Why the Pentland Firth is basically a liquid motorway (and why that’s brilliant for clean power)

If you’ve ever looked at a map of the very top of Scotland and thought, “That bit between the mainland and Orkney looks… narrow,” congratulations: you’ve just spotted the perfect recipe for tidal power.

The Pentland Firth is a squeeze-point. Twice a day, enormous volumes of seawater rush through it like commuters late for the 08:17 to Thurso. Except this “traffic” doesn’t tailback — it accelerates. Marine Scotland notes that spring-tide current speeds in the Pentland Firth can exceed 5 m/s (that’s properly rapid).

So yes: it’s a liquid motorway. And we’re finally starting to put some “toll booths” in it — turbines that turn predictable tidal flow into electricity.

1) What makes it a motorway?

A. It’s a choke point
Water moving between the Atlantic and the North Sea has limited options. The Pentland Firth is one of the main routes, and narrow routes force higher flow speeds — the same way traffic speeds up when everyone funnels into fewer lanes (on a good day, anyway). The Royal Society highlights the Firth’s exceptionally fast currents and explains they’re driven by differences in water level around Orkney as the tide propagates.

B. It has rush hours you can set your watch by
Tides are wonderfully boring in the best possible way: they’re predictable. This doesn’t mean constant power (there are slack-water lulls), but it does mean planners can forecast output far ahead — a handy complement to wind and solar.

C. It’s energetic enough to be worth the engineering pain
The catch is that “energetic” also means “trying to shake your equipment to bits”, which brings us neatly to…

2) What’s been done so far?

The headline: MeyGen — a real working tidal array in the Pentland Firth

The most important “done-and-dusted (and generating)” milestone is MeyGen, located in the Inner Sound of the Pentland Firth.

• Operational array: 6 MW, running a multi-turbine setup in real sea conditions.

• It’s been operating as a 6 MW array since 2018 (per EMEC).

• The site has produced over 84 GWh of tidal electricity (as of Dec 2025, reported by Proteus Marine Renewables).

And this isn’t just “leave it in and hope”. Real projects involve real maintenance:

• In late 2025, offshore works were completed at the MeyGen site, including turbine recovery and upgrade work — exactly the sort of unglamorous-but-essential activity you need before scaling up.

The next big step: moving from “array” to “properly commercial scale”

MeyGen isn’t meant to stay at 6 MW forever. The project has:

• Consent for 86 MW (Phase 1 generation capacity) at the Inner Sound site.

• A longer-term development envelope/lease potential out to ~398 MW (i.e., “motorway service station chain”, not a single kiosk).

And critically, the UK’s support mechanism is now helping build the next phases:

CfDs: the boring acronym doing the heavy lifting

MeyGen’s next phase has been awarded 59 MW through the UK Contracts for Difference (CfD) scheme across Allocation Rounds 4, 5 and 6, with target commissioning years 2027, 2028 and 2029.

That’s the “what’s been done so far” in one sentence: a working array exists, it’s generating, it’s being maintained like grown-up infrastructure, and it has contracted expansion lined up.

3) Why aren’t we carpeting the whole motorway with turbines already?

Because the Pentland Firth isn’t a gentle canal. It’s more like a river in a hurry… that occasionally gets angry.

A few practical blockers:

• Engineering at speed: fast flow means high loads, plus turbulence, plus the joys of corrosion and biofouling. Maintenance strategies (like recovering turbines for works) are part of making this bankable at scale.

• Consenting and environmental monitoring: large marine projects require extensive assessment and monitoring, and the industry is still working through consenting challenges (EMEC references joint efforts via the Marine Energy Taskforce).

• Grid and logistics: north-coast infrastructure, ports, vessels, weather windows — it all matters. A motorway is only useful if you can actually get to it with your tools.

4) What could be done in the future?

Here’s the exciting bit: the path forward is no longer guesswork. It’s increasingly a pipeline.

A. Build out the 59 MW that already has CfD backing

This is the “near future”: turning contracted support into steel-in-the-water and megawatts on the grid.

Marine Scotland documentation describes “MeyGen 2” in the mix (for example, ~28 MW comprising multiple larger turbines is discussed in screening documentation).

B. Expand towards the site’s wider potential (up to ~398 MW over time)

That’s the “big future”: not one array, but a sustained build-out, subject to planning, consenting, and economics.

C. Keep driving costs down (and prove it with more deployments)

The UK offshore renewables crowd has documented rapid cost reduction in tidal stream energy: ORE Catapult notes that CfD awards in 2022 were an indicator of significant LCOE reduction compared to earlier estimates, while still recognising the value of tidal’s predictability.

And in AR6, 6 tidal stream projects across 5 sites secured contracts totalling 28 MW at £172/MWh, showing the sector is winning more capacity — not just headlines.

D. Add more “lanes” around the region — not just one spot

The Pentland Firth & Orkney Waters (PFOW) region has long been a focal area for development, and future progress is likely to come from a portfolio of sites, not a single hero project. (Think: several motorway junctions, not one roundabout.)

5) The takeaway

If the Pentland Firth is a liquid motorway, then MeyGen is proof we can run a working service on it — not just a concept car doing a press day.

What’s next is turning that first working section into a longer stretch of road: more contracted capacity delivered, more turbines installed, costs pushed down, and the consenting/environmental side handled properly so the whole thing scales responsibly.

And the best part? The “traffic” turns up on schedule.