Could Duke University Be Sitting on a Sustainable Energy Reservoir? Exploring Underground Heat Storage.

Duke University, known for its academic excellence and commitment to innovation, is now looking beneath its feet for a potential solution to sustainable energy: Aquifer Thermal Energy Storage (ATES). But what exactly is ATES, and does Duke’s geology make it a viable option? This is what we are exploring in the PlanetLab. 

What is ATES?

Imagine storing heat in the ground like a giant underground battery. That’s the basic idea behind ATES (Figure 1). During warmer months in the summer, excess heat (like the heat produced by cooling systems) can be pumped into an underground layer of rock called an aquifer or reservoir. Later, in the winter when it gets cold, that stored heat can be pumped back up to heat buildings which is less energy intensive than making new hot water. 

Figure 1. Schematic of simplified doublet Aquifer Thermal Energy Storage system using hot water storage.

What We’re Finding in the Planet Lab

Researchers at Duke are diving deep (literally!) to figure out if the local geology is suitable for ATES. Here’s a glimpse into their work:

• Looking at Sedimentary Rock Layers: By analyzing core samples from a 677-foot borehole drilled at the Central Campus drill site (Figure 2), our team is identifying layers of sandstone that could potentially store hot water. These layers are the heat “storage tanks” of an ATES system.
• Up Close with Rocks: Examining rock samples under a microscope helps researchers understand the mineralogy (what the rock is made of), grain size (how big the sand particles are), and porosity (how much pore space there is for water). These details are crucial for predicting how well the rock can store and release hot water. Rock thin sections were made and preliminary analysis has been started to better understand mineralogy and physical properties of the rocks. 
• Porosity Trends: One fascinating finding is that porosity seems to change depending on the distance from the major geological fault in the area (the eastern Jonesboro Fault). This could have implications for where the best storage zones are located.
• Water Flow: Preliminary tests have been conducted to understand how easily water can flow through the underground rock. This is essential for getting the heat in and out of the storage system. 

Figure 2. An example of a 10 foot section of core log, tan rock (top of image) represents sandstone and brown rock (bottom of image) represents mudstone.

Why is Geology So Important?

The success of ATES hinges on finding the right geological conditions. 

For ATES, we need:

• Thick Sandstone Layers: Thick layers of sandstone acting as underground reservoirs that could potentially hold significant amounts of hot water. 
• Permeability: The rock needs to allow water to flow through it easily so we can inject and extract it at rates fast enough to supply Duke’s demands. 
• Porosity: The rock needs enough empty space to hold the hot or cold water.

The Big Picture

This research is still ongoing, but the initial findings are promising. If Duke University can successfully implement ATES, it could:

• Reduce reliance on fossil fuels at Duke:  Currently, Duke relies 100% on natural gas for heating purposes and ATES technology could greatly reduce the amount of natural gas and carbon emissions associated with heating on campus. Conversely, 100% of the energy required for cooling comes from electricity, which can be produced using renewable (nuclear and renewables). 
• Leader in sustainable energy: ATES can be more efficient than traditional heating and cooling systems and could help Duke become a pioneer in implementing innovative sustainable energy technologies. 
• Community engagement: Most importantly, Duke could serve as a proof-of-concept and then help implement ATES systems in vulnerable communities in Durham fostering a better relationship with the community. 

Beyond Duke’s Campus: Using Earth Systems

Understanding to Build Climate-Resilient Communities

with ATES

The PlanetLab mission is; Understanding Earth Systems and Community Resilience to Reduce Suffering due to Global Change which resonates deeply with the transformative potential of ATES. Demonstrating the viability of ATES on Duke University’s campus is a vital starting point, but its greatest impact lies in extending this solution to communities most vulnerable to climate disruptions. In places like Durham, where under-resourced neighborhoods are increasingly exposed to extreme weather and power outages, ATES represents not just a technological fix, but an opportunity to align energy innovation with justice and resilience.

Understanding Earth systems is central to implementing ATES. This technology stores heat or cold in underground aquifers or reservoirs, using the natural thermal insulating properties of Earth materials. Crucially, this process reduces dependence on fossil fuels and centralized power grids. As global change accelerates the frequency and severity of heatwaves, cold snaps, and storms, systems like ATES can support communities from catastrophic energy loss, especially during blackouts that compromise health and safety for the elderly, children, and medically vulnerable residents.

The PlanetLab framework urges us to use earth system knowledge not in isolation, but as a tool for advancing community resilience. A compelling application of this philosophy is the development of ATES-supported microgrids around community centers (schools, churches, libraries) that can act as resilience hubs. These hubs would maintain critical heating and cooling functions during power outages by operating independently from the main grid, ensuring continuity of care and shelter during emergencies.

Framing this within PlanetLab’s core values yields a powerful vision:

• Systems Thinking for Local Impact: Integrating geologic, hydrologic, and climatic data enables smarter siting and operation of ATES systems, reinforcing resilience at the neighborhood level.
• Reducing Suffering through Adaptation: ATES supports climate change adaptation by helping to minimize the negative effects of energy disruptions during extreme weather events, without increasing emissions.
• Equity-Centered Design: Prioritizing deployment and installation in underserved communities addresses long-standing energy injustices by ensuring fair access to climate-resilient infrastructure.
• Empowered Communities: When faced with a crisis, resilience hubs can evolve into community-driven spaces that provide mutual aid and coordination, going beyond their role as energy nodes.

By leveraging Earth systems understanding for community benefit, ATES exemplifies the kind of innovation PlanetLab champions: one that is grounded in science, driven by justice, and shaped by the lived realities of those on the frontlines of climate change.