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I come from a fairly remote island where we need a 150 min ferry ride to reach the mainland.

While the island has few resources that would encourage a government to investigate the possibility of a large bridge such as the Denmark-Sweden one, there is one resource that we have in abundance - wind.

Would it be possible to combine a mega-bridge with an offshore wind-farm? With turbines in the bridge towers. Possibly also wave-generators underneath? Or is this just fantasy?

If this is a realistic possibility, then maybe, just maybe, we could at least get someone to consider this rather than laugh-out any suggestion of connecting us to the mainland.

The shortest distance is 23-24 km. An alternative would be a total distance of 29Km, but hitting a small island after about 20Km.

I suspect it's just fantasy, but it'd be good to know.

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  • $\begingroup$ Welcome to Engineering! This would be hard to answer without a lot more information. An immediate concern is that wind turbines can usually rotate to get the best angle to the wind, but if the turbine is attached to the bridge's columns, that's more complicated if not downright impossible. So the wind's consistency of direction would be a huge factor. Could you tell us which island (or group of islands) you're on? $\endgroup$
    – Wasabi
    Apr 19 '19 at 21:50
  • $\begingroup$ @Wasabi most of the Øresund bridge the OP mentioned is actually a viaduct rather than a suspension bridge, except where there are shipping lanes under it, so building towers for wind turbines wouldn't have any "geometrical" issues - if there was some way to solve the other problems, which doesn't seem likely. en.wikipedia.org/wiki/%C3%98resund_Bridge $\endgroup$
    – alephzero
    Apr 19 '19 at 23:04
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One huge safety issue would be protection against turbine blade failure. There is no realistic way to catch and restrain a broken piece of blade, and apart from any loss of life during the incident itself, there would be a risk of the bridge being unusable for a long time while repairs to the damage were carried out.

Accident statistics for UK wind farms published in 2011 showed a total of 1500 reported incidents, four deaths, and 300 injuries, over a 5 year period. That may be "acceptable" for people who are voluntarily employed in a high risk industry, but it certainly isn't an acceptable risk for the general public, especially if they are in effect required to use the bridge regularly for transportation.

There is a more general regulatory issue here, since in the UK wind farms are classed for accident reporting purposes as "machines" not as "buildings," and therefore any design regulations relating to the general public's access to such structures may be non-existent.

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  • $\begingroup$ That makes sense - so that alone classifies it as not realistic. Thanks. $\endgroup$
    – MacIomhair
    Apr 19 '19 at 20:15
  • $\begingroup$ But because it isn't practical to put traditional, large scale wind turbines on the bridge, this doesn't exclude covering it some sort of alternative wind turbine, i.e. smaller scale turbines or ones where the rotational axis is transverse to the wind direction. Or just covering the thing with solar panels. You might not want it to be an aftermarket addition but engineered in from day one. $\endgroup$
    – D Duck
    Apr 20 '19 at 9:29
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    $\begingroup$ This is misleading. Most of those "4 deaths and 300 injuries over 5 years" won't be anything to do with blade failure, which is incredibly rare. Most of them are likely to be injuries to people erecting or servicing the turbines (the latter involving climbing up and down 80-metre vertical ladders, and so forth). Wind turbines are placed in other locations where a blade failure would be injurious to the public, so I don't see that that would, in of itself, preclude use on a bridge. $\endgroup$
    – Flyto
    Aug 9 '19 at 21:17
  • $\begingroup$ (note that the article is in The Telegraph, which historically dislikes wind power and is quite prepared to distort facts to make it look bad) $\endgroup$
    – Flyto
    Aug 9 '19 at 21:25
  • $\begingroup$ The large wind turbines have lifts in them to reduce fatigue and increase safety... $\endgroup$
    – Solar Mike
    Aug 9 '19 at 21:28
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Part of the answer to this will be about considering how one optimizes the locations of wind farms and bridges. One of them likes to have a lot of wind. The other (well, the trucks on it) prefers to avoid this. So co-locating the two would necessarily involve compromises. That doesn't mean it's impossible.

More pragmatically, a large wind turbine develops very large forces that try to tip it over: the tower has to take large lateral (sideways) loads. Bridge towers are typically designed for vertical, not horizontal load. My instinct here is you wouldn't be so much "attaching wind turbines to the bridge" as "building a bridge along the line of some offshore wind turbines". Which in capex terms is probably going to cost nearly as much as building the two things separately, although the O&M cost of the wind farm should be substantially reduced.

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  • $\begingroup$ And closing the bridge to maintain the turbine will be popular, hard enough just for bridge maintenance,... $\endgroup$
    – Solar Mike
    Aug 9 '19 at 21:23
  • $\begingroup$ @SolarMike grin true, though I'd like to think that if somebody was going to the trouble of putting these things together, they could design it so that at least for routine turbine maintenance, closing the roadway wasn't necessary. $\endgroup$
    – Flyto
    Aug 9 '19 at 21:25

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