Renewable energy like wind and solar has created a hidden infrastructure problem. The issue is that power grids which carry electricity to homes and businesses weren't designed for wind and solar. And even though renewables have become a larger part of the overall power supply, grid infrastructure hasn't kept up.It's why some grid experts say renewables contributed to the severity of the blackout across Spain and Portugal in April. Conventional power plants like coal and natural gas have inertia built into ...