Solar Technology and District Cooling System in a Hot Climate Regions: Optimal Configuration and Technology Selection

With the increasing need for cooling and the concerns for pollution due to fossil fuel-based energy use, renewable energy is considered an add-on to cooling technologies. The climatic condition in the Middle East, analyzed in this paper, provides the potential to integrate solar energy with the cooling system. Due to the availability of various solar energy and cooling technologies, multiple configurations of solar-cooling systems can be considered to satisfy the cooling demand. The research presented in this paper aims to assess and compare these configurations by considering the energy prices and the installation area. The proposed model is formulated in Mixed-Integer Linear Programming and optimizes the holistic system design and operation. The economic, renewable energy use, and environmental performances of the optimal solution for each configuration are analyzed and compared to the base grid-DCS configuration. Results show that the electricity tariff and the available installation area impact the economic competitiveness of the solar energy integration. When electricity tariff is subsided (low), the conventional grid-based DCS is the most competitive. The PV-DCS configuration is economically competitive among the solar assisted cooling systems, and it can contribute to reducing the environmental impact by 58.3%. The PVT-DCS configuration has the lowest operation cost and the highest environmental performance by decreasing the global warming potential by 89.5%. The T-DCS configuration becomes economically competitive only at high electricity tariffs. 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This publication was made possible by the [NPRP10-0129-170280] from the Qatar National Research Fund (a member of The Qatar Foundation). The statements made herein are solely the responsibility of the authors. The publication of this article was funded by the Qatar National Library.Scopus2-s2.0-8512847810

MODELING AND OPTIMIZATION OF DISTRICT COOLING SYSTEM

This research focuses on modeling and optimization of the design and operation of a district cooling system (DCS). The research investigates two solution paths: (1) the system transformation leading to re-organizing the conventional system (powered by the grid electricity) to achieve better economic and energy performance, and (2) the system integration of solar cooling technologies to enhance sustainable development for decreasing CO2 emissions. The multi-chillers district cooling plant is modeled by using algebraic modeling language (AML). The mathematical model is developed as a mixed-integer linear programming (MILP) problem. Frameworks are proposed to ease the DCS understanding and bridge the system modeling and optimization gap. A Model-Based System Engineering (MBSE) driven by the stakeholders and system requirements is developed. The DCS model includes the design, operation, and control by considering the interconnectivity of its components. The chiller short cycling requirement is modeled as system sequencing control. The optimization leads to reducing the total cost, including the design and operation. Consequently, it becomes cost-effective and reduces energy consumption; hence, decreasing carbon emission. Results show that the change of requirements improves the system performance. Renewable energy is considered an add-on to cooling technologies. Multiple configurations of solar-cooling systems are analyzed through a generalized model by considering the energy prices and the available installation area. The results show that the electricity tariff and the available installation area have an impact on the cost competitiveness of the solar energy integration. The results show that when the electricity tariff is subsided (low), the conventional Grid-based DCS is the most competitive. However, the photovoltaic-DCS configuration is more competitive than the thermal and hybrid systems and reduces the pollution up to 58.3%. The hybrid-DCS configuration has the lowest operation cost and the highest environmental performance as it decreases pollution up to 89.5%. The thermal-DCS configuration becomes economically attractive only at high electricity tariff and medium to high available installation area, and decreases the pollution up to 43.76%. The two developed models are useful for the conceptual design phase of the DCS, where the front end engineering design (FEED) phase requires such information (optimal design and operation) for further detail development

System requirements and optimization of multi-chillers district cooling plants

District cooling systems (DCS) are particularly important in the Middle East due to higher overall temperatures on most days of the year. The design, operation, and control of a new DCS should consider the abundant stakeholders and system requirements transformation using the system engineering processes. Integrating these requirements at an early stage in the system model is essential, specifically, the regulation on energy efficiency or system reliability; without such integration, the system may miss some important aspects and lead to higher energy consumption, lower reliability, higher system cost, greater CO2 emissions and may not satisfy cooling demand of the stakeholders. In this paper, a framework for DCS analysis is proposed by considering inputs, process (core), and outputs. The framework considers the structure and behavior of the DCS system to enhance system design and operation. The core of the framework uses a mathematical model in mixed-integer linear programming (MILP) to optimize the overall DCS cost by integrating the system and stakeholders' requirements. The results obtained from the application of the framework show that addressing the requirements reduces cost and increases energy efficiency, and when the cooling demand is variable, it might be better to have multiple capacities for chillers and chiller storage. The paper is helpful for the decision-makers to understand the impact of requirements and their management in the design, operation, and control of multi-chiller DCS in relief with the cost and energy efficiency. 2022 Elsevier LtdThis publication was made possible by the NPRP award [ NPRP 10-0129-170280 ] from the Qatar National Research Fund (a member of The Qatar Foundation ). The statements made herein are solely the responsibility of the authors.Scopus2-s2.0-8512462610