Étude expérimentale d'un chauffe-eau solaire à vidange récupérée sous les conditions météorologiques nordiques

Abstract

A drain-back domestic solar water heater (DSWH) consisting of 4.3 m² of flat plate thermal collectors and of 300 L tank has been installed and tested in Montreal. Once the test bench was calibrated and installed, the measurements have shown that the water recirculation velocity in the external supply pipes exceeds 90 cm/s, the maximum collectors and pipes water draining time is around 90 s and the maximum heat losses in the external return pipes is 11 % of the useful collectors energy. According to the CSA F379 standard, these results prove the reliability of freezing protection of such apparatus. Thereafter, the daily performance of this system has been studied under a protocol which is based on ISO 9459-2 and ASHRAE 95 standards. Daily domestic hot water (DHW) withdrawals were conducted during two clear and sunny winter days. The tank water temperature exceeded 50 °C despite a minimum ambient temperature of -18 °C. By using a heat exchanger with an efficiency of 89,4 %, a total of 91 L of DHW having a temperature between 40 and 50 °C have been obtained. This quantity, thus, covers 52 % of the daily load of DHW on a daily basis request of 200 L at 40 °C. Night DHW withdrawal was carried out as well in order to simulate the late usage of DHW. So after a clear and sunny winter day, 140 L at a temperature between 40 and 57 °C was produced. Thus, 67 % of the demand was covered. Since the cost is one of the main challenges of DSWHs, the cost of such system has been compared to the cost of a reference glycol DSWH. It has been found that the present concept involves a 2 400 $ cheaper initial investment. Nevertheless, this type of apparatus remains non-cost effective because of the low electricity cost in Quebec. Its payback time exceeds 25 years. By following a realization protocol inspired from CSA F379, ISO 9459-2 and ASHRAE 95 standards, this study showed the potential of the drain-back solar water heater as simpler and less expensive solution that could replace glycol solar water heaters.

Date	3 Jul 2014
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Daniel Rousse (Supervisor) & Alain Moreau (Co-supervisor)