Dual-function Solar Collector Research Articles

The Thermal Behavior of a Dual-Function Solar Collector Integrated with Building: An Experimental and Numerical Study on the Air Heating Mode

This paper presented a novel solar collector that can work in air or water heating mode depending on the seasonal requirement. The dual-function solar collector (DFSC) integrated with a building as well as a reference building without the DFSC were built to test thermal behavior in passive air heating mode during winter. The buildings were equipped with an apparatus to control the room temperature. During the testing procedure, experimental study on the DFSC system was carried out under two conditions, where the indoor temperature was controlled and non-controlled. The results showed that the average temperature of the test room was about 3.43 °C higher than that of the reference room under the non-controlled condition. When the room temperature was controlled at 18 °C, the power consumptions of the test room and reference room were 4.322 kWh and 7.796 kWh, respectively. Consequently, the corresponding daily power consumption saved could reach up to around 3.5 kWh. Moreover, a dynamic numerical model on the DFSC along with the building was developed taking the fin effect of the Cu-tubes into account. The numerical results are found to be well consistent with the measured data. A parametric study on with/without Cu-tubes and depth of the air channel was carried out. It is found that the existing Cu-tubes functioning as water heating can enhance the air heating efficiency when the depth of air channel is of a suitable size.

CFD and comparative study on the dual-function solar collectors with and without tile-shaped covers in water heating mode

This paper presents a dedicated study of a novel tile-shaped dual-function solar collector in water heating mode by using computational fluid dynamics (CFD). This system employs a modular panel incorporating tile-shaped covers that is able to serve as part of building pitched roof, thus creating a building integrated, highly efficient and aesthetically appealing solar heating structure, particularly suitable for the Chinese traditional buildings. A complete 3D CFD model was developed. The numerical prediction was validated using experimental data. It was found that the established model is able to predict the operational performance of the system at reasonable accuracy. With the specified system structure, the efficiency of the solar system was found to be a function of its operational conditions. The results indicated that lower inlet water temperature, higher water flow rate, higher ambient air temperature and lower solar radiation led to enhanced thermal efficiency of the module. Further, the performance of the dual-function solar collector with and without tile-shaped covers was comparatively studied. It was found that the tile-shaped collector is able to achieve higher efficiency at higher temperature operation. This work outlines the impacts of the main operational conditions to the tile-shaped dual-function solar collector's efficiency.

Experimental study of a building-integrated dual-function solar collector system

As a novel building-integrated solar thermal system, a building-integrated dual-function solar collector system are designed with two operating modes: passive space heating mode in cold winter and water heating mode in warmer seasons. Based on a long-term experimental test, the paper investigates the performance of the system operating under these two modes. Experimental results indicated that the characteristic thermal efficiency of the system working at the water-heating mode with natural circulation was calculated to be 40.5% and at the space-heating mode the functional relationship between the temperature difference of the indoor air and the solar radiation on the absorber plate of the solar collector can be expressed as two linear equations.

Experimental Study of the Water Heating Performance of a Novel Tile-shaped Dual-function Solar Collector

Abstract Solar collectors are widely used in buildings for energy saving. However, the conventional solar collector does not match the tile roof of the building in appearance. To solve this problem, we propose a novel dual-function solar collector with tile-shaped Polymeric Methyl Methacrylate (PMMA) covers to match the roof appearance. This novel dual-function solar collector can provide hot air in winter and hot waterin other seasons, with high annual solar thermal utilization ratio. Experiments are conducted to investigate the performance of the tile-shaped collector. The efficiency of the novel tile-shaped dual-function solar collector varied from 53.2% to 69.1% in water heating mode in the test. The daily thermal efficiency of the water heating system with this tile-shaped collector system varied from 54.0% to 61.8%, while the daily thermal efficiency of the dual-function solar collector with semicircle covers varied from 44.7% to 59.2%, compared with the daily efficiency of the conventional dual-function solar collector without PMMA covers varied from 35.5% to 67.4%. It shows that the tile-shaped collector can greatly integrate the solar collector technology in to the local special feature buildings with slightly decrease of thermal efficiency.

