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  • Rising Heat and Humidity Are Shrinking the Free-Cooling Window for Data Centers

    Rising Heat and Humidity Are Shrinking the Free-Cooling Window for Data Centers

    Research highlighted by Phys.org on June 26, 2026 warns that rising global temperatures and humidity are undermining one of the data center industry’s most important energy-efficiency strategies: free cooling, the practice of using cool outside air or water to remove server heat instead of running energy-hungry mechanical chillers. As more hours of the year become too hot or too humid for outside air to do the job, facilities worldwide face growing cooling energy demand.

    The finding lands at a sensitive moment. Data center construction is accelerating to serve AI workloads, and cooling is typically the largest energy consumer in a facility after the IT equipment itself — so any climate-driven loss of free-cooling hours compounds an already steep power challenge.

    Executive Summary

    The core claim is straightforward: free cooling only works when the outside environment is cooler and drier than the conditions servers require, and climate change is steadily reducing the number of hours per year when that is true. Heat is only half the story — humidity matters just as much, because evaporative cooling systems, which cool air by evaporating water, lose effectiveness as the air becomes more saturated. Regions that were designed around thousands of free-cooling hours a year are watching that budget shrink.

    Why it matters: efficiency assumptions made at design time are baked into a data center for decades. A facility engineered in a climate that no longer exists will either consume more energy than its models promised, lean harder on water, or require retrofit investment. For an industry under scrutiny over electricity and water consumption, the research reframes climate not as a sustainability talking point but as an engineering input — one that belongs in site selection, cooling-system choice, and capacity planning from day one.

    Free Cooling Was the Industry’s Efficiency Workhorse

    For the past fifteen years, the biggest gains in data center efficiency — reflected in falling PUE, the ratio of total facility power to IT power — came largely from using the outdoors as a heat sink. Air-side economizers pull in filtered outside air; water-side economizers and evaporative systems use cooling towers to shed heat with modest energy input. Hyperscale operators famously sited facilities in cool climates precisely to maximize these hours.

    The research reported by Phys.org attacks the durability of that playbook. If the number of hours cool and dry enough for economization declines, chillers run more, and the efficiency gap between a well-sited facility and a poorly sited one narrows in the wrong direction. The gains of the last decade were real, but they were partly a loan from a stable climate — and the terms of that loan are changing.

    Humidity Is the Underappreciated Variable

    Public discussion of data center cooling fixates on temperature, but wet-bulb temperature — a combined measure of heat and humidity that sets the floor for evaporative cooling — is the more binding constraint. When wet-bulb temperatures rise, evaporative systems must work harder and consume more water for less cooling effect, and in extreme conditions they cannot reach the setpoints servers need at all. That pushes operators back toward mechanical refrigeration exactly when grid demand for air conditioning also peaks.

    This has a second-order consequence: the trade-off between energy and water gets sharper. Evaporative cooling saves electricity but consumes water; dry coolers and chillers save water but consume electricity. Rising humidity degrades the attractiveness of the water-based option in many regions, forcing a choice between two increasingly expensive resources — often in communities already contesting data center water use.

    Winners: Liquid Cooling, Cool Geographies, and Honest Modeling

    If outside air can carry less of the load, the premium shifts to technologies that tolerate warmer heat rejection. Direct-to-chip liquid cooling and immersion cooling move heat in water or fluid rather than air, allowing higher operating temperatures and, in many designs, year-round heat rejection without compressors even in warm climates. The AI build-out was already pushing the industry toward liquid cooling for density reasons; climate trends add an efficiency rationale.

    Geography gains value too. Sites in cool, dry, or high-latitude regions — the Nordics, parts of Canada, high-altitude locations — become relatively more attractive, though they bring their own constraints in connectivity, latency, and power availability. And engineering firms that model cooling against forward-looking climate projections rather than historical weather files gain a real advantage: a 25-year asset should be designed for the climate of 2040, not 2010.

    Risks: Stranded Efficiency and Rising Operating Costs

    The losers in this shift are facilities whose economics depend on free-cooling assumptions that no longer hold — particularly older air-cooled sites in regions warming fastest. Their operating costs drift upward without any change in workload, and their sustainability reporting deteriorates through no operational fault. For colocation providers, whose customers increasingly scrutinize PUE and water metrics in procurement, that drift is a competitive problem, not just an engineering one.

