08/09/2022

Self-generated electricity in the agricultural sector with KOSTAL

Almost two decades ago, photovoltaic systems in agriculture were a major driver of the energy transition. Today, photovoltaics for self-generated electricity are once again an integral part of productive farms. Last year, young farmer Alexander Kuhn installed a self-generating system on his 70-hectare farm, comprising photovoltaics and an electricity storage unit using technology from solar specialist KOSTAL. After just nine months, it has proven to be the right decision.

Photovoltaics – a signal of sustainability

The Kuhn family farms a 70-hectare farm in the Upper Palatinate, in the small community of Deinschwang about 30 kilometres east of Nuremberg. Now in its seventh generation of working the land, to date the family has always practised conventional farming. "But the trend is towards organic," explains Alexander Kuhn.

The photovoltaic system with KOSTAL components installed on the roof of the dairy barn in October 2021 is the first solar power system on the Kuhn GbR farm – perhaps it’s a visible signal of a generational change and increased sustainability, in terms of energy too. "I’ve always been interested in generating my own electricity with photovoltaics. During the first photovoltaics boom, however, it just didn't happen for us. We did think about it, but at the time the focus was on feeding power into the grid. Now photovoltaics and electricity storage are part of sustainable farm management," Kuhn explains.

The decision to work with PV and KOSTAL

Renewable energies are and have always been an issue in agriculture – be it biomass, solar power generation or wind and hydropower. Alexander Kuhn has done the maths time and again, working out what it would cost to buy a photovoltaic system and also a biogas plant. Systems for fermenting slurry with an electrical output of up to 100 kilowatts are of particular interest to dairy farms because they are run with 80 % slurry and just 20 % biomass. Ultimately, the Kuhn family chose a photovoltaic system with electricity storage because it is easier to install and commission than a biogas plant.

But there is still room for more solar modules on the roof. The farm could install more generating capacity for self-consumption. “We consume around 50 000 kilowatt hours per year. The milking robots, the milk processing plant with its cooling system and our groundwater treatment plant are all large consumers." In addition, Kuhn has swapped his outdated combustion engine vehicle for an electric car, whose batteries are of course charged with photovoltaic power. "A 50-kilowatt peak would have suited our consumption well. The 30-kilowatt-peak photovoltaic system with KOSTAL technology, in combination with the storage unit, currently supplies exactly half of our annual consumption. The 22-kilowatt-hour electricity storage unit lasts us until midnight," explains Kuhn. "A comparatively small contribution is made by the surplus fed into the grid. We are still trying to increase self-consumption by using smart consumers."

New photovoltaics, new roofing

Before the photovoltaics were mounted on the barn roof, Alexander Kuhn had new roof cladding with trapezoidal sheet metal installed. On top of this came a minimalist substructure with short trapezoidal sheet metal brackets. The inverter was installed on the outside wall right next to the entrance to the barn – a 30-kilowatt device from the Commercial Inverter series ("CI" for short) from inverter manufacturer KOSTAL, which was launched in 2021 and features a dust- and water-protected IP65 housing.

Electricity storage unit not installed in the barn

Kuhn had the electricity storage unit installed in the cellar of the house. A cable was laid from the house to the photovoltaic system. In the cellar, the storage unit is dry, warm and protected from ammonia and fluctuating temperatures. Kuhn opted for a BYD storage unit with net storage capacity of 22 kilowatt hours and lithium iron phosphate battery technology. Together with a PLENTICORE battery inverter (also from KOSTAL), the farm can now supply itself with self-generated electricity.

Production and consumption going precisely as planned

After the first nine months, it is clear that the system is working exactly according to plan and is delivering what was calculated: 25 000 kilowatt hours of electricity per year, self-generated for self-consumption, and a saving of around €7000 in energy costs at current electricity prices, which are rising all the time.

Component selection

"I am really pleased that the inverters come from a German manufacturer which also produces the devices here in Germany. My solar installer has worked with KOSTAL for many years and also with the components which were right for us, so he’s familiar with the installation process and has plenty of experience. The KOSTAL PIKO CI inverter and the PLENTICORE battery inverter in combination with a BYD storage unit are a tried-and-tested and well-functioning combination, as is proven by our experience so far," says Kuhn.

The solar installer, an electrical company with a focus on photovoltaics and electricity storage, carried out the installation in full. "The work was completed quickly and smoothly. It was done in under a week," explains Kuhn. 375-watt modules were installed, permitting exactly the 30-kilowatt peak to be fitted on the roof

More power in the future

Alexander Kuhn is struggling with the 20 kilowatts missing from his peak photovoltaic capacity. When you do the figures, a peak photovoltaic output of 50 kilowatts would make the farm self-sufficient: "We’ve actually already decided to extend the system to a 50-kilowatt peak. The only reason we opted for a 30-kilowatt peak in the first instance was the Renewable Energies Act levy. Even though it was only 2.78 cents per kilowatt hour, this made a huge difference to cost-effectiveness. We will also expand the electricity storage unit so that we have a 1:1 ratio between output and storage. And we are thinking about an emergency power system. If you already have PV and storage, it would be unwise not to do so," Kuhn adds.

The energy future on the Kuhn family farm is secured and will ensure stable, calculable energy costs for the business and for mobility for decades to come!

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