Solar radiation analysis can help with the design and layout of solar panels on your site and building. By maximizing the sun’s energy falling on a surface of a modeled solar panel, you can maximize energy generation potential.

Solar Radiation Analysis in Vasari for PV

If you model a specific panel array on your site or building, you can use the solar radiation tool to help predict its output and optimize it. By multiplying the incident solar radiation values by the solar panel’s assumed efficiency and the area of the array, you can estimate the power output.

• Cumulative radiation values will tell you the total amount you can generate over a given period, and how much energy you can save or offset during that time.
• Peak radiation values will tell you the most you can expect to generate, and is useful for knowing the most energy you’ll ever be able to draw from the system in real-time.
• Average radiation values can help you estimate a more stable power output you can expect from the system.

Example of determining PV potential on a specific panel array

1. Create the panel as a mass or object and place it on the desired surface of your building. It is important to include the tilt angle of the panel as well. (A rule of thumb is that the optimum tilt angle over the course of the year is equal to the site’s latitude).

Angled PV panel on a roof surface in Vasari.

2. Measure the incident solar radiation on the panel for the desired time period.

For example, the hourly average solar radiation for the winter months is 6.3 kWh/m2 (or 6.3 kW/m2, since the value is for one hour)

3. Multiply this value by the area of the panel to get the total radiation falling on the surface.

(6.3 kWh/m2) * (1 m x 2 m) = 12.6 kWh

Over this winter time period, we can say that 12.6 kW will fall on the panel’s surface in one hour.

4. Select an efficiency level for your panel and multiply it by the solar radiation on the face of the panel to get the expected electrical output. Vasari and Green Building Studio use the following values.

• 5% – Thin film panel
• 10% – Multi-crystal panel
• 15% – High efficiency panel

Once you determine expected output, multiply efficiency by the solar radiation value (12.6 kW) * (0.10 efficiency) = 1.26 kW 

PV Potential Numbers from Green Building Studio

You can use Green Building Studio’s Photovoltaic Specification Tool to determine how much energy solar panels could generate on your building, and determine the payback period.  This video, although it shows an older interface, shows you the basic tool available in GBS.

• The PV Potential calculation in Autodesk’s energy analysis tools are based on solar radiation analyses on the walls and roof of your building. Note that the calculations assume that the ENTIRE surface of the building is covered with solar panels (including lower efficiency building-integrated PV on the windows).
• This is useful for getting a sense of available energy, but should not be used to size the system because it takes the entire outer surface into account.
• This GBS-based calculation is also what’s behind the “Roof Mounted PV System” values in the Results & Compare tables in the energy analysis tools in Autodesk Revit and Vasari.