The potential for thermal waste energy recovery in industrial kitchens

Industrial kitchens consume significant amounts of energy, largely in the form of heat production by cooking and cleaning equipment, which requires removal by the facility's heating, ventilating, and air conditioning (HVAC) system. One potential means to improve the energy efficiency of industrial kitchens lies in the use of waste energy recovery of hot wastewater from an industrial-scale dishwasher. Examination of an on-campus dining facility suggests that waste heat recovery can occur at the facility gas hot water heater (HWH) and the dishwasher electric hot water booster (HWB). This study suggests that waste heat recovery is more financially viable in existing construction at the electric HWB, despite yielding less recovered heat than the gas HWH. A payback period of approximately two years is calculated for the installation of a 146 kW shell-and-tube heat exchanger. The corresponding annual source pollution reduction is approximately 13 kg of SO₂, 6.5 kg of NO_x, and 6.5 metric tons of CO₂. However, new construction projects in similar building configurations could also include HWH heat recovery, resulting in a similar payback period but with more substantial annual source pollution reduction values: 14 kg of SO₂, 33 kg of NO_x, and 38 metric tons of CO₂.