PERFORMANCE EVALUATION OF HYBRID SOLAR AIRWATER HEATER WITH VARIOUS INLET AIR TEMPERATURE DURING HEATING PROCESS

Research about hybrid solar air-water heater that can heating both air and liquid has been conducted for enhancing the usage of solar thermal energy. In the previous study, thermal efficiency of this collector was investigated with many operating and external conditions, but all of previous experiment conducted using outdoor air as inlet air of collector. Thus, in this study, the performance change of hybrid solar air-water heater was investigated with change of inlet air temperature during air and liquid were heated simultaneously. As a result, thermal efficiency for liquid heating was increased with increment of the inlet air temperature. On the contrary to this, thermal efficiency for air heating of collector was decreased with increment of inlet air temperature. In case of total thermal efficiency of collector considered air and liquid heat gain, it was also decreased with increment of inlet air temperature. From these results, it was confirmed that using outdoor air directly as inlet air of collector is better for the use of solar energy. However it is hard to conclude that which is better between using outdoor air and heated air on the perspective of energy saving of building because heat storage performance was increased if the return air or any heated air is used as inlet air of hybrid solar air-water heater when air and liquid was heated simultaneously even air and total thermal efficiency is decreased. Thus, the necessity of more profound study and consideration about this as a further study was also confirmed

Performance Evaluation of PVT Air Collector Coupled with a Triangular Block in Actual Climate Conditions in Korea

This study experimentally investigated the performance of a PVT air collector coupled with a triangular block. The triangular block, newly suggested by the authors, is a triangular-shaped obstacle and was inserted at the bottom of the PVT air collector to enhance the heat transfer performance of the collector. The experiment was carried out in actual climate conditions in Korea with two air mass flow rate conditions: 0.03606 kg/m2 s and 0.06948 kg/m2 s. Results show the average values of electrical efficiency of the collector during the test period to be 16.15% and 16.43% for each air mass flow rate, while thermal efficiencies were 28.83% and 38.36%, respectively. The average values of total energy efficiencies were found to be 44.99% and 54.79%, respectively. The results show that air mass flow rate has a large impact on thermal and total energy efficiency, while it has a small impact on electrical efficiency. Furthermore, it was confirmed that the PVT air collector coupled with a triangular block can enhance the utilization of solar energy since the thermal performance was higher than that of the collector without a triangular block

Influence of Triangle-Shaped Obstacles on the Energy and Exergy Performance of an Air-Cooled Photovoltaic Thermal (PVT) Collector

A photovoltaic thermal (PVT) collector is a type of solar collector that can simultaneously produce electrical and thermal energy from solar energy. In this research, the daily and annual performances of an air-cooled PVT collector with triangle-shaped obstacles were investigated and compared with those of a conventional air-cooled PVT collector. Based on the thermal circuit model, a numerical model of the air-cooled PVT collector containing triangle-shaped obstacles has been developed and validated using experimental results. A typical meteorological year’s weather data from Ulsan, Korea was used as the weather data. From the results, it was seen that the daily average thermal, electrical, and overall energy and exergy efficiencies for the PVT collector with triangle-shaped obstacles were 24.73%, 15.59%, 62.83%, and 15.57%, respectively, while those values of conventional PVT collector were 17.08%, 15.30%, 54.47%, and 15.13%, respectively. The results also showed that the annual energy and exergy outputs of the PVT collector with triangle-shaped obstacles were 12.84% and 1.98% greater than those of the conventional air-cooled PVT collector. From these results, it was clearly confirmed that the triangle-shaped obstacles can enhance the energy and exergy outputs of the air-cooled PVT collector

Performance Evaluation of Air-Based Photovoltaic Thermal Collector Integrated with Dual Duct and Semicircular Turbulator in Actual Climate Conditions

An air-based photovoltaic thermal collector (PVTC) is a system that generates both electricity and heat using air flowing over a photovoltaic (PV) module. This system offers the advantage of easy maintenance; however, it suffers from lower thermal efficiency compared to other PVTCs, mostly owing to the low heat capacity of air. Thus, this study introduces a novel PVTC incorporating dual ducts and semicircular turbulators, which were experimentally evaluated under actual weather conditions in the Republic of Korea. The proposed PVTC was compared with two other types of PVTC: one is a single-duct PVTC with semicircular turbulators, and the other is a dual-duct PVTC without turbulators. The results showed that the thermal efficiency of the proposed PVTC increased by approximately 88.7% compared to the single-duct PVTC with a turbulator and by 9.3% compared to the dual-duct PVTC without a turbulator. The electrical efficiency showed a slight decrease of about 7.2% compared to the single-duct PVTC but an increase of 1.4% compared to the dual-duct PVTC without a turbulator. Overall, the total efficiency of the proposed PVTC increased by 54.2% and 7.7% compared to the single-duct PVTC and the dual-duct PVTC without a turbulator, respectively. These experimental results demonstrate that attaching dual ducts and semicircular turbulators to an existing PVTC increases the daily thermal energy output, which ultimately enhances the total daily energy output