The Fossil-Fuel-Free Irrigation Project is developing this water pump based on a Stirling engine that concentrates sunlight through Fresnel lenses and stores heat in sand, and it is one of this year's Promising Prototypes. Image: Harry Sangree, SeaFreight Labs
High-altitude balloons for mitigating natural disasters, solar power and safe water in a single, off-grid unit, a portable milk pasteurizer and recycled plastic housing are among the promising...
