UC Merced

This work investigates a novel form of spectrum splitting as a potential pathway for reducing the levelized cost of electricity generated by a hybrid concentrating solar power (CSP/CPV) plant for the purpose of increasing dispatchable solar-to-electric capacity on the grid. While the deployment of solar-to-electric capacity is occurring today at rates never before seen, most installations are variable generators and produce electricity while the sun is shining but have no effective means of storing this energy for nighttime or time-shifted generation. CSP systems are easily paired with cost-effective thermal energy storage (TES), but the plants themselves (solar field and power block) are still too expensive to incentivize rapid deployment. Spectrum splitting has been identified as a technique which would allow pairing of cheap, high efficiency PV with expensive, low efficiency CSP in a hybrid system to increase overall net electric generation efficiency and thus potentially reduce the levelized cost of electricity generated by hybrid plants below that of standalone CSP.

This dissertation is focused on the development of a novel two-stage collector which incorporates spectrum splitting using back-reflecting solar cells integrated into the secondary concentrator. Several different solar cell candidates are investigated as candidates and modelled against existing systems (PV, CSP, and hybrid). The economics of hybrid systems are compared to a side-by-side standalone PV and CSP plant. An early stage prototype was developed and tested on-sun up to 360 °C, after which several major challenges, obstacles, and complications were identified. The optical performance of a CPC profile approximated by segments was explored and developed, ultimately culminating in an optimized design for a secondary with integrated solar cells. Several other manufacturing and assembly techniques were developed and utilized in a second generation prototype which was assembled and tested on-sun up to 600 °C using a suspended particulate heat transfer fluid (HTF). The second generation collector had much better results and has highlighted areas for further development and research.

The concepts, designs, and experimental works in this thesis contribute to the continuous development of solar collectors and systems towards lower cost, higher efficiency, and broader applications.