Modeling of Snow-Covered Photovoltaic Modules

Accurate modeling of photovoltaic (PV) modules is required to predict performance of PV systems in various climatic conditions, often far different than manufacturer specifications. Snowfall during cold months reduces output of PV modules. As the application of PV systems is increasing in cold areas, it is vitally important to address this issue through an appropriate method capable of estimating PV performance due to snow effect. This paper proposes a novel PV modeling approach that can represent instantaneous electrical characteristics of PV modules in the presence of uniform snow coverage. The proposed model utilizes the Bouguer-Lambert Law to estimate the level of insolation reaching surface of snow-covered PV cells. This is achieved by introducing an extinction coefficient which depends on the snow properties. To study the efficiency of PV cells at low insolation levels, a two-diode equivalent circuit model is employed. The simulation results of the proposed model are validated with experimental measurements from field tests for different commercial PV modules as well as real data collected by the SCADA system of a 12-MW grid-connected PV farm. Good agreement was observed between power generation results estimated from the proposed model and those obtained experimentally on snow-covered PV systems. This model would be helpful for researchers and PV systems developers in cold regions.

I. Introduction

Photovoltaic (PV) systems have quickly increased all over the world as one of the most promising alternative energy technologies. The majority of PV systems are installed in regions of the world which experience cold winter and snow like Germany, Czech Republic, Japan, the USA, and Canada [1] . Moreover, solar energy industry is growing rapidly in these countries. For instance in Canada during 2009–2013, the installed capacity of solar PV grew from 95 MW to 1210 MW [2] , and it is envisioned that the capacity of solar electricity will increase to 6300 MW by 2020 [3].