| With the development of society,the Chinese government has increased its focus on environmental protection and reduction of energy conservation.Energy consumption of building accounts for about 20%of the total energy consumption,therefore how to reduce energy consumption and pollutant emissions of building has become a significant research topic.Solar energy is well known as a clean energy which has advantages such as zero-pollution,wide-range and low-cost.Building integrated solar technologies are not only able to reduce the annual energy consumption of the building but also drop the energy proportion of the traditional fossil energy.Hence the faced problems can be solved by the building integrated solar technologies,which include three key methods:building integrated photovoltaic,building integrated thermal and building integrated photovoltaic&thermal.China has vast territory and diverse climate,energy demand of buildings in different regions,seasons and climates are also different.In order to satisfy seasonal demand of the building’s energy consumption,system is not only required to offer space heating in winter but also provide thermal protection in summer to avoid overheat problem.Heating load in winer and cooling load in summer should be decreased simultaneously.The traditional technologies mentioned before are not able to face this challenge.Therefore,a series of improvement studies on the traditional building integrated solar technologies are carried out in this article,the contents are as follows:(1)A hybrid tri-functional solar thermal storage wall system is introduced.There are two working modes:BIPV-Water mode and BIPV-Air mode in order to meet the seasonal requirements of the building.In heating season,the system operates BIPV-Air mode,which is able to provide space heating and generate electricity availably at the same time.In non-heating season,BIPV-Water mode is conducted,system is able to create hot water at useful temperatures and generate electricity efficiently,meanwhile overheat problem is able to be prevented.Based on the experimental results,thermal efficiency and electrical efficiency under BIPV-Water mode are 47.0%and 7.6%respectively,the daily electrical generation is 0.12 kWh.Meanwhile overheat problem is proved to be prevented during the test.The experimental results in BIPV-Air mode proves the daily electrical efficiency and generation are 12.5%and 0.65 kWh respectively.The average temperature of experimental room is 6.6℃ higher than the reference room,which proves the passive heating is achieved during winter test.(2)Mathtatical model of the hybrid tri-functional solar thermal storage wall system under BIPV-Water and BIPV-Air mode are established respectively.Accuracy of the model is verified by the experimental results.Based on the simulation study,the optimum water flow rate in summer is around 0.04 1/s.With the increase of the coverage area,the room air temperature decrease in summer,which proves cooling load can be decreased by the system.In winter mode,based on parameter analysis,the optimum aspect ratio of the system is between 2:1 and 3:1.Annual performance of the system in three typical cities are conducted by simulation research,annual electrical efficiency in Beijing,Hefei and Xining are 11.2%,10.6%and 12.1%respectively.Annual electrical output in three cities are 247.70 kWh,152.60 kWh and 268.40 kWh separately.Annual heating load in three cities are 2112.60 kWh,1482.20 kWh and 3656.10 kWh respectively.Solar fraction in three cities are 49.9%,38.7%and 41.3%respectively.Energy provided by solar energy for hot water generation in three cities are 79.1%,66.8%and 60.4%separately.Energy blocked by the system during summer in three cities are 18.40 kWh/m2,20.20 kWh/m2 and 9.20 kWh/m2 respectively.The annual energy saving in three cities are 2661.80 kWh,1908.40 kWh and 2412.30 kWh separately.Based on simulated results in Beijing,electrical output of the external system is 17.7%higher than internal system.The external system is also able to provide space heating in winter’s daytime.But in summer,external system can only produce 100 1 hot water,reduced by 50%.The annual electrical output of CdTe and Si solar cells are 216.50 and 247.70 kWh respectively,but considering several advantages of CdTe,this new thin film solar cell has great potential in BIPV/T field.With the insulation material installed on walls,annual energy load of the building is reduced significantly.(3)A dual-channel solar PCM thermal storage wall system is putting forward.This system has the following independent functions:passive heating,heat preservation,heat insulation and passive cooling.The system is not only able to provide space heating all day long in winter,but also can decrease cooling load of the building in summer.With phase change material,the function of energy shift and regulation in the building is possible.In the summer’s experiment,the average air temperature difference between experimental and reference room is small,which proves the system is able to avoid overheat problem.During three-day test,the time when experimental room reaches the maximum temperature are 46,42 and 24 minutes later than the reference room,which proves the system can delay the time when maximum cooling load shows up.During winter’s experiment,average room air temperature of experiment and reference room are 16.6℃ and 9.8℃ respectively,with the temperature difference of 6.8℃.Maximum temperature of experimental and reference room are 38.4℃ and 18.7℃respectively,with the temperature difference of 19.7℃.These prove the system is able to provide space heating efficiently.From 16:00 to 24:00 of the third day,temperature difference between south wall with and without the system is 2.8℃,which proves PCM is able to heat the room during the nighttime continually.Based on the experimental results,rationalization hypothesises are proposed for double air channel structure and PCM plates respectively.Mathematical models of the system under different modes are established and verified by the experimental results.(4)A tri-functional dual-channel solar PCM storage wall system is investigated.This system integrates the advantages of the two previous systems,therefore this system is more compact and functional than the previous two systems,and energy demand of the building can be better satisfied.There are three working modes aiming at summer,winter and transition season respectively.Based on twice experimental results during transition season,the electrical output and efficiency in these two experiments are 0.61 kWh,11.6%and 0.59 kWh,11.7%separately.Thermal efficiency is around 55%,and the final water tank temperature is over 50℃.The average air temperature of the experimental room is lower than the reference room during the daytime,this proves the system is able to avoid over heat problem during the daytime of transition season.In the nighttime of transition season,temperature of south wall with the system is 1.4℃higher than south wall without the system.As for the room air temperature,the maximum air temperature between the experiment room and reference room during the night is 1.4℃,and the average temperature difference is 0.7℃,which proves PCM plates release energy in the night continuously.In winter’s test,the electrical power and efficiency are 0.67 kWh and 12.3%respectively.The maximum air temperature difference between the experiment room and reference room is 10.8℃ in winter’s daytime.In winter’s nighttime,take the first day as an example,the PCM plates are able to heat the experiment room from 16:00 to 24:00,and during this time average temperature difference between the experiment and reference room is 1.4℃,which proves the system can heat the room continually. |
PDF Full Text Request