Energy

Solar flow battery efficiently stores renewable energy in liquid form

Solar flow battery efficiently...
A schematic illustration of the new solar flow battery design
A schematic illustration of the new solar flow battery design
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A schematic illustration of the new solar flow battery design
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A schematic illustration of the new solar flow battery design
A schematic illustration of the new solar flow battery design
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An illustration of the structure of the solar cell, comprising an organic-inorganic halide perovskite top layer, and a silicon bottom layer
Researchers Song Jin (left) and Wenjie Li (right)
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Researchers Song Jin (left) and Wenjie Li (right)
The new solar flow battery, which can harvest energy from sunlight and store it in liquid form within the one device
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The new solar flow battery, which can harvest energy from sunlight and store it in liquid form within the one device
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Capturing energy from the Sun with solar panels is only half the story – that energy needs to be stored somewhere for later use. In the case of flow batteries, storage is relegated to vats of liquid. Now, an international team led by University of Wisconsin-Madison scientists has created a new version of these solar flow batteries that’s efficient and long-lasting.

To make the new device, the team combined several existing technologies. It’s a silicon/perovskite tandem solar cell, paired with a redox flow battery, which the team says will allow people to harvest and store renewable energy in one device. Not only is it efficient, but it should be inexpensive and simple enough to scale up for home use.

The energy-harvesting part of the equation combines the long-time industry-leading material – silicon – with a promising young upstart called perovskite. These tandem solar cells have proved better than either material alone, since the two materials capture different wavelengths of light.

For storage, the team turned to a flow battery. Traditionally, these devices contain two liquids, housed in separate tanks, that function as the electrolytes. Electricity from the solar cell charges one of the liquids, where it can sit more or less indefinitely. When the power is needed, the two liquids interact in a middle chamber, creating a chemical reaction that produces electricity.

The new solar flow battery, which can harvest energy from sunlight and store it in liquid form within the one device
The new solar flow battery, which can harvest energy from sunlight and store it in liquid form within the one device

The team used a theoretical modeling method to determine which chemicals would operate at the ideal voltage, to maximize efficiency. They settled on two organic compounds dissolved in saltwater, and tests with the final physical device confirmed that it was a good match.

The team recorded 20 percent efficiency, which is up there with the best. The device was able to maintain a high efficiency, and most of its capacity, over hundreds of hours and charge-discharge cycles. That gives it a much longer life than other flow batteries, whose acidic electrolytes tend to corrode the tanks.

“That’s 20 percent efficiency any time you like,” says Song Jin, lead researcher on the study. “You can use the solar electricity right away during the day and get 20 percent, or you can use it in the evening from storage and get 20 percent.”

The team plans to continue developing the solar flow batteries to improve efficiency, reduce costs and investigate ways to scale them up for practical large-scale use.

The research was published in the journal Nature Materials.

Source: University of Wisconsin-Madison

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3 comments
jerryd
Joining 2 techs that are not viable yet , what could go wrong?
Karmudjun
The Silicone & Perovskite combination has proven to be a cheaper means of attaining the highest efficiency - but the carbon footprint is still large. As far as combining two new technologies, Silicone based PV has been used since the first telstat - for you youngsters that is the first American satellite used for radio, television, & telephone communications in the 1960s. While Perovskite is "New", eleven years of progress has brought the 4% efficiency up to 22-23% efficiency. There are reasons why perovskite PV is not more mainstream, but by combining both technologies (as has been done for a few years now) manufacturing can produce those efficiencies without the required high tolerances that NASA or the Defense Department requires.

The redox batteries - or flow batteries - are also called Edison batteries aren't they? While using salt water suspensions instead of electrodes has not been a commercial success - the weight is the issue - it is also an old technology. So I'm a little amused at the "not viable yet" statement. Both have been viable - with peroskite PV being only 10-12 years of commercial viability.
ljaques
Hmm, a 20% efficiency figure without any data to back it up? And why do you only get 20% efficiency from the battery, which is stored energy? Doesn't that net you 4% of potential power? I'm with Jerryd. Perovskite has a short life due to its fragility, though graphene may help that soon. And Flow is cumbersome and inefficient. While these techs have proven some potential, each is not in wide use because they can't compare with other tech in power density and longevity, which is what's required for commercial popularity. Nope, not yet viable. And I don't see their combination changing that, except in a few small, low-power niches. I wish 'em luck, though.