Most new export connections to Great Britain’s distribution networks are now subject to network access restrictions, resulting in curtailment during certain system conditions. This curtailment can arise from System Operator actions, inter-trip schemes, Load Management Schemes (LMS) or Active Network Management (ANM) schemes.

As more new connections are subject to curtailable connections, driven by increasingly congested networks and recent market and regulatory changes, the ability of developers and investors to understand curtailment impacts on site production has become increasingly crucial. The need for robust, transparent and representative curtailment assessments continues to grow, playing a vital role in project viability, risk allocation, and investment decision-making.

Assessing the Impact of Network Access Restrictions on BESS Site Operations

While DSO curtailment assessments often use generic, fixed-behaviour profiles to represents Battery Energy Storage Systems (BESS) import and export, at Smarter Grid Solutions, we employ more representative and dynamic operational profiles when modelling BESS in curtailment assessments.

In the case of BESS, network access restrictions may apply to power import, power export, or, in some cases, both import and export. Compared with energy production technologies such as solar or wind, the flexible dispatch capability of BESS allows operators to control when energy is imported from, or exported to, the grid.

Where short‑duration or predictable network access restrictions, such as those arising from ANM schemes, can be forecast, a BESS operator may adapt the planned daily dispatch schedule to avoid curtailment altogether. Since BESS dispatch is typically optimised against market price signals, any deviation from an market-optimised dispatch schedule will have an associated financial impact. However, in most cases, proactively modifying the dispatch strategy will be economically preferable to accepting curtailment of the originally planned schedule.

Typically, DSO curtailment assessments consider import and export curtailment via two separate studies, making assumptions that flexible demand does not support reductions in export curtailment and generation export does not support reductions in import curtailment. This conservative, worst-case approach to import/export curtailment assessment does not reflect how ANM systems manage network power flows and overestimates curtailment in many cases. Smarter Grid Solutions has developed what we refer to as a “whole system” approach to curtailment assessments which considers both import and export curtailment in a single study case. 

Applying Advanced BESS Modelling Methods in Curtailment Assessments

At SGS, our analytical approach builds on our experience of designing and deploying ANM control systems, meaning modelling both the control action and the resultant network operational state(s) as close to the operational reality as the analysis can achieve, given data and study time resolution limitations.

In cases of BESS curtailment, we have worked with clients to assess how forecast curtailment may influence daily BESS import/export dispatch strategies. BESS import and export behaviour is typically driven by market price signals, with the objective of maximising financial returns through daily dispatch optimisation.

Curtailment can introduce occasional limitations to BESS market trading revenues. Where curtailment can be forecast on a day-ahead basis however, daily BESS dispatch schedules can be adjusted to reduce the associated financial impact.

While curtailment of production is typically modelled in Megawatt-hour (MWh), the impact on BESS dispatch requires assessment in financial terms, including consideration of lost market revenues and increased BESS charging costs. The benefits of altering daily dispatch schedules to minimise curtailment impacts can therefore also be quantified financially.

Earlier-adopted approaches assessed whether the financial impact of BESS curtailment could be reduced by shifting import and export dispatch windows by half an hour or one hour earlier or later. For constrained network locations with multiple BESS assets, the methodology considered scenarios where some BESS adopted this dispatch-shifting approach while others did not. This departs from the commonly used “herd behaviour” assumption, whereby all BESS assets respond identically to the same market signals and therefore exhibit identical import/export dispatch behaviour.

At SGS we have continued to advance study approaches with the aim of improving the representative modelling of BESS behaviour and thus curtailment impacts. Our latest approach uses a dispatch optimisation algorithm that incorporates day-ahead half-hourly curtailment forecasts derived from a network load flow model, together with historical wholesale market price data for each date and trading interval.

This enables BESS dispatch schedules to be financially optimised while accounting for forecast curtailment and operational constraints such as State of Charge (SoC) limits, warranty restrictions, cycle limits, and minimum and maximum SoC operating ranges. It provides a significantly more representative reflection of BESS operator behaviour when faced with a forecast of day-ahead curtailment.

The results are aggregated over a full year to estimate the annual financial impact relative to either:

• full unrestricted access to the utility network; or
• a scenario where curtailment is accepted without modifying the daily dispatch strategy.

What does this mean for Developers and Investors? 

Modelling a BESS site with consideration of forecast curtailment and market price signals allows import and export dispatch schedules to be optimised to maximise financial returns from market energy trading while accounting for periods of network access restriction. This provides a significantly more representative view of BESS behaviour when compared to more ‘static’ models of BESS dispatch.

By modelling future network conditions, including demand changes, increasing levels of microgeneration and evolving network constraints alongside forecast market prices and trading strategies, future BESS revenues can be estimated with curtailment impacts appropriately accounted for.

This provides valuable insight for investment decision-making, including assessment of project viability, revenue risk, and the potential value of flexible dispatch strategies. These insights are highly valuable not just for BESS Developers but also the Investors and Financiers that fund these developments and their acquisitions.

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SGS is engaged across the electricity sector, providing analysis and advisory support to stakeholders from developers and investors in renewable energy systems to DSOs and Transmission Owners and Operators. For many years we have supplied software systems for energy asset control and delivered specialist advisory services such as constraint and curtailment modelling. We follow industry changes relating to the connection and management of diverse generation and storage technologies. We are keen to capture those experiences and our knowledge to ensure our services are informative and valuable to other stakeholders participating in the energy system.

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