## 1 Introduction
In the combined power and heat/cooling systems, the low-grade waste heat of the topping cycle is transformed into cooling energy or to produce heat in bottoming cycle, which can obtain better gains than transforming high-grade electric energy into low-grade heat/cooling energy because of the lower energy conversion efficiency in the electric power generation process [16]. The absorption refrigeration cycle (ARC) is widely integrated with the sCO\({}_{2}\) cycle to provide electric power and cooling energy simultaneously. [PERSON] et al. [17] investigated an combined sCO\({}_{2}\) cycle/ammonia-water based ARC. The thermal efficiency, exergy efficiency, and total product unit cost of the combined cycle were 26.12% and 2.73% higher, and 2.03% lower than those of the stand-alone sCO\({}_{2}\) cycle, respectively. [PERSON] et al. [18] coupled the lithium bromide-water ARC with a recompression sCO\({}_{2}\) cycle, and compared it with the recompression sCO\({}_{2}\) cycle/ammonia-water ARC. The single-objective optimization results showed that the sCO\({}_{2}\)/LiBr-H\({}_{2}\)O ARC system had a better performance than the sCO\({}_{2}\)/ammonia-water ARC system. Recently, [PERSON] et al. [19] developed a tri-generation system by using biomass energy based on a sCO\({}_{2}\) cycle and a LiBr-H\({}_{2}\)O ARC. Compared to the sCO\({}_{2}\) cycle, the proposed combined cycle presented a large performance improvement in terms of efficiency and environmental impacts. A number of studies proposed combined heat and power (CHP) systems based on sCO\({}_{2}\) cycle to achieve heat and electric power cogeneration. [PERSON] et al. [20] investigated a solar energy powered sCO\({}_{2}\) Rankine cycle, in which the thermal energy of recuperators was recovered by the heating water to provide heat for users directly. [PERSON] et al. [21] studied several types of sCO\({}_{2}\) cycles in a CHP plant, and compared these sCO\({}_{2}\) cycles with steam CHP systems. They concluded that the sCO\({}_{2}\) cycle should be considered as a base for future CHP plants due to its excellent performances. However, in previous sCO\({}_{2}\)-based CHP systems, the waste heat of the sCO\({}_{2}\) cycle was directly supplied to heat users. The temperature of waste heat is much higher than the heating temperature of heat users, which is inconsistent with the principle of energy cascade utilization. Thus, direct heating is not a high-efficiency method to sufficiently utilize the waste heat of the sCO\({}_{2}\) cycle. Compared with the conventional direct heating (DH) systems, the advantage of heat amplification makes absorption heat pump (AHP) a preferable choice that can produce more heat to satisfy the user demand [22], especially when the waste heat of the sCO\({}_{2}\) cycle is limited or insufficient for users. However, very limited efforts were devoted to comprehensively analyzing the feasibility of AHP to recover the waste heat of the sCO\({}_{2}\) cycle based on the principle of energy cascade utilization. Consequently, the purpose of this study is to propose a combined sCO\({}_{2}\)/AHP system for high-efficiency heat and power cogeneration, and to compare it with existing systems to present its advantages quantitatively. On the other side, the most frequently used working fluids for AHP are an ammonia-water solution and a LiBr-H\({}_{2}\)O solution. Both of them were frequently considered for comparison and discussion [23, 24]. The LiBr-H\({}_{2}\)O AHP has a smaller operational pressure and can be easier to achieve than the ammonia-water AHP. Besides, if the working fluid leaks, the water vapor in LiBr-H\({}_{2}\)O AHP is much safer than the ammonia vapor in ammonia-water AHP. Therefore, the LiBr-H\({}_{2}\)O AHP will be the main focus of this study while the ammonia-water AHP will be adopted as a comparison. To the best of the authors' knowledge, the LiBr-H\({}_{2}\)O AHP has never been applied as a bottoming cycle to recover the waste heat of the sCO\({}_{2}\) cycle.