Has passive solar design been implemented in commercial buildings? Is it only possible to do so in new commercial buildings or can existing buildings find ways to do so as well?

I have not seen many passive systems ever in a commercial application, most seem to be active solar systems to convert sun to electricity. Even active systems the cost versus payback is typically more like 7-10 year is general with maybe a few special cases where it might be 5-7 year paybacks.

I think that commercial buildings main energy is the electricity used for cooling not the heating being a big cost. Also the nature of commercial designs often prevents design changes to help a passive system. I have read studies that show that in a commercial application a passive solar system can often increase the cooling demands. There maybe ways to enable passive to be beneficial but in a cost especially in a retrofit basis would likely not make it a short enough payback.

I think for most commercial applications an active solar is the better direction and even then unless it is being done just for the marketing and bragging rights it often needs energy efficiency items outside of solar technology to make it a reasonable payback for most people to consider. The new developments in solar panels has enabled some companies to provide solar in commercial on a power purchase agreement to avoid the capital outlay; those systems do provide a portion of the energy via solar to the owner at no upfront cost but also no significant dollar savings either at least during the often log agreement term 10-30 years?

I am not a solar expert but I hope that gives you some insight as to what I have experienced in commercial buildings.