Session: 03-03: Building Performance Simulations for Sustainable Solutions

Paper Number: 156776

156776 - Evaluating Vertical Building Integrated Photovoltaics With Standard Performance Metrics 

Abstract: 

Buildings are currently one of the major sources of greenhouse gas emissions. Legislations such as the Net Zero policy have been enacted to encourage the construction of energy-efficient buildings. Building Integrated Photovoltaics (BIPV) provides a viable solution to reach such goals. Traditionally limited to roof installation, BIPV faces difficulty when roof access is unavailable. Vertically mounting BIPV on building facades allows consumers greater installation flexibility and are gaining momentum.

However, there is a lack of information on standardized metrics for consumer BIPV product comparison. Since vertical BIPV installations are complex due to varying orientations, the need for established metrics is critical. This paper aims to highlight this need and provide metrics to compare BIPV products for vertical installations.

Outreach to several companies revealed limited responses and a lack of clarity in the information provided about the metrics they use. Some companies mention Standard Test Conditions or STC (an irradiance of 1000 W/m² perpendicular to the surface receiving light with an air mass of 1.5 and a cell temperature of 25°C) as a measure of product comparison while others use a radiance-based simulation tool to quantify their performance. Unfortunately, this information prevents consumers from making well-informed decisions.

Metrics such as energy production ratios, specific yield, and performance ratios can provide comparable results. Energy production ratios help depict the energy at the maximum power point for optimum versus tilt angles for southern, eastern, and western orientation. Specific yield is a useful parameter widely used by professionals in the solar industry. It is the net energy output per nominal power at STC for a given amount of time. This provides consumers with a comparison of the actual energy production produced relative to the capacity of the PV system which shows the efficiency of the system. The performance ratio is defined as the specific yield per reference yield, it represents the ratio of actual energy over the energy at STC. It accounts for the losses in the system and helps consumers observe how well the system is performing.

To implement these metrics, weather data was accumulated from representative regions throughout the United States. Using pvlib, an open-source software used for PV systems, the data for each location was determined for south, east, and west orientation. The energy estimate code utilized the pvlib single diode model to forecast annual energy production at the maximum power point. Furthermore, the specific yield and performance ratio were calculated.

It was found that the annual energy production, specific yield, and performance ratio were the greatest at southern orientation as compared to eastern and western orientation in all regions. These values matched expected trends and were validated.

Overall, with the increasing need for vertical BIPV systems, there must be parameters through which consumers can rapidly assess system performance. The metrics reported in this work will help consumers make well-informed choices regarding BIPV systems.

Presenting Author: Hannah Arnow Rensselaer Polytechnic Institute

Presenting Author Biography: Hannah Arnow is a PhD Candidate in the Mechanical Engineering Department at Rensselaer Polytechnic Institute in Troy, NY. Her research focuses on improving Building-Integrated Photovoltaics (BIPVs) through Luminescent Solar Concentrators (LSCs) integrated with Asymmetric Light Transmitting (ALT) interfaces.