Development and performance evaluation of indigenous flat plate solar water heating systems under Kenyan climatic conditions

This work presents the performance of three solar water heaters equipped with 2 m2 flat plate collectors. The experimental setup included a copper absorber plate manufactured in China (System C), along with two locally built flat plate collectors. One collector was made of aluminum material (System A), while the other was made of galvanized steel material (System B). The systems were tested over a period of three months. For systems A, B, and C; the average maximum outlet water temperatures were measured as 74.1 oC, 69.4 oC, and 78.7 oC, respectively. Systems A, B, and C had mean water outlet temperatures of 61.2 oC, 57.3 oC, and 63.5 oC, respectively. The efficiency of the aluminum-based flat plate collector was 32.8%, slightly below the copper-based flat plate collector, which reached an efficiency of 34%. On the other hand, the galvanized flat plate collector exhibited the lowest thermal efficiency of 28.8%. It can be inferred that even though the galvanized steel solar water heater had low thermal efficiency, it was 20% more cost-effective than systems constructed from copper and aluminum. These results would contribute to the widespread adoption of the inexpensive solar water heaters produced in the region as a reasonable alternative to conventional energy sources including biomass.