Do you want solar panels on your roof or office building? Good idea! But where do you put them so that their energy yield is maximized? Certainly, in a city full of shadow from other buildings and trees, that is a complex question. Delft researchers now have a new way to determine the optimum location for your solar panels.
In addition to tree buildings and other objects, the weather and the position of the sun also play a role in the energy yield of solar panels. The latter two vary daily, per season and during the year. And due to the different positions of the sun, blockades also cause a different shadow fall. This should all be included if you want to know the average solar energy yield.
There are various computer models that can be used to calculate the yield of a solar panel at a specific location. These mathematical models usually calculate the amount of sunlight that falls on the panels per hour. By repeating this calculation every time, for all hours in a year, you arrive at an annual average. And although the weather varies from day to day, it is fairly similar from year to year.
These sunlight calculations are complex for an urban environment. As a result, it requires a lot of computing power and time to determine the best location for solar panels for a full year. The Delft technology simplifies the calculations so that they can be performed up to eighteen times faster. Less computing power is also required. According to the researchers, their system is very accurate despite the simplifications.
The Delft researchers do not have their model calculate the incidence of sunlight every hour, but directly determine the annual radiation that falls on the panels. This is done on the basis of two parameters that are determined on the basis of the skyline profile, says Olindo Isabella of TU Delft. “The skyline profile indicates the amount of air you can see from the location of the solar panel and what the projection on the panel is of the surrounding buildings and other objects.”
This information is combined with the position of the sun during the year and with multi-year climate measurements. This depends on the location. This then determines the two parameters: the sky view factor and the sun coverage factor. The latter indicates how much direct sunlight falls on the solar panel. The second is a measure of the amount of diffuse or reflected sunlight that reaches the solar panel. That is light that has been scattered in the sky, through clouds, or that has been reflected on surrounding windows, buildings or the ground, before it enters the solar cells.
“A solar panel gets the most energy from direct sunlight,” says Isabella. But diffuse light also makes a contribution.
Testing in the sun
The new solar panel model has also been tested. The researchers compared the predictions of the model with the annual yield of solar panels in ten locations in the Netherlands. The model was a maximum of 4 percent wrong. The model has also been tested for different climate types with solar panels in Paris, Washington DC, Cagliari (Sardinia) and Adelaide (Australia). The error varied between 1.5 and 7.9 percent. With this accuracy, the model is not inferior to other techniques that require more computing power and time.
The researchers hope that thanks to this model it will be easier for designers and architects to incorporate solar panels into their designs.