Rooftop vs. shading surface PV energy production
I am modeling a portfolio of buildings with on-site PV generation. Some of the buildings have rooftop PV, and others have ground-mount PV next to the building. I am modeling the rooftop PV using the "Add Rooftop PV" measure, and modeling the ground-mount PV by specifying a shading surface of the desired dimensions in Sketchup, and then using the "Add Simple PV to Specified Shading Surface" measure.
I have noticed drastically different electricity generation values from these two measures, so I performed an experiment on the same surface area, with the same parameters (18% cell efficiency, 75% of included surface area with PV) . I used the add Rooftop PV measure to a building with a rooftop area of 15,000 sqft, and the OpenStudio model shows an annual generation of 473,580 kWh/yr. When I specified a 15,000 sqft as a shading area, and applied "Add Simple PV to specified shading surface," the model shows generation of 70,464 kWh/yr.
Does anyone know what is going on here?
Ah, herein lies the problem. It is light purple. Is there any easy way to flip the shading surface? I can only seem to rotate it within the same plane.
Double click on the shading surface group then click on surface so it is selected. Then right click and choose 'reverse face'
Thanks David. That works and solves my problem.