Research On Energy-saving And Optimization Of University Teaching Office Building Exterior Envelopes

Energy shortage and environmental deterioration have become two major problems that restrain human development.Buildings consume about 40% of energy and emit one-third of greenhouse gas.Therefore,building energy saving is of great significance to alleviate the energy crisis and protect the environment.For China,building energy consumption has accounted for more than 30% of China’s total energy consumption,while public buildings have accounted for more than 50% of total building energy consumption.University building as a kind of public building.Its energy consumption is mainly air-conditioning,lighting and heating,which accounts for more than 60% of total university energy consumption.Among them,the heat transfer loss of the envelope structure cause more than 70% of the total energy consumption of buildings,which have huge energy saving potential.Therefore,a typical university teaching office building was selected as the research object.And the main factors affecting building energy consumption were researched based on the actual university energy use characteristics by spot investigation,theoretical analysis,experiments and numerical simulation.This thesis aimed to provide a theoretical and technical reference for domestic university buildings energy saving design and energy saving renovation of existing buildings.Firstly,universities in Chengdu were taken as an example.Spot investigation was conducted on several typical university teaching office buildings.Based on a comprehensive understanding of university teaching office buildings and their energy consumption characteristics,a case building was selected and tested for a continuous 10 days during the coldest and hottest months.Combined with the heat transfer theory and PMV-PPD index,the current indoor thermal environment,energy consumption characteristics,thermal performance of the envelope structure and the main energy influencing factors were analyzed.Secondly,based on the tested data,the influence and relationships of thermal performance of different envelope structures on energy consumption were simulated and analyzed by using building energy simulation program Energy Plus.Finally,based on the above analysis,considered the construction difficulty,existing materials,material cost,and energy saving rate,an optimization strategy was proposed,and evaluated by using Energy Plus.The research results show that:(1)Under the natural conditions in winter and summer,the indoor thermal environment PPD index of university teaching office building is as high as 60%,and there is high demand for air-conditioning refrigeration and heating;(2)Compared with other walls,the internal thermal insulation wall saves more energy.Its heat load energy-saving rate is 2.1%～10.19%,and the total load energy-saving rate is 0.5%～2.3%;(3)Added on different types and thickness insulation materials,,the heat load energy-saving rate of exterior walls and roofs can reach more than 60%,the total load energy-saving rate gradually stabilizes when reach to 20%;(4)Considering the material cost and energy-saving effect comprehensively,there is an optimal value between the insulation material thickness and the unit building operating total cost.Under the optimal economic thickness,the energysaving rate is above 30%;(5)The exterior wall using external decorative materials with low solar radiation absorption coefficient can save about 10% of the total energy consumption per year;(6)It is more energy-saving to choose K and SHGC value between 2.5～3.5 and0.1～0.5 for the exterior windows,which can save 30% heat load and 15% total load;(7)Selecting a material with a lower solar radiation absorption coefficient on the outer surface of the roof can save about 8% of the cooling load and about 3% of the total load;(8)After the comprehensive optimization strategy is adopted for the exterior envelope structure,compared with the present situation,it can save about 18% of the heat load,about 33% of the cooling load,and about 28% of the total load.The energy-saving effect is obvious;(9)Replacement of energy saving lamps in the lighting system can save about 27% of lighting electricity every year.And based on it,add intelligent control system can save about 50% of lighting electricity.The research conclusions and optimization strategies of this thesis can provide data support and theoretical reference for the energy-saving design of university buildings and the energy-saving reconstruction of existing buildings in Chengdu area.