The Solarflower is an open source solar energy collector which can be made very easily from common recycled and salvaged materials, using basic tools and skills.
It tracks the sun automatically through a simple non-electrical mechanism, can be made almost anywhere, is portable, has no running costs or emissions, and can produce up to kilowatts of power per device.
Applications include electrical generation, water purification, cooking, bio-char and charcoal, heating, gasification, and whatever else heat can be used for.