( Again ( , ( ( the heat ) ( ( is ( used ( to ( ( produce steam ) ( to ( turn ( turbines ( that ( drive ( electrical generators ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB Again)) (, ,) (NP (DT the) (NN heat)) (VP (VBZ is) (VP (VBN used) (S (VP (TO to) (VP (VB produce) (NP (NN steam)) (S (VP (TO to) (VP (VB turn) (NP (NP (NNS turbines)) (SBAR (WHNP (WDT that)) (S (VP (VBP drive) (NP (JJ electrical) (NNS generators)))))))))))))) (. .)))
Again, the heat is used to produce steam to turn turbines that drive electrical generators.
(ROOT (S (NP (DT This) (NN heat)) (VP (VBZ is) (VP (VBN used) (S (VP (TO to) (VP (VB convert) (NP (NN water)) (PP (IN into) (NP (NP (NN steam)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (ADVP (RB then)) (VP (VBN used) (S (VP (TO to) (VP (VB turn) (NP (DT a) (NN turbine))))))))))) (, ,) (S (ADVP (RB thus)) (VP (VBG generating) (NP (JJ electrical) (NN power))))))))) (. .)))