Bosch in search of efficient solar power storage solutions

Robert Bosch GmbH is partnering with the Institute for Power Electronics and Electrical Drives (ISEA) at RWTH Aachen University and münsterNETZ GmbH, the grid operator for the Münster municipal works, in a research project to develop efficient storage solutions for solar power projects.

The 'PV Home Storage System' (PV-HOST) project is part of the German government's energy storage funding initiative that has received a grant of € three million from the German federal government.

The project, started in July 2003, will run for two years.

Optimising technology is key to lowering costs and increasing renewables' share of overall power supply and for this, storage technology has to be further developed.

PV-HOST is piloting alternative forms of energy, for which solar energy storage systems have a big role to play. Efficient storage systems allow more photovoltaic systems to be usefully integrated into existing grids, so that less power is required from conventional power plants.

Compared to central storage systems, battery storage systems have the advantage of presenting a lower investment hurdle. In addition, the self-generated electricity households would find feeding the grid lucrative.

Another key issue is costs, and here the researchers are seeking to optimise battery storage systems to make them even more cost-effective.

PV-HOST is looking at a minimum stationary storage systems capacity of up to ten kilowatt hours that could work cost-effectively and efficiently to feed the surplus electricity generated by household photovoltaic systems into the grid.

The current PV-HOST research project explores precisely this question. The goal of the project is to optimise distributed battery storage from both technical and economic perspectives.

To do this, three research partners are systematically comparing the solar storage technologies currently available from German manufacturers that are potential candidates for use in single-family homes over the next few years.

At present, less than one per cent of German single-family homes with photovoltaic systems have a solar energy storage system despite incentives by the government-owned KfW development bank to invest in this technology.

While previous research projects in this area concentrated on further developing a specific storage technology and generally sought to increase the proportion of electricity households used that they themselves had generated with the goal of making them as self-sufficient as possible, the PV-HOST project is looking for an operating strategy that would allow a household storage system to most effectively serve grid needs.

In other words, the storage system should not just cover the household's own needs, but also reduce supply peaks, ensuring that the grid can absorb more energy from solar installations on the whole.

The project partners are evaluating four battery types - lithium-ion, lead-acid, high-temperature, and redox flow batteries. For each type, the researchers are working out the technical and economic potential.

On top of this, they are investigating three further issues - the optimum configuration of the entire photovoltaic storage system – effectively, the size and power of the various components – the optimum operating strategy for the battery storage system, and the optimum means of integrating distributed storage systems into the power grid.

In particular, the team wants to subject lithium-ion batteries to comprehensive lab and field tests. The goal of the research into high-temperature batteries is to minimise heat loss and thereby improve efficiency.

Diversified industrial group Robert Bosch GmbH guarantees the entrepreneurial freedom of the Bosch Group, making it possible for the company to plan and invest over the long term in  safeguarding its future.

About 92 per cent of the share capital of Robert Bosch GmbH is held by Robert Bosch Stiftung GmbH, a charitable foundation. The majority of voting rights are held by Robert Bosch Industrietreuhand KG, an industrial trust.

The entrepreneurial ownership functions are carried out by the trust. The remaining shares are held by the Bosch family and by Robert Bosch GmbH.