Development and assessment of a solar and natural gas-based integrated energy system with storage options

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In this study, a solar and natural gas-based dual-energy source integrated plant system is designed to be thermodynamically investigated through energy and exergy approaches for multiple useful outputs, including electricity, heat and freshwater. The current system is considered for a hospital building to cover their needs and incorporates heat storage options to provide steady and flexible operation to better offset the mismatch between demand and supply. As a matter of fact, this system is not only appropriate for locations, such as deserts, where the weather is sunny and the air is dry all year round, but it is also suitable for other places where the sunshine duration is relatively shorter and the air is moderately humid by means of a storage system. With this system, which uses natural gas at a relatively modest rate of 20%, the system is enabled to operate primarily on solar energy. Thus, this renewable energy-based, natural gas-supported system obtains more green energy at a lower cost. It also intends to address the community's clean water requirement using the multi-effect desalination unit. Additionally, a molten salt thermal storage subsystem is employed to mitigate energy imbalances in the parabolic trough collector all day long. Furthermore, the necessary energy is supplied using a natural gas-powered boiler, especially in the evening and at peak times in terms of energy demand. The system is uniquely designed based on a real-world scenario using binary energy sources, where some parametric studies have been performed. While the system utilizes solar energy at a ratio of 80%, the remaining 20% comes from natural gas, and the amount of natural gas needed to assist the developed system for steady operation varies between 0.018 kg/s and 0.039 kg/s per day. The energy and exergy efficiencies of the system are determined to be 60.03% and 35.1%, respectively, while both electricity and heating production are 1.3 and 1.5 MW, and the freshwater production is found to be 17.52 kg/s, respectively.