Design a cooling system for a 1MW data center achieving PUE below 1.3.

Target: PUE = Total facility power / IT load power < 1.3 means cooling + overhead < 300kW. Strategy: Economizer-first approach using outside air or water when T_ambient < 20°C (70%+ hours in temperate climates); Hot/cold aisle containment achieving supply T=20-25°C (ASHRAE A1); Raised floor or overhead supply with variable speed CRAC units responding to rack-level temperature sensors; Rear-door heat exchangers for high-density racks (>20kW) using chilled water; Free cooling chillers with water-side economizer (plate HX) bypassing compressor when T_wb < 15°C; Variable primary chilled water flow with ΔT=8-12°C; EC fans throughout (60%+ efficiency at part load); Warm water cooling (40-45°C supply) enabling direct-to-chip cooling and waste heat recovery potential. Controls: CFD-informed setpoints, predictive algorithms for weather-based staging. Monitoring: real-time PUE calculation, leak detection, redundancy management. Achievable PUE: 1.2-1.25 with this approach.