As California struggles with another crippling drought, a Silicon Valley startup that believes robots can grow produce more sustainably said Wednesday it raised $50 million in a funding round led by Bill Gates’ Breakthrough Energy Ventures.Iron Ox uses robots that are integrated with a hydroponic system consuming 90% less water than traditional farms, said CEO Brandon Alexander.The company is putting that system to work at a 10,000-square foot (930 square meter) greenhouse in Gilroy, California, where a self-driving robot named Grover moves pallets of Genovese Basil and a robotic arm system lifts the pallets for inspection.