As fossil fuel costs soar, energy generated from tidal power is gaining more and more attention.

An energy research firm in California has produced a study touting Bay of Fundy tidal power as a viable source of electricity, and has also determined that among the best sites would be the Western Passage of Passamaquoddy Bay in Maine and Head Harbour Passage between Campobello and Deer Island in New Brunswick.

Locally, an engineer from Trescott is proposing a tidal power facility at Half Moon Cove between Eastport and Perry with a link to a site in Cutler.

The study by the Electric Power Research Institute (EPRI) cites Knik Arm in Alaska, Tacoma Narrows in Washington, Golden Gate in California, and Western Passage in Maine “All have good cross-sectional area size (36,000 to 72,000 square meters),” the study states, “good power density…and an interconnection which is easily managed.”

In Atlantic Canada the study notes: “The available tidal energy potential for the Minas Passage, Nova Scotia, is over 1 GW. Harnessing just 15% of the available tidal energy resource base would generate enough electricity to power about 120,000 Canadian homes…”

The study continues: “The Head Harbour Passage site, although large in size (60,000 square meters) is low in power density.” It also mentions sites in the Cumberland Basin, and the possibility of “a joint project with the U.S. in Western Passage [of Passamaquoddy Bay].”

The study proposes underwater turbines and answers a question about surviving “storms and hostile marine environments” this way: “Being totally submerged means that tidal energy conversion systems will not need to bear the full brunt of a storm. Relative to long-term survival in the environment, the anti-corrosion and biofouling technology is such that oil and gas platforms are surviving 50 years.”

As for any navigation problems through an underwater tidal power site, Eastport harbor pilot Captain Bob Peacock doesn’t foresee them. “I don’t believe there would be any effect on the currents as they apply to ships,” he said.

Trescott engineer Normand Laberge is thinking on a much smaller scale than the authors of the EPRI study, although geographically he’s close to the recommended Western Passage.

In his application to the Federal Energy Regulatory Commission (FERC) for a preliminary permit, Laberge, as chair of Tidewalker Associates, wrote:

“An existing dam does not exist at the site of the proposed project; however, the proposed site was once the location of toll bridge connecting Moose Island (Eastport) to the mainland at Perry. The proposed dam will be approximately 1,210 feet long with a maximum depth of 40 feet below mean sea level and a maximum elevation of 27 feet above mean sea level. The rock fill dam with a clay core will contain approximately 125,000 cubic yards of construction material. Two small dams existing along the easterly perimeter of Half Moon Cove were constructed in the 1930s to isolate the tidal basin from Passamaquoddy Bay. Half Moon Cove discharges into Cobscook Bay at the site of the proposed rock fill dam / powerhouse …. The dam will be constructed from rock fill with a clay core. Emptying / filling gates and similar appurtenances would be located adjacent to a concrete powerhouse near the center of the channel. The installed capacity of the project has been estimated as 13.5 megawatts (MWs) from the installation of three (3) bulb-type turbines each with a capacity of 4.5 MWs.”

Laberge continued: “Since a single pool tidal project is incapable of generating continuous power, the project by itself will produce intermittent power either from a high pool or low pool mode of operation. During the course of the study, the possibility of `linking’ the operation of Half-Moon Cove with a site proposed by Tidewalker Associates in the Town of Cutler …will be investigated in order to generate continuous power by coordinating the production schedule from the two sites. Under this mode of operation, one of the two sites will generate power shortly after high tide (i.e., high pool operation) and the other site will start the initiation of power production shortly after low tide (i.e., low pool operation). A decision has not been made on how Half-Moon Cove will operate in terms of low pool or high pool production. The determination will be based on environmental considerations, basin size, tidal range, and on engineering evaluations. Since a difference of nearly one hour exists between the occurrence of high tide in Cutler and in Half-Moon Cove, this feature adds feasibility to the prospects of generating continuous power from two sites separated by approximately thirty-five (35) miles but linked through the electric grid.”

Anticipating the concerns of adjoining residents, Laberge added: The proposed tidal power station will not create a reservoir since the high tide level will not exceed current elevations for high pool operation. The net effect of the proposed tidal power plant will decrease the tidal range within the impoundment by approximately from 20% – 40%; thereby, resulting in the transition of intertidal zones into permanently submerged lands.”

Laberge added: “The proposed tidal power plant is expected to generate forty million kilowatt-hours of electricity annually. Since the tidal range fluctuates in accordance with lunar variations, the average hydraulic head will be approximately 12.2 feet for three (3) 4.5 MW bulb turbine units which will be installed at the proposed site. Due to the intermittent nature of production, tidal power does not provide base-load energy unless linked with a complementary source of energy (i.e., synchronized mode of operation with proposed tidal power facility in Cutler).”

Laberge believes that the EPRI study is focused on “large tide mills with a maximum propeller speed of 125 mph.”

He continued: “I have incorporated a more traditional design for my projects with the inclusion of a dam to retain the tides until a sufficient hydraulic head is available to generate power. The Half-Moon Cove has a secondary benefit associated with the construction of a roadway across the dam to provide an optional access route to Moose Island. The reduction of traffic through the [Passamaquoddy] Reservation would be a benefit to both communities …. I think that the Half-Moon Cove is the best “tidal” site in the region and I plan to continue my efforts in completing the project. Rising oil prices combined with limited supplies will increase the importance of having a decentralized energy resource in the region…I started work on Half-Moon Cove more than 30 years ago, and I think that I have gained the experience to complete a project which is compatible with regional objectives.”