Bosch uses hybrid battery system for energy storage

The Bosch energy storage solution in Braderup consists of a vanadium redox flow battery from Vanadis Power and a Sony lithium-ion battery store.

The Bosch energy storage solution in Braderup consists of a vanadium redox flow battery from Vanadis Power and a Sony lithium-ion battery store. Photo credit: Robert Bosch GmbH

Residents in blustery Braderup, Northern Germany, will be celebrating a Christmas with a difference this year. The energy to cook their Plätzchen will have been plucked from thin air… with help from a groundbreaking energy storage project.In July, the 670-or-so-strong community installed what is believed to be one of Europe’s biggest grid-scale lithium-ion (Li-ion) and vanadium redox flow battery systems to store excess wind energy.

The project, delivered by the German engineering and electronics giant Bosch, is said to have been prompted by a local farmer’s frustration at wind turbines overloading the grid and causing power cuts during gales on the North Frisian coast.

A group of 200 private investors from the community got together, as Braderup-Tinningstedt, to fund their own private wind farm, which installed six 3.3MW turbines at the end of 2013.

Braderup-Tinningstedt then formed Energiespeicher Nord, a joint venture with Bosch, to create the energy storage facility, one of the largest in Europe.

The storage system, installed on a 2,500 square-metre plot of farmland, has a peak output of 2.3MW and a total capacity of 3MWh, enough to cover the electricity needs of 40 average single-family homes for seven days and nights, according to Bosch.

Grid stabilisation

It is made up of a 2MW, 2MWh Sony Li-ion battery store for short-term grid stabilisation and a 325kW, 1MWh vanadium redox flow unit, from Vanadis Power of Nuremberg, Germany, for longer-term storage.

The vanadium redox flow battery contains 80,000 litres of electrolyte, in the form of vanadium pentoxide dissolved in sulphuric acid, which was shipped from China in a dozen containers in September.

A 10km underground cable connects the infrastructure with the local power grid, run by Schleswig-Holstein Netz. Bosch is responsible for developing the control electronics, system integration and testing different operating variants at Braderup.

This includes marketing the batteries in the frequency regulation market, taking part of the energy and using it for the wind farm’s own consumption, trading on the electricity exchange and stabilising the power grid.

“The hybrid storage facility is very flexible,” says Felix Maus, technical project manager at Bosch, in a press release. “On the one hand, it stores electricity for use or sale.

“On the other, it can balance out short-term fluctuations in demand or energy production in order to keep the power grid stable. Remember that production and demand must be in equilibrium at all times.

Voltage fluctuations

“Another problem in the power grid is voltage fluctuations, which can damage grid installations. To prevent this, the storage facility’s power electronics are capable of feeding so-called reactive power into the grid.”

The setup has already been showcased at events such as the II Congreso Smart Grids in Madrid this year.

Meanwhile the farmer who sparked the initiative, Jan Martin Hansen, is now a joint general manager of Energiespeicher Nord, alongside Cordelia Thielitz, head of Bosch’s stationary storage business area.

“Depending on wind strength and state of charge, the electronics allocate the power being generated to the battery type that is best suited to the task,” comments Hansen in Bosch’s press material.

Elsewhere, Thielitz explains that Bosch was keen to combine the high-power capabilities of Li-ion with the high-energy characteristics of vanadium redox flow. “We use both technologies in a roughly equal share in Braderup,” she says.

“The resulting storage facility is an important milestone on the road to the renewable energy supply of the future. We want to demonstrate that wind-turbine power generation does not have to be shut down when the grid is overloaded.”

A promotional video for the Braderup project shows Thielitz advocating the use of energy storage for greater self-sufficiency in rural communities.

Self-generated electricity

“The idea of a green village is to use as much of the self-generated electricity from renewable resources, solar and wind or combined heat-power systems, as possible,” she says.

“The storage is the only controllable element in this system, so storage actually makes it possible that more than 90% of the self-generated electricity can be used by the people who have produced it.”

The community-based aspect of the Braderup project is particularly noteworthy for other energy storage developers, not just in terms of opening up a non-traditional source of funding but also because of the degree of local commitment it results in.

Battery storage plants have yet to face the kind of community opposition frequently encountered in the wind energy sector, for example.

And at Braderup the very opposite appears to be the case: residents seem proud of the potential for energy self-sufficiency and potential shareholder value from sales to the grid.

Local children and teenagers even contributed artwork for the walls of the battery storage facility, underscoring the importance of the project for the future of the community.

Since the vanadium flow battery, at least, has an expected lifespan of around 20 years, it looks like those children will be enjoying the benefits of Hansen’s initiative for many Christmases to come.

Written by Jason Deign

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