The efficiency of many solar energy conversion technologies is limited by their poor response to low-energy solar photons. One way for overcoming this limitation is to develop materials and methods that can efficiently convert low-energy photons into high-energy ones. Here we show that thermal radiation is an attractive route for photon energy upconversion, with efficiencies higher than those of state-of-the-art energy transfer upconversion under continuous wave laser excitation. A maximal power upconversion efficiency of 16% is achieved on Yb 3 þ -doped ZrO 2 . By examining various oxide samples doped with lanthanide or transition metal ions, we draw guidelines that materials with high melting points, low thermal conductivities and strong absorption to infrared light deliver high upconversion efficiencies. The feasibility of our upconversion approach is further demonstrated under concentrated sunlight excitation and continuous wave 976-nm laser excitation, where the upconverted white light is absorbed by Si solar cells to generate electricity and drive optical and electrical devices.

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This paper considers the output synchronization of the Chua's circuit and the Van der Pol system. We first reformulate the problem as a robust output regulation problem with the Chua's circuit as the plant and the Van del Pol system as the exosystem and then solve the robust output regulation problem via internal model approach. Effectiveness of the approach will be evaluated by computer simulation.

Intelligent power metering and measurement systems are important for expanding the category and quantity of power metering. This paper proposes a design and implementation method of an intelligent power metering and measurement system based on IoT technology. Composed of the perception layer, the network layer, the data layer, the analysis layer, and the application layer, the overall design scheme can not only realize the intelligence, automation, and data visualization of power metering and measurement but also improves the standardization of laboratory management through a standardized metering and measurement system.