The story so far: Following sustained local protests and pressure from civil society groups, Google has reportedly said its planned 1-GW data centre in Visakhapatnam district will use air-cooling technology to cool its servers. While air-cooling requires less water, it comes with its own trade-offs.

A large data centre will have several million processors, each with billions of transistors. Each transistor manipulates the electrical current flowing through it to perform operations on data. As it does, the resistance the transistor’s material poses to the flow of current will release some heat, as will the charging and discharging of transistors. Across trillions of transistors, the amount of heat thus generated can be considerable.