ANALYSIS OF HISTORICAL ENERGY ESTIMATES FOR 235 PV SYSTEMS INSTALLED FROM 2007 TO 2011 IN THE USA

摘要

SunEdison pioneered the power purchase agreement (PPA) for PV systems during the last decade inthe United States. The third-party investors who provide financing for the projects require an Independent Engineer(IE), or Technical Advisor, to conduct an initial estimate of the system’s performance over the duration of the PPAcontract. SunEdison retains monitoring and operation of these systems and is able to compare actual performancewith the initial estimates. In this work, we compare energy and performance estimates from a single IE firm for 235projects constructed between August 2007 and December 2010 and operated by SunEdison in the United States. Thestudy looks at the evolution of the various simulation assumptions over time. These 235 projects represent a total of78,337 kWp spread across 12 states with the majority of projects in California (100) and New Jersey (58). Thisportfolio of projects consists of 197 rooftop projects, 30 ground-mount projects, and 8 parking canopy projects. Wehave established an Investor Performance Index (IPI), the ratio of the delivered energy from the solar plant versus thepredicted energy, and the Operational Performance Index (OPI), which is an insolation-adjusted performance index.Utilizing the OPI, this paper examines the evolution of the estimates and the corresponding performance of thesystems as well as whether estimation capability has improved over time. Our analysis shows a steady improvementin the predictions of the particular independent engineer but also highlights the challenges in expanding the scope ofsuch a study.