Mühlacker battery project moves into construction

ADS-TEC Energy has started construction of a 10MW/20MWh battery energy storage system at Stadtwerke Mühlacker’s substation in Baden-Württemberg, moving the municipal utility’s first large-scale storage project from planning into physical delivery.

The start of work follows the project’s announcement in January 2026. ADS-TEC Energy is responsible for planning, implementation, system integration, and operational preparation, with the completed installation scheduled for handover to Stadtwerke Mühlacker in October.

Four containerised BESS5000 systems will form the core of the installation. The units are due to arrive during summer 2026 and will be positioned by crane as civil, cabling, protection, and control work progresses around the operating substation.

The battery is intended to reduce peak loads, shift electricity between time periods, and provide flexibility as demand from electric vehicles, heat pumps, and digital infrastructure increases. Its location at an existing substation provides direct access to network infrastructure, but the project still requires detailed integration before it can operate safely or participate in electricity markets.

Distribution-level storage enters delivery

The construction milestone is more significant than the project’s scale might suggest. Municipal utilities are increasingly expected to accommodate intermittent generation and new electrical loads without allowing short-duration peaks or local export constraints to determine the pace of electrification.

A battery connected at distribution level can absorb electricity during lower-demand or lower-price periods and return it when demand or system value rises. It may also help manage local network constraints, reduce peak demand, and provide balancing or ancillary services where the technical and commercial arrangements permit.

The Mühlacker system has a two-hour nominal duration at full rated output, based on its 10MW power rating and 20MWh energy capacity. That configuration is suited to repeated daily shifting, peak management, and shorter-duration system services rather than prolonged multi-day backup.

The eventual operating strategy will depend on Stadtwerke Mühlacker’s market access, network requirements, forecast accuracy, and the relative value of competing services. A battery cannot provide every potential function at full capacity simultaneously, so its control system must decide how much power and energy to reserve for each use.

Locating the system at an existing substation can reduce the need for a separate connection site, but it does not make integration automatic. Engineers must coordinate transformers, switchgear, metering, protection settings, supervisory control, communications, earthing, fire strategy, and emergency procedures with the characteristics of the surrounding network.

The works must also be delivered around live infrastructure. Delivery routes, crane access, temporary works, cable installation, and testing have to be planned without compromising the substation’s existing function or restricting access needed by network personnel.

Commercial performance will depend on lifecycle control

ADS-TEC Energy’s role extends beyond supplying battery containers. The company is delivering an integrated system and preparing it for long-term operation, reflecting the fact that storage economics depend on far more than installed megawatt-hours.

Availability, round-trip efficiency, auxiliary consumption, thermal management, cell ageing, software performance, and maintenance response all influence the amount of energy that can be traded over the asset’s life. Revenue forecasts can deteriorate quickly where systems experience prolonged outages, unexpected degradation, or limits on how frequently they may cycle.

The utility must also manage changing electricity-market conditions. Services that appear attractive when the system is commissioned may become less valuable as more batteries enter the market, while new opportunities may emerge through local flexibility procurement, congestion management, or revised balancing arrangements.

A control platform able to move between services can therefore be as important as the battery hardware. Dispatch decisions must account for electricity prices, state of charge, network requirements, forecast demand, battery condition, and any commitments already made for the following trading intervals.

Safety remains central to the design. Containerised systems require detection, isolation, ventilation, thermal management, access control, and emergency-response procedures suited to the battery chemistry and site layout. Those arrangements must remain effective during normal cycling, maintenance, component replacement, and abnormal operating conditions.

The four BESS5000 units provide a modular structure, allowing much of the equipment to be manufactured and tested before delivery rather than assembled entirely on site. Modularisation can reduce installation time, although transformers, cabling, civil works, control integration, and final commissioning remain site-specific.

For Stadtwerke Mühlacker, the system also introduces a different operating model. Conventional network assets generally perform relatively stable technical roles, whereas a battery may change function several times in one day, moving from charging to reserve provision, peak support, or market discharge according to system conditions.

The October handover target leaves a compressed period between container delivery, installation, electrical completion, testing, and acceptance. Meeting that programme will depend on the civil and electrical works progressing before the storage units arrive and on control interfaces being ready for commissioning.

Once operational, the more useful measures will be availability, realised revenue, and the contribution made to local network management. Battery projects are announced in megawatts and megawatt-hours; municipal operators eventually have to account for them in operating hours, maintenance interventions, and dependable performance.