The Department of Finance of New Castle County shall receive all light taxes collected, shall keep them in a separate account, and shall pay them out only upon orders signed by the County Executive and approved by the Department. The Department shall receive or charge no compensation for the performance of any duty required of it or New Castle County under this chapter, beyond that expressly authorized by § 2102 of this title. If, after payment of all contracts entered into pursuant to this chapter, there remains a surplus in the light account, the surplus shall be applied to reduce the light tax rate for the succeeding taxable year.