In this study two solar energy collectors were designed and built. To enhance the heat transfer characteristics, flow in curved channel technology is used. Porous media (with 0.1453 porosity) composed of coarse aluminum chips fill the flow channels to provide for further increase in heat transfer performance and for extra energy storage capability. Measured data were recorded water flow rates that range between 50 and 400 l/h. The results show that the enhancement of heat transfer characteristics associated with the existence of porous media does not improve the calculated collector daily efficiency. The collector daily efficiency reduces during sunlight relative to that for that of clean collectors by approximately 1.0% and 2.0% at flow rates of 300 and 200 l/h, respectively. The daily efficiency at 300, 200 l/h flow rates are 60%, 56%, respectively, for the collector without porous media and 59%, 54%, respectively for the collector packed with porous media. It is noticed that using porous medium significantly decreases the rate of decline in water temperature to approximately half its value for the case without porous medium for flow rate of 300 l/h during the absence of sunlight. Also using porous medium will decrease the temperature rise across the collector during sunlight. The maximal outlet temperature reached was 73 degreesC for the collector without porous media at 70 l/h flow rate and 60 degreesC for the collector backed with porous medium at 50 l/h flow rate. (C) 2003 Elsevier Ltd. All rights reserved.