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  "id": "atlas-lesson-cooling-plant",
  "title": "Facility cooling and final heat rejection",
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  "description": "Carries heat from IT equipment to the outdoor environment or an approved reuse path.",
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  "publishedDate": null,
  "revisionDate": "2026-10-07",
  "author": null,
  "topic": "Thermal infrastructure",
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      "title": "Facility cooling and final heat rejection",
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      "title": "Explore in Atlas",
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      "title": "US Department of Energy — Data-Center Cooling Water Efficiency",
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      "title": "Coolant distribution unit and separated loops",
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      "title": "Integrated accelerator rack: GB200 NVL72 example",
      "url": "https://semiaifoundry.com/learn/atlas/rack/"
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  "content": "Thermal infrastructure · Atlas v1.3.0\n\n# Facility cooling and final heat rejection\n\nCarries heat from IT equipment to the outdoor environment or an approved reuse path.\n\n[Explore in Atlas](https://semiaifoundry.com/ai-atlas/#cooling-plant)Building-to-campus thermal infrastructure\n\nLearning objectiveDistinguish cooling-system COP from full-facility power accounting.\n\n## The mechanism\n\nHeat removed from a processor has not vanished; it moves through successive thermal interfaces and fluid or air circuits. The facility cooling chain eventually rejects that heat outdoors or directs it into a useful heat-recovery application. Depending on climate and design, equipment can include heat exchangers, dry coolers, cooling towers, chillers, pumps, and air-handling systems. The atlas follows one unit of heat from the rack to its final destination and keeps water flow distinct from electrical energy use. Different arrangements trade energy and water consumption differently, so liquid cooling alone does not determine the total environmental footprint. Facility performance must be assessed across the complete heat-removal system and its operating conditions.\n\n1.  Collect heat from IT and supporting equipment.\n2.  Transport it through the selected facility cooling stages.\n3.  Reject or reuse the heat while accounting for the supporting energy and water flows.\n\n## Science and assumptions\n\n### Cooling energy boundary\n\n$$\n\\mathrm{COP}=\\frac{\\dot Q_{\\mathrm{removed}}}{P_{\\mathrm{cooling}}},\\qquad P_{\\mathrm{facility}}=P_{IT}+P_{\\mathrm{support}}\n$$\n\nCooling COP is heat removed divided by cooling electrical power. Facility power is IT power plus support power.\n\nSymbols and units\n\nCOP\n\nCooling coefficient of performance\n\ndimensionless\n\nQ̇\\_removed\n\nHeat removed within the specified cooling boundary\n\nW\n\nP\\_cooling\n\nElectrical input to that cooling boundary\n\nW\n\nP\\_facility\n\nTotal facility real power\n\nW\n\nP\\_IT\n\nIT equipment real power\n\nW\n\nP\\_support\n\nAll non-IT support real power within the facility boundary\n\nW\n\nA cooling system uses supporting power to transport heat. Measuring only the chip loop omits the pumps, fans, chillers, and other facility functions that may contribute to the complete system.\n\nAssumptions Steady accounting within an explicitly chosen boundary; COP is a cooling-performance ratio, while total facility accounting also includes non-cooling loads.\n\n## Engineering example\n\nSynthetic plant removes 1 MW of heat with 0.2 MW of cooling electricity, so COP = 5. If IT load is 1 MW and other support uses 0.1 MW, facility input is 1 + 0.2 + 0.1 = 1.3 MW at that boundary; COP is not the facility/IT ratio.\n\n## Distinctions and tradeoffs\n\nLiquid cooling at the chip does not by itself imply zero water use or zero cooling energy across the facility.\n\nCooling choices trade energy, water, and operating range. Local climate and system boundaries change the comparison.\n\nCooling capacity constrains sustainable compute density. The building must carry away the heat generated by active hardware.\n\n## Specifications and interfaces\n\nEnergy balance\n\nHeat is transported and rejected\n\nCooling does not destroy energy.\n\nEquipment mix\n\nDesign- and climate-dependent\n\nNo universal requirement for every listed component.\n\nWater-use metric\n\nLiters per kWh of IT energy\n\nSite water-use effectiveness has a defined system boundary.\n\n### Interfaces\n\nRack and facility return loops Input\n\nCollected heat\n\nEnvironment or reuse system Output\n\nRejected or recovered thermal energy\n\n## Check your understanding\n\n### Where does removed processor heat ultimately go?\n\n1.  It is erased by the coolant\n2.  It becomes extra training accuracy\n3.  To an external heat sink or a heat-reuse system\n\nAnswer and reasoning\n\nTo an external heat sink or a heat-reuse system\n\nCooling transfers energy through the system. A complete explanation must identify the final heat destination.\n\n## Evidence and scope\n\nThe example uses steady matched boundaries and invented loads. Heat-rejection method, environmental conditions and other support equipment affect actual power and water use; circulating water is not automatically consumed water.\n\nNo current calculator directly models this lesson’s main mechanism. Use the library for related bounds while retaining their stated omissions.\n\n## Sources\n\n-   [US Department of Energy — Data-Center Cooling Water Efficiency](https://www.energy.gov/cmei/femp/cooling-water-efficiency-opportunities-federal-data-centers)\n\n[Published lesson data](https://semiaifoundry.com/ai-atlas/lesson-data/cooling-plant-b358ef0e7cccb5b9.json) · [Atlas releases and licensing](https://semiaifoundry.com/ai-atlas/licenses.html)\n\n## Continue exploring\n\n### Foundations\n\n-   [Coolant distribution unit and separated loops](https://semiaifoundry.com/learn/atlas/cdu/)\n\n### Related lessons\n\n-   [Integrated accelerator rack: GB200 NVL72 example](https://semiaifoundry.com/learn/atlas/rack/)\n-   [Rack power shelf and DC busbar](https://semiaifoundry.com/learn/atlas/power-shelf/)"
}