From height information to shadow analysis

How does the Solar Monkey shadow calculator work?

With Solar Monkey you can quickly calculate the efficiency of your solar panels. This is possible regardless of the type of roof. This way you get a good idea of the payback period of the system. At Solar Monkey we are proud of the accuracy of our yield calculations. When providing guarantees on the yield of solar panels, it is very important that the calculation is exact and reliable. Smart calculation models based on height data are developed to correct for shadows from nearby trees or buildings.

How does shadow calculation work?

First, a horizon scan is made for each solar panel. This is shown in Figure 1. The construction and analysis of such a scan involves a lot of issues. As an intern at Solar Monkey I worked on optimising the calculation models. My goal was to find a balance between calculation time and accuracy of the models.

Height maps

We use the Actueel Hoogtebestand Nederland (AHN, Current Height Record of the Netherlands) to determine the 3D environment. This data was obtained from aircraft. Using LiDAR distance sensors, the exact height was determined for every half metre in the Netherlands. Figure 2 shows an example of this AHN data for a section of Rotterdam along the Maas. The colour indicates the height. Water is represented as blue and the height increases from green via orange to red. A red building is therefore higher than an orange building.

For the shadow analysis Solar Monkey views the area 360 degrees around and determines the horizon cut-off. This is done from the point of view of a solar panel. The direction of the yellow arrows in figure 2 corresponds to the part of the horizon behind the yellow lines in figure 1. Two tall buildings are visible near the continuous arrow. This is a large obstacle causing shadow. The dotted arrow has no tall buildings and therefore no obstacle on the horizon. There are a number of other buildings around this address that create shadow. Figure 2 is therefore nothing more than a flattened hemisphere. We do exactly the same with 2D maps of a 3D globe! This horizon cut-out is then used to determine how much sunlight is blocked by the surroundings at what time and year.

Shadow calculation

This research focuses on determining the distance to where the shadow silhouette will reach. The greater this distance, the more environment is included. The calculation also takes longer as the distance increases. To visualise this, Figure 3 shows which buildings are at which distance. The further away, the fainter the building is shown. A distance that is too small can therefore result in certain buildings not being included in the analysis. As a consequence, the expected energy yield is higher than in reality. We have discovered correlations between the distance and the total shadow analysis, so that we can choose the most optimal distance for an accurate yet quick calculation.

In this innovative way, we continue to work on calculation methods that are both fast and accurate. And in doing so we can provide you, our customer, with good insight into the solar panel systems you have designed. Want to know more about how Solar Monkey uses height maps? Then click hereIn this innovative way, we continue to work on calculation methods that are both fast and accurate. And in doing so we can provide you, our customer, with good insight into the solar panel systems you have designed.

Want to know more about how Solar Monkey uses height maps? Then click here.

Want to know more about our software? Please click here.

2021-04-06T13:36:19+01:00