
301Renewable Electricity
while the WWSIS effort also examined concurrent PV penetration as high as
5%. These two studies also extended beyond the 20% study by considering
transmission congestion and contingencies, hourly treatment of wind vari-
ability, and interactions between wind and PV (in the WWSIS). Like the 20%
study, they found nothing to indicate that these levels of VRETs would nec-
essarily jeopardize security or degrade reliability. To accomplish this, they
relied on more aggregated/larger balancing areas, extensive transmission
build-outs, and new market structures with shortened bidding and response
times. Their results did vary fr ...