Ala. Code § 22-21-142
The authority may at any time and from time to time sell and issue its refunding revenue bonds for the purpose of refunding the principal of, and interest on, any matured or unmatured bonds of the authority at the time outstanding and for the payment of any expenses incurred in connection with such refunding and any premium necessary to be paid to redeem or retire the bonds so to be refunded; provided, that the principal amount of bonds the authority may issue for refunding purposes may not exceed the sum of the following: the principal amount of the bonds refunded thereby, the interest to mature thereon from the immediately preceding interest payment date to their respective maturities (or, in the event the bonds to be refunded, or any part thereof, are to be retired prior to their respective maturities, the interest to mature thereon from the immediately preceding interest payment date until the date or dates on which they are to be retired), any premium necessary to be paid to redeem or retire the bonds to be refunded (but only if such bonds are in fact to be redeemed or retired prior to their respective maturities) plus the amount of any expenses estimated to be incurred in connection with such refunding. The authority may also at any time and from time to time sell and issue its revenue bonds for the combined purpose of so refunding any of its bonds and of obtaining funds for any other purpose for which it is authorized by this article to sell and issue revenue bonds, in which event the provisions of this article relating to refunding bonds shall apply only to those of such bonds issued for refunding purposes. Any such refunding may be effected either by sale of refunding bonds, and the application of the proceeds thereof, or by exchange of the refunding bonds for the bonds, or interest coupons to be refunded thereby; provided, that the holders of any bonds or coupons so to be refunded shall not be compelled without their consent to surrender their bonds or coupons for payment or exchange prior to the date on which they may be paid or redeemed by the authority under their respective provisions. Any refunding bonds of the authority shall be payable solely from the revenues derived by the authority from any one or more of its projects, all as shall be specified in the resolution of the board or the indenture under which such bonds are authorized to be issued. All provisions of this article pertaining to bonds of the authority that are not inconsistent with the provisions of this section shall, to the extent applicable, also apply to refunding bonds issued by the authority and to bonds issued by the authority for both refunding and other purposes.
Ala. Code § 22-21-142 (1975)