Beyond Backup: The Strategic Role of BESS in Mission Critical Energy Systems

Introduction

As the global trend of digitisation,  internet penetration and the rise of Artificial Intelligence (AI) accelerates, Data Centres (DCs) find themselves in a challenging position. DCs must balance surging demand with sustainability commitments, all while navigating growing public scrutiny around energy consumption and Carbon emissions.

In theory, Data Centres could rely on economical, green power from the local utility. In practice, mature markets face two mainstream constraints:

• Long wait times for large-scale grid connections
• Difficulty integrating hourly-matched intermittent renewable energy generation at scale. 

These bottlenecks are especially challenging in an industry that values speed to market. As a result, DC operators are increasingly exploring decentralised energy solutions to meet both reliability and sustainability demands. 

The Role of BESS in an integrated energy system  

The concept of a microgrid refers to a decentralised, self-supporting energy ecosystem where DCs can integrate multiple energy sources, including gas turbines, renewables, and to an increasing extent Battery Energy Storage Systems (BESS).

While generation assets can provide reliable baseload power, they are not perfect. For example, gas turbines and engines cannot instantly ramp up to full load and inputs from solar and wind are inherently variable. These instances will lead to power quality issues: voltage fluctuations, electrical surges, harmonics and reactive power distortion that may damage sensitive IT equipment.

Additionally, fossil fuels has supply chain and emission concerns that make them less viable in the long term. This creates a need for a responsive, flexible and sustainable technology to stabilise, balance and connect these assets. This is the role increasingly filled by advanced battery systems.
Traditionally, electrochemical energy storage systems, particularly lead-acid (LA) and recently, Lithium-ion (Li-ion) were deployed extensively within uninterruptible power supply (UPS) systems, designed to provide short-term back-up until baseload generators could take over.

Today, large-scale BESS can operate at the medium-voltage level, providing hours of autonomy. Yet, for much of their lifecycle, these assets often sit idle and remain underutilised, failing to reach their full potential.

A more techno-economically viable engineering approach is to closely integrated BESS into the wider energy ecosystem, not just as an emergency buffer; but with a view to extract the following value:

• Peak demand reduction: most utilities offer incentives for reducing electricity consumption during peak hours, but critical facilities can only participate if they have an alternative power source. BESS are ideal for this purpose as they can charge during off-peak hours at lower rates and discharge during peak periods, which typically last for several hours.
• Renewable energy firming: a well-known application of BESS within a microgrid controller is stabilizing the output of solar PV and wind turbines. This helps smooth out fluctuations in renewable energy output, allowing utilities to avoid curtailing renewable generation and capture energy that would otherwise be lost during ramp-up or ramp-down periods.
• Spinning reserve: engine or turbine generators operate most efficiently typically across 70-80% load range. Frequent cycling of additional generators can reduce efficiency, increase fuel consumption and emissions, and cause wear. Pairing BESS with a generator allows the BESS to handle extra load, keeping generators within their optimal performance range.
• Enhance sustainability credentials: Integrating BESS with the wider energy ecosystem enables a higher penetration of intermittent renewable energy sources by storing excess clean energy. This reduces reliance on fossil-fuel-powered plants and lowers the DC Carbon footprint.

Figure 1: A high level illustration of power vs. energy consumption for various energy storage technologies 

Figure 1 illustrates the diverse landscape of BESS, categorised by their primary application and power rating. In DC microgrids, lithium-ion batteries occupy a strategic “sweet spot”, offering the capacity for both power-intensive applications, like UPS support and energy-intensive roles such as load shifting and participation in grid-scale services. In doing so, BESS can be transformed from a passive insurance mean into an active enabler of resilient, revenue-generating energy systems.

Key design factors

The following table attempts to summarise the most critical technical factors that need close consideration for an efficient BESS integration into mission-critical systems.

Table 1: Critical design considerations for effective BESS integration