Spain’s nationwide blackout this week has put a spotlight on potential vulnerabilities in its system that may offer warnings to other countries, as rising electrification and clean energy sources place new demands on power grids around the world.

Spain's grid operator denied on Wednesday dependence on solar power was to blame for the country's worst blackout, while Prime Minister Pedro Sanchez came under increasing pressure to explain what went wrong.

Electricity is pulsing through Spain and Portugal again after a massive outage knocked out power in both countries on Monday. So too are questions.