For decades, chiller plants have been considered the primary means of chilling. If a data center needed cooling, it needed a chiller plant sized to handle the entire thermal load. That assumption made sense for previous densities, but it doesn’t anymore.
The Old Data Center Cooling Design
Traditional chiller-based cooling exists to close one specific gap: the difference between what a data hall (or a chip) needs and what the outside air can provide on its own. For most of the industry’s history, that gap has been wide. Legacy IT equipment ran cool enough, and ambient temperatures rarely got close enough to useful, so operators built mechanical cooling to do the entire job.
However, that approach comes at a cost – financial, environmental, and community. Chiller plants rely on compressors and refrigerants, some of which are still being phased out for environmental reasons. Many designs are evaporative, consuming significant volumes of potable water to reject heat, and chillers are expensive to build, expensive to run, and inefficient compared to simply using the air or water that’s already outside the building.
The industry has lived with these tradeoffs because the alternative, closing that thermal gap without mechanical help, wasn’t available. Until recently, it wasn’t a realistic design option.
How to Close the Thermal Gap with Trim Chilling
The size of that thermal gap comes down to one number: how close a cooling system can get to ambient conditions before mechanical intervention is required. This is typically referred to as approach temperature, and most of the industry has designed around a fairly wide margin.
Nautilus’s cooling distribution units are built to run at a meaningfully tighter approach temperature than conventional designs. That difference sounds small on paper, but it changes the entire equation. A tighter approach temperature means a facility can rely on ambient air or available water sources to do most of the cooling work, and only needs mechanical chilling to cover the remaining, much smaller gap.
We call this trim chilling: using mechanical cooling to trim the last few degrees rather than carry the entire thermal load.
How A Trim Chilling Approach Changes Design
Trim chilling isn’t a single feature; it’s a shift in how facilities can be designed and scaled.
- Chiller capacity becomes flexible. Cooling distribution units (such as the Nautilus EcoCore® FCD) are designed to carry most of the thermal load on their own, rejecting heat to the available water or air source on site. Instead of committing to a full-size chiller plant on day one, operators can size mechanical cooling to the small gap that’s actually left and add capacity in increments as workload or conditions demand.
- Geography becomes a design input. A facility in a cool, northern climate may need close to zero mechanical chilling across most of the year. A site in a hot, arid climate will rely more heavily on trim chilling, but still far less than a traditional 100%-chilled design. Either way, the mechanical cooling is sized to the actual gap, not to a worst-case assumption at the start.
- Workload becomes part of the equation. As chip water tolerances shift and newer generations of hardware can run on warmer supply water, the size of the gap changes again, often shrinking further. A design built around trim chilling can absorb that shift without a wholesale rebuild of the mechanical plant.
Flexibility for Dynamic Loads and Temps
The point of trim chilling isn’t to eliminate chillers everywhere. Some sites, some climates, and some workloads will always need more mechanical support than others. The point is that operators are no longer locked into a single answer decided at the design table years before a facility opens.
Nautilus’s cooling technology, first developed and proven on our own first-of-a-kind build, was engineered from the outset to close that gap physically, in the hardware, rather than manage around it after the fact. That’s what makes trim chilling possible: not a control layer bolted on top of a conventional system, but a cooling architecture designed from day one to need less mechanical help in the first place.
From 0% to 100% mechanical cooling (which isn’t really a thing anymore), and everywhere in between, the goal is the same: give operators a cooling plant that matches what their site and their workload actually require, not what a worst-case assumption demanded a decade ago.
FAQ
What is trim chilling in a data center?
Trim chilling is a cooling strategy that uses ambient air, available water or another efficient heat-rejection source to handle most of a data center’s cooling demand. Mechanical chillers operate only when additional cooling is required to reach the necessary supply-water temperature.
How is trim chilling different from free cooling?
Free cooling rejects heat without using compressor-based mechanical chilling when outdoor or source-water conditions are suitable. Trim chilling supplements free cooling by lowering the water temperature the remaining few degrees when ambient conditions alone cannot meet the facility’s requirements.
How does approach temperature affect chiller use?
Approach temperature is the temperature difference required to transfer heat between parts of the cooling system. A tighter approach temperature can reduce the gap between the available heat-rejection source and the water temperature required by the IT equipment, increasing free-cooling hours and reducing mechanical chiller operation.
Can trim chilling eliminate the need for data center chillers?
Trim chilling can substantially reduce or, under certain operating conditions, eliminate mechanical chiller use for portions of the year. Actual chiller requirements depend on climate, available heat-rejection sources, IT supply-water temperatures, workload and redundancy requirements.
How does the EcoCore FCD support trim chilling?
The Nautilus EcoCore FCD transfers heat between the technology cooling system and the facility water system with an approach temperature difference as low as 2°C. This tight approach helps facilities use ambient air or available water for more of their heat rejection while reserving mechanical chilling for conditions when additional cooling is necessary.
