Environmentally friendly battery

In a corner of the campus Green Village is a green hut containing 20 drums of water: this is the AquaBattery pilot project. The water battery stores electricity in saline and fresh water and is connected to the five adjoining student apartments.

The campus water battery by AquaBattery, a start-up, is the most environmentally friendly battery conceivable. The BlueBattery, as the company calls it, uses no acid, chemicals or metal, but only saline and fresh water and an active membrane that only allows salt ions to pass through, and not water. 

The idea for the water battery was inspired by a demo model for the production of electricity from a combination of sea water and fresh water set up on the Afsluitdijk causeway. The water battery applies the reverse process (electrodialysis). Salt ions are removed from the brackish (half salty, half fresh) water by passing electrical load through the membrane. The result is an extremely saline solution on one side of the membrane and fresh water on the other. If you place another suitable membrane between these two liquids, electricity will start to flow again. 

The water battery does have disadvantages, such as its size. Two cubic metres is required for the storage of 1 kWh, which is more than 100 times the volume of a lead battery, but the water battery does have a similar efficiency (70%). The membranes take up quite some space too: one cubic metre of membrane is required for 1 kW of power. With the support of membrane manufacturer Fujifilm and grid operator Enexis, development is now focusing on reducing the volume by a factor of ten. The water battery has advantages too: the concept is easy to scale up or down for the required storage capacity and power. 

Moreover, the size of the device is less of a hindrance in built environments; AquaBattery sees opportunities for the storage of solar energy by consumers if the feed-in tariff is lowered, or even better, a water battery as a neighbourhood buffer.