Geothermal Energy from Subways and Parking Garages
- Dhanada K. Mishra
- Oct 15
- 6 min read
Updated: 19 hours ago
No Drilling Required, Just Heat-Transferring Panels
On a chilly morning in Zurich, commuters rush through the humming arteries of the city’s underground train system. Unbeknownst to them, there's a secret in the warm air within the tiled tunnel walls and in the earth and rock through which the tunnel winds: There is a wellspring of human-friendly energy there, lingering quietly in subway shafts, cavernous parking structures, and thermally stable soil and bedrock.
It’s an energy reservoir that, until recently, lay mostly untapped—not because it wasn’t large enough, but because few thought to look for it, and even fewer could capture it efficiently. That is, until a Swiss startup led by civil engineer Margaux Peltier, Professor Lyesse Laloui, and Dr. Alessandro Rotta Loria reframed the way cities approach geothermal energy.
The Swiss Solution
Decarbonizing buildings—especially in densely built, aging cities—is one of the 21st century’s greatest climate challenges. Globally, heating accounts for nearly half of all building energy use, representing both a massive environmental burden and a multibillion-dollar economic opportunity. Traditional geothermal systems, while clean and powerful, have always seemed out of reach for urban cores. The prospect of drilling deep beneath city streets to tap planetary heat is daunting, disruptive, and, in most cases, practically impossible.
However, in many cities, subway tunnels, underground parking garages, and other subterranean infrastructure contain reservoirs of residual heat: from the Earth itself, from vehicles, or simply from human activity. Until recently, this energy has been largely overlooked. A Swiss spin-off from the Federal Polytechnic School of Lausanne (EPFL) called Enerdrape is working to change that, with a technology that installs panels on existing underground walls and ceilings to capture heat without the need for drilling.
How the Panels Work
Enerdrape’s modular, prefabricated aluminum panels function as heat exchangers. Peltier, Enerdrape’s CEO, said in an interview with The Earth & I: The panels are “embedded with a closed-loop piping circuit through which water as a heat transfer fluid circulates. These panels are installed on the walls and ceilings of underground spaces such as parking garages and subway tunnels, absorbing geothermal heat and residual thermal energy present in these structures.” The fluid then channels the captured heat to a heat pump. That pump upgrades the heat for use aboveground (or reverses for cooling).
In terms of heating and cooling efficiency, “Enerdrape panels produce about 100–150 watts of heat per square meter of panel area,” Peltier told The Earth & I, “with real-world operating data showing around 150 W/m² in pilot projects.” Each square meter of panels, she said, can effectively supply heating or cooling to 5 to 20 square meters of building space. “This yield is competitive compared to conventional geothermal energy systems, especially given the extremely low installation impact and the ability to access constant underground temperatures 24/7.”
Speaking of her personal background, Peltier said: “I am French and currently based in Switzerland. The idea of the Enerdrape panel was not a sudden discovery but a result of long years of research in the Laboratory of Soil Mechanics of the EPFL, where I studied civil engineering as an undergrad and master’s student.” The panel concept, she said, is based on research carried out in particular by Laloui and his group.
“We can transform underground car parks into something greener and more sustainable.”
“Instead of going on to pursue a PhD, I chose the entrepreneurial path of bringing research to commercial application, after working for a few years as a scientific assistant myself.”
Projects, Funding, and Impact
Enerdrape has moved from lab concept to real-world deployment in several Swiss and French sites, and is now expanding into the United States. Some highlights:
In 2024, it raised CHF 1.3 million ($1.6 million) in a seed financing round. Among the investors were Swiss entities such as Après-Demain (via the GeneRActions Planet initiative) and Romande Energie. Peltier commented that the investment is “a testament to the confidence our investors place in Enerdrape’s mission and potential. It propels the company to scale operations, enhance product offerings, and strengthen the team with new talent.”
Enerdrape has won recognition through innovation and sustainability awards, including the AMAG Sustainability Challenge 2024.
The company is installing panels in a number of underground structures: car parks, tunnels, etc. In Chicago, for example, it is working on a project in the Millennium Parking Garages (one of the largest public underground parking complexes in North America). In New York, Enerdrape is conducting feasibility studies for pilot programs in several large city buildings. In France, partners such as ENGIE Solutions, a global sustainable technology firm, and Paris Habitat, a government-housing provider, are involved. “Cities like New York” and others, Peltier said, “are pushing electrification and emissions reductions, creating incentives for sustainable heating and cooling technologies. While political and regulatory environments can be complex, the rising focus on urban decarbonization aligns well with Enerdrape’s technology.”
“We see a future,” Peltier said in an interview with the AMAG Swiss automotive group, “where mobility infrastructure not only shapes how our cities look but also their energy supply.” She further noted that “together with companies like AMAG, we can transform underground car parks into something greener and more sustainable.”
One of the compelling advantages of Enerdrape’s approach is avoiding the cost, complexity, and disruption of drilling deep boreholes or excavating new wells. Because the panels are applied to existing structures, installations can be faster, regulatory hurdles potentially fewer, and disruption to urban life more limited. “We aim for a world where every underground infrastructure becomes a well of green energy,” Peltier told ENGIE Research & Innovation News.
A powerful environmental vision: “unleashing the full potential of the subsurface, placing it at the heart of the energy transition.”
Yet there remain technical and regulatory obstacles. Underground spaces present harsh environments: humidity, vibration, chemical exposure, and in many cases older or complex building HVAC systems that must be integrated. Urban regulation around underground retrofits is not yet standard. Peltier acknowledged that “older buildings often have thick walls, protected facades, or space limitations making traditional retrofits difficult.” Yet, she said, Enerdrape’s system is designed to overcome some of these constraints by being noninvasive and modular.
Broader Implications and Outlook
If scalable, the model could become an important component of low-carbon heating and cooling for cities. Heating and cooling in buildings account for a large share of energy use in the built environment, especially in older or high-density urban areas. By using already existing underground structures to harvest residual heat, energy systems could become more decentralized, more resilient, and less reliant on fossil fuels.
Peltier has suggested that the system can “produce renewable heat 24 hours a day,” and that it can be used both in renovations and new construction. She also has emphasized that scaling doesn’t always require huge upfront investment, saying that the panels are compatible with existing infrastructure and that one can start with pilot installations and build up.
When all is said and done, Peltier has a powerful environmental vision: “unleashing the full potential of the subsurface, placing it at the heart of the energy transition,” as she declared to The Earth & I. If Enerdrape and similar technologies continue to perform as in pilot projects, society may be at a turning point: viewing underground infrastructure not as inert voids beneath cities, but as active contributors to urban energy systems. The question now is how swiftly cities can adapt regulation, financing, and building practices to integrate them.
*Dhanada Kanta Mishra is a PhD in civil engineering from the University of Michigan and is currently working as the managing director of a Hong Kong-based AI startup for building technology for the sustainability of built infrastructure (www.raspect.ai). He writes on environmental issues, sustainability, the climate crisis, and built infrastructure.
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