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Michael Dowling

(1)

I find it incredible when I read that a 60m plastic composite blade weighs 17 tonnes! 1700 kg, yes, but 17 tonnes! I can see how old blades would be a recycling problem.

H

(2)

Do you know this type of wind turbine?
http://www.eolienne-a-depression.fr/index.php?option=com_content&view=article&id=54&Itemid=54

Kris De Decker

(3)

@ H

No, never heard of it. Very interesting, thanks !

Troy Parker

(4)

Aircraft wings are made from aluminium, which is indeed energy-intensive to make, but recyclable. Perhaps this could be a suitable material for turbine blades.

L

(5)

Thanks again for another great article.
However, having read the term solid wood, I had to comment that laminated veneer lumber has a substantial amount (up to 8 %) of phenol formaldehyde resin holding it together. As is the case with cross laminated timber (CLT, which has a smaller content of 1 % of polyurethane glue), it often gets called solid wood although it's completey reliant on plastic.

Kris De Decker

(6)

@ L

I'm aware of that, but the number I found for laminated veneer lumber was 2% glue. That's very little compared to the resin content in wood or glass fiber composites, so I found it not really an issue. If you cut a discarded wood blade into pieces, you still have very useful material to do something else with, even if it has some plastic in between the layers.

Nevertheless, if you have more information, feel free to send it along. And if this means that we should go back to the blade design from 1959, I am also OK with that.

L

(7)

@Kris

Thanks for your reply. I'll PM you about the glue content. My concern had to do with 1) when the glued wood is left to decompose and 2) being reliant on the industry that makes the glue. Going for the designs that didn't yet incroporate glue or other problematic chemical compounds gets my vote. You said it best: "If we would reduce energy demand, smaller and less efficient wind turbines would not be a problem."

Kris De Decker

(8)

@ L

Great, thanks. During my research I found a paper that describes a low-tech production method for making laminated veneer bamboo using hand tools, screw-driven mechanical presses, and widely available, economical adhesives.

Mahdavi M, Clouston P, Arwade S. 2012. “A Low-technology Approach toward Development of Laminated Bamboo Lumber”, Elsevier: Construction and Building Materials, Vol. 29, pp. 257–262

Petersen

(9)

Hi I am looking for blueprints to build a small wooden wind turbine for the uses of a school in a developing country. Thank you very much

Kris De Decker

(10)

@ Petersen

Check Hugh Piggott's design in the other article: https://www.lowtechmagazine.com/2019/06/small-wooden-wind-turbines.html

ijk_ijk

(11)

Thanks for your very preciosus article as usual. Just a question: why a composite plastic o carbon blade can't stand forever? Why they have a so short life? If we can extend the life o these blades to many decades or centuries whe can have a more suistanable wind power.

Kris De Decker

(12)

@ ijk-ijk

That's a very good question. It was calculated that the first fiberglass blades from the late 1970s had a life expectancy of 70 years. (And the same was true for the wood-alu blades from the Gedser turbine). The reason was that engineers did not fully understand all the forces that act on a wind turbine blade, and thus built them as strong and durable as they could.

This suggests that the limited life expectancy of today's wind turbine blades is intentional. I assume that this brings cost advantages, but at the expense of sustainability. So indeed another route to lower the environmental impact of wind power would be to build plastic blades stronger again.

Mathew

(13)

Alternatively, we could further develop kite wind power, which is an almost entirely fiber-based system with power generation on the ground. Ground-based power generation helps limit the need for rare earth materials or other lightweight, high embodied energy components.

A commercial system is being spun off by TU Delft:
https://kitepower.nl/tech/

Google is also funding a much worse (sustainabilty-wise) system with Makani power. They are generating power on the kite and sending it down a custom conductor cable.

Both systems result in dramatic material savings, and could have synthetic materials substituted for natural fibers. The soft fabric kites' polyester fabric could easily be replaced with silk without any performance loss.

A stiff cable that transmits mechanical power would be more difficult to make from natural fibers, as their elasticity results in losses. Steel wire could work, but at a significant performance and safety disadvantage.

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