# Energy Optimization in Hotels: Strategies for Efficiency in Hot Water Systems
###### Abstract  
This paper presents a procedure for the energy optimization of domestic hot water (DHW) systems in hotels located in tropical climates that use centralized air conditioning systems. The study aims to maximize heat recovery from chillers and reduce the fuel consumption of auxiliary heaters by optimizing operational variables such as water mass flow in the primary and secondary DHW circuits and outlet temperature of the backup system. The optimization is implemented using genetic algorithms (GA), which enable the identification of the most efficient flow configurations under variable thermal demand conditions. The proposed methodology integrates a thermoenergetic model validated with real operational data and considers the dynamic behavior of hotel occupancy and water demand. The results show that the optimized strategy reduces auxiliary heating use by up to 75%, achieving annual energy savings of 8244 kWh, equivalent to 2.3 tons of fuel, and preventing the emission of 10.5 tons of CO\({}_{2}\). This study contributes to the design of sustainable energy systems in the hospitality sector and provides replicable strategies for similar climatic and operational contexts. energy optimization; heat recovery; domestic hot water systems; energy efficiency +
Footnote †: journal: _arXiv preprint arXiv:1907.  
influencing energy demand. By 2030, global energy efficiency standards are expected to be implemented, improving the energy performance of HVAC systems by more than 50% [4; 5]. In this context, the tourism sector, especially hotels in tropical climates, faces a significant challenge, as air conditioning and domestic hot water (DHW) systems both account for 60% to 70% of their total energy consumption [6]. Various energy-saving alternatives in thermal systems exist to address this high consumption, such as reducing demand, reusing residual energy through heat recovery, installing high-efficiency motors, and improving thermal insulation. Renewable technologies and the automation of operational processes can complement these strategies [7; 8]. The recovery of heat generated during the compression cycle in centralized air conditioning systems is presented as an effective solution to optimize DHW production in hotels [9; 10]. As the use of these systems increases, it is crucial to implement strategies that reduce energy consumption and pollutant emissions and maintain user comfort. Integrating efficient technologies and sound operational practices is critical to ensure a sustainable and cost-effective energy supply in hotel facilities. In hotels, hot water production must be constantly maintained, with temperatures above 50 \({}^{\circ}\)C at the furthest points and the ability to rise to 70 \({}^{\circ}\)C periodically to prevent the growth of bacteria such as Legionella. During the winter, recovered heat may be insufficient due to the part-load operation of chillers, requiring an additional backup source to ensure a hot water supply. Fluctuations in demand and part-load operation affect energy efficiency, creating the need for large volumes of thermal storage and energy-consuming backup systems such as gas or electricity [11; 12; 13]. The existing literature focuses mainly on the sizing and optimal configuration of energy systems, leaving a significant gap in operational optimization based on integral thermoenergetic models. This limitation is especially relevant in contexts where operating conditions vary considerably, such as in high tourism seasons in Cuba, where the energy demand for water heating increases due to the almost permanent use of auxiliary heaters. Despite the importance of these scenarios for energy efficiency and operating cost reduction, few studies address the mathematical modeling of chillers within a scheme to maximize heat recovery in domestic hot water (DHW) systems.