Generate endless hot water without electricity or solar power

According to Appropedia: "When air or water is heated, it gains kinetic energy from the heating source and becomes excited. As a result, the water becomes less dense, expands, and thus rises. In contrast, when water or air is cooled, energy is extracted from the molecules and the water becomes less active, more dense, and tends to "sink." Thermosiphoning harnesses the natural density differences between cold and hot fluids, and controls them in a system that produces natural fluid movement. Several systems based on this technology are currently available—[the one highlighted in the following video uses wood as the fuel source]."

Solar Cooking 101: Harnessing The Sun For Health, Wealth And A Clean Environment

Cooking with the sun is not only eco-friendly, it also contributes to better tasting, more nutritious food. Preparing food in this way encourages energy independence for both developing countries and industrialized nations alike. In areas of the world where disease is on the rise and fuel is in short supply, economical sun cookers are a workable solution.