Subject to the limitations in this section, the Board of Public Works may issue new bonds to refund its outstanding bonds. The power to issue bonds under this section is in addition to any other power to borrow. The Board may issue bonds under this section only for: the public purpose of realizing for the State a savings in the total cost of debt service on a direct comparison or present value basis; or the public purpose of debt restructuring that reduces the total cost of debt service. The Board may: provide that bonds under this section be in 1 or more series; and vary the amount of the series. The total principal amount of the bonds issued under this section may exceed the total principal amount of the bonds that are being refunded. Bonds that are being refunded and that are subject to redemption before their stated dates of maturity may be called for redemption: on the earliest redemption date; or at a later date that the Board determines. The Treasurer shall invest and apply proceeds of a sale of bonds issued under this section to ensure that the principal and redemption premium of, and interest on, the bonds that are being refunded will be paid in full when due. The Treasurer may deposit any part of the proceeds of the sale of bonds issued under this section in a trust fund with a trust company or other banking institution, in the name of the State. The trustee may invest and reinvest money in the trust fund in: obligations of the United States; obligations guaranteed by the United States; certificates of deposit or time deposits secured by an obligation of the United States; certificates of deposit or time deposits secured by an obligation guaranteed by the United States; or any obligation or other investment described in § 6–222(b) of this article. Interest, income, and profits on the investment may be applied in any lawful manner, including to the payment of: the bonds that are being refunded; and the bonds issued under this section. The trustee shall make money in the trust fund available, as the Board requires, for the payment of: the principal and redemption premium of, and interest on, the bonds that are being refunded; the principal and redemption premium of, and interest on, the bonds issued under this section; or any other related costs. The Comptroller shall account for the proceeds of a sale of bonds issued under this section as nonbudgeted funds. All or any part of the bonds issued under this section may be made payable from and secured by: money in the Annuity Bond Fund established under § 8-132 of this subtitle; or other money or security that the State provides. Nothing in this section shall prevent issuance and sale of refunding bonds the interest on which is not excludable from gross income for federal income tax purposes.