Integrated Photovoltaic Charging and Energy Storage Systems: Mechanism, Optimization, and Future

As an emerging solar energy utilization technology, solar redox batteries (SPRBs) combine the superior advantages of photoelectrochemical (PEC) devices and redox batteries and are considered as alternative candidates for large-scale solar energy capture, conversion, and storage. In this review, a systematic summary from three aspects, including: dye sensitizers, PEC properties, and photoelectronic integrated systems, based on the characteristics of rechargeable batteries and the advantages of photovoltaic technology, is presented. The matching problem of high-performance dye sensitizers, strategies to improve the performance of photoelectrode PEC, and the working mechanism and structure design of multienergy photoelectronic integrated devices are mainly introduced and analyzed. In particular, the devices and improvement strategies of high-performance electrode materials are analyzed from the perspective of different photoelectronic integrated devices (liquid-based and solid-state-based). Finally, future perspectives are provided for further improving the performance of SPRBs. This work will open up new prospects for the development of high-efficiency photoelectronic integrated batteries.

Achieving High-Quality Freshwater from a Self-Sustainable Integrated Solar Redox-Flow Desalination Device

Solar-assisted electrochemical desalination has offered a new energy-water nexus technology for sustainable development in recent studies. However, only a few reports have demonstrated insufficient photocurrent, a low salt removal rate, and poor stability. In this study, a high-quality freshwater level of 5-10 ppm (from an initial feed of 10 000 ppm), an enhanced salt removal rate (217.8 µg cm^-2 min^-1 of NaCl), and improved cycling and long-term stability are achieved by integrating dye-sensitized solar cells (DSSCs) and redox-flow desalination (RFD) under light irradiation without additional electrical energy consumption. The DSSC redox electrolyte (I^- /I₃^- ) is circulated between the photoanode (N719/TiO₂ ) and intermediate electrode (graphite paper). Two DSSCs in parallel or series connections are directly coupled to the RFD device. Overall, this hybrid system can be used to boost photo electrochemical desalination technology. The energy-water nexus technology will open a new route for dual-role devices with photodesalination functions without energy consumption and solar-to-electricity generation.

A Small Hybrid Power System of Photovoltaic Cell and Sodium Borohydride Hydrolysis-Based Fuel Cell

Although the hybrid power system that combines a photovoltaic cell and a lithium-ion battery is increasingly mature and practical, long-lifetime auxiliary power will be still needed in severe weather conditions. A small-volume hydrogen-oxygen fuel cell system based on the hydrolysis of NaBH4 is designed. The fuel cell system contains a tiny hydrogen generator, a hydrogen cleaner, and a small fuel cell stack consisting of three units in series. The relationship between the amount of catalyst and output performance is discussed. The long-time discharging results indicate that the fuel cell system has high power capacity. The compact design allows the fuel cell system to integrate the structure with a photovoltaic cell and lithium-ion cell and forms a hybrid power system with a small package. The power management circuit for these power sources without logic devices is designed and tested. The control strategy selects the photovoltaic-battery subsystem as the primary power source, and the fuel cell subsystem works as the backup power source to handle the circumstance when the energy stored in the battery is exhausted. The test results show that the power management system could switch the power supply automatically and timely under various emergency conditions, and the output voltage remains stable all the time.