But: If these tidal kites mean deep-sea trawling goes away, and if they are not hindered by undersea plantlife finally taking hold in the barren, overtrawled regions… that could be a good thing. What then remains is how effective and how economical the technology turns out to be.
Reshared post from +EuroTech
Swedes Harness Tidal Power with a Kite
Generating electricity with a turbine mounted on a wing, swinging in the underwater tide
by , ; Sweden
Gothenburg-based Minesto is developing a kite-inspired tidal power generator that they claim can operate efficiently at low tidal velocities. The “underwater kite,” invented by Magnus Landberg, has so far been thoroughly tested in basins, and a downscaled prototype (1:10) has been operating outside Strangford Lough in Northern Ireland in 2011/2012. A second prototype will be deployed in 2012 and a “multi megawatt installation” is scheduled for 2015, aiming to output 10MW in 2016.
How it works
Basically, the Deep Green “underwater kite” is a generator mounted on a wing, with a tether keeping it attached to the seabed. A rudder operates the wing, keeping it swinging in circles or in figures of eight. The generated current is passed through a wire within the tether. Clusters of units operate together as one power plant.
The tidal kite looks like a very a simple, ingenious design, a lightweight system that accelerates the current velocity by a factor ten, making tidal power operable in low current velocities. “We are increasing the potential tidal energy market with as much as 80% in regions located all over the world,” Anders Jansson, CEO and cofounder of Minestro, states on their web site. 
The design solves many of the problems which tidal energy has been struggling with:
• It utilizes low velocity currents meaning slow-moving water while other solutions need so called hot spots where the tides are strong. These are rare compared to the waters in which the kite can be deployed.
• It’s a direct drive design, the swinging motions keep it at the optimal speed – no gearbox is required.
• It can be installed at comparably large depths, 50-300 meters below the surface, which leads to 80% more exploitable area according to Minesto.
• No tower is needed, making it easy to deploy offshore and less of an eyesore on the horizon.
• Simpler construction using less material compared to other tidal solutions.
• It’s easily maintainable, with a comparably low weight.
• It can operate on all continents, at low tidal velocities and with ocean currents.
Data for the latest model
• Power generation is rated at 850KW at 1.7m/s current velocity or more.
• Up to 16 units can be deployed per square km (~0.4 square miles).
• Clearance is 14-18m or more, meaning even container ships can pass over it.
• The estimated lifespan is at least 20 years.
The latest International Energy Agency report on renewable energy growth “acknowledges the coming-of-age of the renewable energy sector” estimating a 40% growth in renewables of the next 5 years to almost 6400 terawatt hours. To put that into perspective, it’s “about one-and-a-half times the current electricity production in the [entire] United States.” 
One question remains: What will be the impact of “tidal kites” and similar technologies on underwater wildlife?
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