Everything you need to know about heat conducting concrete
Heat conducting concrete is a material primarily used to improve the effectiveness of energy transmission between power infrastructure. These include substations, battery storage facilities, and on- and off-shore wind farms.
In a world where the acceleration of global warming is an immediate concern, increasing the efficiency of energy infrastructure has become a high priority. Heat conducting concrete is a material at the core of improving the efficiency of energy transfer within underground cables. By keeping thermal resistivity low and ensuring consistent thermal conductivity, the ready-mixed concrete is increasing the capacity of high voltage (HV) and ultra-high voltage (UHV) cables - and ensuring safer and more effective longer-term operations.
Whether you’re looking for a specialist heat conductive concrete mix for your project or are keen to learn more about the material’s properties, you’re in the right place.
Is Portland Cement suitable as a binder in cable bedding and infill?
In HV and UHV cable installations, thermal management is critical to maintaining cable performance and longevity. Typically, unbound granular materials are used for cable bedding and backfill, with a maximum allowable thermal resistivity of 2.7 Km/W. When cement-bound materials are used, the thermal resistivity requirement becomes more stringent, with a maximum limit of 1.2 Km/W.
Standard Portland Cement based concrete is generally unsuitable for use around HV cables due to its variable thermal characteristics and difficulty to remove for future repairs. Using inappropriate materials can lead to:
- Insufficient heat dissipation
- Elevated cable operating temperatures
- Increased risk of thermal degradation or failure
Material selection should therefore focus on low thermal resistivity and compliance with installation standards.
The need for specialist concrete mixes
When producing heat-conducting concrete mixes, specialist cements are required to ensure all the desired properties are met. For instance, the proprietary cementitious blended binder used to produce PowerCrete, our heat-conducting concrete.
Thanks to our exclusive use of a binder with extremely high thermal conductive properties, PowerCrete has an incredibly low thermal resistivity of just 0.33 Km/W. To learn more about how PowerCrete is advancing thermal energy storage systems, please read our article, What is PowerCrete and where is it used?, or contact us.
Heat conducting concrete applications
Due to its enhanced heat dissipation properties, heat conductive concrete is commonly used as a cable bedding and/or infill material within the energy sector. It’s particularly prevalent in projects that require high voltage power, for instance, where electrical lines run to and from infrastructure such as:
- Off-shore wind farm landfalls
- Power stations
- Data centres
- Modular nuclear reactors
- Nuclear power plants
- Solar farms
By nature, transferring energy via underground HV and UHV cables generates heat. These rising temperatures cause standard underground power cables to lose capacity, decreasing the overall efficiency of the electrical transfer.
How heat conducting concrete promotes energy saving
When heat-conducting concrete, like PowerCrete, is used to bed the cables or infill the surrounding areas, heat dissipation to the surrounding materials is enhanced. As more heat gets transferred away from the cables, heat build up reduces. Resistance of the cables decreases too, helping to maximise the power capacity of the underground cables.
The impact of reducing HV and UHV cable temperature
Reducing the temperature of HV or UHV cables can lead to improved efficiency. When specialised heat conducting concrete is used instead of a traditional bedding or infill material (such as a standard Portland Cement mix), it typically results in a noticeable increase in energy output.
Below, we’ve outlined the key advantages of choosing a heat conductive concrete mix over more traditional material:
- Improved heat dissipation for HV and UHV cables
- Increased power capacity
- Reduction in magnetic field strength for alternating current
- Allows the use of aluminium conductors
- Reduction of conductor cross-section
- High heat conduction after drying
For more details, please contact our technical team.
Accreditations of our heat conducting concrete
When choosing a heat conducting concrete, you should always check for the following accreditations for confidence that the product is suitable for the intended use:
- Quality Scheme for Ready-Mixed Concrete (QSRMC): This scheme provides ISO 9001 (an international quality management standard) and product conformity certification for the design, production, and supply of ready-mixed concrete.
- Energy Network Association - Technical Specification 97-1:A specification that ensures any backfill materials placed in a cable trench have thermal resistivities in the dried-out state. These must not exceed the limiting values assigned by the contractor or specified by the network owner in the design of the cable installation.
- National Grid Technical Specification 3.05.07: A level 3 specification outlining the requirements for the installation of power cables, their accessories, and associated auxiliary cables, usually for voltages of 132kV and above.
- British Standards: For instance, BS EN 206 and BS 8500, which set the standards for the specification, performance, production and conformity of concrete.
How to enhance thermal performance of cable networks
You’ll be pleased to hear that Heidelberg Materials’ Power product range adheres to the above standards and specifications, with performance speaking for itself. Around the UK, many well-known projects are using our heat-conductive concrete mix to bring about a range of energy efficiency improvements. Other products from our Power range are often used as well, each with its own advantages.
Power range
| Product name | Description |
| PowerCrete | A robust heat-conducting concrete used as a bedding and infill material, and a higher performing option compared to PowerSand. PowerCrete's lower thermal resistivity allows for small trench sizes, making it the ideal choice for cable burials in limited or restricted access areas. |
| PowerSand CBS | A certified and ENA TS 97-1 compliant cable sand for backfilling. |
| PowerSand CBS Extra | Our non-traditional stabilised backfill (as defined in ENA TS 97-1), with optimised performance. |
Explore PowerSand products in more detail by heading to our cement bound sand page. You’ll also find details of all Power products in our brochure, available to download now.
Results from projects that use our Power range
See the real-world impact of using our Power range of specialist concrete and cement bound sand:
PowerCrete
Supporting the landfall connection to the Inch Cape offshore wind farm
We supplied 242m3 of PowerCrete to Charles Brand, the main contractor on the Inch Cape project, to bury HV cables on land from an offshore wind farm. It’s set to become one of Scotland’s largest and demanded a thermally efficient solution.
“PowerCrete was exactly what we needed for Inch Cape and handled the technical demands of the cable installation really well.”
Michael Kelly, commercial manager at Charles Brand
PowerSand CBS Extra
Assisting in the development of a 230MW battery storage facility
We supplied 1,000m³ of PowerSand CBS Extra to Jones Bros Ruthin Civil Engineering Ltd, the main contractor on the Uskmouth Substation project. PowerSand is a lower carbon alternative to traditional backfill solutions and was used across various cable bedding applications.
“Heidelberg Materials’ PowerSand CBS Extra provided the performance we needed for safe and efficient cable installation, and their team was incredibly responsive throughout.”
Rhys Roberts, Contract Manager, at Jones Bros Ruthin Civil Engineering Ltd
Uskmouth Substation case study
Next steps
The closer we get to 2050 (the year emissions need to reach net zero), the more pressure there is on the energy sector to have efficient and robust infrastructure in place. Yet this opens up a realm of opportunity to invest in the materials that are going to help achieve it, such as heat conducting concrete.
For more information about the suitability of our heat conductive concrete to your project, please contact our team. You can also find more details about PowerCrete and PowerSand by clicking the buttons below.