Mitigating offshore wind farm noise

One of the hot topics at the recent International Quiet Ocean Experiment in Paris was the noise impacts of offshore wind farms. It seems that while the American Oilmen are furiously trying to carve up the Arctic for fossil fuel, the Europeans are rapidly developing wind power. Much of this is happening in the North Sea between the United Kingdom and the European continent.

North Sea Wind Farm

While wind power has significantly lower environmental impact than fossil fuel, it does not come without drawbacks. From a noise standpoint the concerns include the noise of installation, and the ongoing noises of operation.

The operation noises include gearbox vibration transmitted down the mast, and the thumping noise generated by the tip vortices as they pass by a boundary (like the ocean surface).

Pile Driving with bubble curtain

The installation noises in the shallow North Sea are from pile-driving the foundations to mount the mast. Percussive noise from pile driving was found to be deadly to fish, and pernicious to marine mammals.

Mitigation for pile driving noise was first developed during the San Francisco Bay Area bridge retrofits and involves the use of “bubble curtains.” By surrounding a driving pile with a ring of air bubbles, the water and noise within the ring can be acoustically isolated from the surrounding environment.

The drawback here is that the process is energy intensive because a high volume of air needs to be continuously forced down to the depth of the seabed to be released in a continuous stream. This can get really expensive: This mandated mitigation doubled the cost of the Richmond Bridge seismic retrofit.

But researchers at the University of Texas, Austin have developed an improvement on the bubble curtain – by encapsulating the bubbles in a latex envelope, a curtain can be installed while pile driving, and then relocated when needed elsewhere.

This promising technology could decrease the expense as well as the noise of developing wind farms in the North Sea – or even off the coast of America!

2 comments for “Mitigating offshore wind farm noise

  1. MD4U
    November 20, 2011 at 1:18 pm

    “While wind power has significantly lower environmental impact than fossil fuel”
    This is a false statement because, wind is an intermittent, unreliable, non-dispatchable source of energy. The result is that for every MW of potential Industrial Wind Turbine installed, an equivalent amount of reliable, dispatchable power must be at the ready for when the wind does not blow. This back up generation must be at the ready 7/24, 365 days of the year, and is overwhelmingly in the format of “boiling water” (BW) steam generation achieved by burning fossil fuels. As you are aware from making tea, water to steam is not instantaneous, thus the BW system is forever boiling water just in case it’s needed instantly. Thus you are ALWAYS burning fossil fuels. Additionally BW systems on standby, are paid for by consumers to be on standby, wether we use them or not. Governments are duplicating the generation system for no justifiable reason except to make Wind Generation companies rich, and the electrical rate payer poorer. IWTs are economic parasites that will ultimately kill the host.

  2. November 20, 2011 at 10:15 pm

    An interesting argument, but a few points are missing here. One is that offshore wind is significantly more persistent, and reliable than the most terrestrial wind sources. Additionally a wind farm is not typically loaded to capacity, so “excess” power can be stored. One of the most efficient methods is storing the power kinetically – running flywheels for example. Another is running pumps to augment tidal capture and thermal gradient systems.

    Additionally, while we do not have the current capacity to “throw the switch” over to wind, we could – and should sensibly increase wind and tidal capacity and wean ourselves off of fossil fuel.

    A lot of wind projects are focused on offshore wind because it is so reliable. And even in the occasion when the wind slows down or stops we do have the ability to predict these patterns because the are not local, or even regional – rather they are hemispheric in scale, so we don’t have to say “oh my gosh! put the kettle on the stove Mavis!”

    Offshore wind energy also puts the farms in close proximity to tidal and wave energy resources – obviating a perfect complimentary blend between wind and tides. The wind may be variable, but the tides?

    In terms of “making the wind generation companies rich” I’d advance that we are currently making the oil companies filthy rich, and it is not doing much to get our economy out of its slump, or our planetary climate out of its tailspin. I’d like to see some of the “energy largess” distributed across a broader sector to sort of level the playing field a bit. It is not good having our entire energy supply monopolized by fossil fuel.

    Holding on to burning hydrocarbons, or shifting over to more benign sources of power – none of this comes without costs, but just some elementary napkin scratching reveals how expensive fossil fuel is once true costs of tax subsidies, military defense of oil supplies, and environmental damage is factored in. If I were boss of the world I’d take half on the petroleum subsidies and hand it over to renewable energy technologies. I believe that this would make it abundantly clear how competitive renewable sources really are.

Comments are closed.