(1) A comprehensive plan may include additional elements, items, or studies dealing with other subjects relating to the physical development within its jurisdiction, including, but not limited to:
(b) Solar energy; and
(2) A comprehensive plan may include, where appropriate, subarea plans, each of which is consistent with the comprehensive plan.
(3)(a) Cities that qualify as a receiving city may adopt a comprehensive plan element and associated development regulations that apply within receiving areas under chapter 39.108
(b) For purposes of this subsection, the terms "receiving city" and "receiving area" have the same meanings as provided in RCW 39.108.010