“…However, the energy grade of the waste heat is quite different from that of the natural gas consumption according to the second law of thermodynamics. (3) The typical values of traditional COPs of electricity-driven vapor compression chillers, gas-fired absorption chillers, double-effect steam-driven absorption chillers, and singleeffect hot-water-driven absorption chillers are 3-5, 1.4, 1.4, and 0.7, respectively [17,18,24,25]. However, the energy costs (e.g., electricity, natural gas, steam and hot water) of the cooling methods are varied in energy grade.…”