Nano-Iron Oxide-Ethylene Glycol-Water Nanofluid Based Photovoltaic Thermal (PV/T) System with Spiral Flow Absorber: An Energy and Exergy Analysis

Abstract

Both electrical and thermal efficiencies combine in determining and evaluating the performance of a PV/T collector. In this study, two PV/T systems consisting of poly and monocrystalline PV panels were used, which are connected from the bottom by a heat exchanger consisting of a spiral tube through which a nanofluid circulates. In this study, a base fluid, water, and ethylene glycol were used, and iron oxide nanoparticles (nano-Fe2O3) were used as an additive. The mixing was carried out according to the highest specifications adopted by the researchers, and the thermophysical properties of the fluid were carefully examined. The prepared nanofluid properties showed a limited effect of the nanoparticles on the density and viscosity of the resulting fluid. As for the thermal conductivity, it increased by increasing the mass fraction added to reach 140% for the case of adding 2% of nano-Fe2O3. The results of the zeta voltage test showed that the supplied suspensions had high stability. When a mass fraction of 0.5% nano-Fe2O3 was added the zeta potential was 68 mV, while for the case of 2%, it reached 49 mV. Performance tests showed a significant increase in the efficiencies with increased mass flow rate. It was found when analyzing the performance of the two systems for nanofluid flow rates from 0.08 to 0.17 kg/s that there are slight differences between the monocrystalline, and polycrystalline systems operating in the spiral type of exchanger. As for the case of using monocrystalline PV the electrical, thermal, and total PV/T efficiencies with 2% added Fe2O3 ranged between 10% to 13.3%, 43–59%, and 59 to 72%, respectively, compared to a standalone PV system. In the case of using polycrystalline PV, the electrical, thermal, and total PV/T efficiencies ranged from 11% to 13.75%, 40.3% to 63%, and 55.5% to 77.65%, respectively, compared to the standalone PV system. It was found that the PV/T electrical exergy was between 45, and 64 W with thermal exergy ranged from 40 to 166 W, and total exergy from 85 to 280 W, in the case of using a monocrystalline panel. In the case of using polycrystalline, the PV/T electrical, thermal, and total exergy were between 45 and 66 W, 42–172 W, and 85–238 W, respectively. The results showed that both types of PV panels can be used in the harsh weather conditions of the city of Baghdad with acceptable, and efficient productivity.

Optimizing MWCNT-Based Nanofluids for Photovoltaic/Thermal Cooling through Preparation Parameters

“…Comparison of the ST of the nanofluids prepared in this study with those from other studies ,,− , reveals that the current study nanofluid has a higher ST (Figure ). This high ST affirms the validity of the methods used during the tests and the success of the accurate measurements taken.…”

“…However, these figures offer evidence of the validity of the results. Analyzing the outcome of the present investigation against the output from refs ( 17 , 42 , 44 , 49 , 74 , 77 − 81 ) displays that the advancement in the TC of the current study is greater than what has been seen in the other studies ( Figure 10 ). This is attributed to the TC of the MWCNTs chosen and the judicious selection of the base fluid, surfactant, and sonication time.…”

“…However, this comparison is not entirely fair as the systems used involve multiple PV panels with varying efficiencies. The research of the ,,,,,,,,,− were all undertaken in different environmental conditions to that of the current study. Even so, this comparison provides an idea of how valid the current study’s methodology is and how much the outcomes are in line with those of other studies.…”

Effect of Different Preparation Parameters on the Stability and Thermal Conductivity of MWCNT-Based Nanofluid Used for Photovoltaic/Thermal Cooling

“…Moreover, there are differences in the base fluid used, so this difference casts a shadow on the final TC of the nanofluid produced. [64] shows that the rate of improvement in the TC of the current study is higher compared to the rest of the studies. This can be considered a result of the TC of the MWCNT used and the optimum selection of the base fluid, surfactant, and sonication time.…”

“…However, this does not preclude the possibility of providing other base fluids with better thermophysical properties. Many references (such as Poloju et al [25], Kazem et al [77], and Al Ezzi et al [64]) have indicated the preference for a mixture of water and ethylene glycol (75% to 25% volume fractions) in its distinguished characteristics, including that the nanoparticles, even after they are deposited at the rest of the nanofluid, return to mix with the base fluid when it is recirculated due to impact of ethylene glycol's lubricating property on the nanoparticles, preventing their adhesion to the inner surfaces of tubes. Therefore, it is preferable to conduct more experiments on several types of base fluids before recognizing that one specific base fluid is optimal for PVT applications.…”