( ( ( If ( , ( however , ) ) ) ( I ( had ( ( come up ) ( with ( ( the idea ) ( of ( ( using ( ( the ( sun 's ) ) energy ) ) ( to ( heat buildings ) ) ) ) ) ) ) ) ) ) ( , ( that ( ( would ( be ( an ( achievable innovation ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN If) (PRN (, ,) (ADVP (RB however)) (, ,)) (S (NP (PRP I)) (VP (VBD had) (VP (VBN come) (PRT (RP up)) (PP (IN with) (NP (NP (DT the) (NN idea)) (PP (IN of) (S (VP (VBG using) (NP (NP (DT the) (NN sun) (POS 's)) (NN energy)) (PP (TO to) (NP (NN heat) (NNS buildings)))))))))))) (, ,) (NP (DT that)) (VP (MD would) (VP (VB be) (NP (DT an) (ADJP (JJ achievable)) (NN innovation)))) (. .)))
If, however, I had come up with the idea of using the sun's energy to heat buildings, that would be an achievable innovation.
(ROOT (S (PP (IN Over) (NP (NP (CD 90) (NN %)) (PP (IN of) (NP (DT the) (NN energy))))) (NP (PRP we)) (VP (VBP use) (SBAR (S (VP (VBZ comes) (ADVP (RB originally)) (PP (IN from) (NP (DT the) (NN sun))))))) (. .)))