▁designs ▁with ▁additional ▁bl ades , ▁such ▁as ▁Chan ▁Shin ' s ▁Multi - unit ▁rot or ▁bla de ▁system ▁integrated ▁wind ▁tur bine . ▁Aer od ynamic ▁efficiency ▁increases ▁with ▁number ▁of ▁bl ades ▁but ▁with ▁dimin ishing ▁return . ▁In cre asing ▁the ▁number ▁of ▁bl ades ▁from ▁one ▁to ▁two ▁yields ▁a ▁six ▁percent ▁increase ▁in ▁aer od ynamic ▁efficiency , ▁whereas ▁increasing ▁the ▁bla de ▁count ▁from ▁two ▁to ▁three ▁yields ▁only ▁an ▁additional ▁three ▁percent ▁in ▁efficiency . ▁Further ▁increasing ▁the ▁bla de ▁count ▁yields ▁minimal ▁improvements ▁in ▁aer od ynamic ▁efficiency ▁and ▁sacrific es ▁too ▁much ▁in ▁bla de ▁st iff ness ▁as ▁the ▁bl ades ▁become ▁th inner . ▁ ▁The oret ically , ▁an ▁infinite ▁number ▁of ▁bl ades ▁of ▁zero ▁width ▁is ▁the ▁most ▁efficient , ▁operating ▁at ▁a ▁high ▁value ▁of ▁the ▁tip ▁speed ▁ratio . ▁But ▁other ▁consider ations ▁lead ▁to ▁a ▁comprom ise ▁of ▁only ▁a ▁few ▁bl ades . ▁ ▁Component ▁costs ▁that ▁are ▁affected ▁by ▁bla de ▁count ▁are ▁primarily ▁for ▁materials ▁and ▁manufact uring ▁of ▁the ▁tur bine ▁rot or ▁and ▁drive ▁train . ▁Gener ally , ▁the ▁lower ▁the ▁number ▁of ▁bl ades , ▁the ▁lower ▁the ▁material ▁and ▁manufact uring ▁costs ▁will ▁be . ▁In ▁addition , ▁the ▁lower ▁the ▁number ▁of ▁bl ades , ▁the ▁higher ▁the ▁rot ational ▁speed ▁can ▁be . ▁This ▁is ▁because ▁bla de ▁st iff ness ▁requirements ▁to ▁avoid ▁inter ference ▁with ▁the ▁tower ▁limit ▁how ▁thin ▁the ▁bl ades