As the prominence of energy storage ramps up, an emerging trend is for the deployment of energy storage systems alongside renewables. Of course batteries are the leading choice for developers looking to capitalise on the abundance of opportunities that storage brings — but the sector isn’t without innovation of a more exotic flavour.

In Germany, the Gaildorf Wind Complext pilot project is taking shape outside the city of Stuttgard which will see deployment of what its developers, Max Bögl Wind, are calling a ‘Water Battery’.

The Water Battery concept involves integrating wind turbines with technologies of pumped hydro power to provide short-term energy storage.

It works like this:

A passive reservoir is built around the base of wind turbine and connected to a lower reservoir in the same way as with traditional pumped hydro; with a power station between the two housing reversible turbines that can generate power when water flows from upper to lower reservoir, or pump water from the lower reservoir to replenish the upper one.

When there’s a surplus of power being generated, it can be used to drive turbines to pump water back uphill to the storage reservoirs of the wind turbines where it becomes potential energy ready to be tapped by allowing the water to run back downhill through the turbines to generate power.

Making good use of surplus power which cannot be fed into a saturated grid by using it in this ways means energy can be stored for later use, perhaps during lulls in wind generation, or to meet periods of higher, peak demand.

Max Bögl’s design places an emphasis on modularity — meaning that key components can be scaled to deliver power and storage to varying requirements. The upper reservoir, for instance, will come prefabricated in varying sizes to allow for smaller or larger storage capacities. Meanwhile, the power station could be fitted with any number of turbines to accommodate varied power and storage capacities too.

 

The Pilot Project

Work is already well underway with a full-scale demonstration of the Water Battery concept.

A total of four wind turbines will be outfitted with storage basins — construction on one can be seen below. The turbines themselves are powerful for onshore ones — 3.4MW machines from GE, with rotor diameters of 137m.

The pilot project will provide 16MW pumped storage capacity and electricity storage capacity of 70MWh, when it comes online in the first half of 2018.

The German Federal Ministry for the Environment, Nature Conservation, Construction and Reactor Safety (BMUB) is supporting the project in Gaildorf with funding of $7.15 million.