Comparison of performance and cost effectiveness of solar water heaters at different collector tracking modes in Cyprus and Greece

The present study is concerned with investigation of the thermal performance and cost effectiveness of thermosyphon solar water heaters with different solar collector tracking modes under the weather and socioeconomic conditions of Nicosia–Cyprus and Athens–Greece. The tracking modes are the traditional configuration with the collector surface fixed to 40 degrees from the horizontal, the single-axis tracking with vertical axis, fixed slope and variable azimuth and the seasonal tracking mode where the collector slope is changed twice per year. The investigation is conducted through computer simulations using the trnsys program. The results of the simulations indicate that the traditional thermosyphon solar water heater with fixed collector surface is the most cost-effective configuration as compared to single-axis tracking and seasonal tracking. For Nicosia, the best performance is obtained with the single-axis mode, which results in a yearly solar fraction of 87.6% as compared to 81.6% with the seasonal mode and 79.7% with the fixed surface mode, while the corresponding figures for Athens are 81.4%, 76.2% and 74.4%, respectively. The payback time of this mode, however, is 10–11 years as compared to 5 years with the fixed collector surface tracking mode.