Thermal comfort in a building with Trombe wall integrated with phase change materials in hot summer and cold winter region without air conditioning

Trombe wall and phase change materials(PCMs)are two effective ways to regulate indoor thermal comfort.However,Trombe wall surfers from overheating in summer and PCMs suffer from low heat transfer rate caused by the limited thermal conductivity.To compensate the shortcomings of the two methods,this paper proposed a Trombe wall system integrated with PCMs.Based on a light-weight building envelope in Changsha,China,the thermal comfort of 10 kinds of Trombe wall systems with PCMs with a melting temperature of 18-28℃ were studied.Taking the integrated indoor discomfort duration(I_(D)),integrated indoor discomfort degree-hour(I_(DH)),indoor air temperature(T_(in)),PCM liquid fraction(γ)and heat flux across wall(q)as evaluation indexes,the indoor thermal comfort was assessed in hot summer and cold winter region.Results show that the Trombe wall helped PCMs complete the phase change process effectively.Trombe wall with PCM25 next to the wall inner surface possessed the lowest annual I_(D) and I_(DH),as 2877 h and 12,974℃·h,respectively.Compared with the values in a traditional building,the I_(D) and I_(DH) were reduced by 7.01% and 14.14%.In order to give full play to the heat storage and heat release of the Trombe wall with PCMs,PCMs with phase change temperature 7℃ lower than the peak ambient temperature in summer or 8℃ higher than the winter night temperature was recommended according to regional climate conditions.

Exploring the impact of evaluation methods on Global South building design—A case study in Brazil

Energy simulation is a valuable tool for evaluating and improving the thermal performance and energy efficiency of buildings during the design phase.Common evaluation methods are thermal load(TL),degree-hour(DH),and design days(DD).The choice of method and its settings may vary depending on regional factors and researchers’preferences,leading to diverse and often incompatible metrics and results.Therefore,this study aims to investigate the influence of these evaluation methods on the assessment of buildings’performance and,consequently,on design choices.For this purpose,this study compared the results of the 3 evaluation methods and different settings for 3 different wall systems,4 ranges of comfort temperature,and 2 residential models located in the 8 Brazilian bioclimatic zones.As result,the best and worst wall systems varied depending on the evaluation method and the threshold/setpoint temperature range considered.Warmer regions showed greater variability in the results.We noticed that it is not possible to compare and interpret results from different evaluation methods,and that the variation of only 1℃in the setpoint temperatures can lead to entirely different practices being considered the best for a given building model.In conclusion,the most suitable evaluation method is the one that best portrays the operation and dynamic reality of the building to be designed,and building regulations and standards can occasionally lead to unrealistic assessments.

Climatic zoning for energy efficiency applications in buildings based on multivariate statistics:The case of the Brazilian semiarid region

This study aimed to propose climatic zones in the Brazilian semiarid region using multivariate statistical techniques and to characterize these zones for energy efficiency applications in buildings.Principal component analysis(PCA)was used to select the variables with the greatest practical relevance.From this selection,hierarchical cluster analysis(HCA)was used to spatially define climatically homogeneous zones.For each defined zone,the most feasible constructive thermal conditioning strategies were defined,and the thermal indexes of heat and degree-hours of cooling and heating were calculated.As result,PCA reduced the dimensionality of the initial database from 104 to 48 variables,among which the climatic and bioclimatic variables related to temperature stood out.From the HCA,three climatic zones were defined for the Brazilian semiarid region.For all zones,there was a high demand for constructive conditioning strategies,which have to be adopted in more than half of the total annual hours.The proposed zoning is adapted to the climatic aspects of the Brazilian semiarid and has significant potential for applications in construction planning in this region.Moreover,the methodology presented can be applied for establishing climatic zones in other regions,which can contribute to increasing the energy efficiency of buildings.