Mihir Nandkeolyar, Director Business Development Global Data Centre Solutions at Johnson Controls
What if, for half, or even more, of the energy you need to cool your on-site generation data centre, you needed almost no electricity at all?
It sounds like wishful thinking, but it’s exactly the kind of breakthrough already possible with absorption chillers, which turn waste heat into cooling power. That kind of dreaming, and doing, is becoming essential as the AI era slams data centers into a very real physical constraint: the electric grid.
Across major markets, operators are facing delayed connections, caps on available power, rising energy prices and mounting uncertainty around future capacity. This tightening grid landscape is fundamentally reshaping how data centres plan, build and scale. As a result, onsite power is rapidly shifting from optional to integral. By 2030, some forecasts suggest that roughly a third of data centres will operate fully onsite-powered campuses. And here’s the opportunity hiding in plain sight: when generating power onsite, only 35–50% of fuel becomes electricity, the rest becomes high temperature thermal energy. Instead of wasting it, that heat can be harnessed to drive cooling “for free.”
The question is no longer just how to cool increasingly dense compute, but how to do it without adding further strain to an already overburdened grid.
Cooling powered by heat, not the grid
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.
Data centres over the next decade
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.
This article appeared in the May 2026 issue of Energy Manager magazine. Subscribe here.
