Subfreezing Absorption Refrigeration for Industrial CHP

Abstract

The design and operation of an advanced absorption refrigeration unit (Thermochiller) as part of an industrial combined heat and power (CHP) system is presented. The unit is installed at a vegetable processing plant in Santa Maria, California. The overall integrated system includes the engine package with waste heat recovery, Thermochiller, cooling tower, and chilling load interface. The unique feature of the system is that both the exhaust and jacket heat are used to supply subfreezing refrigeration. To achieve the low refrigeration temperatures of interest to industrial applications, all components of this integrated system needed careful consideration and optimization. The CHP system has a low emission natural gas-fired 633[Formula: see text]kW reciprocating engine cogeneration package. Both the exhaust heat and jacket heat are recovered and delivered via a hot glycol loop with 105[Formula: see text]C supply temperature and 80[Formula: see text]C return. The 125 ton ammonia absorption chiller (TC125) chills propylene glycol to [Formula: see text]C and has a coefficient of performance of 0.63. TC125 has peak electric demand of 10[Formula: see text]kW for pumps and 8[Formula: see text]kW for the cooling tower fan. The CHP system, including TC125, operates 20[Formula: see text]h per day, six days per week. All operations of TC125 are completely automatic and autonomous, including startups and shutdowns. Industrial refrigeration is typically a 24/7 load and highly energy-intensive. By converting all the engine waste heat to subfreezing refrigeration, Thermochiller brings added value to cogeneration or CHP projects.