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Thermo-Active Solution & Ground-Source Heat Pumps to prevent potholes

Researchers at the University of Surrey are testing a new thermo-active road solution to prevent road potholes caused by freezing and thawing in the winter.

Net zero road maintenance in the UK is an initiative dedicated to making road maintenance environmentally sustainable and reducing its impact on climate change. This involves implementing sustainable practices, utilizing advanced technology, and employing offsetting methods to minimize or eliminate greenhouse gas emissions associated with road maintenance activities, thereby mitigating environmental impacts. To achieve this, a range of strategies and technologies are under consideration. Notably, one approach involves harnessing geothermal energy and ground-source heat pumps to regulate road surface temperatures. This not only extends the lifespan of road surfaces but also reduces carbon emissions and lowers maintenance costs. Additionally, innovative methods like ground-based heat collection are being explored to prevent potholes and road deterioration, contributing significantly to the goal of achieving net-zero road maintenance. These initiatives represent important strides towards a greener and more sustainable road infrastructure in the UK, aligning with global endeavors to mitigate the impacts of climate change.

This project’s primary focus is to assess the feasibility of utilizing geothermal energy, specifically through ground-source heat pumps, to control road surface temperatures. The overarching objective is to prolong the longevity of road surfaces, mitigate carbon emissions, and decrease road maintenance expenses. Led by Dr. Benyi Cao from the University of Surrey in collaboration with National Highways, the initiative intends to implement ground-source heat pumps for the dual purpose of cooling roads during summer and warming them in winter.. The project has received a substantial research fellowship of £625,000 (US$780,000) from the Royal Academy of Engineering. This funding aims to upgrade the UK’s major road networks, making them more resilient to climate change impacts.

Road deterioration caused by pothole

Sustainable Roadwork Solutions

Dr. Cao, underscores that currently, a typical motorway or a road surface has a lifespan of 20 years. However, this is likely to diminish due to increasingly severe weather conditions. Regulating road surface temperatures is envisioned to significantly extend their durability, offering not only safety benefits and reduced vehicle damage but also a substantial reduction in costly and inconvenient roadworks.

Environmental and Financial Impact

The statement accompanying the project notes that current road technologies contribute to an estimated 700,000 tonnes of carbon emissions annually. Additionally, repairing potholes in the UK is projected to cost around £12 billion over the next decade. The innovative approach of using thermo-active roads, a low-cost, low-carbon alternative, could mitigate these issues. Statistics also reveal that potholes on major roads in England have caused 5,000 injuries since 2018. In the previous year, England allocated £1.2 billion (US$1.5 billion) towards road maintenance and repair, a process associated with a substantial carbon footprint.

The Thermo-Active Solution

A thermo-active solution for roads is an innovative approach to road maintenance that harnesses geothermal energy to control and manage the temperature of road surfaces. It involves the use of ground-source heat pumps installed beneath the road, which can either heat or cool the road’s surface as needed. During hot weather, these systems can dissipate excess heat, preventing the road from becoming too hot and potentially causing damage. In cold weather, the heat pumps can provide warmth to prevent freezing and the formation of ice, ensuring safer driving conditions.

One of the key benefits of thermo-active road solutions is their ability to extend the lifespan of road surfaces. By mitigating the extreme temperature fluctuations that can lead to cracks, potholes, and other forms of damage, these systems reduce the need for frequent and costly road repairs. Additionally, they contribute to environmental sustainability by reducing the carbon emissions associated with road maintenance and repair activities. Overall, thermo-active solutions offer a promising way to create safer, more durable, and environmentally friendly road infrastructure.

This innovative approach aims to address various challenges associated with road maintenance and sustainability. Here’s how it works:

  • Geothermal Energy: Thermo-active roads utilize ground-source heat pumps, which tap into the Earth’s natural heat reservoir beneath the road surface. The ground at a certain depth remains at a relatively stable temperature throughout the year.
  • Regulating Temperature: These heat pumps can be used to either cool or warm the road surface as needed. In hot summer months, they can help dissipate excess heat from the road, keeping it cooler. Conversely, in winter, they can provide heat to prevent freezing and the formation of ice on the road.

By controlling the temperature of the road surface, thermo-active solutions aim to extend the lifespan of roads significantly. Extreme temperature fluctuations, which can cause cracks and potholes, are mitigated. This reduces the need for frequent and costly road repairs.

“Climate change poses an extra threat to our roads. Thermo-active roads could help mitigate this,” said Dr. Cao. “They could be introduced gradually as resurfacing takes place, so wouldn’t cause any extra disruption for motorists. I think there will be long-term benefits to drivers and taxpayers. That’s what I aim to demonstrate during my fellowship.”

