Solar photovoltaic panels are great sources of energy, whether on household rooftops or in huge utility-scale arrays — that is, until clouds pass overhead. That can cause solar PV systems to drop output by 70 percent or so in less than 10 minutes, wreaking potential havoc on grid stability. How to manage this intermittency without expensive energy storage? A Lawrence Berkeley National Laboratory study indicates that spreading out solar panels can help balance the sags and surges caused by passing clouds — information that may be taken into account when locating utility-scale solar farms. Tracking weather patterns to predict when and where the sun will stop shining will also help.