Solar Water Heating System Optimization And Suitability Study

With the continuous improvement of residents’awareness of energy conservation and state support for new energy projects, Solar central water heating system(SCWHS) is being taken more and more attention by scholars at home and abroad. So far, some related research of the Key Design Parameters of SCWHS subsist stated disfigurement and deficiency. The key parameters of two typical SCWHS were optimized and system suitability was analyzed under the different building types. The research has important theoretical and practical value for SCWHS.A comprehensive single tank SCWHS model was established. Based on the principle of minimum auxiliary heat, a systematic combinatorial optimization method was proposed considering the impact of technical and economic factors on the performance of SCWHS. Two combinatorial optimization scheme are given and analyzed. The simulation results indicate that the optimal tank volume and the best Angle are gradually increasing with the increase of collector area under the comprehensive optimum scheme. It is more appropriate that the best angle should select in the local latitude φ±7° if choosing appropriate solar fraction(30%-80%) in the engineering design in Xichang area.In order to systematically optimize the key parameters of two-tank SCWHS including the volume and minimum water lever of hot water supply tank, flow rate of make-up pump and the supply water temperature of solar collection tank, the typical numerical simulation model was set up with main optimization index of solar fraction and energy efficiency. The simulation results indicate that the method of reducing the pump flow and increasing the minimum water level should be taken into account firstly in choosing the flow rate of make-up pump and the minimum water lever of hot water supply tank. For the purpose of this article selected project cases, the optimal value of the flow rate of make-up pump was 1100kg/h and the optimal value of the minimum water lever of hot water supply tank was 2.0m3. For the solar collection tank with temperature-difference control, the supply water temperature could be high than user’s water temperature and pump opens at 55℃ and closes at 44℃.The essential difference and their respective advantages of the single tank SCWHS and the two-tank SCWHS was analyzed. Under the two kinds of system corresponding optimization scheme, the two kinds of system comprehensive performance was compared on the different temperature stratification of hot water tank and its’suitability was studied. The simulation results indicate that the system comprehensive performance of the two-tank SCWHS is no obvious advantage than the single tank SCWHS’s in terms of system comprehensive performance as long as the system design is reasonable. In large-scale SCWHS selection stage, two-tank SCWHS is more suitable for 24 hours of continuous water of the building types and single tank SCWHS is suitable for other building types in terms of building type suitability.