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Abstract This research presents the power performance of the backward-bent duct buoy (BBDB) oscillating water column (OWC) wave energy converters (WECs). To achieve that, following steps are detailed: firstly, power conversion from wave power into pneumatic power by coupling the hydrodynamics and the thermodynamics in the air chamber using a linear air turbine power take-off (PTO), with the calculation of the power response curves for the BBDB OWC device in regular waves; secondly, using the power response curve, a power performance curve is then calculated for irregular waves; thirdly, the power matrices for the device is calculated and the determination of the rated power for the device to meet the target capture factor; and finally, the annual energy production will be assessed as the final indicator for the device's power performance. Using the developed approach, some initial optimisations are made to the original design. It is shown that with some simple optimisations, the BBDB OWC device could increase the annual energy production (AEP) significantly. A simple change in making a uniformed water column for the RM6 device could increase the AEP by about 10%, whilst increasing the horizontal duct length by 10 m could increase the AEP by 58%.

Abstract This research presents the power performance of the backward-bent duct buoy (BBDB) oscillating water column (OWC) wave energy converters (WECs). To achieve that, following steps are detailed: firstly, power conversion from wave power into pneumatic power by coupling the hydrodynamics and the thermodynamics in the air chamber using a linear air turbine power take-off (PTO), with the calculation of the power response curves for the BBDB OWC device in regular waves; secondly, using the power response curve, a power performance curve is then calculated for irregular waves; thirdly, the power matrices for the device is calculated and the determination of the rated power for the device to meet the target capture factor; and finally, the annual energy production will be assessed as the final indicator for the device's power performance. Using the developed approach, some initial optimisations are made to the original design. It is shown that with some simple optimisations, the BBDB OWC device could increase the annual energy production (AEP) significantly. A simple change in making a uniformed water column for the RM6 device could increase the AEP by about 10%, whilst increasing the horizontal duct length by 10 m could increase the AEP by 58%.

Abstract The characteristics of the wind at 10 m height were studied over a period of 32 months. The sampling interval was 20 ms and the averaging time was 10 min. Probability density functions are given for the speed, direction, inclination and intensity of turbulence of the wind. Frequency contour plots are given for wind speed vs solar time, wind speed vs wind direction, wind speed vs global solar irradiance and wind speed vs the intensity of turbulence of the wind. Differences between the results for day and night and between various seasons are examined.

Abstract The characteristics of the wind at 10 m height were studied over a period of 32 months. The sampling interval was 20 ms and the averaging time was 10 min. Probability density functions are given for the speed, direction, inclination and intensity of turbulence of the wind. Frequency contour plots are given for wind speed vs solar time, wind speed vs wind direction, wind speed vs global solar irradiance and wind speed vs the intensity of turbulence of the wind. Differences between the results for day and night and between various seasons are examined.

Abstract The north wall of Chinese solar greenhouses (CSGs) plays an important role in maintaining their indoor thermal environment without additional heating during the wintertime. To enhance the heat storage/release capacity of the CSG wall and further improve the indoor thermal environment, an active-passive phase change thermal storage wall system has been developed in this study. The system was composed of 5 concentrating solar air collectors (CSACs), 6 tanks that were embedded in the north wall of the CSG and filled by phase change material (PCM), tubes linking the tanks and the CSACs and a centrifugal fan with variable-frequency drive (VFD). During the daytime, the solar energy was collected by the CSACs and stored in the tanks, whereas during the nighttime, the stored energy was released into the indoor environment of the CSG through a passive heat mode of the north wall or an active heat mode of the system. Then, a numerical model of the active-passive phase change thermal storage wall system has been developed. The simulation results were validated by the experimental data with the maximum relative error and average relative error being 5.6% and 3.9%, respectively. Furthermore, the heat release capacity characteristics in three cases with the air velocities of 2 m/s (Case A), 3 m/s (Case B) and 4 m/s (Case C) at indoor outlet for the active heat mode and a passive heating case (Case D) were chosen as the control groups for study. In the proposed wall, the heat release capacity of ventilation increased and that of inner surface of the wall declined with an increasing ventilation velocity. The total heat release capacities of the cases A, B and C were 38.12 MJ, 40.26 MJ, 42.00 MJ, respectively, higher than that of the case D (33.76 MJ). On the other hand, the calculated temperature distribution indicated that there was no thermal-stable layer within depth of the 360 mm in the wall due to an apparent temperature variation of the PCM layer by ventilation. These results suggested that the proposed system could effectively promote the heat storage/release capacity of the middle layer of the wall.

