Search Results (4)

The transition toward a renewable-based energy structure has significantly accelerated the advancement of energy storage technologies. Compressed air energy storage (CAES) is regarded as a highly promising long-duration energy storage solution due to the advantages of its large scale and long service life. However, the efficiency of conventional compressed air energy storage (CAES) systems remains limited due to the inadequate utilization of thermal energy. Isothermal compressed CAES (ICAES) technology, based on liquid pistons, can overcome the efficiency bottleneck by enabling temperature control during air compression. However, the operation of liquid pistons under high-pressure storage conditions remains a challenge because of the high compression ratio. To enhance the utilization rate of the two-stage liquid piston unit by using the synchronous operations of compression and discharge processes, this paper proposes a coordinated operation scheme. Then, a multi-stage ICAES system under constant-pressure air storage is proposed. Mathematical models and energy efficiency analysis methods of the multi-stage ICAES system are also established. Finally, the operational characteristics are analyzed in combination with the ICAES at 200 kWh. The results show that the proposed system can achieve an overall efficiency of 68.0%, under 85% and 90% efficiencies for low-pressure and linear equipment, respectively. The coordinated operation of the two-stage liquid piston unit can be further extended to multi-stage operations, demonstrating broad application prospects in ICAES systems. Full article

The global demand for energy is on the rise, accompanied by increasing requirements for low-carbon environmental protection. In recent years, China’s “double carbon action” initiative has brought about new development opportunities across various sectors. The concept of energy pile foundation aims to harness geothermal energy, aligning well with green, low-carbon, and sustainable development principles, thus offering extensive application prospects in engineering. Drawing from existing research globally, this paper delves into four key aspects impacting the thermodynamic properties of energy piles: the design of buried pipes, pile structure, heat storage materials within the pipe core, and soil treatment around the pile using carbon fiber urease mineralization. Leveraging the innovative mineralization technique known as urease-induced carbonate mineralization precipitation (EICP), this study employs COMSOL Multiphysics simulation software to analyze heat transfer dynamics and establish twelve sets of numerical models for energy piles. The buried pipe design encompasses two types, U-shaped and spiral, while the pile structure includes concrete solid energy piles and tubular energy piles. Soil conditions around the pile are classified into undisturbed sand and carbon fiber-infused EICP mineralized sand. Different inner core heat storage materials such as air, water, unaltered sand, and carbon fiber-based EICP mineralized sand are examined within tubular piles. Key findings indicate that spiral buried pipes outperform U-shaped ones, especially when filled with liquid thermal energy storage (TES) materials, enhancing temperature control of energy piles. The carbon fiber urease mineralization technique significantly improves heat exchange between energy piles and surrounding soil, reducing soil porosity to 4.9%. With a carbon fiber content of 1.2%, the ultimate compressive strength reaches 1419.4 kPa. Tubular energy piles mitigate pile stress during summer temperature fluctuations. Pile stress distribution varies under load and temperature stresses, with downward and upward friction observed at different points along the pile length. Overall, this research underscores the efficacy of energy pile technologies in optimizing energy efficiency while aligning with sustainable development goals. Full article

This article summarizes the state-of-the-art knowledge gained from field observations and laboratory studies regarding foam as a liquid controlling agent in porous media. Being the least explored property of foam, its effect and potential have often been overlooked or simply ignored. The aim with this review is therefore to demonstrate the abilities that foam could have to block, reduce, delay, suppress, or divert water flow in porous media. As a liquid controlling agent in porous media, foam has potential for industrial processes that involve fluid injections or fluid withdrawals in porous geological formations, such as improved/enhanced oil recovery (IOR/EOR), matrix-stimulation treatments, underground storage of CO₂, hydrogen, compressed-air or natural gas withdrawal, geothermal energy, and contaminated soil-groundwater remediation processes with unwanted aquifer impacts. Improving the water utilization factor and water management in these applications might result in tremendous energic, economic, and environmental incentives that are worth pursuing. Specific focus in this review is given to the post-foam water injection, which determines the ultimate stability and water-blocking capabilities of the foam treatment. Main parameters and mechanisms that can influence foam stability against water injection/intrusion after generation and placement are assessed and discussed. Unresolved issues are highlighted, which give recommendations for further research and field-scale operations. Full article

In recent years, Hydro-pneumatic cycling compressed air energy storage (HC-CAES) has become an important topic in compressed air energy storage (CAES) technology research. In HC-CAES, air is compressed by liquid and driven by electrical equipment when energy is stored, and then, liquid is used to drive the water conservancy equipment to generate electricity. In this study, adaptive hydraulic potential energy transfer technology is proposed to solve a series of problems in the HC-CAES system, including the high fluctuation range of gas potential energy, poor operating stability, low efficiency, and so on. Therefore, fluctuating potential energy can be stably transferred through the variable area hydraulic devices, which can be controlled with an on–off valve. The structure and operation scheme of the adaptive hydraulic potential energy transfer device used in the HC-CAES system are explained in detail; the device can provide a stable water head range for the highly efficient operation of water conservancy equipment. Moreover, an optimal operation scheme was determined through simulation analysis; a physical experiment platform was built to verify the feasibility of the design and stability of system operation. Full article