Energy Efficient Building's Envelopes. Numerical and experimental analysis of innovative solutions

The aim of this study is to set up a simplified and validated numerical platform to describe several technologies concerning the energy performance improvements of glazed and opaque building envelopes. The study included the validation of DIGITHON, a detailed simulation software and the development of a simplified transient numerical model in respect of glazed buildings. DIGITHON, was validated against experimental data, and then a parametric study was carried out through it to evaluate the air pre-heat efficiency of implementing the façade as an energy recovery unit. The simplified model was dedicated to the thermal engineering designers dealing with projects preliminary phases .The simplified model was validated against experimental data. Later an extensive comparison between the detailed software DIGITHON and the simplified model was carried out for different climatic conditions to evaluate the influence of considering indoor zones thermal inertia. Although the simplified model estimates thermal loads higher than DIGITHON, nevertheless this can be considered a beneficial design safety aspect as long as it is implemented in the preliminary design phases. Later an innovative locating of photovoltaic modules at building glazed facades was investigated through the commercial software TRNSYS. The methodology of modelling double skin-glazed façades combined with different strategies of ventilation applying TRNflow software was thoroughly clarified. The results show a reduction in thermal heating loads compared to conventional location of PV on external building surfaces. On the other hand the cooling loads are increased, hence to improve the performance of the system in summer hot season, the technology of phase changing material (PCM) was tackled in the research as a latent thermal storage system. A numerical investigation of the effect of PCM in building sector, solely and combined with PV modules to improve its thermal performance, has been carried out. Two numerical models (equivalent capacitance and enthalpy linearization methods) describing the PCM thermal and optical performance have been developed and validated. Results show that thermal loads reductions of a system implementing PV/PCM modules reach 30% in summer season. Afterwards, the research through experimental campaign and numerical heat transfer modelling optimised the selection and location of two technologies within a residential roof attic: the technologies considered were PCM modules and reflective surfaces; five transient numerical models have been developed and validated. The results clarify the influence of the proper selection for melting-solidification PCM range suiting each application in order to reach optimum specific heat capacity values which could improve the overall thermal balance of the inner zone. Finally, computational fluid dynamics CFD models have been applied to different case studies to describe the thermal performance of vertical glazed envelopes

Implementation of integrated wireless sensors technology in renovation of social housing buildings. A Danish case study.

Social housing units built in the 1960s and 1970s make up one-fifth of all housing units in Denmark. Their renovation is an important step towards meeting the goals of the national energy road map. Sensors based on wireless technology could be considered a feasible solution to increase occupant’s awareness towards their indoor climate and their energy consumption. In the present experimental study, a framework implementing wireless sensors to monitor energy and indoor climate before and after renovation has been applied in two apartments of a Danish social housing site. In the first phase of the study, the accuracy of some commercially available wireless systems was investigated. This was followed by installation in the field, where occupant behavior (e.g. window opening status) was also monitored. Heating energy data monitored before and after renovation indicated savings of up to 34%

PV-PCM integration in glazed building. Co-simulation and genetic optimization study

The study describes a multi-objective optimization algorithm for an innovative integration of forced ventilated PV-PCM modules in glazed fa\ue7ade buildings: the aim is to identify and optimize the parameters that most affect thermal and energy performances. 1-D model, finite difference method FDM, thermal resistances technique and enthalpy method were applied to describe different fa\ue7ade solutions and transient thermal performance of PCM. The coupling between the PV-PCM fa\ue7ade code implemented in MATLAB and the TRNSYS software was developed to estimate the dynamic thermal energy profiles. An exploratory step has also been considered prior to the optimization algorithm: it evaluates the energy profiles before and after the application of PCM to PV module integrated in glazed building. The optimization analysis investigate parameters such as ventilation flow rates and time schedule to obtain the best combination suiting the PCM performance and external-internal loads. A group of solution were identified on the Pareto front. Savings in thermal loads for the best individual reached 26.4% while the best in temperature increment in operating temperatures was recorded as 6.8% comparing to the design set temperature

Advanced R744 solution for supermarkets, hotel chillers and maritime applications in India

