Solar thermal collectors collect free energy through individual pipe-shaped collectors that absorb heat from sunlight. The absorbed energy is transferred into heat in a transfer fluid, for our case water, which then flows through pipes and finally transfers the energy to usable water stored in a storage tank. The heated water can then be used for any hot water requirements including domestic hot water use and space heating. Solar thermal collectors are a great way to reduce energy use in the house by delivering up to 40-60% of hot water requirements throughout the year. For a typical household, over 70% of energy use is dedicated for space and water heating, so a source of free hot water will result in high financial and energy savings.

Transfer of solar energy occurs inside tubes that have been evacuated to create a vacuum. The vacuum facilitates the conversion of energy into the water by greatly reducing heat loss. The vacuum also lets the collectors work efficiently in conditions where there is large temperature difference between the tubes and the environment. These tubes have another tube within them that is filled with water where solar energy is transferred to. The tubes are oriented in such a fashion such that any heated water will travel upwards and out of the collectors and any cooler water will remain inside the collectors to be heated. Once the hot water transfers heat to usable water inside the storage tank, it is sent back to the solar collectors to be heated again.

Solar thermal collectors that we used are roof mounted, but they can also be wall mounted or ground mounted. Our collectors are flat mounted to receive the most amount of sunlight during the day. We installed our collectors as close to the water storage tanks as possible. This reduces heat loss that occurs while the water travels from the collectors to the tanks and also reduces installation and materials costs.

By Teagan Barnes, Solar Decathlon