Comment by barbegal

GPs link doesn't even show what was claimed ("The other 3 have needed costly maintenance").

From that link:

"The first of these turbines is scheduled for redeployment in May 2022, with the final turbine to be deployed in March 2023, complete with a retrofitted wet mate connection system, which more than halves the costs of future turbine recoveries and deployments."

"The company’s AR150 turbine was re-deployed last month, after being out of the water for upgrade and maintenance work."

The single long-running turbine can be compared to the upgraded turbines to measure the effect of the upgrades, and it provides the headlines this thread is about. The upgrades themselves are also clearly valuable R&D work.

Yes, 1 success out of 4 test flights — good news, it's possible!

That's like saying if I roll 4 dice and one of them lands on a six then it should be possible to make one that only rolls sixes.

One benefit that’s difficult to quantify is that the power is extremely predictable compared to other renewables.

1.5mw is likely a nameplate capacity for the turbine, not the actual output (which should be labeled in GWh per year).

The article likely double-dips on this by saying that 6MW could provide for 7k homes, which it obviously can’t at peak use.

Also there is theoretically power in the GW range to be harvested here (specifically, Scotland’s tidal flows), so it’s worth investing a substantial sum to figure this tech out.

Texas’ capacity was 113000 MW yesterday so 1.5MW doesn’t seem significant. Am I understanding this wrong?

https://www.ercot.com/gridmktinfo/dashboards

I used to think the same way, “just use cheaper solar” but I have come around to see the value. Doing science and engineering projects to explore new or different alternatives is valuable. We might find something surprising.

Having different types of power generation provides redundancy. The wind still blows at night, the tide still comes in and out when its cloudy, etc. Grid storage is nowhere near a solved problem, so something like tidal could prove less expensive than storage or overbuilding alternatives to overcome their variability problems. Even if it doesn’t end up being widely useful, it could still end up finding a use in more niche applications.

Finally, it can and will improve. 30 years ago, solar was not price competitive and decades of development and iterative improvements have changed that. We should keep developing alternatives to see their full potential.

I think the charm for a cloudy place like Scotland is that a system like this is unaffected by poor light supply. Your photovoltaics aren't going to fair nearly so well there hence this solution.

> covering some less-useful land in ground mount photovoltaics.

Doesn't even need to be less-useful land (especially in western Europe, ground is becoming a scarce resource), put PV on flat rooves or add them over open car parks. Also helps alleviate pressure on the overstressed energy grid by generating and using power more locally.

But, local power is (overall) a lot more costly than major centralized power generation projects, like a wind farm or what have you.

Carbon fibres themselves may be corrosion resistent, but the fibers by themselves are like a fabric. If you want a solid part instead of cloth, you need to encase the fibers in a resin. Imagine it like a piece of cloth soaked in beeswax or candle wax: it is solid like the resin but if you pull on it, it has the strength of the fibers of the cloth.

The resins used for carbon fibers are usually very bad at contact with water over long periods of time. Even those in aerospace applications require coating/paint if exposed moisture over time. It’s a plastic, even the best ones don’t do so well in water after a few months.

Furthermore, the damage that moisture does to the resin can be difficult to detect and even more difficult if not impossible to fix. It requires clean rooms, skilled labor and machinery that you don’t have in the middle of an ocean.

Then take iron corrosion: it is easy to spot by naked eye, it may not be easy to repair, but it is relatively simple to “halt” further damage by removing the rust and adding new paint.

Don’t get me wrong: carbon fibers are amazing, but sometimes the “boring” solution is best.

PS: steel alloys and coatings can be amazingly high tech too, it’s amazing what can be engineered.

All industrial generators undergo regular shutdowns for maintenance and recalibration. This is costly and time consuming when they are on land.

Also, I am thinking about all the ocean factors beyond salt corrosion. There's tons of crap in the water beyond salt and minerals. Like fine grit suspended in it. Plus the tidal forces etc.

Steel has the benefit of fatigue limit. Which means as long as the cyclic stress on steel is under a certain amount it won't fail. Aluminium has a much lower fatigue strength than steel and will always fail given enough cycles.

While rust can be a problem it can be mitigated. Also steel is easier to repair than many other materials (welding).

BTW. Aluminium does suffer from corrosion as well. I used to have racing bike, the wheel nipples (these connect the spokes to the wheel rim) used to corrode to the point where they would fail, which meant I would end up with a buckle. I ended up having both wheel rebuilt with higher quality brass nipples.

Plastics under time also suffers from a different set of issues. Plastics can become brittle. Anyone working on old computers (especially macs) can attest to this.

Corrosion, the force of water (being 800 times as dense as air and effectively incompressible, water forces can be huge), objects in the water (again, water being heavy it can move heavy objects around in its flow), fouling through, for example, algae and mussels (https://en.wikipedia.org/wiki/Fouling)

AFAIK corrosion is slower underwater. It’s all the shmutz that’s underwater - logs, rocks and boulders that get moved by these huge tidal currents.

Carbon fibres tend to crack under extreme torque.