A review on artificial roughened solar air heaters with and without thermal energy storage

Solar energy is one of the renewable energy sources having the potential to play a significant role in fulfilling increasing energy demand. There are various solar energy systems used in different applications and solar air heater is such a widely adopted technology. Solar air heater is basically used to collect and transfer the solar thermal energy to air that can be further utilized for various purposes such as space heating, crop drying and greenhouse heating. The overall performance of a solar air heater is significantly affected by its thermo-hydraulic aspect and it can be improved by providing artificial roughness and integrating thermal energy storage. There are a number of detailed experimental and numerical studies carried out on the thermo-hydraulic aspect of solar air heaters having artificial roughness and thermal energy storage. The present review covers the solar air heaters having different geometries used to create artificial roughness and thermal energy storage for their performance improvement. The effect of various reported parameters on the thermo-hydraulic performance of solar air heaters is reported and compared. The economic and environmental aspects of solar air heaters are also discussed under the present review.