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Home / Science / A single device generates, stores and releases renewable electricity from the sun

A single device generates, stores and releases renewable electricity from the sun



Solar flow battery device

The integrated solar flow battery device contains both a solar cell that converts sunlight into electrical energy, and a chemical substance that can store electrical energy for later use. Credit: Li Wenjie

Chemists and collaborators at the University of Wisconsin-Madison have created an efficient and durable solar flow battery that can generate, store, and retransmit renewable electricity from the sun through a device.

The new device is made of silicon solar cells and advanced solar materials, which are integrated with optimized chemical components. The solar flow battery manufactured by Song Jin Laboratory of the Department of Chemistry at the University of Wisconsin-Madison has reached a new high efficiency, reaching 20%. This is the best of most commercial silicon solar cells used today and is 40% higher than the record holder of solar flow batteries previously developed by Jin Laboratories.

Solar flow battery

Schematic diagram of integrated solar flow battery. Solar cells (green) are connected to chemical tanks (red and blue) that can store electricity for later use. Credit: Li Wenjie

Although solar flow batteries are still years away from commercialization, they offer the potential to provide reliable power generation and storage for lighting, cell phones, or other basic uses for households in remote areas. They combine the advantages of photovoltaic cells that convert sunlight into electrical energy with the advantages of flow batteries. The chemical reagent tanks used in flow batteries can react to generate electricity and be charged by solar cells.

Researchers published their work in the journal today (July 13, 2020) Natural materials. Li Wenjie, a graduate student at the University of Wisconsin-Madison, is the lead author of the study. Gold Lab collaborates with researchers from the University of New South Wales and the University of Sydney, Australia, Utah State University, King Abdullah University of Science and Technology in Saudi Arabia, and City University of Hong Kong.

Solar flow battery device lighting

Solar experiment equipment at the University of Wisconsin-Madison laboratory. Credit: Li Wenjie

Since the sun does not always shine, storage is essential for practical solar energy, especially in remote and rural areas with sufficient sunlight, such as in the sunshade areas of the United States, Australia, Saudi Arabia, and Africa. Many solar home systems use leadacid Or lithium-ion battery for power storage. Flow batteries use large-capacity liquid chemical storage tanks to store energy, which may be cheaper in large-scale production, and are ideal storage options in combination with solar cells.

Jin Lab spent many years researching and improving the integrated solar flow battery system. In 2018, it developed a solar flow battery using three layers of highly efficient but expensive solar materials, with an overall efficiency of 14%. However, corrosion greatly shortens the service life of the equipment.

In their latest report, the researchers turned to an increasingly popular photovoltaic cell material, the halide perovskite. The solar energy conversion efficiency of these special materials has increased dramatically from a few percent to more than 25 percent in 10 years. Recent research shows that halide perovskites can also improve the efficiency of traditional silicon solar cells by capturing more energy from the sun.

This new type of high-efficiency perovskite silicon solar cell is being commercialized. However, silicon is still the key to making stable equipment that can withstand the chemicals in flow batteries.

“Our motivation for designing solar cells is to combine these two materials, so we have both high efficiency and good stability,” Li said.

Perovskite solar energy

Perovskite structure. Credit: Li Wenjie

Professor Anita Ho-Baillie and postdoctoral fellow Jianghui Zheng of Australia produced perovskite-type silicon solar cells and added a protective layer on the silicon surface. They shipped the solar cells to Wisconsin for testing.

In order to predict the ideal voltage at which a flow battery should operate, Li developed a new theoretical modeling method. The model allows him to select a pair of chemicals in the flow battery that will operate at the ideal voltage according to the characteristics of the solar cell, thereby maximizing efficiency. These chemicals are organic compounds, not expensive metals in traditional flow batteries. They are dissolved in a benign aqueous solution of edible salt, not strong acids.

Utah State University chemistry professor T. Leo Liu and his graduate students provided key matching chemicals. Thanks to the good match between solar cells and flow batteries, the winning device can maintain high efficiency during hundreds of hours and hundreds of charge and discharge cycles, while retaining most of its capacity. This life is several times that of earlier equipment. Overall, the new system has a long service life and an efficiency of up to 20%, making it the best solar flow battery device to date.

Jin said: “You can increase the efficiency by 20% at any time.” “You can use solar energy immediately during the day and get 20% of the electricity, or you can use solar energy from the storage at night and get 20% of the electricity.”

There is still a lot of research to be done before such equipment becomes a practical renewable energy solution. Increasing the size and scale of current small equipment in research laboratories is a challenge. Even though researchers have manufactured batteries for relatively long periods of time, real-world applications still require higher durability. While Jin Lab continued to develop more efficient solar flow batteries, it also made practical trade-offs to reduce equipment costs.

This research may one day produce a new way to collect, store and use the energy of the sun.

“If we can do this, our ultimate goal is to target solar home systems,” Li said. “People without a power grid can use this device to obtain reliable electricity.”

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Reference: July 13, 2020, Natural materials.
DOI: 10.1038/s41563-020-0720-x

This work was partially supported by the National Science Foundation of America (funding 1847674).




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