Performance improvement of flat plate solar collector employing phase change material bags and hybrid nanofluid

• A FPSC enhanced using PCM bags and HNF is investigated experimentally. • Energy, exergy, and economic evaluation for the FPSC are presented. • FPSC thermal efficiency was improved by 10 %, 21 % and 26 %, over the reference system using PCM, PCM with HNF with 0.15 % and 0.2 %, respectively. • FPSC exergy efficiency was augmented by up to 38 %, employing PCM with 0.2 % MWCNT-Al 2 O 3 hybrid nanofluids. • The payback period of FPSC could be shortened by 25%. The current paper explores the dual influence of phase change material (PCM) and hybrid nanofluid to improve and prolong the productivity of a traditional flat plate solar collector (FPSC). Experimentally, two identical FPSCs were designed, fabricated and examined under hot weather conditions, considering numerous thermal, energy, exergy and economic aspects. PCM-microencapsulated thermal bags and Multiwall Carbon Nanotube-Aluminium Oxide (MWCNT- Al 2 O 3 ) nanofluid with 0.15 % and 0.2 % concentrations were investigated in three different cases compared to a reference case. The PCM bags were integrated behind the FPSC absorber in one case, while the other cases explored the improvement of circulating MWCNT-Al 2 O 3 nanofluid with 0.15 % and 0.2 % concentrations. Study findings indicated that the FPSC output temperature was improved by employing PCM bags and enhanced further when introducing MWCNT-Al 2 O 3 hybrid nanofluid. Specifically, energy analysis displayed that the energy gain improvement reached up to 26 %, 47 % and 54 %, for the FPSC integrating PCM, PCM with MWCNT- Al 2 O 3 nanofluid at 0.15 % and 0.2 % concentrations, respectively. Moreover, the thermal efficiency for the FPSC integrated PCM, PCM with MWCNT- Al 2 O 3 at 0.15 % and 0.2 % concentrations, was enhanced by 10 %, 21 % and 26 % over the reference case, while the exergy efficiency was augmented by 9 %, 31 %, and 38 %, respectively. Furthermore, economic analysis displayed that employing PCM with MWCNT-Al 2 O 3 hybrid nanofluids at 0.2 % concentration has shortened the FPSC payback period by 25%, verifying the feasibility of the suggested enhancement techniques.