# Energy Analysis of Kalina and Kalina Flash Cycles Driven by Renewable Energy
## 1 Introduction  
Due to the limited fossil fuel resources and environmental problems, the efficient conversion and storage of renewable energy has been increasingly important [1]. The organic Rankine cycle (ORC) and the Kalina cycle (KC) have been recognized as the feasible and efficient ways of generating power by exploiting a low-grade heat source. KC uses a solution of ammonia in water for working fluid, whose boiling points differ. It usually operates as an absorption cycle with varying concentration during the cycle. An improved efficiency is expected owing to the reduced thermal mismatch between the source and mixture during the heat acceptance process [2; 3]. An earlier theoretical study by [PERSON] and [PERSON] [4] showed a potential of KC for a 10%-20% enhanced thermal efficiency than RC. The early KC proposed by [PERSON] and [PERSON] [5] was shown to produce a higher power output than ORC for a specific geothermal application. KC can be used to generate power by exploiting sensible heat from a variety of sources: geothermal energy, industrial waste heat, ocean thermal energy, solar energy, and others. One of the important design considerations of KC is compatibility with the available sources. In the case of low- to medium-grade geothermal applications, a mixture with ammonia fraction of around 70 wt% is commonly used [6]. However, the optimal concentration depends on many design parameters: concentrations range from 58 to 89 wt% as reviewed in [7]. Next to concentration the key parametersinfluencing the performance of KC are separator temperature and the inlet and outlet conditions of the turbine (pressure and temperature) [7]. [PERSON] [8] used an artificial neural network to obtain optimized power generation and required pump power for a specific geothermal KC of KCS-34. [PERSON] et al. [9] studied KC with a superheater and reported the optimized exergy and energy efficiencies for Kumejima Island as 35.6% and 6.48%. [PERSON] and [PERSON] [10] analyzed 5 years' data logs for the evaporator of a KC. It is worth trying to enhance the power-generation performance by integrating the system with the Kalina cycle. [PERSON] et al. [11] proposed to integrate a gas turbine and a Kalina cycle with a solar-driven power system, with an expectation of peak efficiency of 27.5% and 69% reduction of water consumption. [PERSON] et al. [12] proposed to combine concentrating photovoltaics and a Kalina cycle equipped with absorption chiller to improve both systems' efficiency. [PERSON] et al. [13] proposed to integrate a geothermal Kalina cycle with modules for absorption cooling and hydrogen generation, and showed that energy and exergy efficiencies higher than 40% are expected. Among the studies on the performance optimization of a KC, a solar thermal Kalina cycle equipped with a storage system was investigated by [PERSON] et al. [14] and optimized by a genetic algorithm. Recently, [PERSON] et al. [15] analyzed two novel configurations of the KC employing a flash vessel: Kalina flash cycle (KFC). They conducted an analysis of low-grade heat recovery performance of the system, and their results of thermodynamic and economic analysis show that the optimal solutions of KFCs are superior to KC. The result of recent thermodynamic performance analysis by [PERSON] et al. [16] also confirms superiority of KFC to KC. Exergy analysis is a universal method for evaluating the rational use of energy that can be applied to any kind of energy conversion system, can identify the location, magnitude and causes of thermodynamic inefficiencies, and enhances understanding of the energy conversion processes in complex systems [17]. [PERSON] et al. [18] conducted a data-driven exergy analysis of a grid connected underwater compressed air energy storage facility. In this work, exergetical performance of KC and KFC driven by renewable energy is comparatively analyzed.