Customer application 28 October 2020
Solar Power from Our Own Roof

If distribution networks are loaded to their limits, then network operators cannot issue connection permissions for new renewable energy systems to feed into the network. A pilot project in Bavaria is showing how a photovoltaic system can be economically operated purely for self-consumption.

In the past, operating PV arrays was primarily economical in that supply tariffs for the electricity guaranteed that the power produced could also be sold. However, the falling payments for electrical supply over the last few years have made self-consumption of the energy more important. Self-consumption becomes even more necessary, when the distribution networks are so overloaded that network operators can no longer connect systems for feed-in. This was precisely the case in Pottenstein in Upper Franconia. Klubert + Schmidt, an automotive supplier, wanted to install a PV array on the roof of their production hall there.

Controlling Photovoltaic Systems – Here’s How WAGO Supports You:

How Companies Use Their Own Solar Energy

In cases where solar systems for renewable energy generation cannot be connected a network, the company Münch Energie offers its customers a rewarding alternative with the WAGO Solution Provider “JPs Projects” Solution Provider:
Just use the energy yourself. With this concept, Münch Energie output nearly hits a level of 550 Megawatts a year – as much energy as half a power plant! With this much power, this company is the largest decentralized energy supplier in Germany – and WAGO Technology helps make it possible.

In this video, see how Münch Energie went from vision through pilot project – as seen on this website – to become leading trailblazer in keeping pace with the energy transition.

“Bayernwerk Netz GmbH, which operates the Pottenstein distribution network, was willing to link to the PV array with its peak of approximately 1000 kilowatts. However, the connection point was several kilometers away,” explains Sebastian Kremer, a project manager at M. Münch Elektrotechnik GmbH & Co. KG. The company operates its own photovoltaic and biogas systems and also plans and implements PV systems – including PV modules, brackets, control technology, inverters and network connections – for customers including agricultural and industrial operations. “Because energy costs are increasing just as prices for PV arrays are falling, solar energy consumption is more economical than ever,” emphasizes Kremer, who supervised the project for Klubert + Schmidt.

Although the supply from the planned system would have corresponded to the average electrical consumption of the producing company, the network operator initially balked at the request for a network connection directly at the company location. To obtain the connection release for the system, they had to ensure than no supply into the network would result. The network operator additionally demanded a security circuit that could shut down the system within ten seconds if a feed-in were to occur despite this.

Because energy costs are increasing just as prices for PV arrays are falling, solar energy consumption is more economical than ever.

Sebastian Kremer, Project Manager at M. Münch Elektrotechnik

Safety Circuits from WAGO

Because the economic calculations remained positive, despite the restrictions, Klubert + Schmidt green lighted the project. Münch relies on the WAGO PFC200 Controller to control the entire PV system. “We have already had good experiences with the WAGO 750 I/O SYSTEM on other projects,” states Kremer. “There is a suitable module available for every signal that we have to process.” The controller receives the measured values from the medium-voltage network via Modbus TCP; the 3-Phase Power Measurement Module from WAGO records the data from the low-voltage part of the system and controls the inverter using an RS-485 interface.

Other digital input/output modules and analog input/output modules complete the system. In addition, sensors that measure external temperature, current solar radiation and other essential values are also connected. “Theoretically, we could use this to determine the potential production of the PV array,” explains Kremer. Since the control cabinet with the controller is located outside, Münch relies on components from WAGO’s XTR Series. These are designed for an expanded temperature range from -40°C to +70°C. Therefore, the control cabinet does not need air conditioning.

A conventional feed-in controller, like those used in other photovoltaic systems, is installed on the controller. However, this controller required significantly more programming, because the safety circuit must prevent network feed-in according to the network operator’s provisions. The system went online in the third quarter of 2017; since then, it has produced electricity for the automotive supplier without any problems. Münch can monitor operations at all times using online access, which was likewise implemented via the WAGO controller.

A Business Model with a Future

Kremer describes specifics of this system, “In contrast to systems that are optimized for feed-in, the solar panels at Klubert + Schmid are oriented toward the east, west and south. This allows for the most uniform production during the day.” This is one of the results from the economic calculations, which analyzed the load curves of the automotive supplier and compared them to potential energy production from the PV array.

If we collect positive experience here, then we can safely implement other PV arrays without feed-in.

Sebastian Kremer, Project Manager at M. Münch Elektrotechnik

Of the predicted generation of 652,000 kilowatt hours per year, more than 88% should be consumed on site. Self-consumption numbers at this level made a photovoltaic system economical even without a network feed-in. Since Klubert + Schmidt operate on a three-shift system, the PV array will eventually be expanded to include battery storage. Then, the company will be able to use their solar power overnight to further reduce their energy costs. In addition, the storage device will allow Klubert + Schmidt to actively participate in load management, thus alleviating some of the stress on the distribution network.

The experts at Münch are also satisfied with the success of the pilot project. “The photovoltaic system is a pilot project for areas where the distribution network can no longer accommodate additional feed-in,” says Kremer. “If we collect positive experience here, then we can safely implement other PV arrays without feed-in.” The company has already received their first orders for new systems.

Text: Ulrich Menzel | WAGO

Photo: M. Münch Elektrotechnik