Performance Investigation and Structure Optimization of a Flat Dual-Function Solar Collector

The performance of a dual-function solar collector (DFSC) that can work as either water heater or air heater depending on seasonal requirement is investigated via both experimental and numerical approaches in this paper. The numerical results are well consistent with the experimental results. Daily efficiency of the thermosiphon system with DFSC is more than 55% in water heating mode and the instantaneous air heating efficiency of the collector reaches 60%. The effects of inner parameters on the thermal efficiency of the collector are analyzed by numerical simulations of the operation of DFSC in two working modes. It is found that the depths of the two air channels in DFSC have an optimal range suitable for both working modes. The thickness of back insulation should be no less than 0.06 m to prevent heat loss via backboard, and the diameter and number of copper tubes show notable effect on the efficiency of DFSC in water heating mode but slight effect in air heating mode.

Study of space heating by dual-function solar collectors

A novel solar collector named dual-function solar collector (DFSC) has been proven feasible for supplying warm air for space heating in winter and hot water during none-heating season by theoretical and experimental studies. While integrated with building, the DFSC becomes component of the envelope. Because complexly coupling of several heat transfer modes and subjecting to random weather condition, the thermal influence of DFSC on a building remains obscure. In order to investigate the effect of DFSC for passive and active heating, a demonstrating office building integrated with DFSC panels on the southern wall and roof has been built in Hefei, in the east region of China. A simulation project of the whole building system in winter was built by the software TRNSYS with the new component developed for DFSC and compiled into the TRNSYS library based on the validated theoretical method and experimental results from previous studies. The simulation results show that the energy supplied by the DFSC can meet the heating requirement at most of the time of a sunny day, except early morning. More than 30 % solar fraction can be provided during the whole heating season in Hefei, the value further increases to 59 % in a region of high solar irradiance, such as Lhasa. While active DFSC panels are operated to provide fresh warm air through ventilation system, the flow rate shows strong influence on the solar fraction of heating load. With appropriate operation scheme of the active DFSC, more energy savings and thermal comfort can be achieved.

Thermal Effect of Dual-Function Solar Collector on Building in Autumn

In this study, a numerical study is made on a dual-function solar collector integrated with building when it works in thermosyphon water heating mode with natural circulation. The investigation is achieved to show its thermal effect on the building environment by comparing with cooling/heating loads of the rooms with or without the novel collector for the warm autumn periods. The results show that in autumn the thermal effect of the novel system is not inevitable because the cooling load of the room with the collector has an evidently positive difference and the heating load must reduce.

Performance Evaluation of a Dual-Function Solar Collector Integrated with Building in Water Heating Mode

The study is for the water heating mode of a novel building integrated solar thermal system named as building-integrated dual-function solar collector. The novel system avoids summer overheating in hot climate and water-freezing in cold climate, meanwhile remains low operating cost as passive solar heating system. For the novel system at the water heating mode, experiment study was carried out in a hotbox, and dynamic numerical model has been established. The experimental and numerical results show that the characteristic thermal efficiency of the collector achieves 47.386% in water heating mode.

Energy Performance of a Building-Integrated Dual-Function Solar Collector in Passive Space Heating Mode

The building-integrated dual-function solar collector has two independent operating modes: passive space heating mode in cold days, and solar water heating mode during hot days such as the summer. The novel system avoids summer overheating in hot climate and water-freezing in cold climate, meanwhile remains low operating cost as a passive solar heating system. In this study, the energy performance of the novel system in passive space heating mode was studied by experiment and numerical simulation. The experimental and numerical results show that the system performed a high ability in utilizing solar energy for building when working in passive space heating mode and the value of the transient operating efficiency generally kept as a constant.

Modelling and validation of a building-integrated dual-function solar collector

A novel building-integrated solar thermal system known as building-integrated dual-function solar collector is proposed. The system has two independent operating modes: passive space heating mode and water heating mode, and it uses the following criteria to select the operating mode that during cold days such as winter days it works in passive space heating mode, but in warm seasons such as summer it works in the water heating mode. A testing system was established, and it performed in thermosiphon water heating mode for water heating. Two dynamic numerical models were, respectively, presented for the two operating modes of the testing system. The experimental data on the testing system were used to validate the two models. The results show that the numerical model for the system in the thermosiphon water heating mode can give a fairly good prediction and the model for the system in the space heating mode also gives a good prediction.

