Insights from the Frontlines of Battery Storage

Holistic Operations: Seeing the Entire System

Modern battery energy storage systems (BESS) are far more than a stack of cells. They comprise power-conversion systems (PCS), substations, market interfaces, security systems, and even on-site sensors and cameras. Kay of green flexibility underscored that today’s grid-scale BESS are data engines: every component produces streams of information at intervals ranging from every second to every ten minutes.

Rather than treating batteries in isolation, he argued that operators must ingest and integrate all these diverse data sources into one coherent platform. Doing so transforms raw numbers into actionable insights. It enables teams to spin up new charts in minutes, compare sites side by side, and immediately judge the effect of control changes. For example, annual parasitic loads can exceed 484 000 kWh (≈ €120 k) for a 15 MW/ 30 MWh system. Cutting just 5 % off auxiliary consumption yields meaningful O&M cost reductions.

With roughly 30 million data points flowing each day from a single 15 MW/30 MWh installation, the ability to unify, visualize, and secure that data isn’t just a “nice to have,” Kay insisted - it’s the linchpin for diagnosing issues fast, optimizing efficiency, capturing every revenue stream, and ultimately leading to a competitive advantage in BESS operations.

Watch our on-demand webinar on how you build the right data strategy for BESS!

Toll-Based Long-Duration Assets: Putting Performance on Contract

Roberto of BW ESS and his partner Julian from MIRAI Power described a very different challenge: how do you deliver multi-hour storage under a fixed, seven-year revenue contract?

BW ESS, part of a 70-year-old industrial group, has chosen to own its batteries for the long haul, sweating assets to drive predictable returns rather than flipping them as developers often do.  

Their flagship Bramley project in the U.K. boasts 100 MW of power with a 3+ hour duration - currently the longest-duration storage asset in the country. BW ESS managed to move from first commissioning to commercial operation in just 14 days.

Under a tolling agreement, BW ESS receives fixed payments for seven years, placing a premium on round-trip efficiency and guaranteed usable energy capacity. Any downtime beyond the contract’s tight availability thresholds risks significant penalties, so BW ESS layers in robust insurance, maintenance protocols, and real-time monitoring.

The result is a business model that hinges on operational excellence: the more reliably the batteries perform, the more revenue they lock in.

Quality-First Development: The Devil’s in the Details

Julian took the stage with a provocation: too many developers promise “blue-sky” timelines and grid-access outcomes, only to underdeliver. At MIRAI Power, which opened its doors in Munich in late 2024 on the back of global project experience, the mantra is simple: be honest about lead times, invest heavily in permitting and technical due diligence, and build bankable projects that stand up to lenders’ scrutiny.

That means recognizing that grid-connection agreements vary wildly. Some German DSOs offer so-called “flexible” curtailment windows that in practice ban charging or discharging during business hours, while markets like the Netherlands limit service interruptions to 15 percent of the year based on real-time congestion.

Likewise, revenue stacks in Germany span day-ahead, intraday trading and multiple reserve products. In the future, new markets like capacity markets or locational pricing might emerge. Whereas markets like Sweden remain concentrated on one-hour frequency services with thinner trading volume.  

Developers who understand these nuances and set realistic expectations with landowners, grid operators and regulators will emerge as true partners rather than mere speculators.

A Roadmap for Future Leaders

Taken together, these presentations sketched out a playbook for next-generation energy storage companies:

First, build or adopt operations platforms that unify hardware, market, and security data into a coherent view.

Second, ensure long-term tolling agreements. They facilitate financing. To enable these beneficial tolling agreements, ensure you understand your assets and include premiums for over-achieving performance.  

And third, double down on quality at every stage of project development, from transparent timelines and rigorous permitting to technical due diligence that anticipates grid constraints.

As battery costs continue to fall and markets evolve, companies that combine cutting-edge technology and disciplined execution with honest stakeholder engagement will lead the charge in the global energy transition.

‍

Curious to see what we do at TWAICE? Join our weekly live demo!