Any bonds issued under the provisions of this article and at any time outstanding may at any time and from time to time be refunded by the board by the issuance of refunding bonds of the state in such amount as it may deem necessary to refund the principal of the bonds so to be refunded, together with any unpaid interest thereon; to provide additional funds for the purposes authorized by this article; and to pay any premiums and commissions necessary to be paid in connection therewith. Any such refunding may be effected whether the bonds to be refunded shall have then matured or shall thereafter mature, either by sale of the refunding bonds and the application of the proceeds thereof for the redemption of the bonds to be refunded thereby, or, together with the interest on such proceeds, for the payment of the bonds to be refunded thereby and the interest thereon as the same come due, or by exchange of the refunding bonds for the bonds to be refunded thereby: Provided, That the holders of any bonds to be refunded shall not be compelled without their consent to surrender their bonds for payment or exchange prior to the date on which they are payable or, if they are called for redemption, prior to the date on which they are by their terms subject to redemption. Any refunding bonds issued under the authority of this section shall be payable from the revenues out of which the bonds to be refunded thereby were payable, from other moneys or from the principal of and interest on or other investment yield from investments or proceeds of bonds or other applicable funds and moneys, including investments of proceeds of any refunding bonds, and shall be subject to the provisions contained in and shall be secured in accordance with this article.