How do we model shading?

A bit of background

Most Australian roofs experience little to no shading, making them ideal for rooftop solar. However, some roofs can experience a significant amount of shading at different times of the day and over different points of the year. As solar panels don’t work very well in the shade, this shading will reduce the amount of energy produced (which will have an impact on the value the system can create for you). 

Estimating the impact of shading is difficult because it varies throughout the day and changes significantly across the year due to the seasonal path of the sun. Shading is also entirely dependent on where the panels are installed and the surrounding objects (buildings, trees, etc) which may cast shadows on them.

Unfortunately, there are very few advanced tools in the solar market that can model and forecast the impact of shading. This means that most solar companies will try to understand shading impact by looking at satellite images of the roof at different times of the day and the year. However, as the satellite images are only available for a limited number of dates and times – this can only give companies a rough idea of what the shading impact on a system might be. 

Ultimately, this approach means that many customers are buying solar with limited information on how the system will perform.

The Wattle Powr approach

We believe in giving customers solar options that are driven by data and sophisticated modelling.  

When designing your solar system, the Wattle Powr team are proud to use the UPowr SaaS platform. The UPowr platform includes a high-resolution 3D model of the environment around the house – which includes roofs, buildings, and trees. The platform then takes into consideration the path of the sun for each hour of every day of the year. This gives us a “virtual observation” from the panels towards the sun and shows if the shading of a building or tree is in the way. If so, our model knows that the panel is in the shade at that time.

It’s important to note that when a panel is shaded, it produces less energy, but not no energy. The light hitting a solar panel comes in two forms: beam irradiation and diffuse irradiation. Beam irradiation consists of the rays of light coming directly from the sun. It contains the most energy and is blocked when a panel is in the shade. Diffuse irradiation consists of light rays that have been scattered by the atmosphere. Diffuse irradiation still reaches a panel when it is shaded because it comes from all directions at once. So, a shaded panel still manages to produce some power due to the diffuse irradiation. 

As the platform understands what a ‘typical weather’ year will look like for your house, it’s able to understand the different amounts of sunlight (both beam and diffuse irradiation) and accounts for clouds and other factors that may impact the amount of energy your system will produce.

By combining shading and weather analysis, the platform is able to generate a comprehensive forecast of solar production.

This forecast is then used in the savings calculation that the platform performs, which provides customers with one of the most thorough savings estimates available on the market, as it takes into account the impacts of shading. Our approach allows homeowners to decide with more confidence whether solar is worthwhile on their property.