I can't tell, are they not permitted to be built on landfill, or can they not place their airspace over water?

You're right. They can't be placed on landfill. That's not intentional, but it just hasn't come up. I'll see if I can debug what's going on there and hopefully fix it.

I just ran into this, too. You can place bricks down if you need to work around it.

I'm thinking about not only fixing the landfill issue but also making wind turbines and pylons placeable on water, since offshore wind farms are a thing.

Awesome. In the mean time, I'll be laying those bricks! :)

The landfill issue should be fixed in the latest release. Still thinking about the water placement, but it's less important if you can just put down a few landfill tiles.

cool, thanks! And I love the idea of putting together offshore windfarms. Wiring them up would be a challenge though.

Hey! I have an other problem with windmills. It seems to me, they only produce power, when the solar have also juice in it. Í have the starter set of solar, and accu, and i build 6-7 windmills. Solar panels are enought in daytime,but accus arent. Thats why I wanted to make some windmills, but it seems, they also dont generate anything, or just around 10% at nighttime. At daytime, they work almost at 100%. At night wind dont blows or something like that???

The wind is quite erratic. Time of day is a factor, but it's far from identical to solar. What you need is more energy storage beyond just your accumulators, so that you can capture the full benefit of periods of strong wind. This is very important since wind is even less reliable than solar. And then you will need a lot more wind turbines, since that's your only red science option. At the next tech level you will have much better energy choices.

The FAQ discusses a low tech energy storage method available in the red technology stage. In the next tech level, you will get two more options for storing energy, and then at the tech level after that you will be able to make your own accumulators.