Photovoltaic modules can be integrated in buildings to form part of the exterior envelopelayer. Considering the thermal energy captured by the building integrated Photovoltaic (BIPV)system, their cost-effectiveness is thus improved in comparison with stand-alone systems thatneed a separate support structure. Their electrical conversion efficiency, which is presentlyaround 6-18%, is rather low in comparison with the potential thermal efficiency 50%-70% inthe BIPV-thermal system. Approximately 70-80% of the solar radiation incident on PV panelsis lost by convection and infrared radiation to the outdoor environment (Liao and Athienitis2005). z)NS"n
p:e%X M6r0 C&z,g)h I1w B0By placing the PV modules in the layer of a double façade (attached to the inner or outerglazing), and passing fresh air through the glazing cavity, we achieve the twin objectives ofcapturing much of the absorbed solar energy that would otherwise be lost to outside, whilecooling the PV panels and thereby raising their electrical conversion efficiency. Thus, thewindow or double façade generates both electrical and thermal energy and may also transmitsome daylight if semitransparent PV is utilized. The energy efficiency is greatly increased byusing this BIPV thermal system.绿色建筑博客 p a_9T-c9y;S9m ~/H'w/J 绿色建筑博客*r5YK;`+|&j&y,I Having noticed the great potentials of the BIPV system, many researchers have developedvarious models to study the electrical performance and thermal behavior in the BIPV system.At Concordia’s test facility, two configurations of BIPV are investigated (Figure 1). The first,depicted as Configuration 1 in Figure 1 (left), has the PV on the lower half of the façade,facing the outdoor environment directly. The second, depicted as Configuration 2 in Figure 1(right), has the PV on the lower half of the façade, but placed in the middle of the cavity,permitting air to flow on either side, or both sides at the same time. Both of these BIPV/Tsystems are connected in parallel to a computer-controlled variable speed fan with motorizedinlet dampers. In this thesis, we focus on quasi-steady state performance within 2-3 hoursfrom solar noon in winter and spring in Montreal. Moisture effects are negligible during thisperiod and are not considered in this thesis. Another part of this project will study integrationwith HVAC systems and control of the inlet damper and variable speed fan to achieve desired3average air velocity and supply temperatures. Charron and Athienitis (2003a,b) reported thatwhen the PV modules were installed in the middle of the cavity, as in Configuration 2, the PVsection overall average efficiency was up to 25% higher than if they were installed as inConfiguration 1. However, electricity generation was 21% lower as the extra glazing reflected asignificant portion of the solar radiation out of the system at low angles of incidence and thePV panel was hotter. With the addition of fins to maximize heat transfer from the PV, bothconfigurations could provide combined thermal-electric efficiencies of over 60% (Charron and Athienitis 2003a).绿色建筑博客 O'np8V F gD 
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XmM L0绿色建筑博客-Y@ }A] N Figure 1.1: Schematic of two configurations of BIPV system in Concordia University (leftside using Photowatt panels and right side using Spheral Solar panels) (Charron andAthienitis 2003a)绿色建筑博客+W4t `\
S,V w zPA6Hb0However, among these models, the key parameter which is the convective heat transfercoefficient is not accurately generated. Since the PV panel has geometrically increasingtemperature according to height, and the coupled radiation-convection heat transfer happensinside the cavity, the convective heat transfer coefficients from the literature can hardly fit intothis specific case. Some detailed fluid dynamics model coupled with heat transfer equation isthus needed to provide proper heat transfer coefficient for this photovoltaic integrated air flowcavity.绿色建筑博客a_;k'f1iY |
