LOS ANGELES – It started out modestly enough: David Hertz, having learned that under the right conditions you really can make your own water out of thin air, put a little contraption on the roof of his office and began cranking out free bottles of H2O for anyone who wanted one.

Soon he and his wife, Laura Doss-Hertz, were thinking bigger — so much so that this week the couple won the $1.5 million XPrize For Water Abundance. They prevailed by developing a system that uses shipping containers, wood chips and other detritus to produce as much as 528 gallons (2,000 liters) of water a day at a cost of no more than 2 cents a quart.

The XPrize competition, created by a group of philanthropists, entrepreneurs and others, has awarded more than $140 million over the years for what it calls audacious futuristic ideas aimed at protecting and improving the planet. The first XPrize, for $10 million, went to Microsoft co-founder Paul Allen and aviation pioneer Burt Rutan in 2004 for SpaceShipOne, the first privately financed manned space flight.