Seeking better Backfill Materials for Underground HV Cables

OVERVIEW

Wazoku, the Seeker for this Innocentive Scouting Challenge, on behalf of Omexom Taylor Woodrow, is seeking to find better performing materials as an innovative viable alternative to the present, specifically imported, thermally conductive sand for the backfilling of buried HV transmission and distribution cables. Key needs are the availability of the proposed material to reduce sensitivity on imported specialist sand and find better performing materials that enable the cables to function at higher ratings, notably amperage.

This is a Scouting Challenge seeking a partner or supplier to provide solutions and expertise to develop and prove the material to solve the Omexom Taylor Woodrow business challenge; the Solver is invited to submit a written proposal to be evaluated first by Wazoku and then finalists by Omexom Taylor Woodrow with the goal of establishing a collaborative partnership.

The Challenge timeframe is short, you will already have or be connected with a credible solution in order to participate.

Your proposal must clearly identify your current solution’s maturity and your credibility to be able to collaborate directly, or in partnership with Wazoku. More developmental solutions are welcome if they offer very strong potential. Your stated validation of this potential is key.

Solvers with a viable solution and cost case will be supported by Wazoku:

• With the potential to pitch directly to Omexom Taylor Woodrow
• To be selected for the opportunity to work with Omexom Taylor Woodrow to develop and prove your material at small scale
• Omexom Taylor Woodrow can also provide support to develop the solution through expert input, characterisation testing and physical trials in a safe environment
• Stay involved in a following funding stage to allow for further development and critical network compliance testing
• The solution has the potential for deployment of approximately 33km of underground cables within the Omexon Taylor Woodrow contracts alone
   

In return, Wazoku will retain a share of 25% of any financial benefits you are paid for the collaboration, as a result of the challenge.

Submissions to this Challenge must be received by 11:59 PM (US Eastern Time) on February 25th, 2026.

Please review the later Participation Guidance section before submitting a proposal.
- Login or register your interest to solve!

ABOUT THE SEEKER & ELIGIBILITY

Wazoku is an innovation ecosystem platform encompassing AI, market intelligence, venture building, patent analysis and open talent networks. It centralises data, talent, and tools to make innovation measurable, impactful and able to solve pressing challenges.

Wazoku also operate Innocentive open innovation Challenges like this one, supporting the preeminent problem solver community who have delivered breakthrough results for organisations like NASA, the International Rescue Committee, and ExxonMobil.

Omexom Taylor Woodrow are a leading installer of HV transmission equipment and a key part of the Great Grid Partnership in the UK. One aspect of their site works is the construction of underground transmission and distribution cables; this can be in open country but also urban areas. The cables typically range from 132kV to 400kV, laid in large trenches that can be hundreds of metres to many kilometres in length.

This challenge is open to individual entrepreneurs, academic institutions, start-ups or SMEs.

THE CHALLENGE

Background

The design and installation of underground HV cables is complex; the cable rating (amperage) is governed by its ability to dissipate heat into the surrounding soil mass. An excess of heat diminishes the conductive cable’s ability to carry current and is limited to a maximum cable conductor temperature of 90ºC to prevent possible deterioration of the safety critical multi-layer electrical insulation.

The cables sit within PVC ducts which are in turn bedded on and surrounded by a thermally conductive cement bound sand (CBS), this helps the passage of heat into the natural ground, the use of a cement binder provides protection from mechanical damage.  The excavated trench size and quantity of sand required are related to the thermal conductivity of the sand.

The (simplified) construction sequence is:

1. Excavate trench
2. Place and compact cement bound sand (CBS) bedding layer
3. Install PVC ducts (range from 100-250mm dia)
4. Place and compact CBS around and over ducts
5. Place warning tapes
6. Install protective tiles
7. Place and compact selected excavated material back to ground level
8. Pull through cables (400kV cables are circa 120mm diameter)
9. Generally, infill ducts with bentonite slurry

CBS is typically a coarse sand (under 5mm sieve) with added cement (ordinary Portland cement at 1:14 ratio) to create a semi-dry mix; the sand and cement are generally batched on site for near immediate use. It is compacted by either hand tampers and/or mechanical methods such as wacker plates or rollers.

