EAGER: CET: Underground Thermally Enhanced and Architected Metamaterials (UTEAM)

University Of Texas At Austin, Austin TX

Investigators

Abstract

This EArly-concept Grants for Exploratory Research (EAGER) award is made in response to Dear Colleague Letter 23-109, as part of the NSF-wide Clean Energy Technology initiative. Population growth and urbanization are increasing global demand for energy sources that are capital-intensive, environmentally damaging, and inequitable. Shallow geothermal energy systems are a promising sustainable energy technology, but their applicability in areas where soils are partially-saturated can be limited. Their wider utilization is also hampered by the high capital costs. Here, microbially induced calcium carbonate (CaCO3) precipitation (MICP) can be used to improve the heat transfer and energy storage efficiency of soils, because CaCO3 is low cost, and has a high thermal conductivity, and excellent chemical and thermal stability. Moreover, this enhanced heat transfer can be utilized to trigger the geometric phase transformation of thermomechanical architected metamaterials (TAMs) under thermal loads to generate energy. This research will advance fundamental engineering knowledge by creating an entirely novel shallow geothermal heat exchanger (GHE) that relies on site-specific natural minerals and 3D printable, programmable TAMs for cost-effective geothermal energy harvest with fast installation capability. The technology has the potential to be broadly used for energy and CO2 storage solutions, power transmission/distribution, and construction and heat recovery technologies. The project has four specific educational objectives: mentor and train undergraduate and graduate students; facilitate the retention of underrepresented minorities through workshops and training; integrated modules and dissemination through documentation, publications, presentations at conferences and webinars, and developed COMSOL Apps (user-friendly, accessible interfaces to access complex simulation models); and a USA-UK exchange program. The overall goal of this project is to engineer a novel, cost-effective, and easily deployable concept of shallow geothermal heat exchanger (GHE) that couples Microbially induced calcium carbonate (CaCO3) precipitation (MICP) with thermomechanical architected metamaterials (TAMs). This overall goal will be achieved through three objectives: 1) develop a MICP treatment method for enhanced heat transfer in soils under mechanical loads; 2) develop geometric phase transforming structures tuned by temperature variation; and 3) integrate MICP with TAMs for geothermal energy harvest. The tasks mirror the project objectives and focus on combining experimental and numerical approaches to optimize MICP for enhanced thermal conductivity of soils under in-situ stress conditions, engineer the manufacturing and functionality of TAMs, and evaluate the system design and performance. This evaluation includes the development of a numerical model to investigate the multi-year operation performance of this novel GHE at a household system scale, thereby providing insights into its deployment potential. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.