    There is also a grid-level risk. The hours when data centers lose free cooling are the same hot hours when regional grids are most stressed. Climate-driven cooling demand is therefore correlated demand — it arrives when power is scarcest and most carbon-intensive, which is precisely the scenario utilities and regulators planning for data center growth need to model.

    Background

    Data center cooling has evolved through distinct eras. Early facilities ran cold and relied almost entirely on mechanical chillers. From roughly 2010 onward, hyperscale operators drove a revolution in economization — siting in cool climates, using outside air and evaporative systems, and widening acceptable server temperature ranges — which pushed the best facilities’ PUE from around 2.0 toward 1.1. That efficiency story became central to the industry’s answer to critics of its energy footprint.

    The current AI build-out is testing every part of that model: rack power densities have jumped severalfold, cooling loads are climbing, and communities are scrutinizing both electricity and water consumption. Research showing that climate change is eroding free cooling adds a structural pressure on top of a cyclical boom — and helps explain the industry’s accelerating shift toward liquid cooling and climate-aware site selection.

    Source: Rising heat and humidity challenge energy-efficient data center cooling worldwide — Phys.org report, June 26, 2026, on research into climate-driven erosion of data center free-cooling potential.

  • Nvidia’s Hot-Water Cooling Claims Up to 100% Water-Use Reduction for AI Data Centers

    Nvidia’s Hot-Water Cooling Claims Up to 100% Water-Use Reduction for AI Data Centers

    Nvidia has announced a liquid cooling system for AI data centers that circulates water described as running “hotter than a hot tub,” a design the company says can reduce electricity consumption and cut water use by up to 100%. The announcement, reported June 24, 2026 by Tom’s Hardware, targets one of the AI build-out’s most scrutinized side effects: the enormous water and energy appetite of the facilities that host Nvidia’s chips. The same report notes that sustainability challenges remain despite the headline claims.

    Executive Summary

    Nvidia, the dominant supplier of AI accelerators, is moving further down the stack — from chips and rack-scale systems into the cooling infrastructure that keeps them running. The newly announced system uses hot-water liquid cooling: instead of chilling coolant to low temperatures before it reaches the hardware, the loop runs deliberately warm, hotter than the roughly 40°C (104°F) at which a typical hot tub is kept, which is the comparison Nvidia’s framing invites.

    Why does that matter? Warmer coolant is the key that unlocks both of the claimed benefits. If the water returning from the chips is already hot, a facility can often reject that heat to the outside air with simple dry coolers rather than energy-hungry chillers — cutting electricity — and without evaporative cooling towers, which consume water by design. That is the engineering logic behind the “up to 100%” water-reduction figure. The claim is significant if it holds up at scale, but as reported it is a vendor claim with important qualifiers, and the source coverage itself flags that sustainability challenges remain.

    Water Is Becoming AI’s Second Resource Fight

    Electricity has dominated the AI infrastructure debate, but water is close behind. Many conventional data centers cool themselves with evaporative systems: they literally evaporate water to carry heat away, because evaporation is cheap and effective. As hyperscale and AI campuses have multiplied, their water draw has become a flashpoint in drought-prone regions and a recurring obstacle in permitting and community relations.

    Nvidia has a direct commercial stake in defusing that fight. Its rack-scale AI systems concentrate so much heat that air cooling is no longer practical, which already pushed the industry toward liquid cooling. If the company can also credibly claim its reference designs eliminate on-site cooling water, it removes an objection that slows down the very data center projects that buy its chips. In that sense this is as much a market-access play as an engineering one.

    The Counterintuitive Physics of Cooling with Hot Water

    “Hot-water cooling” sounds like a contradiction, but it rests on straightforward thermodynamics. A chip does not need cold coolant; it needs coolant that is cooler than the chip and flowing fast enough to carry heat away. Liquid is far denser than air as a heat-transfer medium, so even warm water can hold chip temperatures within limits.

    The payoff comes at the other end of the loop. Cold-water systems need chillers — essentially industrial refrigerators — whose compressors are among the largest energy consumers in a data center. Evaporative towers avoid some of that electricity but spend water instead. A loop that returns water hotter than the outdoor air can shed its heat through dry coolers, closed radiators that use neither compressors nor evaporation. That is the mechanism behind both claims in the announcement: less electricity because chillers shrink or disappear, and less water because nothing is evaporated. Hotter return water is also more useful for heat reuse, such as district heating, though the reporting here does not say whether Nvidia is claiming that benefit.