CBS is used in large quantities, on one UK project alone some 100,000cu.m were imported to site. It's engineering performance are a critical part of the cable's electrical performance.

Many UK sands are not suitable for use in CBS as they are not sufficiently thermally conductive. Typically, quarries will be found as near to the site as practicable and the sand laboratory assessed. Once proven the sands continue to be tested to ensure compliance through the project, recognising these are natural materials with potential natural variance.

The Challenge

The challenge is to find better performing materials as an innovative viable alternative to the present, specifically imported, thermally conductive sand for the backfilling of buried HV transmission and distribution cables. Key needs are to reduce sensitivity on imported specialist sand and find better performing materials that enable the cables to function at higher ratings.

The availability of suitable local sand is a significant commercial and technical risk to projects, denudes a natural resource with associated effects on the ecology, and if suitable sand is only found remote from the site has an increasingly large carbon footprint associated with logistics.

The natural ground that is excavated varies considerably by location and may include fine clays or stones.

Omexom Taylor Woodrow are seeking solutions that can specifically address:

• Derisking the availability of suitable sand
• Reducing the net carbon footprint
• Less denuding of natural resources
• Improving cost certainty

And can also address:

• Improving backfill thermal conductivity to reduce the excavation needed and sand imported and/or enable improved rating of underground HV cables
• Reducing the commercial risk of availability from local quarries
• Avoiding the potential need to take surplus excavated materials offsite

This may include and is certainly not limited to solutions that:

• Utilise additives and/or processes that uplift the conductivity of currently unsuitable sands
• Blend unsuitable soils with high conductivity minerals such as metal compounds
• Utilise mine tailings and historic mining spoil
• Utilise high conductivity waste streams such as ceramics waste or suitable demolition materials
• Valorise excavated materials on site to enable use in CBS
• Utilise novel additives that permanently sit within the sand matrix to enhance heat transfer between grains (similar to the effect of water saturation but not sensitive to draining or drying)
• Offer different systems of materials and processes that accomplish the end goal of cables within ducts in a protective, conductive medium or otherwise providing heat dissipation
• Have UK nationwide availability (ideally within 40 mile radius of project sites)

SOLUTION REQUIREMENTS

It is recognised that solutions are likely to require development and then a rigorous National Grid compliance activity.  A timeline of under 18 months to compliance trials with National Grid is proposed; naturally a faster programme would be highly desirable. This aligns to an expectation of commercial readiness at large scale under 4 years.

Solutions are likely to require acceptance by National Grid, the current standards for CBS are within ENA TS 97-1 and the overall cable system within NG.TS 3.05.07, cognizance of these is recommended when considering solutions

The Challenge timeframe is short, you will already have or be connected with a credible solution in order to participate.

Your proposal should clearly identify your current solution maturity and your credibility to be able to collaborate directly, or in partnership with Wazoku, and state the estimated timeline to readiness for compliance testing.

More developmental solutions that may struggle with this timeline are also welcome if they offer very strong potential. Your validation of this potential is key.

Functional Requirements

1. Be available at a sufficient assured scale (please specifically confirm this aspect within your submission)
2. The solution must be able to be practicably placed in situ, under, around and over cable ducts, so that the target thermal conductivity can be assured; this is likely to entail controlled compaction. The minimum CBS surround thickness is 75mm 
3. Currently the thermal conductivity is not measured in situ, instead density is simply measured to determine the void content. If this technique is not appropriate to the solution an effective in situ measurement technique should be identified. (For general guidance of site quality control expectations reference ENA TS 97-1)
4. Be compatible with and in no way deleterious to PVC ducting
5. Be compatible with cement binder and compatible with lime, emergent AACM geopolymers and common cement replacement materials
6. Not cause harm or change to the natural ground (that is often arable land) or watercourses through leaching or other mechanisms- depending upon the potential harm a protection system could be considered
7. Be no more hazardous to work with than current cement bound sand (CBS)
8. Cure to a reasonably hard material to protect the cables from mechanical damage
9. The expectation is for the sand to have negligible clay particles (typically less than 0.06mm) so that it is not overly sensitive to volumetric changes due to heating, cooling or water events

