Solar power plant planning

The challenge 

The aim of this showcase was to produce a solar power plant design. Targeted roof covers a three-story (single-apartment) townhouse with a high/(elevated) groud floor in Ljubljana. Roof access is difficult.  

The Problem

When planning a rooftop solar power plant, an inaccurate plan and or unfamiliarity of a roof surface and possible infrastructural objects (AC, chimney, vents, windows, etc…) is the biggest obstacle. It is difficult to measure the roof to determine its exact shape and slope. It’s not uncommon for a customer to hand over a roof plan which turns out to be faultyunreliable or inaccurate. Installation team arrives at the location only to find an additional snow guard, air vent or an AC unit (that wasn’t in the original plan)/ (they did not expect there). 

The solution

It’s very easy to plan a solar power plant with an accurate 3D model than includes all the roof elements of an object. The 3D model is metric and set in the local/national coordinate system, as such it represents an ideal starting point for the project planning; one can observe the object’s characteristics, foresee the advantages and the shortcomings of the conceptual design. The software enables user to draw the elements of interest and even import CAD drawings into the 3Dmodel.

The project 

With a DJI Mavic mini 2 dron we scanned the roof from the average heigh of 25 m. Images ware take automatically, every 3 m, this ensures sufficient overlap (70-80%). During a short – 5 minute flight the drone captured 83 images. Manual measuring tool was used at the location to provide the scale reference.

With a photogrammetry software – 3D survey, a georeferenced, coloured, 3D point cloud was calculated out of the captured images. The processing took 30 minutes. Based on this point cloud a full 3D mesh was calculated. The measurements we took on site were used to scale the model to a realistic dimensions, original/processing error was less than 2%. Now we have got an accurate 3D model of the house.

Next step was to digitalise the edges of the roof and all the obstructing elements on it. We vectorised the roof ridge, gutter, chimney, windows, air vent, etc. This provided us a canvas to draw the solar panels on each roof plane and arrange them in an optimal position. The panel dimensions are 1134mm x 1722mm. Due to an accurate model, the panels were arranged in less than 30 minutes, positions of limiting elements like windows and chimney were taken into account. Obstacles like chimney and the snow guard ware successfully avoided. 

Vectorized 3D data was exported in DXF format and sent to the Solar Power Plant designer. There they were imported into the SolarEdge software, calculated its power and finalised the project.

Conclusion 

With the aid of photogrammetric process, we successfully designed a solar power plant. We obtained accurate building dimension and ensured the optimal layout of the panels without even stepping on the roof. Thanks to 3D design, the calculation of the power plant’s efficiency was smooth and accurate, further planning of the supporting construction was easy and free of surprises.