Solar Hot Water at the Solar Decathlon

Cornell had the highest solar water heating points at the Solar Decathlon. They used "evacuated solar thermal tubes" and managed to have hot showers despite having overcast weather for most of the week. Apricus, a well-known manufacturer of evacuated thermal tubes, makes their tubes out of recycled glass. Because the tubes are cylindrical, there is always a surface area that is perpendicular to the sun. The tubes also house a vacuum between two layers of glass. Why a vacuum? A vacuum is an excellent insulator. The insulation properties are so good that while the inside of the tube may be 304°F (150°C), the outer tube is cold to touch. This means that solar tube water heaters can perform well even in cold weather when flat plate collectors perform poorly due to heat loss. :: Apricus