Rooftop vs. shading surface PV energy production

asked 2017-08-30 16:57:01 -0500

kmpiscopo
203 ●4

updated 2017-08-31 09:05:26 -0500

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?

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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.

kmpiscopo ( 2017-08-30 17:58:00 -0500 )edit

Double click on the shading surface group then click on surface so it is selected. Then right click and choose 'reverse face'

David Goldwasser ( 2017-08-30 18:01:58 -0500 )edit

Thanks David. That works and solves my problem.

kmpiscopo ( 2017-08-30 19:06:43 -0500 )edit

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@kmpiscopo, make sure you both upvote this answer (it was helpful), and mark it as accepted by clicking on the check mark next to it (it actually solved your problem). Thanks.