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Tidal farm

Tidal Farm Generation in North America
North America has fewer tidal power stations than any other comparable geographical area, in terms of GDP or population. Tidal power has been estimated to be able to account for fifteen percent of the United States’ power consumption if harnessed correctly. The first tidal instillation in North America to connect to a power grid was laid down in 2012, in Cobscook Bay, Maine by the Ocean Renewable Power Company. The preliminary device generates 180 Kilowatts at full capacity. Plans to install two more devices were shelved as of 2013. Tidal generators were installed in 2009 by OpenHydro and Emera the Bay of Fundy. These tidal generators suffered damage, losing several blades in the process, due to the powerful tides in the Bay. In the autumn of 2016 a joint venture by the same two companies successfully placed a 2-Megawatt tidal generator in the Bay of Fundy, of which Cobscook Bay is a constituent area. The successful integration of the new tidal generators to local power stations, and the connected power grid supplies an estimated 150 to 200 homes per day.

The Effects of Tidal Farms on Ocean Geography and Tidal Patterns
Tidal farms present many possible environmental and ecological changes to the environment they are placed in. The structures of these farms produce changes in tidal patterns, sediment flow, and water column turbulence. Tidal patterns can be affected in different ways depending on the structure of the farm itself. The structure is referring to the size and cross-sectional area because the number of blades or the load that is put on the farm doesn’t make much of a difference on the overall height of the water. These effects can be seen to lower both the high tide and low tides which means that the water level will be lower in total. The number of blades and load on the system however does affect the tidal range vastly. Tidal range can be reduced up to 42% with observations of the densest farms which can cause destruction to 32% of the areas around them, but it can be controlled. Damage can be reduced to 19% by using a two-rotor spaced turbine and only 5.4% with five-rotor spaced turbines. This is done by spreading the water's work over a large surface area on the turbine itself to mitigate the alteration of the flow in the water column.

Sediment flow is affected by the introduction of tidal farms to an area. Not only does it create turbulence that moves the sediment, but it changes the ecosystem around it. By moving more sediment into areas that didn’t gain much before, places like grass beds could be wiped out by being covered in sediment. The geography on the ocean floor would be changed by the new sediment flow patterns because of the new turbulence. New things like sandbars could form around the farms causing even more of an impact to the surrounding environment by influencing more changes than originally expected.

The water column also faces multiple chances since the force it transfers through turbulence is being absorbed by the tidal farms. Waves would be directly affected by the reduced energy behind the water causing them to be weaker which too could destroy multiple ecosystems. There would also be an effect on the inter-tidal zones with there being less turbulence which many species like fish and crabs use for sustenance and survival. Other things like noise and electromagnetic fields also pose problems for the environment, but not to the scale that the last effects had on the geography and life in an ecosystem.

The Effects of Tidal Farms on Ecology
The prime placement of tidal farms occurs in tidal barrages, marshes, lagoons and other intertidal bodies of waters most commonly home to migratory wetland birds. The placement of tidal farms raises the water levels to a point where the feeding areas of the birds are submerged. With the loss of feeding areas, mortality rates increase. Furthermore, studies were conducted by University of Exeter faculty for wetland birds in the Solway Firth, UK. These studies concluded that the effect of certain types of tidal farms are negligible. The impacts of tidal farms on water foul habitats in the Solway Firth were found to be relatively low, even for the largest case. The study highlighted that current installations with similar capacities as the simulations had a lower loss of intertidal area than that of its computer-generated counterpart . One conclusion reached was that future studies should focus on the vulnerability of a individual species, as compared to the effect on maritime birds as a whole.

The construction of tidal barrages within a bay, inlet, or estuary is one of the few cases where inter species relations were universally affected. The retention of tidal water alters the timetable of species which dominate the upper to intermediate shore habitats. Simultaneously the lower shore remains submerged for longer periods of time. The resulting forced ecosystem is disruptive to the majority of species present, with the exception of fish whom are tidal feeders. The extended periods of high tide allow for greater foraging opportunity, hence a growth in population can be observed in these cases.

The structures of larger tidal barrages alter the scour and deposition in their respective habitats. Scour and deposition refers to the movement and exchange of sediment along the floor of a water body. The U.S. Army Engineer Research and Development Center in Vicksburg, Mississippi stated that the interruption of natural sediment deposits directly led to an increased mortality rate of seabed grass, as the shoot could not properly grow in the altered seafloor. This would be even more devastating for benthic life which resides under the ocean floor since they are easily affected by changes in the flow over the bottom of the ocean. It would be hard to prevent this too since these organisms aren’t easily relocated since they are so sensitive to changes in their atmosphere.