| Work Detail |
Developed by Malaysian scientists, the new photovoltaic-thermal system is based on a nanoparticle-enhanced phase change material (Nano-PCM) and twisted absorber tubes. The system consists of a 30W PV module, absorber tubes fixed to the back of the panel using an improved silicone glue, and a PCM container surrounding the tubes.
Researchers at the Solar Energy Research Institute (SERI) at Universiti Kebangsaan Malaysia have designed a prototype photovoltaic-thermal (PVT) system based on a nanoparticle-enhanced phase change material (Nano-PCM) and tubes braided absorbers.
The main objective of their work was to evaluate the costs of absorber tubes, the choice of working fluid and the use of Nano-PCM, in an effort to investigate the economic feasibility of the system.
“The economic viability of photovoltaic collectors depends on their ability to capture solar energy profitably and efficiently,” Adnan Ibrahim, author of the study, told pv magazine . “In our research, we thoroughly analyzed the annual cost (AC) and annual energy gain (GEA) of PVT collectors, using the AC/GEA ratio as a key profitability indicator.”
PCMs are materials that can absorb, store and release large amounts of latent heat in defined temperature ranges. They have often been used in research for cooling photovoltaic modules and heat storage.
To create the Nano-PCM, the scientists combined a silicon carbide (SiC) nanoparticle-based nanofluid with water and paraffin. “The volume fractions of the nanofluids were 0.3% and 0.6%, respectively, and the nano-PCM had a volume fraction of 1%,” they explained, noting that SiC offers high thermal conductivity, low cost and stability.
The PVT system consists of a 30W PV module 64cm x 30cm in size, absorber tubes attached to the back of the panel using silicone glue enhanced bonding, and a nano-PCM container surrounding the tubes. . The facility also includes a fluid reservoir, heat exchanger, pumps, and a refrigeration unit.
The group tested the systems with different absorbers and working fluid configurations at an ambient temperature of 25ºC, a working fluid temperature of 20ºC and a solar irradiation level of 800 W/m2. He verified that the panel has a surface temperature of 77.59 ºC, a photovoltaic efficiency of around 7% and mass flow rates ranging between 0.008 and 0.04 kg/s.
“The thermal efficiency increased by 12% when the flow went from 0.008 to 0.04 kg/s using the circular tube and around 13.5% with the twisted tube,” the academics noted. “This improvement was attributed to the increase in the convection heat transfer coefficient, which resulted in a higher heat transfer rate between the photovoltaic panel and the absorber tubes.”
They also verified that the use of the twisted tube significantly reduced the temperature of the photovoltaic unit and that the prototype with a concentration of 0.6% SiC achieved thermal and photovoltaic efficiencies of 84.74% and 9.61%, respectively. “Its electrical production was 16 W, compared to 10.49 W for the bare photovoltaic panel,” they added.
“Our main objective is to optimize the use of thermal and electrical energy from solar sources,” Ibrahim explained. “Interestingly, the AC/AEG ratio of a standard PV panel was $0.0982/kWh. However, the most promising results were observed with a configuration incorporating nanofluids, twisted absorber tubes and nano-PCM, achieving an impressive AC/AEG ratio of $0.0485/kWh.”
“Our research sheds valuable light on the potential of PVT systems, underlining their role as a compelling avenue for sustainable energy solutions,” he stressed.
The scientists presented the system in the article “ Nanofluid-based photovoltaic thermal solar collector with nanoparticle-enhanced phase change material (Nano-PCM) and twisted absorber tubes ” [Nano-PCM] and twisted absorber tubes), published in Case Studies in Thermal Engineering .
“Future research opportunities in this field include the use of braided tape in PVT braided absorber tubes to improve performance, exploration of improved convective heat transfer coefficients, and investigation of the application of braided tubes in other absorber tube designs for potentially improved results,” they noted, referring to future directions their research should take.
Other research groups at Universiti Kebangsaan Malaysia have recently designed a bifacial photovoltaic-thermal (PVT) panel using impinging circular jets as a cooling medium, a photovoltaic-thermal system based on PCM cooling, multi-level finned heat sinks for solar module cooling and a passive technology for solar module cooling based on finned heat sinks. |
