Identify the number of independent and subordinate clauses in the following group of words.

Energy can be gathered by using solar power

Energy can be gathered by using solar power. This is an independent clause; there are not any subordinate clause. There is not a secondary sentence or clause that depends on the main clause. Energy can be gathered by using solar power. This clause has meaning by itself; the idea is complete.

Energy is the subject

can be gathered by using solar power is the predicate; can be is the verb group and by using solar power is the adjunct of means: it tells how energy is gathered.

I think it's a subordinate clause.