Design and Development of a Novel Isobaric-Adiabatic Compressed Air Energy Storage System for Renewable Energy Application

Abstract

Energy is a fundamental driver of productivity, healthcare, education, telecommunications, and transportation, thereby underpinning global economic growth. Thus, energy availability is crucial for human welfare, economic development, and poverty reduction. However, reliance on traditional energy sources has precipitated global climate change and other environmental challenges. Addressing these socio-economic and environmental issues necessitates a shift towards cleaner energy sources within the global energy consumption pattern. Renewable energy sources such as hydropower, wind, solar, geothermal, ocean thermal (OTEC), biomass, and tidal energy offer numerous benefits, including reduced greenhouse gas emissions, local job creation, increased consumer choice, and enhanced health, education, agriculture, income, social bonds, and community development. Despite these advantages, renewable energy sources face limitations, notably their intermittency. Consequently, effective energy storage solutions are critical to harmonize energy supply and demand. The primary energy storage technologies encompass mechanical (pumped hydro storage), electrochemical (batteries), and electrical (supercapacitor, superconducting magnetic) systems. Among these, Compressed Air Energy Storage (CAES) systems are particularly notable for their scalability, long storage duration, high-energy capacity, low cost, environmental benefits, geographic flexibility, longevity, and durability. CAES systems, when integrated with thermal energy storage, can significantly enhance system performance and grid stability. Despite their potential, CAES systems are underutilized. This research explores the hybridization of thermal energy storage with CAES systems, evaluating their performance and potential in future energy systems. CAES systems store excess grid or renewable energy by compressing air into reservoirs during periods of low demand or off-peak times. This compressed air is then released during peak demand to generate electricity. CAES systems can be classified as Diabatic (D-CAES), Adiabatic (A-CAES), Advanced Adiabatic (AA-CAES), or Isothermal (I-CAES) based on thermal energy management during compression. Operationally, they can function under isothermal, isobaric, or isochoric conditions. Commercial CAES systems typically operate isochorically, but isobaric systems have shown superior performance, albeit with significant challenges in maintaining constant pressure and geographic constraints. Various solutions have been proposed, such as underwater CAES (UWCAES) systems, subsurface CAES connected to aboveground water reservoirs, and CAES systems using water pressure to maintain air pressure. These solutions, however, have their drawbacks, including complex technology requirements and reduced system efficiency. This work presents a novel isobaric adiabatic CAES system design incorporating a spring-actuated scissor-jack mechanism to maintain constant pressure within the storage tank. Structural analysis using ASME standards and energy storage analysis using MATLAB r2021 indicate that a stainless steel tank with a 6 mm thickness can achieve a maximum air pressure of 15 bar. For this study, the scissor-jack system was designed for an operating pressure of four-bar, with an average theoretical energy storage tank efficiency of 97.5%. Furthermore, this research investigates the preparation and testing of packed bed (PB) materials for thermal energy storage (TES) to store the thermal energy generated during air compression in CAES systems. The study utilizes mortar-based admixtures incorporating waste glass powder (WGP), graphite powder (GP), and waste glass sand (WGS), selected for their availability, cost-effectiveness, and sustainability. The thermo-physical assessment identifies two categories of PB materials: low volumetric heat capacity (CP) for short-term TES and high CP for long-term TES, with GP enhancing CP due to high porosity. An experimental and numerical study analyses the performance of small-scale hybrid thermal and CAES systems operating under isochoric and isobaric conditions at 4-bar, 6-bar, and 8-bar pressures. The experimental setup includes conventional isochoric and custom isobaric storage tanks with a spring-actuated scissor jack, while the simulated TES segment features single material and multi-layered packed bed tanks. Results demonstrate that the round-trip efficiency (RTE) varies with configuration, with higher efficiencies observed in isobaric storage tanks with intercalated thermal resistance layers. In conclusion, the integration of novel CAES and TES systems offers a promising pathway for enhancing renewable energy storage, addressing intermittency issues, and improving grid stability.