Optical model for multilayer glazing systems: Application to laminated glass and photovoltaic modules

Abstract

This article provides theoretical developments broadening the scope of previous optical simulation models for multilayer glazing systems. The applicability of existing models will be extended through additional characterization of the multilayer optical components from global spectrophotometric (UV-Vis-NIR) measurements. A more complete interlayer film characterization, including reflectivity in the film-glass interface, will be provided. Singular solutions of the related equation systems will be derived for situations involving components with very low or null transmissivity. As a contribution to the fundamentals of the formalism, the condition relating the symmetry of the transmittance of the system with the symmetry of the transmissivity of its optical components will be studied. Finally, with the extension for the calculation of energy fluxes through the components of a multilayer system, analytical expressions for the components absorptivity will be derived. These results are particularly useful to quantify differences in energy absorption of the constituents of a laminated glass, as a tool to define, from the glazing design phase, the thermal and mechanical processing needed for each glazing component. Additionally, the model provides a procedure for the calculation of the absorptivity of encapsulated photovoltaic cells, which is directly related to cell efficiency in each particular configuration.

Optical model for multilayer glazing systems: Experimental validation through the analytical prediction of encapsulation-induced variation of PV modules efficiency

“…This magnitude is intrinsically associated to the cell, so that once it has been determined for a specific encapsulation scheme, it can be used for the calculation of any other configuration of the same type of cell and similar refractive index of superstrate and polymer film. It can be shown (Rubin, 1982;Baenas and Machado, 2016) that typical polymeric encapsulation materials have close refractive indexes, also similar to those of, e.g., soda-lime glass substrates.…”

“…Following Baenas and Machado (2016), the opaque cell may be described within this formalism by means of a virtual internal coating component, which allows the introduction of (front) reflectivity inside the system ( ), shown in Fig. 1.…”

“…The theoretical problem of the distribution of the short-wave absorptivity inside an incoherent optical system with planoparallel optical interfaces, with application to glazing systems energy performance, has been recently revisited by Baenas and Machado (2016). This approach is based in a convenient use of the classical matrix transfer methods, limited to the usual modeling features of the standards (ISO 9050, ISO 15099, etc.…”

“…The absorptivity of the opaque component is then obtained as a function of this reflectivity. The corresponding equations were obtained in summary form by Baenas and Machado (2016), for a typical photovoltaic (PV) module (encapsulation materials -glass and polymer -and opaque PV cell).…”

“…As an alternative to numerical approaches, the specific analytical expressions from the optical model of Baenas and Machado (2016) for the determination of the energy absorptance of encapsulated PV cells are applied in this paper to crystalline silicon and CIGS cells in combination with extraclear (low-iron), float and thin glass as covers, together with thermoplastic polyurethane (TPU) and ethyl vinyl acetate (EVA) as encapsulation materials. The results of the optical model are compared with the corresponding experimental short-circuit current values as obtained from External Quantum Efficiency (EQE) measurements.…”