Twelve years ago, reading his wife’s letters about the Nigerian hospital where she was observing maternity care, Hal Aronson began sketching the outline of a stand-alone solar power system that would ensure the maternity ward had electricity 24 hours a day instead of only 12 hours.

He taught solar power at a California university; his wife, Laura Stachel, was an obstetrician-gynecologist who had been forced to give up her medical career as a result of a severe back injury. After her recovery, she began studying public health, which is how she wound up in Nigeria, trying to understand why it had such a high maternal mortality rates.