Utilizing Ground-source heat pumps

Ground-source heat pumps (GSHPs) utilize the ground as a heat collector, making use of the relatively stable temperatures below the Earth’s surface to provide heating, cooling, and hot water for buildings. These systems consist of a ground loop buried underground, typically containing a mixture of water and antifreeze, which absorbs heat from the ground during the winter to provide heating and releases heat back into the ground during the summer to provide cooling. GSHPs can significantly reduce the energy consumption and carbon emissions associated with traditional heating and cooling systems, making them a valuable tool in the transition to more sustainable energy solutions.

The placement coils of pipe across the road every 5-10 meters, connected via a heat pump to a loop of underground pipes 5-10 meters down, surrounded by soil that’s been impregnated with phase-change microcapsules designed to store and release

Ground acting as a heat collector

Dr. Cao’s innovative approach to addressing the issue of potholes revolves around utilizing the ground beneath road surfaces as a natural heat collector and storage system. He identified the key factors contributing to pothole formation: surface cracks induced by traffic, the presence of water, and the freeze/thaw cycle. 

Dr. Cao realized that the ground beneath the road offers a consistent and sustainable heat source. In the winter, when temperatures drop significantly, water within these surface cracks freezes and expands, causing damage to the road’s asphalt binder. To combat this, Dr. Cao’s concept involves using the ground as a reservoir for heat during the summer months, effectively storing thermal energy. Then, in the winter, this stored heat can be strategically released to warm the road surface, preventing the freezing and expansion of water within cracks. By doing so, Dr. Cao aims to eliminate the primary cause of pothole formation and enhance the overall durability of road surfaces, ultimately offering a more efficient and sustainable solution to this persistent road maintenance challenge.

Cao’s designed system operates as follows: during road construction, workers will lay slim, 10-mm-diameter plastic pipes across the road at intervals of approximately 5-10 meters. Simultaneously, they will excavate to a depth of 5-10 meters beside or below the road to create additional piping loops underground. The surface loops and the underground loops will connect at a heat pump.

The subgrade soil surrounding the underground loops will be infused with tiny microcapsules, as explained by Cao: “These capsules will be composed of a phase-change material, potentially similar to paraffin or wax, known for its ability to store a significant amount of heat. The outer shells of these capsules will consist of graphite or graphene-based materials to facilitate rapid heat transfer.”

The primary function of the heat pumps is to gently circulate a mixture of water and antifreeze through the loops. Importantly, this circulation does not need to be continuous. Once sufficient heat is stored underground, the pumps can be deactivated and need not be reactivated until the road temperature drops to just a couple of degrees above freezing.

Cao suggests that a single set of underground coils and a heat pump could likely manage a road segment exceeding 100 meters (330 feet) in length effectively. He elaborates, “For each unit of electricity used to operate the heat pump, it can move four units of thermal heat.” This level of efficiency surpasses that of electric road heating systems significantly.

Dr. Cao’s innovative idea emerged during his search for a more efficient and sustainable solution. He said, “Considering that roads sit atop a vast expanse of underground ground, why not utilize this ground as a heat collector and storage unit during the summer, and then extract and use that stored heat in the winter?”

Collaborative Efforts for Innovation

During the five-year research fellowship, Dr. Cao’s team intends to collaborate with Versarien, an advanced materials engineering company, to develop graphene-enhanced microcapsules. These capsules will enhance heat conduction and storage beneath road surfaces.

Laboratory Testing and Advanced Modeling

This groundbreaking approach will be put to the test at the University of Surrey’s Advanced Geotechnical Laboratory. Structured as a five-year research fellowship, the project employs a multifaceted approach to achieve its objectives.

The project includes the creation of a laboratory-scale model road segment with a heat pump at the University of Surrey’s Advanced Geotechnical Laboratory. This setup will facilitate the evaluation of thermal performance and resilience under controlled climatic and traffic conditions. The integration of advanced numerical modeling, incorporating meteorological data and findings from laboratory experiments, will provide insights into the construction of thermo-active roads.

Full-Scale Field Trials and Lifecycle Assessment

To ensure the feasibility and effectiveness of thermo-active roads, full-scale field trials will be conducted on UK roads. A comprehensive life cycle assessment will be performed to understand both the environmental and financial implications of this innovative road maintenance approach. 

An Economic Perspective

Regarding the economic aspect, Dr. Cao acknowledges that a cost analysis cannot be conducted until the field trial is complete. Implementing this approach will undoubtedly incur additional costs in transportation infrastructure. However, the benefits in terms of reduced carbon emissions from pothole repairs, estimated at 700 tons per year, and the extended lifespan of new roads, are significant.


The pioneering project, funded by the Royal Academy of Engineering, aspires to transform road maintenance in the UK by harnessing geothermal technology for controlling road surface temperatures. This sustainable approach not only addresses the challenges of climate change but also promises long-term advantages in terms of road safety and cost-effective maintenance.



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