Flow batteries are nothing new and metal-free inorganic flow batteries are nothing new either (see for example the polysulfide bromide battery) but the set is not complete with an metal-free organic variation as well. The new flow battery described here works with two flows that meet separated by carbon paper. In the charging mode one flow 9,10-anthraquinone-2,7-disulphonic acid (AQDS) (a quinone) in sulfuric acid is reduced to the corresponding AQDSH2 diol and in the other flow hydrobromic acid is oxidized to bromine. The carbon paper is permeable for proton-exchange. The researchers report a cycle (charging / discharging) efficiency of 99%. They also mention the following advantages: sulfonated anthraquinones are already used in wood pulp processing and the crude reaction product of oleum and anthracene could do the trick. The voltage of the flow cell can be enhanced by adding hydroxyl groups. Hydroxylated derivatives are known biomolecules and a quinone solution could be sourced from natural resources. The researchers kindly suggest rhubarb.