Via Grist, this is pretty nifty:
A carpenter in the rural Chinese village of Qiqiao has cobbled together a solar water heater for his mother's house using only beer bottles and hoses. A few years ago, Reuters reported that more than 30 million Chinese households are now using solar water heaters, but the professional models start at $190—still something of a middle-class luxury. Maybe the beer-bottle version can change that.
--Bradford Plumer