underwater_ocean_turbines
September 1, 2016 Ecotech Gallery No Comments

Underwater Ocean Turbines

 

THE CONCEPT

A new technology that harnesses the power of ocean currents could provide a clean and limitless form of renewable energy. The idea is to use giant underwater turbines to capture the energy from deep-ocean currents, such as the Gulf Stream off the coast of Florida. While energy generated from these turbines may not be able to completely replace fossil fuels, the devices could still be an important source of clean energy.

Ocean currents are one source of natural energy that no one has tapped before, either because they weren’t aware of it or didn’t have the technology to capture it. Most people are familiar with solar or wind power, but while they are promising, they are limited by their quality and consistency.

Underwater (or tidal) turbines are a fairly straightforward concept, as far as cutting edge energy technology goes. They are essentially windmills installed onto an ocean floor or river bed. The underwater current produced by the tides spins blades arranged like an airplane propeller. These turbines are attached to a gear box, which is connected to an electrical generator. This produces the electricity that is carried by cable to shore. Once it’s plugged into an electrical grid, the electricity can be distributed.

 

THE ADVANTAGE

Although underwater turbines are essentially the same thing as windmills, they have a few advantages over their above-ground cousins. Windmills require land, especially wind farms — assemblages of dozens or hundreds of windmills. The future of land use (how land is developed and what it’s used for) is becoming a major topic of discussion. With 6 billion people on the planet and counting, space is at a premium – not just for housing, but for crop production and more. Underwater turbines overcome this problem.

Another advantage of underwater energy capture comes from water’s high density. Water is denser than air, which means that the same amount of energy can be produced by an underwater turbine as a windmill, but at slower speeds and over less area. What’s more, while the amount of wind that passes over any given area of land can be unpredictable, the kinetic energy of tidal areas is dependable. The ebb and flow is so predictable, a given tidal region can be expressed in the amount of kilowatt hours of electricity it can produce per turbine.

Scientists have been examining the amount of energy found in a tidal pool in monthlong periods. There are two main measurements. Mean spring peak velocity is the highest velocity of tidal movement that can be found in an area during a single month. Mean neap peak cycle is the lowest point in velocity that a tidal area experiences in a month. These two measurements can help approximate the greatest and least amounts of velocity found in any given tidal pool over the course of a month.

 

GENERATING METHODS

Tidal power can be classified into four generating methods:

  1. Tidal stream generators (or TSGs) make use of the kinetic energy of moving water to power turbines, in a similar way to wind turbines that use wind to power turbines. These turbines can be horizontal, vertical, open, or ducted and are typically placed near the bottom of the water column where tidal velocities are greatest.
  2. Tidal barrages make use of the potential energy in the difference in height between high and low tides. When using tidal barrages to generate power, the potential energy from a tide is seized through strategic placement of specialized dams. When the sea level rises and the tide begins to come in, the temporary increase in tidal power is channeled into a large basin behind the dam, holding a large amount of potential energy. With the receding tide, this energy is then converted into mechanical energy as the water is released through large turbines that create electrical power through the use of generators.
  3. Dynamic tidal power (or DTP) is an untried but promising technology that would exploit an interaction between potential and kinetic energies in tidal flows. It proposes that very long dams (for example: 30–50 km length) be built from coasts straight out into the sea or ocean, without enclosing an area. Tidal phase differences are introduced across the dam, leading to a significant water-level differential in shallow coastal seas.
  4. Tidal lagoon, a newer tidal energy design option is to construct circular retaining walls embedded with turbines that can capture the potential energy of tides. The created reservoirs are similar to those of tidal barrages, except that the location is artificial and does not contain a preexisting ecosystem. The lagoons can also be in double (or triple) format without pumping or with pumping that will flatten out the power output.

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