Engineer David Mummery's Swimmer Turbine Aims to Power Coastal Towns
A 50-kilowatt tidal generator that sits invisibly below the surface could supply about 30 homes, its designer says
By AXY Business Desk ·
Key points
- Engineer David Mummery has developed the Swimmer Turbine, a 50-kilowatt tidal generator anchored to the sea floor.
- The developer says the device can generate enough electricity to power about 30 homes.
- The idea grew from Mummery's experience in a fast-flowing river in the Scottish Highlands more than a decade ago.
- A prototype has been shown at Strangford Narrows in Northern Ireland, but the source does not report trial results.
- Tidal power is predictable, but small-scale tidal systems still face cost, maintenance and environmental questions.
Engineer David Mummery has developed a small-scale tidal energy generator that he says could change lives in coastal communities. The device, called the Swimmer Turbine, is a 50-kilowatt machine anchored to the sea floor and designed to sit beneath the water's surface, where it is largely out of sight. According to Mummery, it can generate enough electricity to power about 30 homes. The idea came to him during an unusual experiment in a fast-flowing river in the Scottish Highlands more than a decade ago, and a working prototype has been shown at Strangford Narrows in Northern Ireland.
The story, reported by the BBC on 18 October 2026, centres on whether tidal power, which has long been seen as a niche technology, could be scaled down to suit small communities rather than only large offshore projects.
A Lesson From a Fast-Flowing River
Mummery's inspiration began with a physical test rather than a drawing board. According to the BBC's account, he tied a length of cord tightly across a river in a remote Highland location, swam out, gripped it, and let the current pass over him with his head below the surface. He described the experience as a way of understanding the forces involved in moving water. As he put it, "As an engineer we do the maths and stuff, but sometimes you can get a lot more from actually touching the water and feeling it."
That hands-on approach shaped the design. Mummery said he lay in the rapids and tried to picture how a turbine would need to interact with turbulent flow, the uneven and churning movement of water that engineers must account for when a machine is placed in a current. For a designer, understanding turbulence is central, because a turbine that works smoothly in calm, predictable flow can face very different stresses when water is rough, fast and irregular.
What the Swimmer Turbine Is
The Swimmer Turbine is described as a 50-kilowatt tidal generator made from fibreglass and steel. A kilowatt is a unit of power equal to 1,000 watts, and a 50-kilowatt machine is considered small compared with the large tidal and offshore wind installations that feed national grids. Its scale is the core of the pitch: rather than generating power for an entire region, it is intended to serve a community-sized load, which the developer puts at roughly 30 homes.
Because the device is anchored to the sea floor and lies below the surface, it does not dominate the view from shore in the way that a tall wind turbine does. That low visual profile may matter for coastal areas where residents and planners are sensitive to changes in the landscape and seascape. The BBC report does not give details of the construction costs, the expected lifespan or the number of units that have been built, so those remain open questions.
Why Tidal Power Is Different
Tidal power draws energy from the movement of water caused mainly by the gravitational pull of the Moon and the Sun. Tides are highly predictable, which is one of their main advantages over sources such as wind and solar, whose output varies with weather and daylight. Engineers generally distinguish between tidal range systems, which use dams or barrages across estuaries to hold water and release it through turbines, and tidal stream systems, which place turbines directly in fast-moving currents much as a wind turbine sits in moving air.
The Swimmer Turbine appears to belong to the second category, since its design is based on the behaviour of water rushing past a device. Tidal stream technology has attracted interest in parts of the British Isles where currents are strong, including the Pentland Firth off northern Scotland, which is widely known for powerful tidal flows. The challenge has been cost. Marine environments are harsh, saltwater corrodes materials, and installing and maintaining equipment underwater is expensive, which is why many projects have struggled to move from prototype to commercial operation.
Analysts who follow renewable energy generally note that smaller, modular systems can sometimes be easier to finance and deploy than very large projects, because they require less upfront investment and can be installed in stages. Whether the Swimmer Turbine can achieve that advantage in practice will depend on its performance data, its maintenance needs and the cost of electricity it produces, none of which the source material quantifies.
Where the Technology Has Been Tested
The prototype has been shown at Strangford Narrows, a strait in Northern Ireland that is known for strong tidal flows through the narrow channel connecting Strangford Lough to the Irish Sea. Test sites with strong currents are valuable to developers because they allow engineers to see how equipment behaves in real conditions rather than only in simulations or laboratory tanks.
Testing in a real marine environment is important for a device of this kind. Developers must consider the effects of debris, marine life, sediment movement and the forces that tides and storms place on anchoring systems. The BBC report does not describe the results of any trials, including how much electricity the prototype has produced or for how long it has operated, so readers should treat the 30-home figure as the developer's own estimate rather than a measured outcome.
Why It Matters for Coastal Communities
For many coastal communities, the question of energy supply is more than a technical matter. Remote and island areas often depend on expensive or vulnerable connections to the wider electricity grid, and they can face higher costs and greater exposure to supply interruptions. A local generator that draws on the sea could, in principle, reduce reliance on fuel imports and provide a more stable local source of power, although that depends on how the technology performs and how it is financed and owned.
Mummery's claim that the technology could change lives reflects this practical goal. The BBC describes the Swimmer Turbine as an innovation aimed at people living in coastal communities, and its appeal lies in matching power generation to the scale of a village or small town. Any benefit for households would ultimately depend on electricity prices, grid connection arrangements and whether local communities have a say in ownership or revenue.
There are also trade-offs. Marine energy projects must be assessed for their potential impact on wildlife, fishing activity and shipping. Although a submerged device may be less visible than a surface structure, planners typically require environmental studies before any installation in coastal waters, and those processes can take considerable time.
What to Watch Next
Several questions will determine whether the Swimmer Turbine moves beyond a prototype. The most important is evidence of performance over an extended period, including how consistently it generates power in changing tides and how it withstands harsh conditions. Readers should also watch for independent assessments of cost per unit of electricity, information on maintenance requirements and any plans for installation at a named coastal site.
Another key issue is funding. Renewable energy projects often depend on public grants, private investment or community energy schemes, and the route chosen can shape who benefits. Regulatory approval, environmental review and agreement with the grid operator would also be needed before any device could supply homes on a commercial basis.
For now, the Swimmer Turbine remains a promising design at the prototype stage, with its developer making clear claims about its potential. Whether those claims hold up under sustained operation in the sea will determine whether a device born in a Highland river can help power the coastlines it was designed for.
Topics: David Mummery, Swimmer Turbine, Tidal energy, Strangford Narrows, Northern Ireland, Scottish Highlands, Renewable energy, Coastal communities
Sources: BBC Business RSS