Energy, Exergy and Economic (3E) analysis of evacuated tube heat pipe solar collector to promote storage energy under North African climate

초록

Evacuated tube solar collectors are solar water heating devices known to be technically viable and economically attractive. In contrast, these systems encounter several problems owing to the unavoidable heat and water losses along the manifold, essentially conduction and convection losses. In warm weather, heat pipes become partially filled with water and boil, increasing the need for a pressure vessel. One of the popular strategies used to tackle this technical trouble is integrating Phase Change Materials (PCMs) into the evacuated tube solar collectors. In this paper, this problem was approached with a broader perspective by assembling three collectors technically modified, thermally optimized, and economically profitable. The first configuration presents a normal industrial solar collector (1). While in the second and third configurations, the solar system was improved through several modifications. In the second system, the manifold was re-insulated all around (2). In the third, the manifold was surrounded by PCM filled into a copper cavity (3). To well highlight the performed amendments, a comparative approach between the three vacuum tube heat pipe solar collectors is presented. The established methodology is based on energy and exergy analysis and is supplemented by an economic evaluation. It was found that the energy and exergy efficiencies for the conventional collector were 41 % and 15 % respectively. While the thermal energy performance recorded for the second collector was ranged between 60 % and 80 %. Concerning the third collector with insulation and thermal storage unit, the total solar energy absorbed during a typical day was 39.68 MJ, the total useful energy recuperated during a day was 4.11 MJ and the daily thermal efficiency was 13 %. The efficiency of the improved collector (3) was further improved until 28 MJ of energy storage was recorded of which 4.3 MJ were delivered to the water overnight. Moreover, an economic feasibility study was carried out, in which the economic feasibility for the last new system. showed an amortization period of five years.

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