What is WUE and what is its denominator?

Water Usage Effectiveness (WUE) = annual site water consumption (L) divided by annual IT energy (kWh). The denominator is IT energy, not facility energy. This simulated cockpit adopts 1.20 L/kWh and derives 600 L/min cooling makeup at 30,000 kW IT; it does not claim a live meter.

What is makeup water versus circulation water?

Makeup water is the net fresh water added to the cooling tower to replace evaporation, blowdown, and drift losses. It is what the WUE formula quantifies. Circulation water is the total recirculating flow through the tower basin and heat exchangers, which is orders of magnitude larger. The two must not be conflated — confusing them overstates consumption by ~20–50×.

What filtration differential-pressure threshold does this cockpit use?

The adopted simulated threshold is 0.80 bar and the current value is 0.40 bar. A real backwash threshold must come from the selected filter manufacturer and commissioned clean/dirty pressure-drop data.

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Technical Manual · Water & WUE

Water System & WUE — Cockpit Methodology & Formulas

Every input, formula, constant, output, and reference behind the site-wide municipal Water Treatment & Service cockpit. Site balance and WUE values derive from CONV_CALC v2.0.0; treatment-process states are explicitly labelled, deterministic page-authored simulation values because the engine has no treatment-train telemetry authority. No live meter overrides are implied. Missing or stale site authority fails closed to UNAVAILABLE.

Engine CONV_CALC v2.0.0 WUE Basis 1.20 L/kWh IT Inputs water-quality probe + valve controls Source conv review 09

▶ Open the live Water System cockpit

01 Purpose & engineering basis

The cockpit models one site-wide municipal treatment train: incoming meter, raw-water storage, media filtration, duty/standby booster pumps, dosing, UV treatment, treated-water storage, cooling makeup, domestic/process service and drain. Hall A-D are downstream electrical/thermal operating views; they do not partition the municipal plant.

v2.8.0 drawing scope: the cooling make-up branch is drawn to its destination — the evaporative cooling-tower cell and basin that the engine's water-cooled centrifugal chillers reject to (cooling.chiller_type) — with the engine's evaporation, blowdown and drift balance on the drawing and the condenser-water loop to the chiller plant at the engine's CDW planes. The raw tank is a page-authored design selection sized as four hours of the engine's total treated flow (608 L/min × 240 min ≈ 146 m³ → 150 m³ nominal); the domestic tank is 30 m³. Values inside the drawing that come from the engine carry a registry hook and an evidence mark; simulated instrument readings and page-authored capacities are declared as such and are never presented as telemetry.

Truth boundary: current site IT is 30,000 kW. WUE-included cooling makeup is 600 L/min; domestic/process service is 8 L/min; total treated flow is 608 L/min. Selecting or inspecting a Hall must not change these site quantities.

The WUE definition follows the Uptime Institute site-water-to-IT-energy denominator. Treatment flow, cooling makeup and domestic/process flow remain separately labelled so the total is auditable.

Rule 3 — WUE denominator: WUE = annual site water consumption (L) ÷ annual IT energy (kWh). The denominator is IT energy only, not facility (total) energy. Using facility energy (PUE × IT) deflates WUE by ~PUE (1.45×) and understates the cooling-system water intensity. This rule is accuracy-gate-enforced in CONV_CALC.

02 Inputs — simulated point model & control states

The cockpit binds adopted engine constants and deterministic simulated instrument/control states. The tags model what a commissioned system would expose, but no point is presented as live telemetry.

Input	Symbol	Unit	Type	Meaning
Site IT load `it_load_kw`	`P_IT`	kW	Current (30,000 kW)	Adopted simulated site authority from CONV_CALC.
WUE basis `wue_l_per_kwh`	`WUE`	L/kWh	Adopted (1.20 L/kWh)	Site water-usage effectiveness from the governed snapshot.
Makeup flow `flow_lpm`	`Q_mu`	L/min	Engine-derived	600 L/min WUE-included cooling makeup.
Conductivity / TDS `tds_ppm`	`TDS`	ppm (mg/L)	Simulated probe	Current deterministic treated-water value; a live implementation would drive blowdown from a quality-qualified point.
Feed-water TDS `tds_feed_ppm`	`TDS_feed`	ppm	Simulated input	Municipal/feed-water quality context.
Filtration ΔP `delta_p_bar`	`ΔP`	bar	Simulated transducer	Current 0.40 bar; 0.80 bar triggers the modelled backwash threshold.
Valve states `valve_*`	—	open / closed / %	Control feedback	Blowdown valve, makeup valve, bypass valve positions — logged for audit and interlock checks.
Chemical dosing `dose_*`	—	L/hr or kg/day	Controller feedback	Biocide, scale inhibitor, and corrosion inhibitor dosing rates — inputs to ASHRAE 188 Water Management Plan compliance log.

