Transient simulation of a solar absorption cooling system

International Journal of Low-Carbon Technologies, Feb 2016

With non-renewable energy sources depleting quickly, solar energy could prove a viable option owing to its abundance and eco-friendliness. Modeling and simulation of a solar energy-driven single-stage absorption chiller was carried out using the transient simulation software ‘TRNSYS’. An evacuated tube collector coupled with an insulated tank served as heat source for the absorption chiller. Experiments were conducted to evaluate the efficiency parameters of the collector as well as the loss coefficient for the storage tank. These parameters along with standard chiller performance data were used to model the system. The influence of climatic conditions, storage capacity and various control schemes with and without auxiliary heating on the output of the system is analyzed and presented in the paper.

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Transient simulation of a solar absorption cooling system

International Journal of Low-Carbon Technologies Transient simulation of a solar absorption cooling system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . With non-renewable energy sources depleting quickly, solar energy could prove a viable option owing to its abundance and eco-friendliness. Modeling and simulation of a solar energy-driven single-stage absorption chiller was carried out using the transient simulation software 'TRNSYS'. An evacuated tube collector coupled with an insulated tank served as heat source for the absorption chiller. Experiments were conducted to evaluate the efficiency parameters of the collector as well as the loss coefficient for the storage tank. These parameters along with standard chiller performance data were used to model the system. The influence of climatic conditions, storage capacity and various control schemes with and without auxiliary heating on the output of the system is analyzed and presented in the paper. solar cooling; evacuated tube collector; thermal storage; absorption chiller; controls; simulation; TRNSYS New Delhi 110016, India Abstract 1 INTRODUCTION In tropical countries like India, which experience extreme summers in the mainland, demand for electricity shoots up due to the need for cooling. The high electricity demand not only overloads the grid but harms the environment as well due to the burning of fossil fuels, which are the primary source of power. Solar energy for cooling applications provides an opportunity to overcome this problem. The fact that cooling demand in summer is proportional to the availability of solar energy has been spurring the researchers to further exploit solar energy. In cooling applications, different types of sorption systems can be employed. Vapor absorption is a mature technology that can be integrated with solar thermal collectors. A single-effect lithium bromide – water (LiBr – H2O) absorption cooling system operates at a generator temperature in the range of 70 to 958C and requires water as cooling fluid in the absorber and the condenser [1]. A number of simulation and experimental studies [2 – 9] on various solar-powered absorption systems have been carried out by researchers to make this technology more competitive. Assilzadeh et al. [2] presented the simulation and optimization of a LiBr solar absorption cooling system with evacuated tube collectors (ETCs) for the local weather conditions of Malaysia. The simulation of the solar absorption cooling system was carried out using TRNSYS software. The results showed that for a continuous operation, a 0.8-m3 hot water storage tank is essential and the optimum design for a 3.5 kW (1 TR) system required 35-m2 evacuated tube solar collector sloped at 208. Mazloumi et al. [3] simulated a parabolic trough collector-based absorption cooling system with LiBr – H2O as absorbent refrigerant pair. The results showed that the minimum value of the required collector area was 57.6 m2, which could supply the cooling loads for weather conditions of Ahwaz, Iran, in the month of July when the maximum load reached 17.5 kW. Martinez et al. [4] simulated a hot-water-fired, double-effect LiBr – H2O absorption system using TRNSYS and also validated the model with experimental data. The model predicted 30% lower energy consumption as compared with experimental results. This difference was attributed to steady state modeling, which did not consider the transient performance. It was deduced that the simulation time steps should be lower than 1 h. Monne et al. [5] conducted a two-year experimental analysis (2007 and 2008) to study the effect of outdoor temperature of Spain on the performance of LiBr – H2O absorber cooling system. They found that the performance of the chiller was better in the year 2007 because the heat rejection temperature and the outdoor temperature were more favorable than those in 2008. Ge et al. [6] carried out simulation of a low-temperature gas-fired ammonia – water absorption chiller using TRNSYS. The chiller model was validated against experimental results obtained on a 12 kW absorption chiller and was further used to analyze the effect of important design and operating parameters on its performance. The study concluded that the increase in generator heat input from 20 to 30 kW increased the cooling capacity from 11.26 to 14.85 kW and slightly decreased the COP from 0.56 to 0.49. Florides et al. [7] modeled a solar absorption cooling system using TRNSYS for the local climate of Nicosia, Cyprus. The model predicted an optimized system consisting of a 15-m2 compound parabolic collector tilted at 308 from the horizontal and a 600-L hot water storage tank. The collector area was determined by performing (...truncated)


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Akshaya Budania, Suhail Ahmad, Sanjeev Jain. Transient simulation of a solar absorption cooling system, International Journal of Low-Carbon Technologies, 2016, pp. 54-60, 11/1, DOI: 10.1093/ijlct/ctt060