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Equation 1 · Part 5 · Comparing the Main Approaches to AI Datacenter Power and Cooling

subscript

WUEsite=VwaterEIT\mathrm{WUE_{site}} = \frac{V_{\mathrm{water}}}{E_{\mathrm{IT}}}
subscript

What this part means

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

Its job in the formula

A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

Water Usage Effectiveness, the metric LBNL uses throughout its modeling, is defined analogously to the more familiar Power Usage Effectiveness: WUEsite=VwaterEIT\mathrm{WUE_{site}} = \frac{V_{\mathrm{water}}}{E_{\mathrm{IT}}}. where VwaterV_{\mathrm{water}} is total on-site water consumption in litres and EITE_{\mathrm{IT}} is the electricity delivered to IT equipment, giving WUE units of litres per kilowatt-hour rather than PUE’s dimensionless ratio [ 4 ] . What LBNL’s simulations across roughly 965 US weather stations and multiple facility archetypes show is that this number is driven overwhelmingly by which heat-rejection route a facility uses at the plant level — an economizer decision layered on top of, and largely independent from, the cooling method at…

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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Sources cited in the surrounding passage

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