The UK’s National Grid Electricity System Operator (ESO) has said that it expects it will be able to operate the grid with 100% renewable electricity by 2025. The announcement comes amidst questions around the world as to whether it would be feasible to operate a grid stably as more renewable power is added to it, and those questions appear to have been valid ones – the director of ESO has said that preparing the grid for 100% renewables will require fundamental changes to how the system is designed to operate. The organisation will now commence the process of identifying systems and services it will need and begin designing a marketplace to deliver them. The news is sure to attract the attention of other grid operators around the world.