Some ideas are so satisfying that you wonder how they haven’t been done before. Solar canals, which will get their first U.S. pilot later this year in California, fit that mold. Western states are crisscrossed by thousands of miles of irrigation canals, some as wide as 150 feet, others just 10 feet across. By covering those channels with solar panels, researchers say, we could produce renewable energy without taking up precious land. At the same time, the added shade could prevent billions of gallons of water loss through evaporation.