Conference article

One of the most expensive components of a solar thermal system is the storage tank. Retrofitting conventional domestic hot water heaters when installing a new solar hot water system can decrease the total investment cost. In this study; retrofitting of existing water heaters using forced circulation flow was investigated. A comparison with a standard solar thermal system is also presented. Four simulation models of different system configurations were created and tested for the climate in Lund; Sweden. The results from the simulations indicate that the best configuration consists on connecting the collectors to the existing heater throughout an external heat exchanger and adding a small heater storage in series. For this retrofitted system; preliminary results show that an annual solar fraction of 53% is achieved. In addition; a conventional solar thermal system using a standard solar tank achieves a comparable performance for the same storage volume and collector area. Hence; it is worth to further investigate and test in practice this retrofitting. Furthermore; using the same system configuration; solar collectors can also be combined with new standard domestic hot water tanks at new installations; accessing a world-wide developed and spread industry.

Solar thermal; Storage tank; Water heater; Retrofit; Domestic hot water