there are two important ways to "COLLECT" electric energy from skyscrappers
!, collect the waste water into one single tank on each floor -- and then use the potential energy of that to propel a generator to create electricity atleast the parking area can be lit with that without expensive electric power !!!
2, use micro wind powered generators on the higher windows and let the air do the magic --- your laps and mobile will atleast be charged with that if the air is not that high flowing !!
additional idea by Ideabulb:
micro wind fans can be set in vehicles, while running the micro wind mills can generate enormous electricity to store small batteries and cells.