So, whats this all for again?

As cool as the lab work is, its meaningless without the context of what its ultimately being used for and the overall subject of this project, Solar thermal energy. Solar thermal energy collection comes in many forms, from solar ovens, solar water heaters, to solar thermal power plants, but all of them follow the basic principle of converting solar energy to thermal energy to eventually perform work.

The project is mostly concerned with the large scale solar thermal power plants. At such a large scale, almost all solar thermal power plants rely in some way on the concentration of solar energy to achieve maximum efficiency. Two of the most common ways are doing this are solar power towers and parabolic trough collectors. Solar power towers, also known as heliostats, use a massive field of mirrors to focus sunlight to the top of a tower in the center of the field, where as parabolic trough collectors use lines of parabolic mirrors to focus sunlight along a line that runs along them. The sunlight collected from all solar thermal power plants is used to heat a so called "heat transfer fluid" (HTF) to temperatures ranging from 400 degrees Celsius to 600 degrees Celsius. This HTF is then pumped to a heat exchange where the heat is transferred to water, creating steam to spin turbines like other fossil fuel based power power plants. While the conversion of solar energy to thermal energy of the HTF is very efficient, the second part of the process, the transfer of heat from HTF to water is not. This inefficiency is a major factor contributing to the high price of solar thermal power generation. The graph below shows how the efficiency of solar thermal power plants is dependent on the temperature at which they operate.

However, solar thermal power generation is promising because it allows energy to be stored in the form of thermal energy, allowing electricity to be generated during the night and while intermittent clouds are over head. There are many ways to store this thermal energy (which I need to research more), but the freezing of HTF must be avoided, which currently occurs at temperatures higher than room temperature.

Therefore, the development of better HTFs will both mitigate the limitations and heighten the advantages of solar thermal power generation. At temperatures approaching 1000 degrees Celsius, the efficiency of the heat transfer between HTF and water increases dramatically. At such high temperatures, heat transfer by radiation can be considered, potentially increasing the efficiency further. At higher temperatures, heat transfer fluid can be stored for longer periods of time, and research is being conducted to find a HTF that can remain liquid at lower temperatures, making it easier to store. The lab work that I am involved with is trying to develop these new HTFs and quantify the radiative properties of the fluid.

Citation
 Glatzmair G. Summary Report for Concentrating Solar Power Thermal Workshop. Rep. no. NREL/TP-5500-52134. Washington D.C.: US. Dept. of Energy, 2011. Print.