The amount of power consumed by data centres continues to rise, as does the focus on sustainability. While much of the current focus is on sourcing renewable energy, via PPAs, microgrids and the like, there also needs to be increased attention paid to the resilience systems inside the data centre itself – the batteries, the generators and overall on-site energy management.
Lithium-ion batteries and diesel generators have been mainstays of data centre backup power for more than a decade. They offer a compelling combination of cost, performance, and reliability. However, supply chain vulnerabilities, resource constraints, environmental impacts, and regulatory pressure are driving the industry to explore new, cleaner alternatives. The emergence of post-lithium energy storage technologies, together with more sustainable generator solutions, marks the beginning of a new era in data centre power resilience.
Lithium-ion batteries have served the industry exceptionally well, but they come with limitations. Lithium mining has well-documented environmental and geopolitical challenges, including water depletion, habitat disruption, and concentration of supply chains in politically sensitive regions. As battery demand from electric vehicles and consumer electronics continues to surge, data centre operators also face increased competition for materials and fluctuating prices.
Additionally, lithium-ion batteries present, all be it minimal, fire-risk considerations that require stringent safety measures. Although incidents are rare, the consequences of thermal runaway in a mission-critical environment are significant. Many operators are therefore evaluating battery chemistries that remove this risk entirely.
Finally, the push toward circularity is highlighting end-of-life concerns. Recycling lithium batteries is technically complex and not yet widely implemented at scale. For an industry deploying thousands of battery cabinets every year, this raises long-term sustainability concerns.
These challenges are encouraging the exploration of post-lithium solutions -technologies that promise improved safety, longer life cycles, reduced environmental impact, and, in some cases, better performance.
Sodium-Ion Batteries
Sodium-ion technology is one of the most promising successors to lithium. Sodium is far more abundant across the world. It can be extracted without the environmental damage associated with lithium mining, and the chemistry avoids cobalt and nickel - two materials with controversial supply chains.
Although sodium-ion batteries currently offer lower energy density than lithium-ion, this is less of an issue for stationary applications like UPS systems, where weight and volume constraints are less critical. Improvements in charging efficiency, safety, and low-temperature performance make sodium particularly attractive for edge and hyperscale facilities in cooler climates. With major manufacturers scaling up production, sodium-ion could become a mainstream data centre option before the end of the decade.
Zinc-Based Batteries
Zinc is another abundant, inexpensive, and safe material that supports several battery chemistries, including zinc-air, zinc-manganese dioxide, and zinc-nickel. These systems eliminate the thermal-runaway risk associated with lithium and offer extremely long cycle lives. Zinc batteries can also be fully discharged without degrading, making them suitable for hybrid UPS-plus-energy-storage applications where operators want to perform peak-shaving or grid-support functions.
Because zinc batteries do not rely on flammable electrolytes, they dramatically reduce the fire-loading inside a data centre. This opens the door to simpler rack integration and potentially lower insurance and compliance overheads.
Flow Batteries
Vanadium redox flow batteries (VRFBs) and alternative chemistries such as iron flow batteries are gaining attention for their long-duration storage potential. Flow batteries separate energy storage from power delivery, allowing extremely flexible sizing and very long operational lifetimes, often exceeding 20 years without major degradation.
For data centres seeking to combine backup power with renewable-energy integration, flow batteries offer the ability to store large amounts of energy and discharge for extended periods. Although their footprint currently makes them more suitable for campus-scale or hyperscale sites, ongoing innovation may reduce their space requirements over time.
Solid-State Batteries
While still emerging, solid-state battery systems promise improved energy density and safety by replacing liquid electrolytes with solid materials. These systems are less prone to thermal runaway and could offer extended lifespans. Many analysts expect solid-state technologies to enter commercial stationary-storage markets within the next decade, potentially transforming data centre UPS design.
Beyond Batteries
Even the most advanced battery technologies cannot fully replace generators, at least not yet. Data centres still need long-duration backup power to maintain operations during extended outages. Traditionally, diesel gensets have filled this role due to their reliability and rapid start-up characteristics. However, diesel combustion is a major source of CO₂, NOₓ, and particulate emissions, and sustainability commitments are pushing operators to rethink their dependence on diesel.
Hydrotreated Vegetable Oil (HVO) has quickly become one of the most realistic near-term diesel alternatives. It is a drop-in fuel that can be used in most existing diesel generators without modification and can reduce net lifecycle emissions substantially, depending on feedstock and production processes. Because HVO burns cleaner than fossil diesel, it also reduces local air pollution, which can help ease planning constraints in urban locations.
Many operators across Europe and North America have already transitioned at least part of their generator fleets to HVO. While questions remain about feedstock sustainability and long-term supply availability, HVO offers an immediate opportunity to reduce generator emissions without compromising reliability.
Longer-term, hydrogen is emerging as a potential replacement for diesel in critical power applications. Several generator manufacturers are developing engines capable of running on a blend of hydrogen and natural gas or, ultimately, on 100% hydrogen.
Hydrogen combustion emits no carbon dioxide, although NOₓ emissions must be carefully managed. The primary challenge today is the availability of green hydrogen, produced using renewable electricity, at the scale required by hyperscale facilities. Nevertheless, pilot projects are already underway, and hydrogen-ready gensets could become more mainstream as infrastructure develops.
Fuel cells offer another path toward hydrogen-based backup power. Unlike combustion engines, fuel cells generate electricity electrochemically, producing only water and heat as by-products when using hydrogen. Solid oxide fuel cells (SOFCs) and proton exchange membrane (PEM) systems are attracting significant investment.
Fuel cells operate more quietly and efficiently than diesel generators and can run for extended periods, as long as fuel is available. Their main limitation is cost and the complexity of hydrogen storage. However, for campuses with integrated renewable energy and hydrogen production, fuel cells could eventually serve as both backup and primary power sources.
The shift toward post-lithium batteries and low-carbon generator technologies is part of a broader evolution in how data centres manage energy. Increasingly, operators view themselves not just as power consumers but as active participants in flexible, renewable-driven energy systems.
Future data centres may combine multiple sustainable technologies: sodium-ion or zinc-based UPS batteries for immediate backup, flow batteries for long-duration storage and grid support, and hydrogen-ready generators or fuel cells for rare but extended outages. Some may integrate on-site solar generation, renewable-power purchase agreements, or microgrid architectures to improve resilience and reduce carbon intensity.
The challenge is not merely technical; it is also economic and regulatory. Operators need to balance capital investment with lifecycle sustainability benefits, navigate evolving emissions standards, and ensure that new technologies meet the industry’s stringent reliability requirements. Yet momentum is clearly building. As energy systems decarbonise globally, data centres cannot afford to remain dependent on fossil-based resilience infrastructure.
The shift beyond lithium and diesel marks a pivotal moment in the evolution of data centre power strategy. As operators embrace sodium-ion and zinc-based batteries, invest in flow storage, deploy HVO fuels, and test hydrogen-ready generators and fuel cells, the industry will transition toward a more sustainable and resilient future.
These innovations reflect a broader vision: a world in which data centres support the energy transition rather than merely adapt to it. By pioneering cleaner, safer, and more flexible power solutions, the sector is poised to play a central role in building a digital infrastructure that is both resilient and environmentally responsible.