Tidal range technology harnesses the natural rise and fall of the tide to generate electricity. It typically uses a lagoon or barrage to capture and release water, and offers a predictable and long-term energy resource. Wales is home to two of Britain’s most promising tidal range opportunities in Britain; the Severn Estuary and the North Wales Coast.

Both regions offer exceptional tidal resource, alongside a strong network of supportive local authorities, industry, academia and development organisations. Yet whilst tidal stream technology is progressing towards commercial deployment, tidal range in Wales is still laying its foundations.

The technology offers enormous long-term opportunity. It is proven to be able to lower wholesale electricity prices, integrate into the grid with minimal impact, and critically, deliver predictable power.

In 2025, The National Energy System’s Operator (NESO) published its first system-level assessment of tidal range technology in almost a decade. It confirmed what years of feasibility studies across the Severn Estuary, Mersey, and other UK sites have already demonstrated; well-sited tidal range projects can deliver not only energy but grid stability, flood protection, habitat creation and long-term economic benefits.

Their report marked a turning point for the sector but also exposed a critical gap between how tidal range projects are modelled at a national level, and how they are designed, permitted, and financed by developers on the ground.

Delivering tidal range

The evidence for harnessing the Severn Estuary’s tidal range has been extensively examined by The Severn Estuary Commission. After a year of engagement with more than 500 people across over 200 organisations, it concluded that developing the technology in the Severn Estuary is feasible.

The Commission judged that whilst a large barrage should not be pursued at this stage, the development of a commercially viable lagoon, which could become the world’s first, would generate substantial low-carbon electricity and provide a platform to fully evaluate the environmental impact of a full-scale project.

The Commission has since laid out several recommendations. They include aligning UK and Welsh Government policy, including tidal range in NESO’s Strategic Spatial Energy Plan, and a Wales-led demonstration project, co-designed by engineers and environmentalists.

Crucially, The Commission calls for tidal range to be assessed on the same evidence-based terms as other major infrastructure, albeit with a different financing model.

Tidal range projects are massive infrastructure schemes, requiring enormous upfront capital expenditure. Their operational lifespans are measured in decades or centuries, and they could deliver returns for generations.

It means that conventional project finance models are not necessarily an appropriate route. NESO’s modelling identified the Regulated Asset Base (RAB) model as the most promising route to affordability for tidal range schemes in the UK. It is how water, gas, electricity networks and roads are currently financed.

turning readiness into delivery

The foundations to deliver tidal range in Wales are firmly in place – world-class resource, decades of feasibility evidence, established partnerships ready to act, and a national assessment that confirms the technology’s longterm potential.

The next chapter now hinges on turning readiness into delivery. It means aligning policy and financing frameworks, grounding planning in real-world experience, and supporting a pioneering Welsh project that can demonstrate delivery at scale.

Together, these steps could move tidal range from promise to practice and help shape a more resilient future for Wales’ marine energy sector.

This article originally appeared in Marine Energy Wales’ State of the Sector 2026 Report.

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AMREDIAD LLANW YNG NGHYMRU: O DYSTIOLAETH I GYFLAWNI

Mae gan Gymru ddau o’r cyfleoedd amrediad llanw mwyaf addawol ym Mhrydain, Aber Hafren ac arfordir Gogledd Cymru. Mae’r ddau yn cynnig adnoddau llanw eithriadol, yn ogystal ag awdurdodau lleol cefnogol, diwydiant, academia a chyrff datblygu. Eto, er bod technoleg ffrwd lanw yn symud ymlaen tuag at ddefnydd masnachol, mae amrediad llanw yng Nghymru yn dal i osod ei sylfeini.

Mae’r dechnoleg yn cynnig cyfle cenedlaethol, hirdymor. Mae wedi’i brofi i allu gostwng prisiau trydan cyfanwerthu, integreiddio i’r grid gyda’r effaith leiaf, ac yn hollbwysig, darparu pŵer rhagweladwy.