Technical Requirements

1. Design life in excess of 40 years without degradation
2. The solution must achieve a (dry) thermal resistance of less than 1.2K.m/W
3. And should ideally achieve a (dry) thermal resistance of less than 1.0K.m/W - amperage governance is a critical requirement in any winning solution
4. The solution must be structurally competent and reliable so able to withstand reasonable compressive load once cement bound and consolidated.
5. The solution must not contain any particles exceeding 5mm (95% to pass 5mm sieve)
6. The solution should have consistent resistivity from 0 to 110ºC
7. The solution must not increase in thermal resistivity from 70 to 110ºC

Operating Conditions

The solution should:

1. Not be limited in processing, placing and compaction by UK weather such as wind and rain, extreme cold excepted which would equally restrict the use of CBS.
2. Not be vulnerable in use when exposed to the range of UK weather including permeation from rain, water courses and groundwater.
3. With the addition of cement binder be able to be placed and be stable at a batter of 2:1 from the horizontal

Cost Requirement

At scale, the solutions should not significantly exceed the cost of compliant quarried sand, typically £120/$150 per tonne from the quarry.
Their cost effective and non sensitive supply into the UK is critical.

Out of Scope

• We are not specifically seeking low-carbon cements/binders, unless they form a critical part of the overall solution  
• Materials that cause environmental harm
• Materials that significantly increase the operator hazard above current CBS; fine ground glass has been trialled and found unsuitable due to the hazards to operatives when it is wind blown
• Materials that degrade: the systems are designed with a 40-year design life

Proposals will be assessed on:

• Relevance to the defined challenge
• Credibility of the applicant
• Maturity or potential readiness of the solution; development potential
• Suitability and availability for the UK market
• Benefit of implementation
• Feasibility/cost viability
• Innovative nature
• Ability to launch in line with expected timescales

YOUR SUBMISSION

Please login and register your interest, to complete the submission form and add attachments.

The submitted proposals must be written in English and include:

1. Participation type – you will first be asked to inform us how you are participating in this challenge, as a Solver (Individual) or Solver (Organization).
2. Idea Summary - Please identify your technology and its advantages for the potential solution to the challenge (Keep this summary under 300 words. Below, you can also upload up to 3 supporting documents - PDF, Word, PowerPoint and images (jpg and png), Max 10MB per file).
3. Technology Readiness - Please select which TRL (Technology Readiness Level) your technology is currently at.
4. Describe your technology readiness level (Keep the description under 300 words).
5. Intellectual Property - Describe your intellectual property (IP) status. Have you, or do you intend to, protect IP status associated with your technology? Please identify the IP status for any supporting technology. (Keep the description under 300 words).
6. Expertise - Expertise, skills and use cases you or your organization have in relation to this challenge (up to 300 words).
7. Non-AI Subject Matter Expertise - Please describe this in relation to your know-how you have presented in your proposal. A statement detailing your roles in relevant real-world industry projects is required (up to 150 words).

PARTICIPATION GUIDANCE

1. Submission Close Date: Submissions to this Challenge must be received by 11:59 PM (US Eastern Time) on February 25th, 2026.
2. Late submissions: Late submissions will not be considered.
3. Multiple submissions, One Maximum: In case of multiple submissions by the same Solver, only one submission – the final one submitted – will be considered. Any other submissions will be deleted prior to evaluation.
4. Submission form and attachments: Your submission will first be evaluated by Wazoku and finalists by the Omexom Taylor Woodrow evaluation team, first reviewing the information and content you have submitted at the submission form, with attachments used as additional context to your form submission. Submissions relying solely on attachments will receive less attention.
5. Evaluation notification steps: After the Challenge submission close date, Wazoku will review and select the solutions it will propose and position with Omexom Taylor Woodrow, according to the timeline in the Challenge header. Everyone who submits a proposal will be notified about the status of their submissions.
6. Use of AI: Please note that any submissions produced solely with generative AI are not of interest.
7. Learn more: Find out more about participation in Innocentive Challenges.