providing a threshold time period and determining {HEAD ~ the energy} generated by {TAIL ~ each said renewable power system} for said threshold time period 
generated by
providing a threshold time period and determining { HEAD ~ the energy } generated by { TAIL ~ each said renewable power system } for said threshold time period
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH