Absorption Chiller Efficiency Increasing at Waste Heat Recovery of Co-generation Plants using a Vapor Compression Chiller as a Backup Cold Source

Abstract

Cooling efficiency in a trigeneration cycles is one of the most frequently problems. A single-stage hot water absorption chiller is a universal solution for the gas engine waste heat utilization. However, trigeneration centers exploitation experience shows the need for a more detailed tech-nical and economic analysis to achieve maximum efficiency of the three-generation cycle. The purpose of this article is to substantiate the use of two-stage absorption cycles increasing the uti-lization rate of waste gas heat. The study presents the results of assessing the efficiency of using energy resources on the example of a three-generation center with more than 14 years of exploi-tation experience, including two single-stage absorption chillers (Q0= 0.65 MW each) and a chiller with a screw compressor (Q0= 0.8 MW). A comparison of actual energy consumption with designed indicators was carried out. The influence of external and internal factors on the efficiency of heat recovery from a gas engine in single-stage absorption refrigeration machines with a water-heated generator is considered. The dependence of the change in the average annu-al cooling coefficient during the calendar year was obtained. Based on the study, proposals were formulated to improve the energy efficiency of refrigeration supply, giving an increase in refrig-eration capacity of 6.1% with a commensurate reduction in the load on the screw chiller. The option of using a combined two-stage cycle chiller (type 2) under similar operating conditions showed a COP=1.43, which provides savings of 67.45 MWh of electricity or 5.4%, on an annu-alized basis (assuming only waste heat is used). Additional advantages of such a cycle include increased accuracy and stability of maintaining the water temperature at the absorption chiller evaporator due to more flexible adjustment of the temperature of the lithium bromide solution in the high-temperature generator.

Keywords

• energy efficiency
• trigeneration cycle
• absorption lithium bromide single-stage chiller
• heat utilization.