This challenge provides an opportunity to collaborate with Omexom Taylor Woodrow to develop and prove better solutions for backfilling underground cables.  The wider benefits are valorisation of waste streams, reduced sensitivities on imported specialist sand, better performing materials that enable the cables to function at higher ratings.  

If successful you will have the opportunity to work with Omexom Taylor Woodrow to develop and prove your material at small scale and then participate in attaining funding to allow further development and critical network compliance testing. 

Omexom Taylor Woodrow are a leading installer of HV transmission equipment and a key part of the Great Grid Partnership. 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.
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&rsquo;s ability to carry current and is limited to a maximum cable conductor temperature of 90&ordm;C to prevent possible deterioration of the safety critical multi-layer electrical insulation.

Background

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The cables sit within PVC ducts which are in turn bedded on and a surrounded by a thermally conductive <ins cite="mailto:Tom%20Warren" datetime="2025-10-27T18:17">cement </ins>bound sand (CBS), this helps the passage of heat into the natural ground, the use of a cement binder provides protection from mechanical damage.&nbsp; The excavated trench size and quantity of sand required are related to the thermal conductivity of the sand.
The (simplified) construction sequence is:
<ol>
<li class="MsoListParagraphCxSpFirst">Excavate trench</li>
<li class="MsoListParagraphCxSpMiddle">Place and compact cement bound sand (CBS) bedding layer</li>
<li class="MsoListParagraphCxSpMiddle">Install PVC ducts (range from 100-250mm dia)</li>
<li class="MsoListParagraphCxSpMiddle">Place and compact CBS around and over ducts</li>
<li class="MsoListParagraphCxSpMiddle">Place warning tapes</li>
<li class="MsoListParagraphCxSpMiddle">Install protective tiles</li>
<li class="MsoListParagraphCxSpMiddle">Place and compact selected excavated material back to ground level</li>
<li class="MsoListParagraphCxSpMiddle">Pull through cables (400kV cables are circa 120mm diameter)</li>
<li class="MsoListParagraphCxSpLast">Generally, infill ducts with bentonite slurry</li>
</ol>
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7be8cc4b-2dea-431e-8636-f329969aad76/OTWTrenchSectionsnip.png

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 a Dorset 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 identified 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 availability of suitable local sand is a 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.&nbsp;
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:
<ul>
<li>Derisking the availability of suitable sand</li>
<li>Reducing the net carbon footprint</li>
<li>Less denuding of natural resources</li>
<li>Improving cost certainty</li>
</ul>
And can also address:
<ul>
<li>Improving backfill thermal conductivity to reduce the excavation needed and sand imported and/or enable improved rating of underground HV cables</li>
<li>Reducing the commercial risk of availability from local quarries</li>
<li>Avoiding the potential need to take surplus excavated materials offsite</li>
</ul>
This may include and is certainly not limited to solutions that:
<ul>
<li>Utilise additives and/or processes that uplift the conductivity of currently unsuitable sands</li>
<li>Blend unsuitable soils with high conductivity minerals such as metal compounds</li>
<li>Utilise mine tailings and historic mining spoil</li>
<li>Utilise high conductivity waste streams such as ceramics waste or suitable demolition materials</li>
<li>Valorise excavated materials on site to enable use in CBS</li>
<li>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)</li>
<li>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</li>
<li>Have nationwide availability (ideally within 40 mile radius of project sites)</li>
</ul>
It is recognised that solutions are likely to require development and then a rigorous National Grid compliance activity.&nbsp; 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.
More developmental solutions that may struggle with this timeline are also welcome if they offer very strong potential.
Your proposal should clearly identify your current maturity and the estimated timeline to readiness for National Grid compliance testing.

The Challenge

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It is recognised that 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, cognisance of these is recommended when considering solutions and is available here: &nbsp; &nbsp; <a href="https://iuk-business-connect.org.uk/wp-content/uploads/2025/11/ENA_TS_97-1-Issue-2-2016-Special-Backfill-Materials-for-Cable-Installations.pdf">ENA TS 97-1 LINK</a> &nbsp; &nbsp;&nbsp;
Omexom Taylor Woodrow are also assessing alternative binder materials to OPC to reduce the carbon footprint, this is a separate exercise and outside the scope of this challenge. Potential providers of low-carbon cementitious materials should contact&nbsp;<a href="mailto:neil.appleton@iukbc.org.uk">neil.appleton@iukbc.org.uk</a> to ensure that IUKBC are aware of their technology and it is put forward to Omexom Taylor Woodrow.

