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Pictures of the Future
The Magazine for Research and Innovation

Smart Grids and Energy Storage

Swarm Solution for Energy Users

Thanks to Caterva, Andreas Seubert can use much of the electricity produced by his photovoltaic modules himself. An app shows him how much he uses and how much is fed into the grid.

Caterva, a startup cofounded and partially supported by Siemens, has developed a revolutionary energy management system. The system makes it possible for homes outfitted with photovoltaic systems to rent out part of their battery power to network operators. The operators, in turn, pay the homeowners to temporarily store excess regeneratively-produced energy, which can be used to stabilize the network, thus supporting homeowners, network operators, and, of course, Caterva.

In his rural home in Bavaria, Andreas Seubert has a 1.8-meter high steel cabinet in the basement that houses stacks of lithium-ion batteries on one side, while the other side contains inverters, a smart meter, electronic switchgear, and a card-size circuit board with a processor and a mobile communications unit. Together with a number of solar panels on the roof, the systems provide an impressive example of what experts mean by decentralized power distribution.

Pilot Test

If Germany succeeds in its energy transition, energy storage systems (ESS) such as the one in Seubert’s basement will become an important part of a sustainable energy network in the future. That’s because such systems will help keep grid frequency stable and offset power deficits when the sun isn’t shining and the wind isn’t blowing. This task is currently still performed by conventional power plants, such as quick-start gas-fired power plants.

The Caterva solution consists of lithium-ion batteries and a mobile communication network. When linked with units in other buildings, they form a virtual storage system.

However, Caterva, a young Munich-based company, is demonstrating that there is also another way. “Caterva is the Latin word for swarm,” says the company’s managing director, Markus Brehler. The swarm principle is simple, and involves storing the electricity produced by photovoltaic modules such as those on the roof of Seubert’s home in lithium-ion batteries. Each cabinet of batteries has a total output of 20 kilowatts and a capacity of 21 kilowatt-hours (kWh). Cabinets in buildings throughout a region are connected through the grid, creating a swarm or virtual storage system with an output of over one megawatt. The cabinets are controlled via mobile radio, and electronic systems in the cabinets allow a control center to tap or recharge Caterva participants’ batteries. If there is demand for additional electricity in the grid, “the control center draws power from the swarm of batteries” in order to offset fluctuations, Seubert explains.

This innovative concept was originally developed by Siemens Novel Businesses, and then enhanced by various departments at Siemens Corporate Technology until the basic version of the swarm software was completed. Experts at SNB also helped establish Caterva, because it is their job to create new companies whenever a promising business idea cannot be further developed by Siemens AG as well, as quickly, or as flexibly as by an external firm. Before becoming the managing director of Caterva, Brehler gained extensive experience at another Siemens spinoff: EnOcean GmbH. Siemens will continue to support Caterva in many ways in the future. For example, it connects the cabinets to all of the hardware and is also a minority shareholder in the company.

Several months ago, in cooperation with energy supplier N-Ergie, Caterva launched a pilot test involving some 65 private owners of photovoltaic systems and storage batteries. Since July 2015, these participants have been generating and storing over one megawatt of electrical energy, thereby contributing to the stability of Germany’s grid. Thanks to the batteries in their homes, project participants can now consume more of their own electricity than they would without such an energy storage system — between 60 and 80 percent on average compared with just 30 percent, which would otherwise be the case.

Seubert, a 52-year-old sector manager for packaging machines at Siemens, is the first person to take part in the project. When he and his family moved into their new home in the little town of Dettelbach in the fall of 2013, he installed solar panels on the roof as a matter of course. The panels produce vast amounts of electricity on sunny days, and Seubert was annoyed that he could use relatively little of it himself. Although the electricity that is not immediately used is fed into the grid and Seubert is paid for it, his longterm goal was to become independent of energy suppliers.

