What's the limiting factor in wind turbine size? Is it regulatory, construction capital, materials technology, supportive infrastructure, something else?
Not an expert, but the blades are already tricky to transport on land. If they keep increasing in length, it might be only feasible to transport them via ship or transport helicopter. There’s a new planned wind turbine factory on the coast of north east England where they can pump out turbines and deliver via ship.
The biggest turbines stopped being land based years ago. Onshore wind caps out around 6 MW, while offshore wind is pushing 16 MW. There's just no practical way to handle these huge turbines (and their massive blades) onshore.
Turbine factories are near where the wind farms are for shipping reasons. For offshore wind you need to be at a good port so you can get the blades directly to a ship. For inland wind farms you locate near where someone is willing to make a long term commitment to buy your windmills.
I have no idea what current numbers are, but I expect long term most factories will be inland and produce wind turbines of a size that is limited by local transport roads/laws. At sea might be better, but one factory can produce windmills for any ocean in the world. Inland shipping is far more expensive and so we need more factories scattered around.
If your country is near the sea then off-shore wind is best. However a lot of land isn't close enough to the sea to make off-shore practical and so they need a different option.
For land based installations, start as simple as transportation. You certainly don't want to assemble the blades on-site and the contortions they go through for trucking the finished blades are already quite crazy. Had the Cargolifter airship not been abandoned, I'm sure it would be used exclusively as a wind turbine parts carrier.
I was thinking of portable autoclaves. What about manufacturing blades on-site?
Large scale composites are still largely manual labour, and there are few pieces of tooling which themselves need to be one big piece. Mould can be split into sections rather easily.
Manufacturing needs a highly controlled environment. The industry's trend has been towards simplifying the installation process as much as possible. Smaller crew, simpler equipment, less that can go wrong on-site, etc.
You want as few humans off the ground as possible for safety reasons. Someone needs to get to the top of the tower to attach things, but as little as possible.
Most wind farms (on shore) are in fields that the farmer has planted. you want to disturb the crop as little as possible while installing which means the factory will be elsewhere so that you don't need to tear up more crop in manufacturing.
one funny limitation for US only is the Jones Act from 1920, it requires that the vessels that install these offshore wind turbines to be built, owned, crewed and registered in US. And there aren't many boats that can install turbines the size of modern offshore wind turbines.
So I don't believe the Jones Act would come into play in this situation. The Jone Act controls shipping between US ports, so if all you are doing is taking the pieces of the turbines out to be installed and coming back to the same port you haven't shipped anything between ports. It would fall under the same loop hole that cruise ships use, which is since they drop of passengers at the same port they picked them up at nothing has been "shipped between ports".
Generally construction and materials. Particularly for offshore the supportive infrastructure and maintenance takes up a big chunk of the cost - the expectation is that those costs won't scale with turbine size.
