Integrated Vapor Compression Chiller with Bottoming Organic Rankine Cycle and Onsite Low-Grade Renewable Energy

Muhammad Tauseef Nasir,Michael Chukwuemeka Ekwonu,Javad Abolfazali Esfahani,Kyung Chun Kim

doi:10.3390/en14196401

Muhammad Tauseef Nasir, Michael Chukwuemeka Ekwonu + Show 2 more

Open Access

https://doi.org/10.3390/en14196401

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Abstract

The present study offers a scheme to improve the performance of existing large-scale chillers. The system involves raising the temperature of the chiller’s cooling water stream using renewable energy sources by incorporating an organic Rankine cycle (ORC). The thermal analysis was conducted by raising the temperature of one-third of the approximately 200 ton chiller’s cooling water. The investigation was considered for ORC evaporator inlet temperature of 90~120 °C by the step of 10 °C. Various working fluids for the different ORC evaporator inlet temperatures were examined. Sensitivity analyses conducted on the degree of superheating, degree of subcooling, condenser saturation temperature, pinch point temperature differences of the ORC evaporator and condenser, and the mass flowrates of the heating and cooling streams were also reported. Genetic algorithm was employed to carry out the optimization. The best options for the ORC working fluid at the heating source ORC evaporator inlet temperatures of 90 °C was found to be DME, presenting an improvement of 48.72% in comparison with the rated coefficient of performance (COP) value of the VCC, with a renewable energy input requirement of 710 kW. At the heat source temperatures of 100 °C and 110 °C, butene, which presented an improvement in the COP equal to 48.76% and 68.85%, respectively, with the corresponding renewable energy requirements of 789.6 kW and 852 kW, was found to be the ideal candidate. Meanwhile, at the heat source inlet temperature of 120 °C, R1233zd (E), representing an improvement of 140.88% with the renewable energy input of around 1061 kW, was determined to be the most favorable ORC working fluid candidate.

Highlights

The modern-day rapid development of humanity as a whole and the burning of fossil fuels has caused an enormous strain on the environment [1,2]
The sensitivity analysis was performed to assess the effects of varying the design parameters, organic Rankine cycle (ORC) boiler superheat, ORC condenser saturation temperature, ORC condenser degree of subcool, ORC evaporator point temperature difference (PPTD), the ORC condenser
PPTD, the heating source mass flowrate variation, and the cooling source mass flowrate on the reduction in electrical power consumption of the vapor compression cycle technology (VCC), the renewable energy input, and the required supply water mass flow rate to lower the temperature to the specified cooling tower inlet temperature

Summary

Introduction

The modern-day rapid development of humanity as a whole and the burning of fossil fuels has caused an enormous strain on the environment [1,2]. With all determination, the Paris Accord [3] was proposed and duly signed by 196 signatories at. France on 12 December 2015 and came into effect on 4 November 2016. The agreement was signed to concert a global effort to ebb the harmful and catastrophic effects of global warming. Under such circumstances, air conditioning, an important utility, in urban areas, is estimated to consume approximately 30–40% of generated electricity [4]. According to [5], the United States consumes the same amount of power, for cooling alone, as the whole of continent of Africa. The growth in the cooling demands of commercial

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