MODULE 05 · THERMAL ARCHITECTURE · ALY-DC-MECH-001

440 MW of heat, zero cooling towers.

GB300 NVL72 puts ~93% of its heat straight onto a closed liquid loop at 45–50 °C — hot enough to reject to Perthshire air through dry coolers all year, with no compressors on the primary path and near-zero water. Pick a season and watch the plant re-dispatch.
Peak heat rejection
440MWth
~420 MWth continuous
Liquid captured
~93%
direct-to-chip cold plates
Annual PUE
1.12
1.06 winter · 1.16 summer peak
WUE
0.05m³/MWh
adiabatic trim only
Free cooling
6,800h/yr
>75% of the year
Heat recovery
35–55°C
offtake stubbed for Alyth

The Closed Loop

Technology Cooling System (TCS) inside the hall, Facility Water System (FWS) outside — coupled at the CDU, sealed end to end.
DATA HALL — TCS LOOP (sealed, treated water/PG25) NVL72 RACK ROWS cold plates: GPU · Grace · NVSwitch ~125 kW liquid per rack REAR-DOOR HX + AHU AIR residual ~7% · hot-aisle contained ROW CDUs liquid-liquid plate HX N+1 per row · VSD pumps TCS 32 → 50 °C FWS 27 → 45 °C isolates rack loop chemistry leak detect + auto-isolation 32 °C supply 50 °C return FWS 45 °C FWS 27 °C CENTRAL PLANT — FWS LOOP (closed, glycol) DRY / ADIABATIC COOLERS 8 × 15 MWth (N+1) per hall block 45 °C loop vs −8…8 °C ambient — huge ΔT, fans at part speed TRIM CHILLERS — OFF 16 × 8 MWth air-cooled (N+2) R-1234ze low-GWP · COP 5–7 at high CHW temp series trim on FWS return, summer only HEAT RECOVERY SPUR 35–55 °C offtake (stubbed) Alyth heat network · greenhouses Heat Networks (Scotland) Act ready BESS THERMAL (SELF-CONTAINED) ~18 MWth at full dispatch per-container glycol + rooftop DX/free-cool cells held 20–30 °C · no central plant load AMBIENT: Perthshire winter −8…8 °C · 100% free heat rejection Sealed loops — no evaporation, no blowdown, no cooling-tower plume · make-up <5 m³/h campus-wide (adiabatic pads + humidification)

Winter dispatch

Seasonal PUE Model

Plant Schedule

SystemCapacityConfigDuty
Row CDUs (liquid-liquid)~1.6 MWth each · 288 campusN+1 per rowTCS ↔ FWS exchange, rack loop control
Dry / adiabatic coolers56 × 15 MWth (840 MWth installed)N+1 per blockPrimary heat rejection, year-round
Air-cooled trim chillers16 × 8 MWth (128 MWth)N+2Summer FWS trim >22 °C ambient
AHUs (residual air side)24 × 20 MWth (480 MWth)N+2Rear-door/room air, free-cooling economiser
FWS pumpsVSD, primary-variableN+1Campus distribution, ring main
Adiabatic water<5 m³/h peak campusmains + borehole TBCPads on >22 °C days only
Planning position. No cooling towers → no plume, no legionella regime, no abstraction licence for cooling (EASR 2018), plant noise 65–75 dB(A) at 10 m handled by acoustic screens and the perimeter bund. The 420 MWth continuous heat stream is offered to the Alyth community as a heat-network opportunity — the data centre that heats the glen.

Standards

ASHRAE TC 9.9 · W45 liquid classEN 50600-2-3 · environmental control OCP coolant spec · PG25BS EN 378 · refrigeration safety CIBSE Guide BF-Gas / low-GWP R-1234ze Heat Networks (Scotland) Act 2021UKCP18 +5 °C 2080 margin
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