Analysis of factors influencing the annual energy production of photovoltaic systems

Abstract

The most relevant basis for designing photovoltaic systems is their annual energy production, which is also the best metric for monitoring their long-term performance. An accurate array performance model based on established testing procedures is required to confidently predict energy available from the array. This model, coupled with the performance characteristics of other baiance-of-system components, provides the tool necessary to calculate expected system performance and to compare actual versus expected energy production. Using such a tool, this paper quantifies the affect of the primary factors influencing the dwnergy available from different photovoltaic module technologies. and contrasts these influences with other system-level factors that oflen result in significanUy less acenergy delivered to the load than the array is capable of providing. Annual as well as seasonal energy production is discussed in the context of both grid-tied and stand-alone photovoltaic systems.

The effect of uncertainty in modeling coefficients used to predict energy production using the Sandia Array Performance Model

“…As previously reported, the effect of temperature coefficients on predicted annual energy production for mc-Si is different for Albuquerque as compared to Buffalo, NY, where it's much colder and less sunny [3].…”

“…This study specifically addresses only variation in temperature coefficients and coefficients relating the behavior of Vmp and Imp to solar irradiance. As discussed elsewhere, there are many other factors influencing both the DC performance characteristics of a PV array as well as the AC performance of the overall system [3]. All of these factors must be considered in modeling or monitoring PV system energy production.…”

“…This paper documents the impact of uncertainty associated with five model coefficients used in the Sandia Photovoltaic Array Performance Model [1]. Previous work has already put some bounds on the effect of the temperature coefficients relative to other system level factors in determining ac-energy available from PV systems [3]. We use the model to calculate the range of predicted annual energy production from three small systems installed at Sandia National Laboratory's outdoor test site as a way of estimating the impact, or sensitivity, of each coefficient on the model residuals.…”

Photovoltaic array performance model.

“…So, the spectral influence illustrated at air mass values higher than 3 is of somewhat academic importance for the system designer. As documented elsewhere [1], the cumulative effect of the solar spectral influence on annual energy production is typically quite small, less than 3%. Nonetheless, using our modeling approach, it is straightforward to include the systematic influence of solar spectral variation.…”

“…The performance model can be used in several distinctly different ways. It can be used to design (size) a photovoltaic array for a given application based on expected power and/or energy production on an hourly, monthly, or annual basis [1]. It can be used to determine an array power 'rating' by 'translating' measured parameters to performance at a standard reference condition.…”