Design and Numerical Analysis of a Solar-Based Thermal Energy Storage System for Industrial Hot Water: A Case Study at Addis Pharmaceutical Factory (APF)

Abstract

Solar thermal energy storage (TES) provides a sustainable solution to growing energy demands by storing excess solar energy for later use, particularly in regions with high solar availability. With rising fuel costs and increasing greenhouse gas emissions, adopting energy efficiency improvements and integrating renewable energy sources are crucial in our country, Ethiopia. At APF, furnace oil consumption for process heating is substantial. Additionally, air conditioning (HVAC) systems and process heating rely on hot water produced by an indirect furnace oil system. In this setup, steam is generated in a boiler and then used to produce hot water through a heat exchanger. This is due to water being preferred over steam for certain applications it is easier to control. At APF, 32.5% of the total furnace oil consumption is allocated for hot water production, resulting in an annual cost of approximately 2.88 million birr. This study focuses on the design, analysis, and modeling of a solar-powered TES system for hot water consumption at APF, aiming to enhance system efficiency by selecting the optimal heat transfer fluid (HTF) and energy storage material based on thermal performance and cost-effectiveness. The research evaluates three TES methods: sensible, latent, and thermochemical storage. While phase change materials (PCMs) offer high energy storage density, they have material limitations. Sensible heat storage, despite being cost-effective, has a low heat capacity, making storage units impractically large. Chemical heat storage, though providing high storage density, is hindered by complex reactor designs and stability concerns. Key parameters such as HTF mass flow rate, heat transfer coefficient, flow velocity, and Reynolds number were calculated. The study also includes thermal design analysis, Computational modeling, and performance simulations. The results include calculations of boiler power, total energy consumption, water mass flow rate, energy storage capacity, and trough area. Additionally, SolidWorks geometric modeling was utilized to visualize the concept and aid in solution development. The findings demonstrate the potential of the designed TES system to improve energy efficiency, reduce operational costs, and lower greenhouse gas emissions, contributing to the advancement of sustainable thermal energy storage solutions. Based on comprehensive thermal analysis and ANSYS computational simulations, Shell Heat Transfer Oil S2 was identified as the most effective HTF, while Sodium Thiosulfate Pentahydrate was determined to be the optimal storage material for low- to medium temperature applications. Additionally, an optimal insulation thickness of 16 mm was found to minimize energy loss and cost. To mitigate the intermittent nature of solar energy, the TES system addresses the annual operating cost saving of 0.58 million birrs for the eight-hour operating period, which is 58.2 kW.