A current account for renewable energies

The Electricity Bank is charting new territory in the energy landscape

Banks play a key role in our economy when it comes to managing the flow of money. They collect savers’ money and lend this to investors. This approach serves as the model for the "Electricity Bank" research project we have been promoting as consortium leader since 2013 and that is being supported by the State of Baden-Württemberg as part of its BWPLUS programme. The project participants are the battery manufacturer ads-tec (Nürtingen), the Mannheim grid operator Netrion and the University of Stuttgart with the Institute of Photovoltaics and the Zentrum für interdisziplinäre Risiko- und Innovationsforschung.

The idea: electricity storage on location
The Electricity Bank addresses a topic that is set to become ever more important given increasing volumes of renewable and decentralised electricity generators in the grid. If the electricity generated from solar and wind power can also be consumed where it is generated, this eases the strain on electricity grids and avoids transmission losses. Since electricity cannot always be used when the wind is blowing or the sun is shining, it makes sense for it to be stored on location.

The electricity is kept in the "safe"
The "safe" within the Electricity Bank offer this kind of storage facility. Here, the surplus electricity generated at participating households is stored and then fed back into the grid when needed. The participants are connected to the storage facility via an internet-based "Energy Cloud". This means that all participants always have access to their "Electricity Accounts".

The practical trials
The operator model was tested in the Mannheim district of Rheinau Süd from December 2014 to March 2016. A total of 18 project participants and prosumers (14 PV and four CHP plants) were connected to the storage facility via cloud-based management software. Each participant received specific storage capacity and an account at the electricity bank. An application developed within the project visualised the account balances and recorded data for each participant.

Given the different generation characteristics of the PV and CHP plants connected to the facility, the account sizes were based on dynamic, season-specific factors rather than on fixed storage volumes. This enabled the storage facility’s total capacity to be put to optimal use while also doubling proprietary utilisation rates to 60 percent to 80 percent at times. Based on marketing within the district, the remaining energy volumes could also be traded locally. Over the year, this reduced the volume of electricity fed into the next-level grid by 75 percent, while the quantity of electricity taken out of the grid fell by 40 percent. This way, the electricity bank made a substantial contribution to balancing generation and consumption on a local level. The burden on the grid was further reduced by applying a peak-shaving algorithm. Furthermore, the district storage facility was prequalified for secondary balancing energy purposes. The project participants were consistently positive in their assessment of the electricity bank system following completion of the project.