Water Use at an On-Site Data Center Power Plant

Simple-cycle plants use little water

A simple-cycle gas turbine or a reciprocating gas engine with air-cooled radiators needs very little water in normal operation. The main uses are occasional compressor washing on turbines, top-up of closed cooling circuits on engines, and domestic water for staff. For many campuses this is the lowest-water way to generate on site.

The trade-off is efficiency. Without heat recovery, a large share of fuel energy leaves as hot exhaust, and the plant burns more gas per unit of electricity.

Inlet cooling on hot days

Gas turbine output falls as air temperature rises. Evaporative coolers and inlet fogging restore some of that output by cooling the intake air with water. On a hot, dry site the gain can be significant, and so can the water use during peak hours.

Mechanical chillers on the inlet use electricity instead of water but add equipment and parasitic load. Some campuses accept the hot-day derate and add a spare unit instead, avoiding inlet water use altogether.

Water injection for emissions control

Turbines without dry low-emission combustors, or turbines running on liquid fuel, may use water or steam injection to control nitrogen oxides. That water must be demineralised, which adds a treatment plant and a waste stream.

Choosing dry low-emission combustors for gas operation, and limiting liquid fuel running to genuine backup use, keeps this demand small.

Washing and maintenance water

Offline compressor washes, online washes, filter house cleaning and general maintenance all use water, usually in modest quantities. Wash water from turbines contains detergents and contaminants and must be collected and disposed of properly.

Plan collection tanks and disposal routes in the design so maintenance teams are not forced into improvised solutions.

Heat recovery and steam cycles

Adding a heat recovery steam generator and steam turbine raises overall efficiency but brings a steam cycle that needs make-up water and condenser cooling. Wet cooling towers evaporate large volumes. Air-cooled condensers save water but cost more, take more space and reduce output on hot days.

For a water-constrained campus, a combined plant with dry condensers or no steam cycle at all may be the better fit, even at some efficiency cost.

Absorption chilling for the data halls

Exhaust heat can drive absorption chillers that cool the data halls, reducing electrical load for cooling. Absorption chillers reject heat, often through cooling towers, so the water balance must be checked carefully.

With dry coolers on the absorption system, the campus can gain efficiency without a large new water demand.

Dry cooling and its derate

Dry coolers and air-cooled radiators use fans to move heat to the air. They use almost no water but grow large on hot sites and lose capacity as air temperature approaches the coolant temperature. Engines and turbines may need derating, or more cooling area, to hold output on the hottest days.

Model the hottest expected conditions, not average weather, when sizing dry cooling.

Water sources and permits

Where the plant needs water, options include municipal supply, groundwater, recycled wastewater and rainwater harvesting. Each brings its own permits, treatment needs and reliability questions. Recycled water may need extra treatment before use in sensitive equipment.

Permitting timelines for water can rival those for air emissions. Our article on power plant site selection discusses how water availability affects the choice of site.

Linking water to the generation design

Water use should be an explicit design criterion alongside cost, efficiency, emissions and reliability. Setting a water budget at the start, for example near zero for normal operation, steers technology choices toward air cooling, dry low-emission combustors and limited inlet cooling.

Our overview of on-site generation design shows how these criteria fit together in the early design stages.

Measuring and reporting

Meter water by use: inlet cooling, washing, make-up, treatment reject and domestic. Report it alongside electricity generated so the campus can track water per megawatt-hour over time. Investors and regulators increasingly expect this data, and it helps operators spot leaks and waste.

Combine power plant water figures with data hall cooling figures for a complete campus picture.

Engaging neighbours and regulators

Water is often the issue local communities raise first when a large campus is proposed. Publishing a clear water budget for the power plant, showing the design choices made to keep it low and committing to metered reporting builds trust. It can also shorten permitting, because regulators see that water demand has been designed out rather than argued about later.

Fuel supply and water together

Water and gas planning often run in parallel during development. Both need routes across land, permits and agreements with utilities. Coordinating the two, as described in our article on the gas supply lateral, avoids duplicated surveys and conflicting easements.

Where pipeline and water routes share a corridor, joint design can save time and cost.