Modelling and evaluation of the performance of building-integrated open loop air-based photovoltaic/thermal systems

Building-Integrated Photovoltaic/Thermal Systems (BIPV/T) systems are photovoltaic installations incorporated as the exterior layer of the building envelope with the additional function of recovering thermal energy, which can then be used for space heating, domestic water heating and possibly for cooling. Some advantages of a BIPV/T system over an autonomous PV array include lower installation costs due to the replacement of cladding material, elimination of extra support structures and reduced electrical transmission losses. In addition, recovering the heat from the photovoltaic panels cools them and thus improves their electrical efficiency. Due to the novelty of BIPV/T systems, there is a need for the measurement of convective heat transfer coefficients and development of correlations for their prediction. The development of an integrated energy model, including correlations for the prediction of convective heat transfer coefficients in BIPV/T systems was one of the main objectives of this thesis. Accurate measurements of convective heat transfer coefficients have been carried out for two open loop BIPV/T configurations: smooth and ribbed. The BIPV/T systems were tested at 30°-45° tilt angles and had a length/hydraulic diameter ratio of 38 which is representative of roof applications. It was found that for the BIPV/T ribbed case, the calculated Nusselt numbers are on average 2.6 times higher than the Nusselt numbers predicted by the Dittus-Boelter correlation. Pressure drop measurements were performed for the two configurations and the results are presented in terms of the Darcy friction factors and compared to the Blasius equation. For both cases, the friction factors are higher compared to the ones predicted by the Blasius equation. Previous existing electrical photovoltaic models have been used to couple their features to the lumped parameter thermal network modelling approach used in this thesis. Two thermal network models, steady state and transient, have been developed in this work and validated against experimental data. The steady state model is useful for a quick evaluation of the thermal/electrical performance, while the transient model gives a more accurate representation of the system by considering the thermal storage capacity of the materials. Finally, conclusions and general recommendations and guidelines for the design and construction of BIVP/T systems are provide

Characterization and modeling of unsaturated water liquid transport in softwoods

Moisture sources in the building envelope are, in order of magnitude: rain penetration, moisture brought through air movement and moisture diffusion. As rain water impinges onto the wall and runs off the surface, water may seep into cracks and accumulate within the wood frame structure. Water can move by capillary action into wood-based components and the water vapor can also be diffusing through the structure. In the hygroscopic range, the theory has evolved considerably, and by the use of sorption curves, it is possible to explain the absorption of water in the vapor phase for a range of relative humidity (from 0 to 95% RH). However, liquid mass diffusivities of water for many Canadian wood species have not yet been investigated. The main objectives of this study are to quantify averaged values of diffusivities for a specific type of wood (jack pine), and to develop a transient modeling approach for liquid-phase water transport in wood considering the orthotropic effect of the wood structure and compare it to experimental results

Development and On-Field Testing of Low-Cost Portable System for Monitoring PM2.5 Concentrations

Recent developments in the field of low-cost sensors enable the design and implementation of compact, inexpensive and portable sensing units for air pollution monitoring with fine-detailed spatial and temporal resolution, in order to support applications of wider interest in the area of intelligent transportation systems (ITS). In this context, the present work advances the concept of developing a low-cost portable air pollution monitoring system (APMS) for measuring the concentrations of particulate matter (PM), in particular fine particles with a diameter of 2.5 μm or less (PM2.5). Specifically, this paper presents the on-field testing of the proposed low-cost APMS implementation using roadside measurements from a mobile laboratory equipped with a calibrated instrument as the basis of comparison and showcases its accuracy on characterizing the PM2.5 concentrations on 1 min resolution in an on-road trial. Moreover, it demonstrates the intended application of collecting fine-grained spatio-temporal PM2.5 profiles by mounting the developed APMS on an electric bike as a case study in the city of Mons, Belgium