Design and Performance Analysis of A Solar Water Heater with Variable Elevation Angle

• Main Authors: HUNG, YU-CHIEN, 洪宇芊
• Other Authors: HUANG, MING-HUEY
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/ce6kwc

碩士 === 國立聯合大學 === 能源工程學系碩士班 === 107 === Although solar water heater (SWH) is widely used in Taiwan, there are still many problems. In the summer, user don’t need much hot water, but the SWH absorbs more solar energy, so the water temperature is higher. In the winter, user need more hot water, but the SWH absorbs less heat and water temperature is not high enough. So the auxiliary electric heaters must be installed. To reduce the usage of electricity in SWH, this project design a SWH with variable elevation angles, so that the water heater can be adjusted to different elevation angles in different months to absorb the maximum heat. This thesis first introduces the principle of the system, and then simulates the heat absorbed by the water heater during the whole year to find the best angle for winter usage; finally collects data from a real SWH and then analyzes its performance. The winter is defined as the interval when the average daily temperature is below 20C. The simulation result shows that the optimization angle is about 41. The total solar radiation, total absorbed energy, and efficiency at the two elevation angles are calculated. Without considering the heat loss effect, the final experimental results show that the solar hot water system at 41 receives about 22% more insolation energy then that at 23. However, the SWH absorbed thermal energy only increases by 3% at 41. Preliminary analysis found that the overall heating efficiency was lower at 41. Further analysis of the data in the same daylight conditions, the heating efficiency is similar, but the absorbed energy increase due to the elevation angle change, confirming the expected results in the simulation of this experiment. However, the enhancement effect of absorbed energy is not as good as expected from the simulation, which is presumed to be affected by heat dissipation.