Storage: value in 'unloading grid'

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The potential of small battery solutions to increase stability and prevent surges of PV electricity has been highlighted at the 8th International Renewable Energy Storage Conference (IRES), which concludes today in Berlin, Germany.

High levels of PV penetration into electricity grids is characterized as being a destabilizing force, increasing grid costs and electricity rates for consumers.

The IRES conference has largely focused on the role of distributed battery storage to mitigate this by absorbing production and peak times.

"This saves money for all of us by reducing the need for grid expansion," said Dirk-Uwe Sauer, from RWTH Aachen University, during a session at the event. He explained how relatively small batteries installed into homes can reduce the amount of electricity being fed into grids during peak hours of production by around 40%, thereby stabilizing the grid. Sauer suggested that voltage levels on the grid be used a signal for electricity to be fed into batteries rather than onto the grid itself.

Sauer said that this solution would be relatively straightforward, requiring software to be added to systems rather than additional hardware, such as grid-level storage or grid expansions.

Lower capital cost

Sauer offered a further argument for PV installation battery systems to be used in "unloading the grid": The cost of capital for installing many thousands of small battery systems would be much less than that required to build large grid storage.

Private households would be happy to install a battery in their home with their PV system but could expect a return on investment of only around 3%. In contrast, institutional investors — required for larger storage projects or grid expansions — could expect returns of around 7% to 10%. "If we can activate the investment from the people at these low interest rates, we can all save," said Sauer.

Current incentive feedback

The effectiveness of the current battery incentive program in Germany, which was introduced in May of this year, was also assessed in a presentation at IRES. The incentive program helps to promote the installation of batteries with PV systems by subsidizing loans required to fund the batteries themselves. The government set aside a €25 million budget for the first year of the scheme. A requirement for battery installations to qualify for the program is that they have an open interface for external control to qualify — allowing grid operators to affect the grid unloading function.

Bernhard Regel, from battery supplier Hoppecke, reported that there had been 1,720 applications for funding under the battery program since its commencement in September of this year. These applications required €28.6 million in funding.

Regel said the majority of applications under the scheme came from households installing new PV arrays rather than for retrofits. Installer and solar organisations had reported that up to 75% of consumers opted for a battery without the subsidy, many of whom objected to the requirement for the open interface for external control, he added.

Regel recommended that the program be expanded beyond 2015 and that annual funding be increased to €50 million on an annual basis.