Building a standard approach for luminescent solar concentrator performance evaluation : enabling design flexibility and annual energy production forecasts

Abstract

The use of photovoltaic (PV) solar energy technologies has grown substantially over the past ten years, and an increasingly sophisticated industry has developed. Yet, even as the solar industry has become more adept at handling complexity, building-integrated photovoltaics (BIPV) have remained a niche portion of the industry due largely to the difficulty of creating solar products that can double as effective building products (and vice versa). Unlike other energy-harvesting building products, luminescent solar concentrators (LSCs) are solar devices that focus sunlight through red-shifted internal reflection towards solar cells that make up only a part of their overall structure. This fundamental difference allows LSCs to increase solar cell power output per unit area, while offering additional design flexibility relative to other forms of BIPV. A myriad of LSC geometries have been studied in the literature, incorporating various absorbing-emitting luminescent materials, emulating a vast host of distinct building products, and asserting the potential to overcome many of the architectural challenges associated with BIPV. Radiative transport modeling is at the core of the analysis, design and optimization of LSC devices. However, just as there are many forms of LSCs, there is also a corresponding, growing list of disparate Monte Carlo (MC) ray-tracing, modeling tools that are specific only to particular LSC configurations. Furthermore, despite the fact that power generation is at the core of what differentiates BIPV, annual energy estimates have largely remained unavailable for LSCs. Therefore, to overcome these challenges, this thesis proposes a standard approach to forecast annual LSC power generation, enable design flexibility through a generalized, open-source MC ray-tracing tool, and evaluate the fundamental trade-offs associated with a device that is both a solar product and a building product. To illustrate the potential of LSCs as BIPV, an analysis that demonstrates periodic performance estimates for vertical installations of wedge-shaped LSCs and solar panels is provided, highlighting the unique behavior of such LSCs on a daily, monthly, and yearly basis. Next, an MC ray-tracing tool capable of handling a wide variety of LSC geometries is described in extensive detail and is validated against experimental data for both planar and wedge-shaped LSCs under a variety of incidence angle combinations. Following this, conventional methods to evaluate annual solar panel power generation are combined with two primary metrics, LSC optical efficiency and LSC spectral mismatch factor, to estimate annual energy production for LSCs. Lastly, surrogate-based optimization is employed to minimize the levelized-cost of electricity (LCOE) of both mirrored and transparent LSCs as a function of LSC geometry and composition.