DOE/Pacific Northwest National Laboratory have announced a new organic aqueous flow battery, which uses inexpensive and readily available materials. Energy storage system owners could see significant savings from a new flow battery technology that costs about 60% less than today’s standard flow batteries.

The organic aqueous flow battery, described in a paper published in the journal Advanced Energy Materials, is forecast to cost $180 per kilowatt-hour once the technology is fully developed. The lower cost is due to the battery’s active materials being inexpensive organic molecules, compared to the commodity metals used in today’s flow batteries.

Imre Gyuk, energy storage program manager for the Department of Energy’s Office of Electricity Delivery and Energy Reliability (OE), which funded this research said, “Moving from transition metal elements to synthesized molecules is a significant advancement because it links battery costs to manufacturing rather than commodity metals pricing.”

Electrolytes in Vials. PNNL’s all-organic aqueous flow battery uses two inexpensive and readily available electrolytes, one containing methyl viologen and another with 4-HO-TEMPO. Image Credit: Pacific Northwest National Laboratory. Click image for the largest view.

Electrolytes in Vials. PNNL’s all-organic aqueous flow battery uses two inexpensive and readily available electrolytes, one containing methyl viologen and another with 4-HO-TEMPO. Image Credit: Pacific Northwest National Laboratory. Click image for the largest view.

PNNL materials scientist Wei Wang, one of the paper’s corresponding authors explained, “The battery’s water-based liquid electrolytes are also designed to be a drop-in replacement for current flow battery systems. Current flow battery owners can keep their existing infrastructure, drain their more expensive electrolytes and replace them with PNNL’s electrolytes.”

Flow batteries generate power by pumping liquids (flowing) from external tanks into a central stack. The tanks contain liquid electrolytes that store energy. When energy is needed, pumps move the electrolytes from both tanks into the stack where electricity is produced by an electrochemical reaction.

Both flow and solid batteries, such as the lithium-ion batteries that power most electric vehicles and smartphones today, were invented in the 1970s. Lithium-ion batteries can carry much more energy in a smaller space, making them ideal for mobile uses. The technology gained market acceptance quickly, for both mobile uses like cell phones and larger, stationary uses like supporting the power grid.

Lithium-ion batteries now make up about 70% of the world’s working, grid-connected batteries, according to data from DOE-OE’s Global Energy Storage Database. However issues with performance, safety and lifespan can limit the technology’s use for stationary energy storage.

Flow batteries, on the other hand, store their active chemicals separately until power is needed, greatly reducing safety concerns. Vanadium-based flow batteries have become more popular in recent years, especially after PNNL developed a new vanadium battery design in 2011 that increased storage capacity by 70%. Three different companies have licensed the technology behind PNNL’s vanadium design.

Nearly 79% of the world’s working flow batteries are vanadium-based, according to data from the Global Energy Storage Database. While vanadium chemistries are expected to be the standard for some time, future flow battery cost reductions will require less expensive alternatives such as organics.

PNNL’s new flow battery features two main electrolytes: a methyl viologen anolyte (negative electrolyte) and a 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, or 4-HO-TEMPO catholyte (positive electrolyte). A third, supporting electrolyte carries sodium chloride, whose chloride ions enable the battery to discharge electricity by shuffling electrons in the central stack.

Wei said, “Using readily available materials makes our all-organic aqueous flow battery more sustainable and environmentally friendly. As a result, it can also make the renewable energy it stores and the power grid it supports greener.”

To test the new battery design, Wang and his colleagues created a small, 600-milliwatt battery on a lab countertop. They repeatedly charged and then discharged the battery at various electric current densities, ranging from 20 to 100 milliAmperes per square centimeter. The test battery’s optimal performance was between 40 and 50 milliAmperes per square centimeter, where about 70% of the battery’s original voltage was retained. They also found the battery continued to operate well beyond 100 cycles.

Next, the team plans to make a larger version of their test battery that is able to store up to 5 kilowatts of electricity, which could support the peak load of a typical U.S. home. Other ongoing efforts include improving the battery’s cycling so it can retain more of its storage capacity longer.

Consumers, small and medium businesses have no or only the vaguest sense of the destruction occurring in power generation. The current administration throttled the nuclear field over several years through the Nuclear Regulatory Commission and is hard at destroying generation fueled by coal through the Environmental Protection Agency. These two sectors generate more than half of U.S. power needs.

Leaders in power generation are responding with deals for large users to cut use, economize and gain efficiency and these programs are tricking down to smaller users as time goes by. These plans can only go so far and over time will consume huge amounts of the economy’s capital.

The next steps will include more plants running at full capacity during off peak filling batteries to then discharge into peak grid draw. It will be a huge market in a country with an economy as large as the U.S.A.

The power generation industry has done a spectacular job in getting this enormous disruption capitalized and operating at low cost to consumers. A battery technology coming that reduces the capital cost by more than half is going to help.

There is a power generating disaster happening in very slow motion. Perhaps the industry can cope, the consumers can pay without causing a recession, and research will find ways to cut these huge expenses.

Lets hope the PNNL’s new technology gets developed to a wonderful commercial result, and soon. It would be one more good brick in the wall defending the nation from a zealous regulatory regime.


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