03 Calculation methodology

All formulas below are implemented in js/conv-engine.js. Function names are exact. The engine is ES5-safe, deterministic, and zero-build.

WUE definition (Rule 3 — IT-energy denominator)

WUE = Annual_water_L / Annual_IT_kWh [L/kWh] WUE = (Q_mu_Lpm × 60) / P_IT_kW (instant back-compute from live flow) In wueFromFlowLpm(m, flowLpm). Denominator = site IT energy. The 1.20 L/kWh value is an adopted simulated project basis; a future live mode would require a quality-qualified municipal/cooling makeup meter and site IT meter.CONV_CALC v2.0.0 · Uptime WUE definition

Instant makeup-water flow from WUE

Q_mu = (WUE × P_IT) / 60 [L/min] In waterFlowLpmForWue(m). Converts the WUE rate to a site cooling-makeup equivalent. Check: (1.20 × 30,000) / 60 = 600 L/min.CONV_CALC v2.0.0 · DERIVED

Makeup vs treatment vs circulation: Q_mu = 600 L/min is WUE-included cooling makeup. Site treatment total is 608 L/min after adding 8 L/min domestic/process service. Neither value is condenser-water circulation flow; circulation is a separate hydraulic quantity.

Annual water consumption

Annual_water_L = WUE × P_IT × 8760 [L/yr] At the adopted steady load: 1.20 × 30,000 × 8,760 = 315,360,000 L = 315.36 ML/yr of WUE-included cooling water. Adding 8 L/min domestic/process continuously would make total treatment 319.565 ML/yr.CONV_CALC v2.0.0 · DERIVED

Cycles of concentration & blowdown

CoC = TDS_basin / TDS_feed (dimensionless, target ≤ 5) Q_drift = 0.005 × Q_mu [L/min] (adopted model fraction) Q_bd = (Q_mu − Q_drift) / CoC [L/min] Q_evap = (Q_mu − Q_drift) × (CoC − 1) / CoC At the adopted CoC 4 and 600 L/min makeup, the deterministic model gives 3.0 L/min drift, 149.3 L/min blowdown and 447.8 L/min evaporation after display rounding. These are simulation allocations, not commissioned water chemistry.water-system.html current split algorithm

Filtration differential pressure

ΔP_clean ≈ 0.3–0.5 bar (new media, design point) ΔP_current = 0.40 bar; ΔP_backwash = 0.80 bar (adopted simulation) A differential-pressure transducer would be installed across the media filter. Rising ΔP can indicate fouling, but the production backwash threshold must come from the selected filter manufacturer and commissioned clean/dirty curves.Project simulation · manufacturer authority required

Legionella / microbiological monitoring (ASHRAE 188)

Program limits = site Water Management Plan / AHJ authority Laboratory method = approved Legionella sampling and enumeration procedure ASHRAE 188 establishes a risk-management and Water Management Program framework; it does not supply one universal numerical action level for every site. ISO 11731 provides a Legionella culture method. Project limits, sampling cadence and corrective actions must be approved and documented separately.ASHRAE 188 · ISO 11731

04 Constants & data sources

Every constant lives in the deep-frozen CONV_MODEL with a // source: comment citing the review document and line number. Water-relevant constants:

Constant	Value	Unit	Source	Type
`wue_l_per_kwh`	1.20	L/kWh IT	doc-09 line 13; doc-01 §3	Basis (target)
`it_load_kw`	30,000	kW	CONV_CALC v2.0.0	Adopted current site basis
Annual hours	8,760	hr/yr	Calendar constant	Fixed
Max CoC	5	—	Water management practice; ASHRAE 188 guidance	Operational target
Filtration ΔP backwash threshold	0.80	bar	Adopted simulated operating basis	Instrument threshold
Legionella action level	UNAVAILABLE	site-defined	Water Management Program / AHJ	No universal value asserted
Laboratory method	Project-selected	method	ISO 11731 context	Test method, not an operating limit

Simulated authority boundary: site water balance, IT load and wue_l_per_kwh = 1.20 are engine-derived. Raw/domestic tank level, filter ΔP, TDS, chlorine dose, UV intensity and booster-pump state are authority-gated deterministic page-authored process simulation values; CONV_CALC does not provide treatment-train telemetry. A future live mode must qualify both water and IT meters for freshness and quality before computing actual WUE; no simulated value is presented as a field measurement.

