A main goal is to try to come up with other sources of energy, like trying to harness the energy of water, sunlight and wind, efficiently enough to replace the existing methods.
(A main goal; is; to try to come up with other sources of energy, like trying to harness the energy of water, sunlight and wind, efficiently enough to replace the existing methods)
A main goal
is
to try to come up with other sources of energy, like trying to harness the energy of water, sunlight and wind, efficiently enough to replace the existing methods