section_path: Causes/Variable renewable energy
section_name: Variable renewable energy
paragraph_text: Variable renewable energy
  
  At the time of the incident, solar energy accounted for approximately 59% of Spain's electricity supply, with wind providing around 12%, nuclear 11%, and gas 5%. The initial fault is believed to have originated in Extremadura, a region that hosts a large proportion of Spain's solar farms, hydroelectric facilities, and the 2 GW Almaraz Nuclear Power Plant, Spain's most powerful nuclear power plant.
  
  The exact cause of the blackout remains under investigation, but it has prompted discussion about the stability of electricity systems with high shares of variable renewable energy.
  
  In power systems, mechanical inertia is used to provide stability. In hydropower and thermal power stations, (the latter including fossil-fueled, nuclear and solar thermal) the inertia typically comes from spinning turbines. A major aspect of transitioning to renewable electricity systems is the reduction in inertia on the grid. Solar, which accounted for the majority of Spain's electricity at the time, uses grid-following inverters for 80% of the supply and provides little rotating mass to the grid. An energy consultant also pointed to the small amount of controllable inertia, comparing the blackout to the 2016 South Australian blackout, and suggesting the same solutions for Spain as Australia did; synchronous condensers and large batteries. REE and Experts at Montel Analytics pointed to the relative isolation of the Iberian grid as a contributing factor to the blackout, as neighbouring grids were less able to provide stability.