Yn 2025, cyhoeddodd y Gweithredwr Systemau Ynni Cenedlaethol (NESO) yr asesiad lefel system gyntaf o’r dechnoleg mewn bron i ddegawd. Cadarnhaodd yr hyn y mae degawdau o astudiaethau dichonoldeb ar draws Aber Hafren, Merswy, a safleoedd eraill yn y DU eisoes wedi’i ddangos; gall prosiectau amrediad llanw sydd wedi’u lleoli’n dda ddarparu nid yn unig ynni ond sefydlogrwydd grid, amddiffyn rhag llifogydd, creu cynefinoedd a manteision economaidd hirdymor.

Roedd adroddiad NESO yn nodi trobwynt i’r sector ond datgelodd hefyd fwlch critigol rhwng sut mae prosiectau amrediad llanw yn cael eu modelu ar lefel genedlaethol, a sut maen nhw’n cael eu cynllunio, eu caniatáu, a’u hariannu gan ddatblygwyr ar lawr gwlad.

cyflawni amrediad llanw

Mae’r dystiolaeth ar gyfer harneisio amrediad llanw Aber Hafren wedi cael ei harchwilio’n helaeth gan Gomisiwn Aber Hafren. Ar ôl blwyddyn o ymgysylltu â mwy na 500 o unigolion ar draws dros 200 o sefydliadau, daeth i’r casgliad bod datblygu’r dechnoleg yn Aber Hafren yn ymarferol.

Barnodd y Comisiwn, er na ddylid mynd ar drywydd morglawdd mawr ar hyn o bryd, y byddai datblygu lagŵn masnachol hyfyw, a allai ddod y cyntaf yn y byd, yn cynhyrchu trydan carbon isel sylweddol ac yn darparu llwyfan i werthuso’n llawn effaith amgylcheddol prosiect ar raddfa lawn.

Ers hynny, mae’r Comisiwn wedi cyflwyno nifer o argymhellion. Maent yn cynnwys cyd-fynd â pholisi Llywodraeth y DU a Llywodraeth Cymru, gan gynnwys amrediad llanw yng Nghynllun Ynni Gofodol Strategol NESO, a phrosiect arddangos dan arweiniad Cymru, a gyd-ddyluniwyd gan beirianwyr ac amgylcheddwyr.

Yn hollbwysig, mae’r Comisiwn yn galw am asesu amrediad llanw ar yr un telerau sy’n seiliedig ar dystiolaeth â seilwaith mawr arall, er gyda model ariannu gwahanol.

Mae prosiectau amrediad llanw yn gynlluniau seilwaith enfawr, sy’n gofyn am wariant cyfalaf enfawr ymlaen llaw. Mesurir eu hoes weithredol mewn degawdau neu ganrifoedd, a gallent ddarparu elw am genedlaethau.

Mae’n golygu nad yw modelau cyllido prosiectau confensiynol o reidrwydd yn llwybr priodol. Nododd modelu NESO fod y model Sylfaen Asedau Rheoleiddiedig (RAB) fel y llwybr mwyaf addawol i fforddiadwyedd ar gyfer cynlluniau amrediad llanw yn y DU. Dyma sut mae dŵr, nwy, rhwydweithiau trydan a ffyrdd yn cael eu hariannu ar hyn o bryd.

Mae’r sylfeini i gyflawni amrediad llanw yng Nghymru yn gadarn yn eu lle – adnodd o’r radd flaenaf, degawdau o dystiolaeth o ddichonoldeb, partneriaethau sefydledig yn barod i weithredu, ac asesiad cenedlaethol sy’n cadarnhau potensial hirdymor y dechnoleg.

Mae’r bennod nesaf bellach yn dibynnu ar droi parodrwydd yn gyflawniad. Mae’n golygu alinio fframweithiau polisi a chyllido, seilio cynllunio ar brofiad byd go iawn, a chefnogi prosiect arloesol Cymru a all ddangos cyflawniad ar raddfa fawr.

Gyda’i gilydd, gallai’r camau hyn symud amrediad llanw o addewid i ymarfer a helpu i lunio dyfodol mwy gwydn i sector Ynni’r Môr Cymru.