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SERIES 23 / Module 04 Battery Storage


Battery energy storage: from niche technology to core grid asset


James Hancock MSc MIET – head of innovation at Swanbarton Ltd B


attery energy storage systems (BESS) have changed from relatively small-scale demonstration sites to large-


scale installations in under a decade. BESS provides a range of services including frequency response, peaking capacity, constraint management and system resilience for small and large power systems. For commercial and industrial (C&I) sites, batteries are not confined to peak shaving applications; with the proper control system, they are a cornerstone of energy management, enabling higher uptime, making better use of on-site renewables and lowering costs. This article outlines the essentials


for practitioners across engineering, operations, and energy management. It covers applications where storage delivers value, the key technical building blocks, safety and standards, project delivery, and economics. It also explains why intelligent control – such as the Swanbarton Microgrid Management System (MMS) – is the difference between a battery that looks good on paper and one that delivers reliable performance and bankable savings in the real world.


1. Why storage – and why now? The drivers are familiar: the rapid rise of variable renewable generation, ageing and retired thermal generation plants, and the cost of network reinforcement and an ever-increasing fluctuating load from the transition to electrical energy. The operational response is to add fast-acting flexibility, which can absorb surplus energy and return it when needed, thereby providing voltage and frequency support. Electrochemical storage is well-suited because it can ramp instantly, is modular, and can be deployed anywhere with a network connection. For C&I users, three practical needs


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dominate: ● Cost control: time-of-use arbitrage


(both ways) and demand charge reduction. ● Resilience: maintaining critical


services during grid disturbances and outages, specifically ensuring controlled ride-through for sensitive processes. ● Integration of on-site generation:


matching PV output to demand, limiting export, and using storage to keep inverters online during weak-grid events. All three share a common thread of


control. Dispatching without situational awareness erodes batteries because of unnecessary cycles and a control system that can dispatch with good forecasting, constraints, and market signals becomes an asset that rapidly pays for itself.


2. Where BESS sits in the system Front-of-meter (FoM) batteries connect to the network at medium or high voltage and participate directly in the ancillary services and energy markets. Behind-the-meter (BtM) systems sit within a customer’s electrical boundary to optimise site imports and exports while supporting local resilience, and in some cases can also supply network services. The physical building blocks are similar in both cases – batteries, power conversion system (inverters), transformers and switchgear – but the control philosophy differs. FoM assets prioritise market-led dispatch and grid codes; BtM assets must respect site constraints, protection settings and process priorities. For microgrids in particular, controls


must manage not only the battery but also generation (e.g., PV, wind, CHP), controllable loads, and any standby generation. Grid-forming capability, either from the battery inverters or a rotating machine, is increasingly important for stable islanded operation. Well-designed systems transition smoothly between grid-connected, islanded, and resynchronised states without manual intervention.


3. Technology essentials – a brief tour


3.1 Batteries and chemistries Lithium-ion remains the dominant technology for short to medium duration storage. Within the lithium family, LFP


(lithium iron phosphate) has become the default choice for stationary systems because it offers robust safety characteristics, good cycle life, and a competitive cost. NMC (nickel, manganese, cobalt) is chosen where higher energy density is valuable, but in many stationary storage applications, space is not often the critical constraint. Alternative chemistries, such as sodium- ion and a range of flow batteries, are gaining market share and are serving longer-duration roles where four-hour or longer duration storage is needed. However, for most C&I microgrids today, LFP is the pragmatic choice. Cycle life and temperature


management are key. Elevated temperatures accelerate degradation, so thermal design and monitoring are not optional add-ons; they are life-extension functions.


3.2 Power conversion and grid support The power conversion system (PCS) connects the battery’s DC bus to the AC network. Modern PCS units are bidirectional and can also provide reactive power control. Many can operate in grid-forming mode, to regulate voltage and frequency, providing synthetic inertia and active damping to stabilise weak grids. For microgrids, this enables them to operate in island mode without relying on a diesel generator to ‘hold up’ the system. System designers must consider


DC voltage levels, PCS sizing and redundancy, short-circuit current capability for protection coordination, and harmonic performance. The PCS control limits (ramp rates, droop characteristics) should be aligned with site protection settings and any network or grid-code requirements.


3.3 Thermal management Containerised systems often incorporate distributed direct-expansion air conditioning; larger plants may adopt centralised liquid cooling for efficiency and maintainability as thermal control is crucial to safety and longevity. The aim is temperature uniformity across


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