05 Outputs

Output	Formula	Unit	Interpretation
WUE (basis)	`CONV_MODEL.environment.wue_l_per_kwh`	L/kWh	Target value from engineering review. Green chip on cockpit.
WUE reconciliation	`wueFromFlowLpm(lpm)`	L/kWh	Computed from the same simulated site cooling-makeup and IT authority.
Cooling makeup	`waterFlowLpmForWue(m)`	L/min	600 L/min WUE-included site basis.
Total treatment	`cooling makeup + domestic/process`	L/min	600 + 8 = 608 L/min.
Annual cooling water	`WUE × P_IT × 8760`	L/yr (ML/yr)	315.36 ML/yr at the adopted steady load.
Cycles of concentration	`TDS_basin / TDS_feed`	—	Target ≤ 5. Amber alert at CoC > 4.5, red at CoC > 5.
Blowdown flow	`Q_mu / (CoC − 1)`	L/min	Required blowdown to maintain target CoC.
Filtration ΔP status	ΔP transducer reading	bar	Current 0.40 bar; backwash threshold 0.80 bar.
Legionella / HPC status	Approved laboratory result	method-dependent	Compared only with the site Water Management Program; UNAVAILABLE in this simulation.
Chemical dosing status	Dosing controller feedback	L/hr / kg/day	On-duty/off indicator per biocide and inhibitor channel.

06 Worked example

Scenario: current site IT 30,000 kW, WUE 1.20 L/kWh, 600 L/min cooling makeup, 8 L/min domestic/process service, TDS 140 ppm, and filtration ΔP 0.40 bar. Water treatment is one site-wide municipal process train.

Cooling makeup: Q_mu = (1.20 × 30,000) / 60 = 600 L/min.
Total treatment: 600 + 8 = 608 L/min.
Annual WUE-included cooling water: 600 × 60 × 8,760 = 315.36 ML/yr.
Current cooling split: evaporation 447.8 L/min + blowdown 149.3 L/min + drift 3.0 L/min = 600.1 L/min after display rounding.
Annual components: evaporation 235.364 ML, blowdown 78.472 ML, drift 1.577 ML.
Filtration ΔP = 0.40 bar → NORMAL (backwash threshold 0.80 bar).

Engineering reading: the displayed evaporation/blowdown/drift split is an adopted simulation balance. Real optimization requires measured conductivity, ambient wet-bulb, cycles of concentration, drift-eliminator performance and water chemistry. Hall selection is intentionally absent because the treatment train is a site utility.

07 References & standards

ASHRAE 188 (2021) — Legionellosis: Risk Management for Building Water Systems. Mandates a Water Management Plan for cooling towers including control targets, sampling schedules, corrective actions, and record retention. The cockpit's biocide dosing and Legionella status indicators are ASHRAE 188 WMP deliverables.
ISO 11731-2 — Water quality — Detection and enumeration of Legionella — Part 2: Direct membrane filtration method for waters with low bacterial counts. HPC ≤ 1×10³ CFU/mL operational target cited from this standard.
Uptime Institute WUE Metric — Water Usage Effectiveness white paper. Defines WUE = annual site water ÷ annual IT energy. Source of the IT-denominator Rule 3.
Governed project authority — current 30,000 kW site IT, WUE 1.20 L/kWh, 600 L/min cooling makeup and 608 L/min total treatment.
Engine source — js/conv-engine.js (CONV_CALC v2.0.0). Functions: waterFlowLpmForWue(), wueFromFlowLpm().

08 Assumptions & limitations

The WUE basis (1.20 L/kWh) is an adopted site target at 30,000 kW IT. Actual WUE varies with ambient conditions, partial load and plant mode. This simulated cockpit does not claim live metering. The annual 315.36 ML cooling figure and 319.565 ML total-treatment figure assume 8,760 hours at constant flow. Blowdown, dosing, filtration and microbiological limits require site commissioning records and a formal water-management plan authored by qualified specialists.

▶ Open the live Water System & WUE Cockpit