Positive Response

He thought it would be unprofitable for him to buy the batteries for storing the solarpower. “Experts advised me against it, because they still consider high-performance batteries to be too expensive for private households,” he says. By chance, he found out about the Caterva project. “My colleagues at Siemens who are working on technologies for smart grids told me how batteries and smart technology could make me part of the energy supply system,” says Seubert. After he registered to take part in the pilot project, Caterva installed its new ESS unit in his basement in the early summer of 2014. People like Andreas Seubert are the pioneers that Caterva needs in order to demonstrate the swarm concept’s capabilities. The same applies to N-Ergie, which is involved in the pilot project. “We are working hard on ways to implement the energy transition,” explains project manager Ingo Sigert from NErgie’s Strategic Corporate Development unit. Sigert is convinced that energy supply companies will have to offer innovative solutions in order to survive on the market over the long term. That’s why N-Ergie recently put a 70-meter hot water heat storage system into operation. The storage system, which is one of the tallest in Europe, is connected to a combined-cycle plant that has an integrated biomass heating station. One of the main issues that N-Ergie is addressing is how to solve the problem of energy storage and grid regulation in a network characterized by widely fluctuating amounts of electricity from renewable sources of energy. “We were immediately captivated when Caterva came to us and presented its swarm concept,” explains Sigert. The two companies quickly agreed to form a partnership and also brought Friedrich Alexander University (FAU) in Erlangen on board. Scientists from the university will support the pilot project until 2017. “We can now gain experience for a time in the future when more and more electricity will be obtained from renewable energy sources,” says Sigert.

Each project partner is responsible for specific tasks. N-Ergie contacts customers in its grid area who have relatively new solar panels installed on their roofs. “The response has been very positive. We quickly found more than 25 potential participants and expect to find the rest soon,” says Sigert. Caterva is the contract partner for the participants. It supplies them with the system for the steel cabinet and connects it to the network. “Participants pay a single rental fee for this service. This fee amounts to around €4,000 during the pilot phase,” Brehler explains. Households recoup this through the difference between the amount that they would have to pay for electricity from the grid in Germany — currently about 27 Eurocents per kWh — and the amount that the use of their own electricity would cost them. This currently results in savings of 10 to 15 ct/kWh. Caterva can offer such favorable rental terms because of the income it gets from supplying primary controlling power to the transmission grid operator.

Swarm Coordination

N-Ergie, in turn, provides the overarching infrastructure. In the future, its control center will manage not only the company’s power plants but also the Caterva project swarm. “One of its key tasks is coordination of the swarm,” says Brehler. Mobile radio is used to transmit data from ESS units in participants’ basements to the control center. As a result, N-Ergie knows the batteries’ charge levels at all times.

At the same time, the ESS units “know” when the grid frequency fluctuates due to an imbalance between the supply and demand for electricity. This is the case, for example, when the distributed power producers generate too much electricity or when conventional producers such as power plants break down. In such situations, electricity has to be immediately fed into or taken out of the grid so that the difference between electricity production and consumption can be offset and grid frequency kept at 50 hertz. This is traditionally done by conventional power stations such as gas-fired power plants.

Since 2011 Germany has also allowed distributed energy producers to perform this task, provided they feed at least 1 megawatt of controlling power into the grid. In its system services roadmap for the year 2030, the German Energy Agency (dena) plans to have more and more distributed producers take over this task. But before that can happen, Germany will have to test and use new technologies such as those from Caterva. “We have to act now so that we will have solutions to keep the grid stable five years from now,” says Brehler.

This pilot project, which was only recently launched, is just the beginning of a far-reaching development. N-Ergie is thinking of integrating owners of photovoltaic modules from all over Germany, because “the bigger the swarm, the bigger its contribution to grid stability,” says Sigert. Germany is especially well suited for the implementation of the Caterva concept, whose slogan is “Mit der Sonne im Netz” (Into the grid with the sun). At approximately 1.1 million, Germany has far more owners of private photovoltaic modules than any other country in the world — a figure that highlights the potential opportunities for new business concepts associated with the energy transition. Markus Brehler is convinced of this as well. “We are now looking for infrastructure investors who are interested in business models for future energy concepts,” he says. But that’s still a long way off. For now, Seubert is satisfied that the system in his basement works reliably. “I hope that I will one day have enough energy for my household even if there is a widespread power outage,” he says. “I would even be satisfied if I had enough energy to watch an important soccer game on TV.” That should already be possible today.

How Siemens is Testing New Business Models

Siemens Novel Businesses has been a part of the Innovative Ventures department at Siemens Corporate Technology since 2012. Its mandate is to establish startup companies in fields of business that could be of interest to Siemens. In doing so, it creates opportunities for quickly and flexibly testing innovative business models. Such startup companies are managed independently of Siemens and led by experienced entrepreneurs. Siemens Novel Businesses finances these spinoffs just as a venture capital investor would. Siemens can later decide wether it wants to incorporate these startups into its organization so that their business operations ca be expanded within the company.  

Katrin Nikolaus