<ol>
<li class="MsoListParagraphCxSpFirst">The solution must be able to be practicably placed insitu, 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&nbsp;</li>
<li class="MsoListParagraphCxSpMiddle">Currently the thermal conductivity is not measured insitu, instead density is simply measured to determine the void content.&nbsp;If this technique is not appropriate to the solution an effective insitu measurement technique should be identified. (For general guidance of site quality control expectations please see ENA TS 97-1)</li>
<li class="MsoListParagraphCxSpMiddle">Be compatible with and in no way deleterious to PVC ducting</li>
<li class="MsoListParagraphCxSpMiddle">Be compatible with cement binder and compatible with lime, emergent AACM geopolymers and common cement replacement materials</li>
<li class="MsoListParagraphCxSpMiddle">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</li>
<li class="MsoListParagraphCxSpMiddle">Be no more hazardous to work with than current cement bound sand (CBS)</li>
<li class="MsoListParagraphCxSpMiddle">Cure to a reasonably hard material to protect the cables from mechanical damage</li>
<li class="MsoListParagraphCxSpMiddle">Be available at a sufficient assured scale (please specifically confirm this aspect within your submission)</li>
<li class="MsoListParagraphCxSpLast">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.</li>
</ol>

Functional Requirements

<ol>
<li class="MsoListParagraphCxSpFirst">Design life in excess of 40 years without degradation</li>
<li class="MsoListParagraphCxSpMiddle">The solution must achieve a (dry) thermal resistance of less than 1.2K.m/W</li>
<li class="MsoListParagraphCxSpMiddle">And should&nbsp;ideally achieve a (dry) thermal resistance of less than 1.0K.m/W</li>
<li class="MsoListParagraphCxSpMiddle">The solution must be structurally competent and reliable so able to withstand reasonable compressive load once cement bound and consolidated.</li>
<li class="MsoListParagraphCxSpMiddle">The solution must not contain any particles exceeding 5mm (95% to pass 5mm sieve)</li>
<li class="MsoListParagraphCxSpMiddle">The solution should have consistent resistivity from 0 to 110&ordm;C</li>
<li class="MsoListParagraphCxSpLast">The solution must not increase in thermal resistivity from 70 to 110&ordm;C</li>
</ol>

Technical Requirements

The solution should:
<ol>
<li class="MsoListParagraphCxSpFirst">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.</li>
<li class="MsoListParagraphCxSpLast">Not be vulnerable in use when exposed to the range of UK weather including permeation from rain, water courses and groundwater.</li>
<li>With the addition of cement binder be able to be placed and be stable at a batter of 2:1 from the horizontal</li>
</ol>

Operating Conditions

<ol>
<li class="MsoNormal">Materials that cause environmental harm</li>
<li class="MsoNormal">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</li>
<li class="Normal1">Materials that degrade: the systems are designed with a 40-year design life</li>
</ol>

Out of Scope

At scale, the solutions should not significantly exceed the cost of compliant quarried sand, typically &pound;120 per tonne from the quarry.

Cost Requirement

The solution has the potential for deployment of approximately 33km of underground cables within the OTW contracts alone.
Successful applicants will be given the opportunity to pitch to Omexom Taylor Woodrow.
Selected solutions can benefit from collaborative support from Omexom Taylor Woodrow to develop their solution through expert input, characterisation testing and physical trials in a safe environment. From this it is likely that more substantial funding will be needed to prove suitability to National Grid. This could be through the Network Innovation Allowance (NIA) funding secured through collaborative partnership with Omexom Taylor Woodrow.
The benefits package for a successful applicant may also include:
<ul>
<li>Support from Innovate UK Business Connect</li>
<li>Support in the development of a prototype or pilot</li>
<li>Technical support</li>
<li>Invitation to attend or present at Innovate UK Business Connect events</li>
<li>A potential business collaboration</li>
<li>Investor introductions (if investment is required)</li>
</ul>
Support if any Innovate-UK or similar competitions are relevant.

