Energy Management and Optimal Control of a Multifarious Water Heating Systems with Waste Heat Recovery and a Solar-Assisted Heat Pump: A Case of Large-Capacity Healthcare Building

• Hospitals consume large amounts of energy, with water heating being a major contributor to high costs and emissions. • Traditional electric water heating systems increase operational expenses, peak demand, and carbon emissions. • A novel energy management strategy combines waste heat recovery, a solar-assisted heat pump, and optimal control. • The system reduces energy use by 15, 001. 93 kWh/year, CO₂ emissions by 15. 93 tons/year, and saves 10, 505. 44 annually. • This integrated approach improves efficiency, lowers costs, and provides a sustainable solution for hospitals. Healthcare facilities are among the most energy-intensive buildings, with water heating accounting for a significant portion of their total energy use. Conventional electric storage tank water heaters (ESTWHs) rely on grid electricity, leading to high operational costs, increased peak demand, and elevated carbon dioxide (CO 2) emissions. To address these challenges, integrating renewable energy sources and advanced energy management strategies is essential. However, traditional energy conservation measures often fail to optimise both cost-effectiveness and load shifting, necessitating a hybrid approach that incorporates waste heat recovery (WHR), thermal energy storage (TES), solar-assisted heat pump (SAHP), consisting of solar thermal collectors and heat pumps and intelligent control strategies. This study proposes a novel approach of an optimised large-scale water heating systems in large capacity buildings incorporating energy management strategy, renewable energy systems and optimal control strategy. The proposed system integrates TES system, utilizing waste heat recovered multifunctional chiller systems from a large capacity healthcare building in South Africa (used as a case study), and retrofitted the SAHP, as supplementary heat source. This approach is used to preheat sanitary water supplied to a multifarious water heating system, consisting of 57 electric storage tank water heating systems. An optimisation strategy is applied to shift energy consumption to off-peak periods, reducing overall costs and the performance of the system is evaluated through simulations based on real-world data from the case study, comparing conventional water heating with the proposed optimised system. Results indicated significant improvements in energy efficiency and cost savings with potential annual energy savings were 15, 001. 93 kWh, equivalent to approximately 49. 6% per annum, which may may equate to 15. 93 metric tons of CO 2 reduction per year. This quantity corresponds to the operational cost savings of 10, 505. 44 USD, which is equivalent to 63. 80%, at the end of the first year. Additionally, the implementation costs of the baseline and proposed systems were approximated to 40, 464, 82 USD and 93, 335. 37 USD, respectively, and considering the cumulative energy costs, replacement costs, operation and maintenance costs and the salvage costs over the period of 20 years, the total life-cycle costs (LCC) of the two systems may therefore be estimated to 1, 064, 745. 62 USD and 543, 567. 18 USD, respectively. These estimates equate to the cost savings of 521, 178. 43 USD, which is about 48. 95% of the costs of the baseline system saved. Moreover, the break-even point of this project is estimated to occur after 4. 5 years at a cost of 129, 385. 76 USD, demonstrating the economic viability of the system. These findings highlight the potential of integrating WHR, TES, SAHP, and intelligent control systems to enhance energy efficiency, lower operational costs, and promote sustainability in healthcare facilities. The study provides a scalable solution for hospitals and other high-energy-demand buildings seeking to transition toward low-carbon and cost-effective energy systems.