Multi-objective optimization study on photovoltaic arrays on roofs of existing buildings
Based on the background of energy saving,emission reduction and the dual-carbon goal,green retrofit of existing buildings is an urgent need.Adding photovoltaic arrays on the roof is a favorable way for energy-saving retrofit of existing buildings,but laying fixed photovoltaic panels based on the geographically optimal inclination angle has problems,such as unattractive appearance and low economic benefits.How to optimize and determine the tilt angle of fixed photovoltaic panels with the help of digital technology,so as to reap good economic and environmental benefits,has become a hot issue of concern.An existing building's roof in Chengdu,Sichuan Province,is selected as the research target,and the PV array is laid along the north slope direction of the roof,with the overall lateral width equal to the length of the roof.The length of the PV panels in this system is selected from 700 to 1 260 mm in combination with the commonly used specifications in the project.The minimum value of the PV panel spacing is taken as the value of the smallest specification of PV panels laying densely along the plane of 0.7 m,and the maximum value is taken as the width of the roof of 14 m.Due to the need to take into account the effect of the wind loads on the PV arrays,the maximum angle of the PV panels with the roof surface is taken as 45 degrees,also the thickness of the PV panels is taken as the commonly used specification of 35 mm.Taking the south edge of each PV panel as the axis and the roof surface as the starting plane,the PV array can be rotated along the axis according to the tilt parameter,and the distance between each other can be changed according to the spacing parameter.The semiconductor cell side of the PV panels is used as the receiving solar radiation object,and the roof and the PV panel blocks are used as the relevant shading objects.With the help of Grasshopper tool,a parametric simulation optimization platform is established.SPEA-II genetic algorithm is selected as the optimization algorithm.Optimization objectives include the total solar radiation and unit area solar radiation.Genetic algorithm calculations obtain 14 pareto frontier on the scheme,which means 14 programs as the optimal design of the single PV panel vertical width,PV array spacing and PV array tilt angle of PV arrays under the design conditions.There are two programs comprehensively better than the other programs.And then the study considers the expected cost of the optimization of the most in line with the project's actual needs of the program filtered out.Taking the two conventional design forms of direct laying along the roof and intensive laying according to the optimal inclination angle in Chengdu as the comparison group,the screened multi-objective optimization scheme has a greater improvement in the radiation per unit area and the total radiation than the comparison group.Through data analysis,some design recommendations regarding comparable design in this district was found:array tilt angle to take the maximum value of the range of site conditions;at the same time,the PV array aspect ratio to meet the sinusoidal function of the tilt angle of the relationship between the solar radiation per unit area of the PV array designed by this program and the total solar radiation is relatively in line with the economic benefits of the needs of the PV array.It is shown that this multi-objective optimization method process is oriented to the green performance of the building,using genetic algorithms to generate the results of the scheme in a self-organized manner,compared with the other two scheme-simulation-optimization of the traditional parametric design techniques in reducing the workload at the same time to obtain a more excellent performance of the energy-saving retrofit of the building and resource conservation play a positive effect,and the results of this method can be used to improve the performance of the PV array.It confirms the feasibility of optimizing the design of fixed PV arrays on the roofs of existing buildings through genetic algorithms.The optimization design idea,framework and non-dominated solution selection proposed in the study can be used as a useful supplement to the design method of additional PV arrays on the roofs of existing buildings.
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