Performance Enhancement of Solar Water Heaters
Upon successful completion of the project - Boiler Feedwater Pre-heating using Solar Water Heaters – further performance enhancement was envisaged. Though performance of the solar water heater field was satisfactory, further modifications were thought of to capture the radiation lost due to the gap between two evacuated tubes. This constituted roughly about 30% of the potential surface area that can be used for capturing the solar radiation.
Most common collector design to capture such radiation is shown below.
However, it is not feasible to retrofit an existing evacuated tube collector in the above manner due to manufacturing/fabrication challenges in creating a reflector similar to the above. Also, the cost of material and manufacturing reflector on such small scale was not commercially viable.
Therefore, a simpler design (with some loss of efficiency) was implemented that was commercially and technically viable. A reflective glass was used to reflect the radiation falling in the gaps back to the collector tubes as shown the diagram below.
The picture below shows the actual installation of the reflectors.
There was a significant improvement in performance of the solar water heater field as the average water temperature rose from 70 deg C to 85 deg C.