1.6.2 Photovoltaic (PV)
Convert sun light into electricity, based upon current PV module technology.
(a) Thin film PV modules are flexible, light weight , and available in different levels of transparency. They can be integrated into glazing units or applied to exterior surfaces. (b) Single (mono) crystalline modules are thin wafers cut from a single cylindrical crystal. The cells may be round to minimize waste or they may be trimmed into other shapes. Because each cell is cut from a single crystal, it has a uniform dark blue color. (c) Polycrystalline cells have a jumbled look with many variations of blue color like sheets of gemstone.
Seek strategies that integrate PV technology at highest design and aesthetic standards. Determine the client’s motivation and define project goals: Is the primary goal to generate electricity at the highest possible churn, or is it motivated by brand perception and marketing -- or both? Conduct a solar analysis to quantify solar exposure and determine the most energy and cost-efficient type of PV for your project.
The cost of PV is coming down, especially in the energy-cost competitive environments of developing nations. Capitol cost for Thin-film PV is roughly 35% of the cost of crystalline cells, based on the current US-market. Additionally, solar developers lease roof areas for PV installations, providing free equipment, installation, and maintenance at reduced energy cost to building owners.
Vertically installed thin-film PV panels, are 50% less efficient than crystalline cells, but are also much more forgiving toward solar harvesting from oblique angles. Light from overcast sky conditions and even reflecting light from neighboring buildings can be harvested. Diffuse day lighting affects their output performance only marginally. From an aesthetic point of view, thin-film panels are valued for their homogenous and minimalist appearance and can be laminated right up to the edge of glass. IGUs with an integral thin-film application of surface #2 not only generate electricity but achieve a SHGC of 0.1, equivalent to exterior shading. (Source: Schott, ASI Glass) Crystalline cells, by contrast, come in rigid, cell-specific shapes and frames and offer less aesthetic choices. They rely on direct sunlight exposure and their optimum orientation for locations in the northern hemisphere is toward south, and at an angle of 30deg from the horizontal.
For crystalline cell technology to perform at its best ensure that the system is unshaded during the peak solar collection period: three hours on either side of solar noon. In addition, ensure good ventilation behind the PV-module. Cold, clear days will increase power production, while hot, overcast days will reduce array output. Manufacturer requirements and performance data vary. Check for performance criteria, electricity output, availability of standard and custom modules, sizes, product testing and performance, materials recycling, and waste minimization. For aesthetic reasons when using crystalline PV products seek-out “frameless” modules. Quality and performance reliability have suffered over the recent years. Compare manufacuters' warranties and inquire about panel failure rates.
1.1.3 Building Orientation; 1.4.8 Solar Hot Water; 1.7.3 Solar Cooling; 1.7.9 Active Solar Heating; 1.8.3 Phase Change Material