Harvard researchers believe that flow cell batteries could be a rival to the Tesla Powerwall battery storage system. Professor Michael Aziz claims the new battery technology he is developing with his team of researchers will not only become a significant competitor to Tesla’s battery systems, he believes the flow-cell battery is in fact a superior design.
Flow-cell batteries are made up of a liquid electrolyte which is circulated between two tanks, passing through a membrane which produces an electrical current. The process is similar to that of hydrogen fuel cells, whereby particles pass through a membrane to produce energy.
The size of the tanks holding the liquid determines the capacity of the flow-cell battery and can be changed accordingly. Similarly power output can be adjusted through the size of the membrane.
Adding to the many advantages of these batteries, their adaptability holds strong potential as demand for battery storage increases. The Harvard team claims their batteries can remain idle for long periods without a loss in charge, as well as being immune to extreme temperatures.
Not only do these batteries claim to be highly efficient and durable, their price point is set to be significantly lower than the revolutionary lithium-ion batteries. The materials required for flow batteries are also far more readily available and safer than lithium batteries.
Using a less-corrosive alkaline solution, prototypes are able to use extremely lightweight plastic tanks which further cut down costs of production.
A Big Improvement on Previous Models
Previous prototypes of flow cell batteries relied on vanadium and bromine dissolved in acid in order to produce energy. This method was highly expensive, dangerous and toxic in comparison to the latest developments in flow technology.
The chemical vanadium has been replaced by a more environmentally friendly option, quinones, which are natural chemicals produced through photosynthesis. The bromine element has also been replaced by a common kitchen chemical, ferrocyanide, which is added to salt for an anti-caking effect.
An alkaline environment is also far superior to previous acidic chemical reactions, allowing for cheaper and lighter-weight materials.
Size and Space – the Limitations of Flow Cell Technology
Flow battery efficiency is predicted to be over 99 percent, with a life cycle of 1900 uses which is far more than the lithium ion cells.
The one drawback of flow cell technology is that it has relatively low energy density in comparison to its lithium counterpart, with only 19Wh per litre as opposed to 300Wh per litre in lithium batteries.
This introduces the dilemma of space as flow cells would become extremely large in order to match the power levels of compact lithium cells. The low cost and high efficiency in other areas, however, makes battery usage in situations without space restrictions a promising alternative to lithium technology.
Photo credit Harvard School of Engineering and Applied Sciences
