Renewable energy sources are considered the cornerstone to achieve this goal. As stated in [1], locally-produced and imported electricity from renewable energy sources are to account for 80% of the gross electricity consumption by 2050. Using molten salt single-phase heat transfer media in linear concentrating solar thermal power plants represents a very promising opportunity [2]. In addition to the increased temperature, as compared to oil-operated plants, the heated fluid could be directly stored to achieve longer operation periods. On the other hand, shut down and maintenance costs are significantly higher for solar fields with molten salt as the heat transfer fluid. That is due to the risk of fluid solidification or tube corrosion as the fluid temperatures drop or rise, respectively, beyond certain limits. In this PhD project, it is planned to develop a model to simulate whole fields and provide control information to account for changing irradiation conditions. Simulations of transient processes for single loops and subfields have already been sought and computed, for example in [3] and [4]. However, a more flexible, efficient and robust tool is required to better investigate larger fields in a timely manner. The tool could be used to optimize the system response to passing clouds and to improve the efficiency of startup procedures. The authors seek to simulate the field using a more detailed model for the hydraulic network and the mass flow distributions among the loops. The efficient calculation of mass flow distributions and pressure drops represent a challenge for the large systems of varying temperatures and fluid properties. The PhD project runs for the upcoming 3 years and is funded by DLR and DAAD. References: [1] Federal Ministry of Economics and Technology, Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Energy Concept for an Environmentally Sound, Reliable and Affordable Energy Supply, September 2010 [2] Wagner, P.H., Wittmann, M., Influence of different operation strategies on transient solar thermal power plant simulation models with molten salt as heat transfer fluid, Conference paper, SolarPACES 2013 [3] Hirsch, T., Feldhoff, J.F., Schenk, H., Start-up Modeling for Annual CSP Yield Calculations, Journal of Solar Energy Engineering, 2012, 134 [4] Giostri, A., Transient effects in linear concentrating solar thermal power plant, Dissertation, Energy Department, Politecnico Di Milano