Temperature Distributions inside Concrete Sections of Renewable Energy Storage Pile Foundations

Abstract

A new pile foundation system is being developed for renewable energy storage through a multi-disciplinary research project. This system utilizes the compressed air technology to store renewable energy inside the reinforced concrete pile foundation configured with hollowed sections. The compressed air can result in high air pressure to which the structural response of the pile foundation subjected has been studied. However, the temperature in the pile foundation can be affected by the compressed air if sufficient cooling is not provided. The temperature change can generate thermal stresses and affect the structural safety of the pile foundation. As a first step to investigate this thermal effect, this paper studies temperature distributions inside the concrete section for the pile foundation through non-steady state heat transfer analyses. Several parameters were considered in the study, including thermal conductivities of the concrete, specific heat capacities of the concrete, and dimensions of the pile foundation. It has been found that the temperature distribution along the concrete section varies significantly during a daily energy storage cycle as well as subsequent cycles due to the cumulative effect of residual temperatures at the end of each cycle. The temperature distribution is largely affected by the thermal conductivity of the concrete and the geometry of the pile foundation. The obtained temperature distribution can be used for investigation of the thermal stress inside the foundation and surrounding soil.

Group Pile Effect on Temperature Distributions inside Energy Storage Pile Foundations

“…Figure 1. Thermodynamic processes of compressed air energy storage (CAES) (modified from [7]). Figure 1.…”

“…In addition, an ideal isolated pile foundation case was considered as a reference case. This isolated pile was modeled with a soil layer of 41 m. At this distance, the soil temperature remains at the initial value and is not affected by thermal loading for the isolated pile case only [7]. The selected values of pile spacing for 6 different cases are s = 2 m, 4 m, 5 m, 6 m, 7 m, and the isolated pile case.…”

“…The predefined initial temperature of the model was assigned as 12 °C, which resides within a range of normal underground temperatures (10 to 15 °C according to [30]). The thermal properties of concrete were selected based on the results of the parametric study discussed in [7]. Since the energy storage pile requires high-strength concrete according to [5], this paper selected values of the thermal conductivity (2 W/m•°C) and specific heat capacity (940 J/kg•°C), respectively, which are suitable for high strength concrete [31,32].…”

“…The temperature distribution inside the pile foundation for isolated piles has also been investigated [7]. On top of these research results, the pile foundation for isolated piles has also been investigated [7]. On top of these research results, this paper presents a study on the temperature changes and distributions for the group pile construction since it is a common construction practice.…”

“…The structural responses of the foundation subjected to high pressure have been studied extensively [5,6]. The temperature distribution inside the pile foundation for isolated piles has also been investigated [7]. On top of these research results, the pile foundation for isolated piles has also been investigated [7].…”