variavel0=<b>José Manuel dos Santos Cruz</b> - jcruz@fam.ulusiada.pt Universidade Lusíada
<b>Geoffrey Paul Hammond</b> - ensgph@bath.ac.uk University of Bath
<b>Albino José Parente da Silva Reis</b> - areis@fam.ulusiada.pt Universidade Lusíada
<b>Abstract.</b> A simple, low-cost solar water heater has been developed for operation in Mediterranean Europe or regions of similar latitude (40º-45º north). It takes the form of a trapezoidal-shaped water store in direct contact with an inclined flat-plate solar collector assembly. This cross-section induces thermal stratification in the water store, and provides sufficient energy storage to meet typical daily hot water demand. Its thermal performance is critically dependent on the waterside convective heat transfer coefficient on the backward-reclining collector plate; previously evaluated by Cruz et al, (1999). In the current design, the absorber plate inclination to the horizontal was fixed at 45º (close to the local latitude) in order to yield maximum solar gain over a typical year. The energy saving provided by the solar collector/thermal store demonstrator largely depends on the amount of thermal stratification within the trapezoidal storage cavity. This was evaluated via both computations and measurements of the temperature field. A thermal network analysis model was then used to assess the energy saving potential of the composite system. It indicated that a 30 to 70% reduction could be obtained in contrast to direct heating; where the smaller saving occurred at times of greatest use or hot-water take-off.
<b>Keywords.</b> Solar Energy, Solar Collector/thermal Store, Buoyancy-driven Convection.