Google shifted non-urgent compute to sunny, windy hours to cut grid carbon.

Google matched all its energy with renewable purchases by 2019, but wanted cleaning 24x7 carbon-free energy, which requires using solar and wind when they are available, not merely buying credits. A data center that runs flat all day is still drawing from the grid in the evening when the sun has set.

A small team built a carbon-intelligent platform. Every day it pulls two forecasts: the projected hourly carbon intensity of the local grid, and the power the data center will need for its compute tasks. It then optimises hour-by-hour guidelines to align compute with low-carbon supply.

The trick is that a lot of Google's work is flexible. Creating filter features for Google Photos, transcoding YouTube video and adding words to Google Translate can happen hours later without a user noticing. Shifting those tasks into sunny and windy periods needs no extra hardware and no slowdown for Search, Maps or YouTube.

Early pilots showed it worked, and in 2021 Google extended the platform to shift flexible compute between data centers, favouring regions whose grids are running on carbon-free power that hour. The whole system was designed to get every job done, just at a cleaner time and place.