The Challenge

For Los Angeles County to achieve a 100% renewable energy future, developing highly efficient and innovative systems that take advantage of its abundant natural resource—solar energy—is critical. So far, two well-developed technologies, photovoltaics (PV) and concentrating solar power (CSP), have advanced solar energy conversion in different directions. While PV is cheaper and relatively more efficient, CSP is dispatchable (can be turned on or off by operators) and can be used on-demand. Thus, efforts have been made to develop hybrid solar and thermal systems to increase PV "dispatchability." However, these hybrid systems suffer from the elevated temperature of the PV cell, which decreases overall efficiency. Realizing such a technology gap, the UCLA research team aims to develop a novel technology that is both a highly efficient and dispatchable form of solar energy conversion and storage to help the county achieve its sustainable goals. 

The Solution

Researchers developed a high-performance solar energy device based on the Integrated Spectral Leverage Amplification (iSLA) system. The novel design of iSLA integrates a hybrid solar and thermal energy convertor and a thermal energy storage circuit to capture the entire solar spectrum. Such an integrated design allows more efficient energy usage over traditional devices, by avoiding excessive heating of a PV cell. More importantly, the integrated design is low-cost, dispatchable and highly flexible so it can be easily combined with other energy technologies. 

Results

• The dispatchable and high-performance feature of the iSLA device has not been demonstrated in the past. It is a new technological innovation that can transform the current energy usage and its harvesting pathways in Los Angeles County.  
• The energy efficiency is significantly improved using the design of two-dimensional, tin selenide thin film. The iSLA device demonstrated record-high, overall solar harvesting efficiency of 72.5%.  
• The system-level efficiency of the iSLA device is competitive in terms of electrical energy conversion efficiency at 21.4% using low-cost building blocks. In comparison, commercial photovoltaic systems alone based on high-cost materials, such as GaAs, has an efficiency of 18.1%.  

Next Steps

Technology-to-market analysis is ongoing to improve the cost-competitive performance in terms of dollars per Watt against conventional solar cells.  

Additional Outcomes to Date

Hu and his team received a 5-year grant support from the National Science Foundation and a 2-year grant from the Petroleum Fund of American Chemical Society, both during the first phase of this research project.  

Publications and Reports

Kang, J. S., Ke, M., & Hu, Y. (2017). Ionic Intercalation in Two-Dimensional van der Waals Materials: In Situ Characterization and Electrochemical Control of the Anisotropic Thermal Conductivity of Black Phosphorus. Nano Letters, 17(3), 1431-1438. doi:10.1021/acs.nanolett.6b04385 

Kang, J. S., Wu, H., & Hu, Y. (2017). Thermal Properties and Phonon Spectral Characterization of Synthetic Boron Phosphide for High Thermal Conductivity Applications. Nano Letters, 17(12), 7507-7514. doi:10.1021/acs.nanolett.7b03437 

Lin, Z., Hollar, C., Kang, J. S., Yin, A., Wang, Y., Shiu, H., . . . Duan, X. (2017). A Solution Processable High‐Performance Thermoelectric Copper Selenide Thin Film. Advanced Materials, 29(21), 1606662-n/a. doi:10.1002/adma.201606662 

Rongione, N. A., Hguyen, H., Wu, H., & Hu, Y. (2017). Nanotechnology for Lower Grade Waste Heat Recovery. IEEE 12th International Conference on Nano/Micro Engineered and Molecular Systems (NEMS), pp. 826-831. doi:10.1109/NEMS.2017.8017146