VGW Aar-Einrich: PV system and intelligent storage system as a backup power system (BPS) for the Niederneisen wastewater treatment plant
IWR was commissioned by Verbandsgemeindewerke Aar-Einrich to plan a sustainable and resilient energy supply for the Niederneisen wastewater treatment plant. The aim is to reduce CO₂ emissions, optimize operating costs and increase operational reliability through an integrated emergency power concept.the project includes a photovoltaic system with approx. 90 kWp for self-supply (lot 1) and a battery storage system with 80 kWh (lot 2). The storage system is intended to cover peak loads and help stabilize the supply in critical operating situations.
Implementation in two lots
Lot 1 comprises the installation of the photovoltaic system (without the associated inverters).
Lot 2 comprises the installation of the inverters (PV system and battery storage), the energy storage, the emergency power supply and the integration of all new components into the existing control technology.
The division enables a step-by-step implementation, coordinated with the ongoing operation of the wastewater treatment plant.
Battery storage, energy management and consumer prioritization
The Niederneisen wastewater treatment plant is operated via a WinCC control system and Siemens S7-400 automation. The new components are planned in such a way that they can be fully integrated into this system environment. A particular focus is on the automated switchover to emergency power operation in the event of a power failure in order to ensure the availability of the plant. The battery storage system is designed as a lithium iron phosphate system (LiFePO) with high cycle stability and low self-discharge. The planned depth of discharge is between 90 and 98 %. The storage system is controlled via the central energy management system of the wastewater treatment plant. Consumers are managed via defined priorities in order to use energy efficiently. Surpluses are to be stored depending on the grid load and forecast availability.
Emergency power concept: stationary and mobile
Two gensets are provided for the emergency power supply:
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Stationary emergency generator (80 kW), primarily natural gas operation with option to switch to diesel, with sound insulation hood.
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Mobile emergency power generator (64 kW) for flexible applications (e.g. outstations) with self-sufficient fuel supply for at least 36 hours at nominal load.
The integration should take place via automated synchronization to enable seamless switching between the energy sources.
Commissioning, trial operation and documentation
The integration is planned in phases: The PV system (lot 1) and battery storage system will initially be installed and commissioned independently of each other. This will be followed by integration into the energy management system.
The commissioning phase comprises a four-week trial operation with load scenarios, grid failure tests and simulations of the synchronization processes. Accompanying documentation is created and training is provided for the operating personnel. This includes EPLAN P8 circuit diagrams, grid synchronization plans and maintenance and inspection concepts.
Schedule
The photovoltaic system was already installed in 2025. All further work is scheduled for spring 2026.
Selection of further PV projects from the engineering office IWR:
PV system on screw lift
Solar power for elevated tanks
Photovoltaic system at the Breitenbach pumping station