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The Disadvantages of Tidal Power

Tidal power is growing rapidly in interest as countries look for ways to generate electricity without relying on fossil fuels. Tidal schemes have a number of advantages, including their lack of greenhouse gas emissions and 100% renewable nature. Tidal power schemes do have several disadvantages as listed below.

Disadvantages by Tidal Scheme

Disadvantages of Tidal Barrages

  • They change the movement of water into and out of estuaries, which can disrupt the life cycles of certain marine life.
  • They can prevent the movement of fish and other wildlife into and out of estuaries, which can disrupt spawning.
  • Turbines can kill wildlife that tries to swim through them.
  • They can increase silt deposits, which can block out sunlight and prevent plants from growing
  • They can change the structure of the coast and lead to erosion of dunes and other critical habitat
  • They prevent access to rivers and cut off shipping
  • Costly to build
  • Locations are highly limited

Disadvantages of Tidal Stream Generators

  • Spinning blades can kill marine wildlife
  • Acoustic disturbances can affect migration and other aspects of marine life
  • They can change the movement and rise of tides
  • They can interfere with shipping channels
  • They are more prone to damage by high waves and rough water than other systems

Disadvantages of Dynamic Tidal Power Schemes

  • They are very costly
  • They are untested and therefore their usefulness and environmental impacts are unknown
  • They can disrupt migration of marine life
  • They can change coastal structures in unpredictable ways

Cost and Aesthetics

One of the largest disadvantage to tidal power is its large upfront cost. The few installations that have been tried have demonstrated that the long term cost of electricity generation is lower with tidal power systems, but the large upfront costs can make any such venture risky for private investors. Thus, while there are some private companies working in the industry, most of the cost of building large tidal power systems is falling to governments and taxpayers.

The costs of tidal systems stem from two primary areas. First, the construction of any power generation facility in moving ocean water is a technologically challenging feat. The equipment and expertise required make these projects very expensive from the standpoint of construction. The second branch of expense arises from the need for careful analysis of the impact a tidal power scheme will have on a given ecosystem. Many ocean ecosystems, particularly in tidal estuaries, are not only sensitive to interference, but are often home to species that aren’t found elsewhere. In fact, estuaries are the most important ocean ecosystems as they are were spawning takes place, where species spend winters, and where fresh and salt waters mix to create unique habitats for larval stages of many species that are critical to the ocean food chain. Assessing the impact of any activity in an estuary is critically important, but does contribute to costs substantially.

As has been pointed out elsewhere, aesthetics can be difficult to judge. However, some people find that tidal power schemes, particularly barrage schemes, negatively impact the look of coastal areas. It isn’t just the structures themselves that have impact either. The change in the speed and rise of tides as a result of tidal power schemes can be dramatic, detracting markedly from the aesthetics of more inland areas  of estuaries.

Location Limitations and Transmission Difficulties

This disadvantage isn’t unique to tidal energy, but rather plagues a number of renewable technologies like solar and wind. The simple fact is that tidal power schemes can only be built along the coast and even then not all coastal areas are suitable. Suitability is determined by tidal flow, tidal rise, ecosystem vulnerability, exposure to weather, and more.

Adding to the didadvantage of limited locations for building plants is the fact that transmission systems in most countries are not equipped to handle long-distance power transmission. Older systems are generally local and highly inefficient for long-distance transmission. In fact, the benefits of building a tidal power plant can be completely negated if the majority of the energy is lost by inefficient transmission lines. Upgrading transmission systems is a massive expense that adds to the cost of renewable energies.

Corrosion and Maintenance

Salt is a uniquely corrosive substance as anyone who lives in areas where the roads are salted to prevent ice will tell you. Corrosion resistant materials are not only difficult to create, but also expensive to research and design. Everything from turbines to transmissions cables need to be redesigned for underwater use and that has the disadvantage of increased expense. Furthermore, because these systems are not tested for long term resistance to corrosion, there is some element of risk to companies that install tidal systems expecting them to last long enough to make payout profitable.

The goal of most tidal schemes is to make them as maintenance free as possible and with good reason. Working on a dam or a turbine that is submerged below dozens of hundreds of meters of sea water is no easy task. Maintenance of tidal power systems is much more difficult on other systems, even hydroelectric river dams where water can be diverted if necessary to allow for maintenance.

Environmental Impact

Of all the factors mentioned above, impact on the environment is the single quality of tidal power systems most likely to prevent their installation. Barrage systems are the most damaging, but no system is free from ecological impact. The need to protect sensitive ocean ecosystems means that the already limited availability of sites for tidal systems if further limited by ecological concerns. Because many ocean systems are unique, the impact of each tidal installation has to be separately assessed. This may seem like an unnecessary burden, but the critical importance of the oceans to life on this planet mean that special care must be taken.