Abstract:
Sun is intermittent and therefore any solar energy harvesting technology needs a storage mechanism to improve the supply reliability. Solar hot water systems have been using water storage tanks for this purpose. The latest addition to solar hot water technologies is the Evacuated Tube (ET) system. This research was focused to improve the efficiency of ET solar hot water systems. In the modified system, a Parabolic Trough (PT) collector was placed underneath, such that the ET is on the focal line of the PT. In addition, a solar tracker and a small circulation pump were incorporated. Due to these modifications, the temperature achieved at the opening of the ET tube was increased to the boiling point whereas the temperature remained below 80o C without the concentrator, under the same insolation conditions. In other terms, the number of ETs required to produce the same quantity of hot water was reduced, giving a financial advantage. The introduction of the circulation pump caused faster heating of water and increased the peak temperature in the water tank. Placing inserts in the evacuated tubes also increased the peak temperature in the water tank. Moreover, comparatively higher water temperatures were achieved on cloudy days. These observations confirm that the suggested modifications have the potential to introduce noticeable economic and operational advantages to the evacuated tube solar water heating systems.
