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Power – Photovoltaic – Commercial – Performance analysis / Canada

Template assignment

Photovoltaic panels with a total capacity of 25 kW were installed on a roof near Toronto Buttonville airport, Ontario, Canada. The panels slope is 15º and the azimuth is 30º. The supplier estimated that the annual production will be 28,000 kWh in a normal (average) year. The facility operator would like to know if snow accumulation during winter affects the amount of electricity produced by the photovoltaic system. Using RETScreen Plus, calculate the actual production losses since the initial installation of the system due to snow accumulation on the photovoltaic panels. Also, calculate the photovoltaic electricity production losses due to snow accumulation for a normal (average) year.

Teacher's notes

Follow these steps:

Start

►Select climate data for Toronto Buttonville Airport

Data

Step 1 - Production: Import photovoltaic electricity production data (Template_PV_Commercial_Performance_Analysis_Canada.csv)
Step 2 - Factor of influence: Download NASA weather data
Step 3 - Data processing:
a. Calculate daily solar radiation on the tilted surface
b. Merge tilted daily solar radiation weather data into the electricity production data table

Analytics

Whole data set: 2007-2011

Step 1 - Baseline: Establish the baseline based on the entire duration of the data set using the regression analysis
Step 2 - Target: Set the target to 0 or skip this step
Step 3 - Comparison:
a. Generate a CUSUM graph
b. Generate a control chart

2008 – No snow cover

Step 1 - Baseline: Establish a second baseline based on months without snow accumulation in 2008 using the regression analysis
Step 2 - Target: Set the target to 0 or skip this step
Step 3 - Comparison:
a. Generate a CUSUM graph
b. Generate a control chart
Note: The photovoltaic electricity production losses due to snow accumulation on the photovoltaic panels are represented by negative slopes in the CUSUM graph; while the periods where the slope is 0 show that the energy performance of the system is as predicted by the baseline regression analysis.
►Tools - Graph:
a. Generate a time series graph showing the actual electricity production and the predicted electricity production without snow. The user can insert a new column in the Data worksheet and calculate this value using the 2008 – No snow cover baseline equation.
b. Generate a climate data graph showing the normal (average) daily solar radiation on a horizontal surface for this location

The 2008 – No snow cover CUSUM graph shows that, for 2009, 2010 and 2011, the combined actual photovoltaic electricity production for these 3 years was approximately 7,400 kWh less than what was predicted by the 2008 – No snow cover correlation. This represents approximately 2,465 kWh per year difference. It is assumed that the electricity production loss is mostly due to snow accumulation on the photovoltaic panels.
 
The table below is generated for a normal (average) year using RETScreen Version 4 Photovoltaic Power Model for the slope and azimuth of the photovoltaic panels at the project location.

Applying the regression equation for the whole data set to the normal (average) year daily tilted solar radiation, the predicted photovoltaic production is 21,200 kWh. Using the 2008 regression equation for the normal year daily tilted solar radiation, the predicted photovoltaic electricity production is 24,800 kWh. In other words, this analysis indicates that the losses due to snow accumulation on the panels during the winter months in a normal (average) year is approximately 3,600 kWh or 14.5% of the predicted photovoltaic electricity production for this particular photovoltaic power system. Note that this snow accumulation might be due in part to the relatively low tilt angle of 15º for the photovoltaic panels.

Reporting

Step 1 - Report: Create a report for managers
Step 2 - Edit: Insert an optional text page to describe the analysis
Step 3 - Output: Export the report in PDF (*pdf) format

Solution

The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.