Abstract The north wall of Chinese solar greenhouses (CSGs) plays an important role in maintaining their indoor thermal environment without additional heating during the wintertime. To enhance the heat storage/release capacity of the CSG wall and further improve the indoor thermal environment, an active-passive phase change thermal storage wall system has been developed in this study. The system was composed of 5 concentrating solar air collectors (CSACs), 6 tanks that were embedded in the north wall of the CSG and filled by phase change material (PCM), tubes linking the tanks and the CSACs and a centrifugal fan with variable-frequency drive (VFD). During the daytime, the solar energy was collected by the CSACs and stored in the tanks, whereas during the nighttime, the stored energy was released into the indoor environment of the CSG through a passive heat mode of the north wall or an active heat mode of the system. Then, a numerical model of the active-passive phase change thermal storage wall system has been developed. The simulation results were validated by the experimental data with the maximum relative error and average relative error being 5.6% and 3.9%, respectively. Furthermore, the heat release capacity characteristics in three cases with the air velocities of 2 m/s (Case A), 3 m/s (Case B) and 4 m/s (Case C) at indoor outlet for the active heat mode and a passive heating case (Case D) were chosen as the control groups for study. In the proposed wall, the heat release capacity of ventilation increased and that of inner surface of the wall declined with an increasing ventilation velocity. The total heat release capacities of the cases A, B and C were 38.12 MJ, 40.26 MJ, 42.00 MJ, respectively, higher than that of the case D (33.76 MJ). On the other hand, the calculated temperature distribution indicated that there was no thermal-stable layer within depth of the 360 mm in the wall due to an apparent temperature variation of the PCM layer by ventilation. These results suggested that the proposed system could effectively promote the heat storage/release capacity of the middle layer of the wall.

Abstract Climate responsive strategies contained in traditional native dwellings can provide theoretical basis for the development of sustainable buildings. This study focused on a quantitative analysis of cliff-side cave dwellings located in cold region of China. Field measurements in summer and winter were carried out. Based on the monitoring data, thermal environment of the cave dwelling and thermal characteristics of the adobe massive building envelope were evaluated. Results showed that the cliff-side cave dwelling was well adapted to local environment for its good ability of thermal insulation under the natural conditions. Furthermore, in order to assess the whole annual thermal performance and thermal comfort level, numerical simulations on the cliff-side cave dwelling models was also performed using the software Energyplus. Results showed that 52.50% time of the year was comfortable of the living room. Meanwhile, some technical strategies of making full use of solar energy and natural ventilation was proposed in the end of this paper, which can provide technical support for the regeneration design of traditional residential buildings.

Abstract Climate responsive strategies contained in traditional native dwellings can provide theoretical basis for the development of sustainable buildings. This study focused on a quantitative analysis of cliff-side cave dwellings located in cold region of China. Field measurements in summer and winter were carried out. Based on the monitoring data, thermal environment of the cave dwelling and thermal characteristics of the adobe massive building envelope were evaluated. Results showed that the cliff-side cave dwelling was well adapted to local environment for its good ability of thermal insulation under the natural conditions. Furthermore, in order to assess the whole annual thermal performance and thermal comfort level, numerical simulations on the cliff-side cave dwelling models was also performed using the software Energyplus. Results showed that 52.50% time of the year was comfortable of the living room. Meanwhile, some technical strategies of making full use of solar energy and natural ventilation was proposed in the end of this paper, which can provide technical support for the regeneration design of traditional residential buildings.