Molten salts as heat transfer fluids for solar thermal power plants

Carbon dioxide, primarily created by burning fossil fuels, is an overwhelming component to the global warming problem. With these environmental issues surrounding fossil fuels, it is important to fully develop alternative energy options. Solar thermal power is a viable solution to the world’s energy problem and is an environmentally friendly and safe solution. The purpose of this thesis is to determine melting temperature, heat capacity and density of molten salts and investigate their viability as a heat transfer fluid for a solar thermal power plant. The solar thermal power plant model developed by Powell and Edgar [1] was utilized and altered to implement the properties determined for NaCl and KCl molten salt systems. The unit cell structures for NaCl and KCl were developed in MATLAB to determine the necessary material properties for the solar thermal power plant simulation. The melting temperature was determined using Tosi-Fumi interaction potentials. Using the simulation results for the melting temperature, the heat capacity and density were determined for the NaCl and KCl melt and crystal structures. The parameters of NaCl and KCl were used in the power plant simulation to study their effect on power. Both molten salts did not perform as well as the original molten salt used by Powell and Edgar. An additional study was conducted to determine the effects of density and heat capacity on power. As anticipated, a higher heat capacity increases the power output, whereas density does not affect the power output. Due to the low heat capacities of NaCl and KCl, these are not realistic options for heat storage. Overall, molten salts possess high thermal stability and high thermal conductivities. The simulations created in this study provide the building blocks for future work in more complex molten salts, such as “solar salt.”