Experimental and theoretical study of the efficiency of a dual-function solar collector

A design of solar collector that is able to provide both hot water and hot air has been proposed to increase annual thermal conversion ratio of solar energy. By modifying the conventional flat-plate solar water heater, the collector with L-shape fins can also function as a double-flow solar air heater. Experiments have been conducted to investigate the dual functions of the collector. It is shown that the thermal efficiency of the collector reached 50% in water heating, and varied from 41% to 55% in air heating depending on the ambient condition and flow rate. Mathematical model has been presented for the collector working in air heating mode. The theoretical results are in good agreement with the experiment results. Theoretical results show that the air flow rate is a dominant factor to determine the efficiency. The enhancement of the L-shape fins on the performance of the collector in air heating is also proved from the theoretic results.

Thermal characteristics of a building-integrated dual-function solar collector in water heating mode with natural circulation

As a modified building-integrated solar thermal system, building-integrated dual-function solar collector here proposed is able to provide passive space heating in cold winter, and water heating in warm seasons. In this study, evaluations were made on this modified collector system for the warm period operation under the water heating mode with natural circulation of flow. A dynamic numerical model has been developed and validated by experimental data. Based on practical air-conditioned room design conditions, numerical analysis was performed to study the water heating performance, as well as to compare the solar transmission through building facade in different seasons with or without its presence. The results show that when working in the water heating mode, the system performs well in providing services hot water in the warm seasons without bringing in summer overheating problem.

Effect of a dual-function solar collector integrated with building on the cooling load of building in summer

As a building integrated solar thermal system, the dual-function solar collector integrated with building works for passive space heating in cold winter season, and for water heating in warm seasons. In this paper, the study is made on the dual-function solar collector integrated with building when it works in water heating mode with natural circulation. The coupled model of the collector and building’s environment is established and validated. A numerical simulation is achieved to show the thermal effect of the novel system on the building in summer. By comparing with the cooling loads of the rooms with or without the novel collector in summer, the results show that when in summer, the novel solar system is available for serving hot water, and it does not have the summer overheating problem, and can even improve the thermal environment of its building slightly.

A numerical and experimental study of a dual-function solar collector integrated with building in passive space heating mode

A newly designed solar collector named dual-function solar collector is proposed. The dual-function solar collector integrated with building can perform in two different modes: working as a passive space heating collector in cold sunny days such as in winter, or working as a facade water heating collector in hot days such as in summer. An experimental study has been carried out to investigate the performance of the novel system in space heating mode, whilst, the dynamic numerical model has been established and validated. The experimental and numerical results show that during the period of the measurement from 9:00 to 17:00, the mean indoor temperature was up to 24.7°C while the mean ambient temperature was only 4.8°C, and a temperature stratification was present in the room. Moreover, a numerical study on the effect of optical property of coatings has been carried out.

Wood pulp pollution of streams

Solar collectors are widely used in buildings for energy saving. However, the conventional solar collector does not match the tile roof of the building in appearance. To solve this problem, we propose a novel dual-function solar collector with tile-shaped Polymeric Methyl Methacrylate (PMMA) covers to match the roof appearance. This novel dual-function solar collector can provide hot air in winter and hot waterin other seasons, with high annual solar thermal utilization ratio. Experiments are conducted to investigate the performance of the tile-shaped collector. The efficiency of the novel tile-shaped dual-function solar collector varied from 53.2% to 69.1% in water heating mode in the test. The daily thermal efficiency of the water heating system with this tile-shaped collector system varied from 54.0% to 61.8%, while the daily thermal efficiency of the dual-function solar collector with semicircle covers varied from 44.7% to 59.2%, compared with the daily efficiency of the conventional dual-function solar collector without PMMA covers varied from 35.5% to 67.4%. It shows that the tile-shaped collector can greatly integrate the solar collector technology in to the local special feature buildings with slightly decrease of thermal efficiency.