In Hünfeld, Germany, Pixii’s PowerBase XL battery storage system is enhancing the efficient utilization of solar energy to meet the continuous power demands of the local wastewater treatment plant. By increasing energy independence from the grid and maximizing the use of renewable resources, Pixii’s solution not only supports sustainability goals but also alleviates strain on the grid during peak solar production during the day.

The challenge 

The wastewater treatment plant in Hünfeld, operated by Stadtwerke Hünfeld, has a steady energy demand of approximately 300 kW, with energy-intensive wastewater treatment processes running continuously day and night. Around 70% of daily energy consumption occurs during nighttime hours.

To reduce energy costs and lower carbon emissions, the city installed a 1 MWp solar PV system on a nearby greenfield site. However, the mismatch between fluctuating solar production-peaking during the day and ceasing at night-and the plant’s constant energy consumption resulted in inefficient utilization of the generated solar power.

Both Stadtwerke Hünfeld and the City of Hünfeld required a flexible and cost-effective solution to store surplus solar energy for nighttime use, optimize energy generation, and align it more closely with the specific demands of wastewater treatment, further minimizing the plant’s environmental impact.

The solution

The City of Hünfeld chose to deploy Pixii’s PowerBase XL system, a modular and preconfigured Battery Energy Storage System (BESS) with a total power and capacity of 540 kW / 1.39 MWh. It seamlessly links to the solar PV plant by positioning directly to the mid-voltage transformer station, which has been erected for the PV power plant.

By delivering pre-installed battery units on a skid, the PowerBase XL minimized installation time and waste, ensuring a fast and efficient deployment. With stored solar power now available during peak nighttime demand, the wastewater treatment plant can operate more efficiently while reducing reliance on grid electricity.

“This delivery is a great example of how the PowerBase XL can provide practical, scalable solutions for communities looking to optimize their energy use. We’re excited to see the positive impact this will have on Hünfeld and look forward to continuing our work with other forward-thinking partners.”

Konja Wick, Key Account Manager for Europe in Pixii

The Benefits 

Pixii’s BESS has transformed energy management at Hünfeld’s wastewater treatment plant. By enabling the storage of surplus solar energy for use during periods of low production, the facility now operates more efficiently on renewable power, significantly reducing grid dependence, operational costs, and carbon emissions.

From a financial perspective, the project capitalizes on Pixii’s value-stacking approach to maximize returns, with the behind-the-meter installation directly cutting the plant’s energy expenses.
In a second initiative, the municipal utility, Stadtwerke Hünfeld, deployed a utility-scale storage system with a capacity of 6.4 MW/21.6 MWh to stabilize the grid and generate new revenue streams for the city. This strategic investment reflects the recognition that oil and gas are becoming less viable as future energy sources. The project directly benefits Hünfeld’s residents, as the revenues support local public transportation, social initiatives, and public services.

The municipal utilities are considering installing Pixii’s PowerShaper systems at 150 transformer stations. These systems would eliminate the need for costly grid upgrades by managing peak demand and minimizing losses through reactive power management. During periods of low demand, the systems can integrate with the existing utility-scale storage to form a virtual power plant (VPP) locally, unlocking additional revenue opportunities. With wastewater treatment requiring significant energy during nighttime hours, battery storage solutions like PowerBase XL are expected to play an even greater role in the sector moving forward.

“Our goal was to make our wastewater treatment process as energy-efficient and environmentally friendly as possible. The PowerBase XL with the high scalability was the best solution for us. Especially under the consideration to handle multiple further storage projects and different use cases, with only one single product.”

Manuel Gollbach, CEO in Stadtwerke Hünfeld

The results  

In Hünfeld, Germany, Pixii’s PowerBase XL Battery Energy Storage System (540 kW/1.39 MWh) optimizes the use of solar energy at the local wastewater treatment plant. By storing surplus solar power from a 1 MWp solar PV system, it ensures efficient operation of the plant, even during periods of low solar production. The pre-mounted system directly connects to the plant’s mid-voltage transformer, minimizing installation time and waste. This solution directly addresses the high nighttime energy consumption of wastewater treatment, reducing grid dependency, lowering operational costs, and significantly cutting carbon emissions.

Background

Stadtwerke Hünfeld is the local utility provider for Hünfeld, responsible for supplying electricity, natural gas, and water to the community. They are committed to sustainability and innovation in local energy management.

Project contacts
Pixii Oslo
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Visiting address: Sommerrogata 13-15, 0255 Oslo

Project manager Pixii
Konja Wick
Key Account Manager for Europe in Pixii
E-mail: Show Email

Download the case study

Pure power – Pixii maximizes solar energy for smarter wastewater treatment