    Reading the “Up to 100%” Claim Carefully

    “Up to 100%” is a ceiling, not a promise. Real-world results will depend on climate — dry cooling gets harder on very hot days, when some designs fall back on water assist — as well as on facility design and how much of a site’s load actually sits on the new system. The reported claim does not, on its face, distinguish between a best-case new build in a favorable climate and a typical deployment.

    There is also a boundary question. Eliminating on-site cooling water does not eliminate a data center’s water footprint, because the power plants that generate its electricity often consume water themselves. Reduced electricity consumption helps on that front too, but “water-free” at the fence line is not the same as water-free end to end. The source’s own caveat — that sustainability challenges remain — is best read in this light: the announcement addresses a real problem without dissolving it.

    Who Feels This Announcement

    Cooling incumbents and the liquid-cooling supply chain feel it first. When the dominant chip vendor blesses a particular thermal architecture, it tends to become the default for new AI capacity, shaping demand for cold plates, coolant distribution units, and dry coolers, and putting pressure on vendors invested in evaporative or chilled-water designs. Operators, meanwhile, gain a potential permitting and siting advantage: a campus that can credibly promise near-zero cooling-water draw is an easier sell to water-stressed municipalities.

    The open competitive question is whether this arrives as an open reference design others can build on or as another layer of the Nvidia-specified stack. The reporting available here does not say. Either way, buyers should expect warm-water readiness — higher allowable coolant temperatures across IT hardware — to show up in procurement requirements, because the economics above only materialize if the whole rack tolerates the heat.

    Background

    Nvidia is the world’s leading supplier of the GPUs (graphics processing units) that train and run modern AI models, and its data center business has grown into one of the largest in the technology industry. As its systems evolved from individual chips into full pre-integrated racks drawing unprecedented power, the company has taken an increasingly active role in specifying the surrounding infrastructure — power delivery and cooling included — because its hardware roadmap now depends on facilities that can handle the heat.

    Data center cooling has historically split between air cooling, chilled-water systems, and evaporative designs that trade water for electricity. AI’s density has pushed the industry rapidly toward direct liquid cooling, and water consumption has become a headline issue in siting battles. Warm-water liquid cooling — long used in some high-performance computing installations — is the established engineering idea this announcement scales up and brands for the AI era.

    Source: Nvidia announces liquid cooling system that runs ‘hotter than a hot tub’ — promises to reduce electricity consumption and cut water use by up to 100%, but sustainability challenges remain — Tom’s Hardware coverage, June 24, 2026, of Nvidia’s hot-water liquid cooling announcement for AI data centers.

  • Why Data Centers Still Cling to Evaporative Cooling Despite Water Backlash

    Why Data Centers Still Cling to Evaporative Cooling Despite Water Backlash

    Data Center Knowledge published a report on June 18, 2026 examining why the data center industry continues to rely on evaporative cooling — a heat-rejection method that consumes large volumes of water — even as public and regulatory backlash over water use intensifies. The piece frames the industry’s position as hesitation rather than refusal: operators broadly acknowledge the water problem but have been slow to abandon a technology that remains cheaper and more energy-efficient than the alternatives.

    Executive Summary

    The report’s core subject is a tension the industry has lived with for years and that the AI build-out has sharpened: evaporative cooling rejects heat by evaporating water, which makes it highly energy-efficient but water-hungry, while the main alternatives — dry (air-cooled) systems and refrigerant-based chillers — save water at the cost of higher electricity consumption, larger equipment footprints, or both. In markets where power is the scarcest commodity a data center can buy, trading water savings for a bigger electrical load is not a simple upgrade; it is a genuine engineering and economic trade-off.

    That trade-off is why the headline speaks of hesitation. Operators face mounting pressure from drought-affected communities, local governments, and sustainability commitments to cut water use, and technologies such as closed-loop liquid cooling and hybrid systems are maturing. But retrofitting existing facilities is expensive, and for new builds the calculus depends heavily on local climate, water price, and power availability — variables that differ from one metro to the next. The result is an industry moving unevenly rather than uniformly, which is precisely the dynamic worth understanding for anyone siting capacity or evaluating operators’ sustainability claims.

