East River Turbines Face Upstream Battle

From the Gothamist, following up a story about which, for some reason, I never heard (my wife emailed this story to me). I did not know there were turbines hanging about in New York’s East River. Possibly not for long, though:

The alternative energy company that has plans to install hundreds of turbines in the East River to harness tidal energy and generate zero-emission electrical power is running into trouble due to the massive amount of energy they are dealing with. The small number of turbines already placed in the East River by Verdant Power have been temporarily removed as the strong currents continue to overwhelm the physical construction of the underwater “windmills.” The six turbines that were placed in the water last December and were capable of supplying 1,000 daily kilowatt hours of power and serving the Gristedes supermarket on Roosevelt Island could not withstand currents.

The East River is not actually a river; it’s a tidal strait, and one can easily observe the current moving in opposite directions with the tides. Verdant Power’s plan is to install a field of turbines anchored to the bottom of the East River and use the currents to generate pollution-free electricity for the city. The currents have proven so strong, however, that the turbine propellers have been sheared off a third of the way down, and stronger replacements were hampered by insufficiently strong bolt connections to the turbine hubs.

Well, that’s …promising? Hydro-electric has a couple of basic forms: tidal, meaning windmills underwater, and non-tidal(?), meaning the Three Gorges Dam or Niagara Falls. In the case of the former, the river is dammed, such that water that is allowed through comes through with sufficient pressure to spin the turbines. In the case of Niagara, some of the water (about 80%, I’ve been told) is piped off to the turbines, using simple speed and gravity (rather than placing the turbines on the falls themselves), and piped back to the river afterwards.

The environmental impact of dams hardly needs to be discussed. As I understand the mechanics of the hydro-electric engines at Niagara, environmental disruption is minimal-to-nil.

Here, though? For a start, the scattered pieces of broken turbine probably ought to be swept out of the river. But allowing for the eventuality of turbines strong enough (with strong enough bolts) being stuck in the mud, ready to go. How much tide do they stop? Oddly enough, this testing phase of the East River project was, in part, designed to figure that out, so I guess we still don’t know.

I do know of studies on on-shore or basin tidal energy projects, where the consensus is that wave heights, though not tide heights, are affected. Suggesting that the water would still go up and down the East River, but the current will dissipate, possible significantly. Sadly, I just don’t know enough about the river to say what that means. As long as the river still actually runs, it should be fine. If it slows down too much, it will most likely just start dumping crap at the end and not taking it back out – it will also demonstrate that turbines in rivers defeat their own purpose.

I imagine, also, that the true impact will depend on the river, how fast it goes and what is at either end. According to Eco-Geek:

Preliminary site approvals for in-stream turbine farms have already been given for 25 sites along the Atlantic and Pacific coasts of the US, and a further 31 sites are under consideration. Other companies are developing other forms of tidal turbines, some with as much as 1 megawatt capacity.

I don’t know what that suggests. I don’t much like the idea of all that commercial pressure building up on one side of an as-yet undetermined environmental impact debate, though.

Finally of interest – I noticed that the turbines in this story:

gothamist turbine

match the conventional windmill-type, but not others, such as the ones seen in this 2001 article on tidal energy:

Double-helix turbine

I believe that is the Gorlov Helical Turbine (designed by the author of the article). It’s an adaptation of another type again, the Darrieus Turbine:

Darrieus Turbine

I wonder if replacing the tide-mills (no, that doesn’t work at all) with the Helical Turbine would make a difference to the problem of being over-powered? Amongst other things, the Gorlov adaptation can be moored-and-floating, which would help protect against being sheared off at the bottom by the current.


3 comments so far

  1. Branden on

    I have 2 ideas that would improve this in water. First if you start the blades in the middle on a single pole you will have more surface area. Second if you curve those to wrap around that pole the water will have a longer distance to flow and push it if you put it under water. Second flair the ends out so that it catches better on one side and even less on the other. This works really well in wind but i think that horizontal in the water off coasts would be a really great idea also.

  2. Anonymous on

    what if you make a tunnel to protect the blades like the augmented design. it increases the efficiency and the output

  3. wewantbo on

    Is it possible submerged debris could have struck the blades?

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