Manufacturing company grew weary of volatile prices – now it is looking forward to becoming self-sufficient in electricity

Rooftop solar plant forecast to offset 100% of company’s electricity use from March to October, with excess power sold to the grid or used for frequency balancing

11th July 2024 - After becoming weary of volatile electricity prices, a manufacturing company in Dalarna County took the decision to install a solar plant on its facility to power its operations. It is now expecting to become completely self-sufficient in electricity from April to September each year, with the plant also supplying about 50% of the site’s energy needs from October to March.

The installer, Isorent, chose SolarEdge DC-optimised inverters and Power Optimizers to overcome design challenges that would have otherwise limited the number of modules it could put on the roof. As a result, the investment is expected to pay for itself in eight years, while providing stable energy at a predictable cost.

Radonett in Rättvik manufactures filters that remove harmful radon from the water supply in households that have their own well, as well as backflow protection for municipal sewage treatment plants.

“Electricity costs started to skyrocket when our electricity contract expired two years ago. In a short time, electricity costs multiplied almost five-fold. Now, we have a secure, predictable electricity supply, using solar energy," says MD Martin Geber.

The solar plant is mounted on the roof of the manufacturing facility. Due to the staggered expansion of the site over many years, the roof is divided into ten different areas facing different directions.

In a traditional string inverter system, solar panels must be placed in identical string lengths and at exactly the same pitch and orientation. However, with the SolarEdge solution, no such limitations apply.

“When we looked at all the possibilities, we realised that with so many different roof angles, using a traditional string inverter system would have resulted in an extremely complicated installation. Or meant we could only use part of the roof, which would have reduced energy production and extended the payback period,” says Pontus Vallström, MD of Isorent.

"We wanted to use all roof surfaces and directions to make the best use of the sunlight from early morning to late afternoon. In our analysis, SolarEdge’s DC-optimized solution was the best way to achieve this," says Pontus Vallström.

The plant has 578 solar panels which are transformed into smart modules with SolarEdge Power Optimizers, and is controlled by two SolarEdge inverters. Isorent is also in the process of adding an energy storage unit to the system, with 180kW power output and a storage capacity of 297kWh. Among other things, the unit will help to distribute and even out the available solar energy over the hours of the day.

The base load peak power at Radonett is 60 kW. On an average overcast day, 90 kW is generated by the solar power plant. The resulting surplus can be stored in the battery, sold to the grid, or used for frequency regulation with the grid.

Electricity production and consumption can be monitored in real time using the online monitoring platform. This shows the current production of each pair of panels at any given time. It is also possible to see whether a panel is underperforming or has a fault. With a traditional string inverter system, such detail would not be visible at all.

“Now we are expecting to become completely self-sufficient in electricity from April to September and it is even possible that we can make a small profit during these months. We expect a payback period of around eight years, but we do not see it primarily as an investment – the future price of electricity is far too unpredictable to calculate any alternative cost. We have done this to get predictable costs and because it is the right thing to do as part of our sustainability program," concludes Geber.