R744 integrated systems can meet oscillating heating and cooling demands efficiently and become a game changer in countries such as India. The present work aims to develop and present R744 system designs and disseminate the knowledge under the framework of the INDEE+ project in India, with the focus on three vital sectors: supermarkets, hotels, and seafood industries. Ejector-supported R744 systems are observed to be an ideal solution to increase the R744 system efficiency at high ambient temperature operations as in tropical regions. The strategy is also to evaluate the system operations to deal with an individually proposed R744 system performances to fulfil the thermal load handling demand on both heating and cooling side. Furthermore, students, vendors and end-users are planned to train by utilizing the upcoming demonstration sites with R744 technology. Support is being provided to communicate and finalize the R744 system design specification for the various system configurations. Each development aspect will be evaluated critically to make the proposed R744 technology demo units a success and to become flagship developments supporting India to transfer towards clean cooling and heating technologies.Advanced R744 solution for supermarkets, hotel chillers and maritime applications in IndiaacceptedVersio

Development of intermediate layer systems for direct deposition of thin film solar cells onto low cost steel substrates

The functionalisation of low-cost steel over large areas with low cost intermediate layers (ILs) for utilisation as substrates in thin film solar modules is reported. Three approaches for the deposition of ILs are demonstrated and evaluated; a thick SiOx sol–gel based on a one-step acidic catalysis applied by spray technique, a commercial screen-printable dielectric ink, and an epoxy-based material (SU8) deposited by screen printing or bar coating. These ILs demonstrated the properties of surface levelling (quantified by mechanical profilometry), electric insulation (tested using breakdown voltage and leakage current) and acted as an anti-diffusion barrier (demonstrated with glow discharge mass spectrometry). Moreover, the performances of amorphous silicon (a-Si:H) and organic photovoltaic (OPV) thin film solar cells grown on carbon and stainless steels (a-Si:H: 5.53% and OPV: 2.40%) show similar performances as those obtained using a reference glass substrate (a-Si:H: 5.51% and OPV: 2.90%). Finally, a cost analysis taking into account both the SiOx sol–gel and the dielectric ink IL was reported to demonstrate the economic feasibility of the steel/IL prototypes

PV-PCM integration in glazed buildings. Numerical study through Matlab/Trnsys linked model

The paper describes the implementation of a 1-dimensional transient model based on the enthalpy method to analyse the thermal behaviour of a Phase Change Material (PCM) layer integrated in a window. The model and algorithm have been validated by comparison with experimental data. The model has then been expanded to couple a PV layer with the PCM layer. The complete model is implemented in MATLAB and linked to TRNSYS in order to estimate the dynamic thermal energy demand of a building equipped with a double skin fa\ue7ade with a PVPCM layer in a ventilated cavity. A parametric study was carried out, investigating three different cavity ventilation strategies for two European cities (Venice and Helsinki). The results show that, when the PCM layer is coupled with the PV layer, in Venice the cooling energy demand is 60 % lower, while in Helsinki the heating demand during the winter season is 36 % lower

A simplified mathematical model for transient simulation of thermal performance and energy assessment for active facades

The extended use of double skin fa\ue7ade (DSF) in different kinds of buildings imposes HVAC (Heating Ventilation Air Conditioning) designers to use quick and accurate software to help in taking the right decisions related to energy consumption and thermal comfort. The lack of such methods was the motive to present this paper. Validation of a simplified mathematical model for dynamic simulation of the thermal performance of DSF was presented by comparing results with another detailed simulation model DIGITHON, for a complete year. Moreover the mathematical model was developed to calculate thermal energy due to convection losses from outer facade layer, solar gains and internal loads. A more detailed comparison of energy consumption at different climatic conditions of four cities in Europe has been shown. Implementation of the simplified model in thermo-active-building-system-(TABS) also was illustrated, and how such a model could be useful in one of four methods mentioned in standard ISO-11885-4 to predict heat transfer on TABS. This particular method needs the solar gains and losses due to transmission determined with a constant room temperature by another software which the mathematical model could be implemented in