There’s a counterintuitive way to reduce the electricity required for data centre cooling: use heat. Absorption chillers can take high-temperature waste heat from onsite generation and convert it into chilled water, enabling a sizeable portion of the cooling load to be met with very little additional electrical demand.
This matters because the AI buildout is making grid limitation a practical design constraint. Across major markets, operators are encountering longer connection lead times, tighter limits on deliverable capacity, higher power prices, and less certainty about when upgrades will unlock future headroom. In many cases, it’s no longer the building or the IT that sets the pace of expansion, it’s the availability of power.
That pressure is accelerating a shift toward onsite generation as a standard part of campus planning. Some forecasts suggest that by 2030, roughly one-third of data centres could be operating as fully onsite-powered sites. But generation onsite also comes with a predictable energy balance: only around 35–50% of the fuel energy becomes electricity. The rest exits as high-grade thermal energy.
Instead of treating that heat as an inefficiency, operators can treat it as an input, using it to produce cooling and reduce the amount of electrical power devoted to thermal management.
Cooling delivered by thermal energy, not grid power
One pivotal approach is the application of absorption chillers to create a Combined Cooling and Power (CCP) plant. These plants recover otherwise wasted energy from gas turbines, fuel cells or engine-driven generators to power the thermally driven chiller to produce cooling.
Absorption chillers are not new; Johnson Controls deployed YORK absorption systems over a century ago and today have many thousands in operation worldwide. Their use has been common where thermal energy is more easily or economically available than electricity. Today’s absorption chillers represent a major leap forward in cooling innovation, enhancing reliability and sustainable performance. Modern systems are engineered to maintain optimal operating conditions with ease, ensuring smooth, uninterrupted cooling even in demanding environments. By harnessing a combination of varying grades of waste heat as their energy source, next generation absorption chillers provide a powerful and sustainable alternative to traditional electric cooling, cutting energy and water use, reducing emissions, and helping organisations move toward a cleaner, more efficient future.
For this reason, their application at large data centres where vast amounts of high temperature waste heat is abundantly and economically available from onsite generation sources – is ideal. They also deliver significant energy efficiency benefits: for every 2 MW of cooling supplied, an absorption chiller needs only 20 - 25 kW of electrical input compared to 500 kW or more for an electric chiller. That’s more than an 90% reduction in needed electricity.
Absorption chillers use waste heat as the driving force for cooling, replacing the mechanical compressor found in traditional refrigeration systems with a thermally driven process. In these systems the shifting concentration of the absorbent solution is both a powering mechanism and a heat transfer mechanism. Through a coordinated sequence of evaporation, absorption, generation, and condensation - each governed by changes in temperature and pressure - the refrigerant and absorbent circulate to produce chilled water.
Absorption chillers can be easily combined with other thermal management technologies if additional cooling demand is needed.
A new baseline for data centre efficiency
Moving forward, data centres will not be defined by raw compute power alone, they will be defined by how intelligently they utilise energy, heat and water. Efficient cooling is quickly becoming an enabler for competitiveness in an increasingly constrained environment. Absorption chillers are reshaping what is possible in real time at onsite-powered data centres.
While some operators will remain stuck with long grid connection delays and rising energy costs, those operators that turn waste heat from a costly byproduct into a strategic resource gain a significant edge, becoming more efficient, resilient, and sustainable while delivering greater benefits to their communities.
By turning waste heat from a costly byproduct into a strategic resource, operators can become more efficient, resilient, sustainable and positively impact their communities.
