The library board of any public library organized under the provisions of this Act may accumulate and set apart, as reserve funds, for the purchase of sites and buildings, for the construction and equipment of buildings, for the rental and repair of buildings acquired for library purposes, and for planned or emergency repairs and alterations of library buildings and equipment, the unexpended balances of the proceeds annually received from taxes not to excess of the statutory limits, provided the library board in its annual appropriation determination to the corporate authorities specifies that a specific fund is to be or is being accumulated for this purpose and has further resolved to develop and adopt a plan or plans pursuant to this Article. The plan required herein will be developed in general form within 2 years of the adoption of the ordinance establishing a special reserve fund; such plan subsequently may be amended as circumstances may require. No plan is needed for the emergency expenditures from this fund for the repair of an existing library building or its equipment.