Investigating the performance of a novel solar lighting/heating system using spectrum-sensitive nanofluids

Solar lighting is considered as a promising technique, which has huge potential in conserving energy and relaxing the residents. However, current solar lighting systems used a filter to allow only visible light to enter buildings, releasing all the other energy contained in the long wave of the solar into the surrounding air. Such practice leaded to low efficiency of solar energy utilization and high costs. In this paper, a solar lighting/heating system was developed which used a hollow lens filled with ATO nanofluid to separate the long wave and short wave of solar energy. A series of tests were conducted to explore the performance of system. Results indicated that under the test condition of Case 1 (0.025%/0.0001% ATO/Graphite nanofluid, 100 L/h flow rate), the light transmission efficiency was 19.5% which was comparable to that of current solar lighting systems, and the heat absorption efficiency was 25.35%. The heat energy collected by the such a system from June to August (three months) in the city of Harbin was about 466.4 MJ in per square meter of collection area. The volume concentration of nanofluids had great influence on both the light transmission efficiency and the heat absorption efficiency. The flow rate had little influence on the light transmission efficiency, but had great influence on the heat absorption efficiency of the system.