Abstract

Hot water is essential for industries and households, as well as for smooth running of hospitals. A novel inexpensive flat plate solar water heater was designed using black Plexiglas instead of the conventionally preferred material of copper or metal. This design differs from conventional solar water heaters as black Plexiglas plates are used as energy insulator as well as absorber. Its function as an insulator retains solar energy; the direct thermal contact between the plates and water results in elevated thermal transfer. This design was motivated to reduce the loss due to theft in developing nations by not having metal parts. Based on initial laboratory scale tests and theoretical analysis, a solar water heater with a surface area of 1.67m2 was designed, fabricated and tested. The test results showed that the solar water heater was able to increase the outlet water temperature by 11.7 °C and produced a flow rate of 34L per hour with a thermal efficiency of 68% on sunny days. The efficiency of using this design and material is comparable or better than that of conventional ones, yet the cost of black Plexiglas is much lower than that of copper or metal. The invention is a sustainable water heating system since black Plexiglas can be produced from recycled plastic waste, which has the added benefit of lower fabrication cost of 13.7% when compared to metallic solar collectors. Proposed solar water heater in residences, hospitals and hotels will reduce greenhouse gas emission if the electric water heaters are replaced. A complete package of design drawings is provided for large scale implementation in developing nations.

Keywords: Solar water heater; Efficiency; Temperature; Irradiation; Black plexiglas; Plastic; Thermosiphon