A 'virtual' storage system by German solar storage pioneer Sonnen has reached the milestone of 250MWh – which it said is the largest in Europe – and the Shell unit said plans to breach the 1GWh barrier in coming years.

The virtual system dubbed ‘SonnenVPP’ consists of 25,000 Sonnen batteries in private homes that are linked in order to provide a decentralised buffer to smooth out supply and demand of renewable energy.

It currently is providing capacity to compensate for frequency fluctuations (primary control power) in the transmission grid or to participate in electricity trading on the power exchange. The network of batteries can shift the time at which solar power is fed in to make it compatible with the grid, Sonnen said. The midday peak, for example, can be stored by PV systems instead of putting a strain on the electricity grid.

“The energy transition must not get stuck in the power grids. With our virtual power plant, we have an instrument for intelligently integrating PV systems, e-cars or heat pumps into our power grids,” said Sonnen CEO Oliver Koch.

“Our power plant is already in people's households and doesn't need any additional space. The storage resource can only be fully utilised when it is intelligently networked.

“Currently, many processes in the power grids are not yet digitised or regulated accordingly, so that we are far from exploiting the potential of our technology.”

Shell in 2019 had taken over Sonnen, which is a major producer of solar storage systems in Europe’s largest solar market, Germany. The company is also operating virtual solar storage plants in Italy, the US and Australia.

Sonnen said it would like to also offer the storage capacity of its systems for grid stabilisation in distribution grids but added that those still lack market mechanisms and corresponding regulation to use virtual power plants.