Sorry I missed this. With respect to reuse of the modules, that old array's inverters are likely dead. As a nonprofit reuse guy, I would still recommend the municipal building owner pursue a new system given the 20-year age of the equipment. With regards to doubling up two modules to a single microinverter, we have done this on some low-income residential rooftop arrays and these work fine.
-Rich
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Rich Stromberg
ESS Prog Dir / PhD Student
Equitable Solar Solutions / Univ of Alaska Fairbanks
Chair, PV Technical Division at ASES
Colorado
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