Liquid flow batteries – in which the positive and negative electrodes are each in liquid form and separated by a membrane – are not a new concept, and some use same lithium-ion technology as today's batteries. In this case, key components are not solid slabs that remain in place for the life of the battery, but rather tiny particles that can be carried along in a liquid slurry. Increasing storage capacity simply requires bigger tanks to hold the slurry.
Previous versions of liquid batteries have relied on complex systems of tanks, valves, and pumps, adding to the cost and providing multiple opportunities for possible leaks and failures.
The passive, gravity-fed arrangement similar to an old-fashioned hourglass, could offer great advantages due to the system's low cost and the simplicity of its design and operation, say the researchers at the Massachusetts Institute of Technology (Cambridge, MA). The new version, which substitutes a simple gravity feed for the pump system, eliminates that complexity.
The rate of energy production can be adjusted simply by changing the angle of the device, thus speeding up or slowing down the rate of flow. The design is not expected to go into production as it is but demonstrates some new ideas that can ultimately lead to a real product, says Yet-Ming Chiang, Kyocera Professor of Ceramics at MIT.
The design has particles flowing through a narrow opening from one tank to another. The flow can then be reversed by turning the device over. In this case, the overall shape looks more like a rectangular window frame, with a narrow slot at the place where two sashes would meet in the middle.