Flow Battery Could Smooth Irregular Wind and Solar Energy Supply
Scientists in the US have developed an alkaline flow battery that they hope will help to tackle the tricky problem of storing energy from renewable power sources such as wind and solar. The new battery’s performance is similar to current commercial flow batteries but uses cheap and non-toxic organic molecules to store energy. By contrast, conventional flow batteries use expensive and hazardous transition metal solutes.
Solar and wind energy resources are a growing issue for utilities as they try to match fluctuating consumer demand for electricity to the intermittent nature of renewable energy generation. In order to stop energy companies from resorting to established coal and gas infrastructure to prop up the electricity grid, many see long term energy storage as a way to effectively integrate renewables into national energy strategies.
Batteries are one technology that offers an answer to this problem, but the market is flooded with different products, from lithium–ion to lead–acid cells, that are costly, potentially hazardous on an industrial scale and unable to store energy for extended periods. But there may be an alternative.
‘Flow batteries are significantly different than conventional batteries,’ comments Robert Savinell, an electrochemical energy storage expert from Case Western Reserve University, US, who was not involved in the work. ‘The reason is that they’re more adaptable for large scale energy storage.’
‘[A flow battery] closely resembles a fuel cell where normally … you have hydrogen and oxygen gas streams entering into an energy conversion device separated by a membrane and you have two electrodes,’ explainsMichael Marshak from the University of Colorado Boulder, who led the team that created the new battery. But, in the case of a flow battery a positive and negative liquid electrolyte are pumped into the cell from separate reservoirs. The positive electrolyte gives up electrons, which pass through an external circuit to combine with the negative-charged electrolyte, with cations from the electrode being free to pass through the ion-selective membrane. Following this charging process, the electrolytes can be stored in external tanks and, as the battery current flow is reversible, pumped backed through the central battery for discharging at a later time.