Verfahrenstechnische Untersuchung zum Entleerungsprozess solarthermischer Kraftwerke mit Flüssigsalz

Abstract

In the course of climate change, the demand for renewable energies is increasing. Concentrating solar power (CSP) could play an important role in the energy revolution. In CSP power plants, solar radiation is focused onto a receiver and gets absorbed. The energy is then transferred by a transfer fluid to storage tanks and can be stored in form of heat until it is needed. As part of the HPS2 research project, a parabolic trough plant is being built and operated in Évora, Portugal. Liquid salts are used as the heat transfer fluid, which offer several advantages over thermal oils in commercial plants. For example, thermal efficiency can be increased and plant complexity reduced. This is expected to lead to a significant reduction in the LCOE (Levelized Cost of Electricity) for electricity from CSP power plants. In the demonstration plant, the salt mixture will be replaced after an initial test phase. Since the plant design does not foresee a complete discharge, a process for diluting molten salt with water will be developed in this thesis. The melting temperature can be significantly reduced so that the salt-water solution can be extracted from the plant without special salt pumps. To determine suitable operating parameters, the expected vapor pressures are predicted in the theoretical part (Chap. 4) using the extended BET model. Subsequently, laboratory tests were carried out on the solubility of the salt mixture and clear point temperatures were determined as a function of the water content (Chap. 5). With the findings from the theoretical and experimental part, a process concept is worked out. (Chap. 6). In addition, a software model is developed which ist abled to simulate the time characteristics of the most important process parameters and thus enables a comparison of different process designs. Boundary and initial conditions are identified for the process, for which the implementation does not imply an elevated risk.