Cooling Plant Selector

InputsChange any value; results update instantly

1. Weather

City

Built-in cities use an approximate hourly year generated from 1991–2020 monthly normals. Upload an EPW file for design-grade results.

2. Data hall cooling load

Cooling load (MW)

Frequent load (%)

Liquid cooling loop

Share (%)

Supply (°C)

Return (°C)

Air cooling loop

Supply (°C)

Return (°C)

3. Site

Water availability

Design condition (extreme)

Design dry-bulb (°C)

Design wet-bulb (°C)

Leave blank to use the hottest dry-bulb and most humid wet-bulb hour in the weather data. For design, enter ASHRAE extreme values (e.g. 20-year return period, per ASHRAE 90.4 practice) from the ASHRAE Climatic Design Conditions.

Utility tariffs (running cost)

Electricity ($/kWh)

Water incl. treatment ($/m³)

Demand charge ($/kW per month)

Running cost of cooling only (not the IT load). The demand charge is applied to the cooling electrical peak every month. Indicative defaults; enter the local tariff.

Chillers (ASHRAE 90.1 / AHRI 550/590 basis)

Air-cooled rated COP

Water-cooled rated COP

Duty chillers per loop

Max COP (low lift)

Air-cooled max ambient (°C)

Max entering condenser water (°C)

Defaults are ASHRAE 90.1-2019 Path A minimums (air-cooled; water-cooled ≥ 2,110 kW). Enter selected equipment values to override.

Heat rejection and pumps

Dry cooler approach (K)

Tower approach (K)

Plate HX approach (K)

Adiabatic effectiveness

Adiabatic on above (°C)

Tower cycles of conc.

Primary pumps, FW / CHW (% of load)

Condenser pumps (% of rejected)

Data hall terminal units (CRAH / FWU / CDU)

CRAH / FWU fans (% of air-loop load)

CDU pumps (% of liquid-loop load)

Electrical input including motor and drive losses. Counted as cooling energy (as in the ASHRAE 90.4 MLC), and added as heat to its loop, so the chillers and heat rejection remove it too.

Electrical losses

UPS efficiency (%)

Transformer + distribution losses (%)

UPS losses apply to the IT load; transformer and distribution losses apply to the whole facility (IT + cooling). Used for the annual PUE only; electrical peaks are the cooling plant only. Cooling for electrical rooms is not included.

Initial cost rates ($ per kW of capacity)

Redundancy (%)

Indicative installed rates for screening only. Replace with local quotes.

ResultsRanked systems, then details in the tabs below

All options side by side

Highlighted cells are the best value among feasible options. Score weighs energy (4), water (3, doubled when water is limited), peak power (3) and initial cost (2). Click a row to see that system in full.

Design-day check

Method and equations

Psychrometrics (ASHRAE Handbook Fundamentals, Ch. 1): saturation pressure by the Hyland–Wexler equations; humidity ratio W = 0.621945·p_w/(p − p_w); wet-bulb solved from W = [(2501 − 2.326t*)W_s* − 1.006(t − t*)] / (2501 + 1.86t − 4.186t*). Station pressure from elevation.
Each loop, every hour: return water is first cooled by the outdoor device, leaving at T_out; free-cooling fraction FF = (T_ret − T_out)/(T_ret − T_sup) (0–1); the chiller trims the rest.
Terminal units: CRAH / FWU fans (air loop) and CDU pumps (liquid loop) draw a set % of their loop load. Their power is cooling energy, and the same power is added to the loop as heat: Q_loop = Q_IT × (1 + terminal %), which the pre-cooling, chillers and heat rejection must remove. Chillers are sized for this load.
T_out: dry cooler T_db + approach; adiabatic T_eff + approach + HX with T_eff = T_db − ε(T_db − T_wb) (ASHRAE Systems & Equipment, evaporative cooling); tower T_wb + approach + HX.
Chillers (DOE-2 / EnergyPlus EIR form): P = (Q_cap/COP_rated) × EIRFT × EIRFPLR. COP_rated at AHRI 550/590 conditions (defaults: ASHRAE 90.1-2019 Path A minimums). EIRFT scales with lift at constant Carnot fraction, because 20–30 °C chilled water is outside published curve ranges. EIRFPLR from EnergyPlus reference curves: water-cooled VSD centrifugal 0.0731 + 0.1514·PLR + 0.7709·PLR²; air-cooled screw = PLR. Duty chillers stage to keep PLR high.
Condensing temperature: air-cooled T_db + 15 K; water-cooled T_ECW + 7.6 K, where entering condenser water = T_wb + tower approach or T_eff + cooler approach.
Water: tower evaporation 0.8·Q_rej/h_fg plus blowdown E/(CoC − 1); adiabatic water only when pads are wet (above the switch temperature).
Design-day check: each option at 100% load at the design dry-bulb and wet-bulb (applied together, which is conservative). Fails if a chiller would exceed its condenser limit (air-cooled max ambient, max entering condenser water).
MLC (ASHRAE 90.4): annual mechanical energy (compressors, heat-rejection fans, primary, condenser and CDU pumps, CRAH / FWU fans) ÷ annual IT energy.
Peaks: at 100% load on the worst hour of the year. Electrical peak (cooling) = compressors + heat-rejection fans + pumps + CRAH / FWU fans + CDU pumps. It excludes the IT load and the electrical equipment and its losses. Water peak = make-up water rate in m³/h (tower evaporation and blowdown, or adiabatic pad water). Chillers are staged each hour to the number that gives the lowest power.
Electrical losses and PUE: UPS losses on the IT load, transformer and distribution losses on the whole facility. Annual PUE = (IT + cooling + losses) ÷ IT. Simplified; not the full ASHRAE 90.4 ELC method. CRAH / fan-wall fans and electrical-room cooling are not included.
Running cost: cooling only, at the frequent load: electricity × tariff + water × tariff + cooling peak × demand charge × 12. Simple payback against air-cooled chillers = extra initial cost (mid estimate) ÷ running cost saved, with no discounting, maintenance or tariff escalation.
Recommendation: metrics normalised across feasible options and weighted: energy 4, water 3 (doubled when water is limited), peak power 3, initial cost 2. Options that fail the design day, or need water you don't have, are excluded. Screening-level; confirm with vendor selections and a detailed model.

All options side by side

Design-day check

How it runs over the year

Equipment and cost

Strengths and watch-outs

Energy efficiency

Electricity and water consumption

Running cost (cooling)

Initial cost (estimated range)

Climate: free-cooling potential by month

Method and equations