Using Tidal Energy to Make “Green Hydrogen”

“Green hydrogen” is hydrogen gas produced by using renewable electricity to split water into hydrogen and oxygen with little or no carbon emissions. Now, a demonstration project at the European Marine Energy Centre (EMEC) on the island of Eday in Scotland’s Orkney Archipelago [Google Maps] uses tidal energy to supply the renewable electric power for the hydrogen-oxygen splitting process.

Electrolysis, the process employed by EMEC on Eday, is a well-known technology that conducts electric current through water to produce hydrogen. What’s different about the EMEC center is their source of electricity: a tidal turbine located about a mile (1.6 kilometers) offshore, where it generates power from the strong tidal currents in the region. The 243-foot (74-meter) O2 tidal turbine, built by Orbital Marine Power, is tethered to the ocean floor and floats on the surface, deploying two 33-foot (10-meter) rotors that extract energy from tidal current flowing past its stationary hull. (The O2’s power capacity is 2 megawatts, enough to power about 2,000 homes.)

Hydrogen gas EMEC produces can be used for powering hydrogen fuel-cell vehicles, a carbon-free transportation mode. Hydrogen can also be used for fueling rockets, producing ammonia for fertilizers, and for several other industrial processes.

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Study Challenges Tidal Energy Ecology Fears

Sihwa Lake Tidal Power Station in South Korea. It cost $560 million (USD) to construct and started operation in 2012. With an output capacity of 254 MW, it is the largest tidal power installation in the world (Wikipedia). (Image credit: Kimhs5400, CC BY 4.0, via Wikimedia Commons.)

No barrage-type tidal energy projects have been initiated in 25 years, mostly due to concerns about high construction costs and fears of negative ecological effects. While construction costs continue as a roadblock for such projects, some negative ecological effects now taken for granted might be “misplaced fears.”

That’s one of the conclusions of a study published in early October in Ecological Solutions and Evidence, a journal of the British Ecological Society. Titled “Misplaced fears? What the evidence reveals of the ecological effects of tidal power generation,” the study reviewed 54 articles related to tidal power system construction and operation and concludes that “few of the widespread [tidal energy ecological] concerns are substantiated by evidence or in long-term monitoring of existing projects.”

The study points out how objections to tidal power projects “often stem from perceptions of adverse ecological effects.” It states, however, that only a few of these adverse effects are backed by evidence or by long-term monitoring of existing tide power installations. What’s more, some projects may have positive ecological effects. The key to minimizing harmful effects, say the authors of the October study, is keeping a tidal regime similar to its original state.

The articles and papers reviewed in this study confirm that tidal projects can change hydrodynamics and sediment changes at barrage-type (tidal range) installations such as the LaRance station in France and the Annapolis Royal station in Canada. But many other objections to such projects “remain unsubstantiated” or have only neutral effects on marine ecosystems. Some positive effects identified are more productivity and greater species diversity in tidal range basins.

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Video: Harpswell’s Many Tide Mills

The picturesque town of Harpswell on Maine’s jagged coast was once home to up to 15 tide mills. Tide Mill Institute co-founder, architectural historian, and historic preservation expert John Goff recently gave a highly entertaining and educational presentation about these mills at the Bowdoin College Schiller Coastal Studies Center. Thanks to Harpswell Heritage Land Trust and Harpswell Community TV, a recording of his talk is now available on line. (To view, click the frame.)

John’s meticulous research covered many topics related to the Harpswell mills and tide mills in general. For viewers new to tide-powered mills, he explains tide mill operating principles and technology transferred from England to America, including mill stone designs, mill building features, and the grain milling process. He also provides economic, historical, and geographic context for these long-gone and almost forgotten structures. Never one to ignore the social side of the local milling industry, John also presents his recent findings about mill owner and operator genealogy.

Register Now for the Sept 2025 SPOOM Conference in Kentucky

The 1877 Mill Springs Mill features a 40-foot steel waterwheel. (Photo courtesy of SPOOM.)

Our friends at the Society for the Preservation of Old Mills (SPOOM) urge you to register now for their Sept. 19th and 20th conference in Monticello, Ky., before the early registration discount expires on Aug. 15th. While no tide mills appear on this year’s conference slate, three historical fresh water mills and a 1940s hydro-electric station are on the schedule – in addition to two historical houses and the Wayne County Historical Museum.

For tour details and registration instructions, visit the SPOOM website (SPOOM.org).

EU Grants $36 Million to French Tidal Energy Project

The European Union has granted $36 million USD (€31.3) to French company Normandie Hydroliennes for developing a tidal energy pilot project at Alderney Race, 3.4 km (2 miles) west of the Cotentin Peninsula in Normandy, on the French shore of the English Channel. Normandie Hydroliennes will install four 3MW turbines on the sea floor, which are expected to generate 34 GWh annually – enough to serve 15,000 people, according to the company’s announcement. The company describes the project, called NH1, as one of France’s “first commercial-scale tidal energy pilot projects.” It is expected to be operational by 2028.

The Alderney Race is the location of Europe’s strongest tidal stream. The race is known for its intermittent but powerful tidal current, which can run up to 12 knots (22 km/h or 14 mph) during some tidal cycles [Wikipedia]. The turbines will operate at least 38 meters (125 feet) below the surface to avoid visual impact and navigation hazards. The company says studies in other locations show that the turbines do not disturb marine life. The turbine array will transmit power to a shore station and the power grid through a single undersea cable.

The turbines will be manufactured by the UK-based Proteus Marine Renewables. The horizontal axis units have three-blade composite rotors 24 meters (79 feet) in diameter with a pitch control system for adapting to power and speed changes and protecting the system in storm conditions. The turbines are currently under construction in the French town of Cherbourg, about 30km (19 miles) east of the installation site.

Concept drawing of turbines in place on sea floor. (Courtesy of Normandie Hydroliennes. Click to enlarge.)

Approximate NH1 project location at Alderney Race. (Google Maps.)

Long Island Tide Mill Owner Gets Preservation Award

Anthony Martignetti, owner of the Mattituck Creek Tide Mill in Southold, N.Y., on the north shore of Long Island, recently received a preservation award for project excellence from Preservation Long Island, a regional non-profit for protecting and celebrating historic places.

The mill building dates from the early 1820s and operated as a tide-powered grist mill until 1902, when it was converted to a restaurant and tavern. It continued under several owners and Martignetti purchased it in 2018. Since then, he has been working to restore and renovate the structure. According to Preservation Long Island, “the mill remains a rare example of this engineering type, retaining its characteristic timber framing, form, and placement over water.”

Martignetti, a New York City restaurant owner, says the mill will open as a restaurant this coming spring. For more about the project and other preservation awards, visit the Preservation Long Island website. The Tide Mill Institute’s database also contains a paper describing the mill.