    The Water-for-Energy Trade at the Heart of Cooling

    Every data center must move heat from chips to the outside world, and the physics offers no free option. Evaporative systems — cooling towers and their variants — exploit the fact that evaporating water absorbs enormous amounts of heat, which lets a facility reject heat with comparatively little electricity. Dry coolers and air-cooled chillers avoid consuming water but must push heat into the air mechanically, which takes more fan and compressor power, especially on hot days when the temperature difference working in the operator’s favor shrinks. In plain terms: saving water usually means burning more electricity, and in an era when grid connections are the binding constraint on data center growth, extra megawatts spent on cooling are megawatts not available for revenue-generating compute.

    This is the economic logic the Data Center Knowledge piece points at with its framing of industry hesitation. An operator that switches a large campus from evaporative to dry cooling is not just paying for new equipment; it is accepting a permanently higher power draw — degrading power usage effectiveness, the industry’s standard efficiency metric — and potentially reducing the sellable IT capacity of a power-constrained site. Where water is cheap and power is scarce, the incumbent technology keeps winning on spreadsheets even as it loses in public opinion.

    Why the Backlash Is Getting Harder to Price at Zero

    For most of the industry’s history, water was effectively an afterthought in site selection — abundant, inexpensive, and invisible to the public. That has changed. Data center water consumption has become a recurring flashpoint in drought-prone regions, a subject of local permitting fights, and a standard line of questioning for journalists and community groups evaluating new projects. Operators now routinely publish water usage effectiveness figures and, in some cases, commit to becoming “water positive” — replenishing more water than they consume.

    The practical consequence is that water carries a growing shadow price beyond the utility bill: longer permitting timelines, conditions attached to approvals, reputational exposure, and in the worst case the loss of a site altogether. The report’s premise — that the industry hesitates rather than transitions — suggests that many operators still judge those risks manageable relative to the hard costs of switching. Whether that judgment holds depends largely on how regulators and communities act next, which varies enormously by jurisdiction.

    The Alternatives Are Real, but Not Drop-In

    The transition options are well understood in engineering terms. Dry cooling eliminates onsite water evaporation at the cost of energy and space. Hybrid systems run dry most of the year and evaporate water only during peak heat, cutting consumption substantially without the full energy penalty. Direct-to-chip liquid cooling and immersion cooling — increasingly common in AI deployments because high-density chips demand them — move heat in closed loops that consume little or no water onsite, though the heat still has to be rejected somewhere, and that final stage can itself be wet or dry. None of these is a simple swap for an operating facility: cooling infrastructure is capital-intensive, deeply integrated with a building’s design, and typically replaced on decade-plus cycles.

    That replacement cycle is the quiet variable in the whole debate. The realistic path for the industry is less about retrofitting the installed base and more about what gets designed into the enormous wave of new construction now underway. If new AI-era facilities standardize on low-water designs where climate and economics allow, the fleet’s water profile shifts over years, not quarters. If they default to evaporative cooling because power constraints dominate, the backlash the report describes is likely to intensify.

    Winners, Losers, and the Siting Chessboard

    The cooling transition redistributes advantage. Cooler, water-rich regions gain appeal because they make both wet and dry cooling cheaper; hot, arid markets that boomed on cheap land and power face the sharpest version of the water-versus-energy dilemma. Vendors of hybrid and liquid cooling systems benefit from every tightening of water rules. Utilities and municipalities gain leverage, since water service is becoming a negotiated element of large deals rather than a formality. And operators that invested early in low-water designs acquire a permitting and public-relations asset that is difficult for laggards to replicate quickly. Buyers of colocation and cloud capacity should read cooling architecture as a proxy for siting risk: a facility’s water dependence is now part of its long-term cost and continuity profile.

    Background

    Cooling is one of the two great resource demands of data centers, alongside electricity: every watt a server consumes becomes heat that must be removed. For decades, evaporative cooling towers have been a workhorse of large-scale heat rejection across many industries because evaporating water is thermodynamically cheap. Data centers adopted the approach widely as the industry scaled through the cloud era, and it helped drive the sector’s headline efficiency gains. The AI construction boom that accelerated through the mid-2020s raised the stakes on both sides of the equation — far denser computing produces far more heat, while the communities hosting these facilities have grown increasingly vocal about local water and power impacts. Trade publication Data Center Knowledge, which published the report discussed here, has tracked this cooling debate as one of the defining infrastructure questions of the AI build-out.

    Source: Evaporative Cooling in Data Centers: Why the Industry Hesitates to Move On — Data Center Knowledge report, June 18, 2026, on the economics slowing the industry’s shift away from water-intensive cooling.