Rewards and Market Opportunity

Launch: Monday 5th January 2026
Closing date: Monday 2nd March 2026
Notification Date: Tuesday 24th March 2026
Pitch day: WC 13th April in Castleford, Yorkshire WF10

Timescales

Entrants to this competition must be:
<ul>
<li>Established businesses, academic institutions, start-ups, SMEs, or individual entrepreneurs</li>
<li>UK based or have the intention to set up a UK base</li>
</ul>
Applications will be assessed on:
<ul>
<li>Relevance to the defined challenge</li>
<li>Benefit of implementation</li>
<li>Feasibility/economic viability</li>
<li>Innovative nature</li>
<li>Ability to launch in line with expected timescales</li>
<li>Credibility of applicant company</li>
<li>Coherence of the proposed business model</li>
<li>Development potential</li>
<li>Maturity of the solution</li>
<li>Suitability for the intended geographic market</li>
</ul>
Academics and RTO&rsquo;s are encouraged to include or identify potential commercialisation partners or, as a minimum clearly identify the commercialisation route.

Eligibility and Assessment Criteria

Existing background IP associated with a potential solution will remain with Solution Provider(s). Where any new IP generation is envisaged, it will be subject to the mutual IP agreement of the solution provider(s) and Omexom Taylor Woodrow.
Any commercial deployment of a transferred solution or newly developed solution, through licensing, joint venture, partnership, or direct investment, will be subject to the commercial agreement between the solution provider(s) and challenge holder.
Where necessary, a non-disclosure agreement (NDA) may be signed to uphold confidentiality in the engagement between the solution provider(s) and challenge holder. (This would be expected to be after company selection, it is suggested that details of IP be not disclosed, focus on the outcomes of the technology proposed).
Innovate UK and Innovate UK Business Connect do not take any share of IP ownership or enter commercial ventures through the iX programme.

IP and Potential Commercial Route

The application form for this challenge will require applicants to provide company information and answer 3 questions - Idea Summary, Technology Readiness and Intellectual Property &ndash; each with a limit of 300 words.
Optionally, up to 3 supporting documents can be attached to the application. We recommend that supporting documents are limited to those which are directly relevant to the application. Please note that applications with no supporting document will not receive any penalty in assessment. Supporting documents which the Assessment Panel deems to be superfluous may be disregarded. Examples of useful additional documents include product images or short specification sheets, slide decks detailing the solution and/or company background, or solution case studies.
We recommend that you complete the application form in Google Chrome as other browsers may have compatibility issues. The application form does not need to be completed in one session and can be saved for future edits. Please ensure that you toggle &ldquo;Stage Complete&rdquo; for each section before submission. Note that you will no longer be able to edit your application once you have clicked &ldquo;Submit Idea&rdquo; at the bottom of the Summary page.

Application and Technical Guidance

By submitting an application to this Innovation Exchange (iX) challenge, you acknowledge and agree that the information you provide will be shared with Innovate UK Business Connect and the challenge holder for the purposes of assessment and selection. All information submitted will be handled in confidence and shared only with those involved in the assessment and selection process under appropriate confidentiality expectations.
Please consider the level of detail you share in your submission to ensure it aligns with your own internal confidentiality or disclosure policies.
A selected panel of assessors will review and score your application. The panel of assessors will meet and agree a consensus score. Successful solutions will be selected solely by Omexom Taylor Woodrow. Success will be based upon total consensus scores, a portfolio approach and capacity within the challenge holder&rsquo;s organisation to carry out the projects.
For more information on how Innovate UK Business Connect handles personal data, please refer to our&nbsp;<a href="https://iuk-business-connect.org.uk/privacy-policy/" target="_new">Privacy Policy</a>.

Terms and Conditions

<ol>
<li>OTW are not specifically seeking low-carbon cements/binders within this challenge, unless they form a critical part of the overall solution. &nbsp;EG You are using a particular low carbon cement that could not be readily replaced with an alternative as it brings certain distinct properties to your solution as a system. &nbsp;OTW and VINCI are exploring low carbon cementitious materials with us, so please do email <a class="ms-outlook-linkify" href="mailto:neil.appleton@iukbc.org.uk" data-ogsc="">neil.appleton@iukbc.org.uk</a> with details of your cement and we will ensure that OTW are made aware.&nbsp;</li>
<li>It is only possible to make one submission per login.&nbsp; We do welcome alternative solutions from the same organisation, this will require you to create a seperate login&nbsp;</li>
</ol>

Enhanced thermally conductive backfill for underground HV cables

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Enhanced thermally conductive backfill for underground HV cablesCopy Link

Opportunity

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Background

This challenge is brought to you by:

Enhanced thermally conductive backfill for underground HV cables