There is a technology fix for the mast hazard to low flying aircraft. It's called a LIDAR unit and the L stands for laser. It waves a laser beam upwards and uses the reflections to calculate wind at various heights. There are also SODAR units where the S stands for sound which do the same thing with ultrasonics. Both are about 2m in height and would eliminate the hazard to low flying aircraft as well as not upsetting the neigbouring NIMBYs by alerting them to the wind prospecting going on in their back yards. (We make power supplies for some of these things, and some met masts as well).
Many of the environmental impact assessments are being commissioned by people who are anti-wind so be careful as some have spin on them. There are a range of views on things.
The UK approach to putting up wind farms onshore is so $%^&& up by the planning system that we basically penalise them with high costs, which in turn means they need more subsidy to level the playing field (don't make the mistake of thinking that coal, gas, oil, nuclear, hydro are unsubsidised).
Payback time in energy and carbon terms on a well sited large wind turbine is of the order of 18 months. That's a wells-to-wheels costing for those of you into minutiae. Economic payback depends on a range of factors including which subsidy regime you happen to be in, but I wouldn't be rushing to invest in the UK ones as this country is about to be forced to dash for gas once again due to lack of strategic planning. In the USA prior to a recent price spike in turbines they were about to be installed on an unsubsidised basis as the cheapest form of generation, so the world is changing.
Payback time on a small turbine on a yacht tends to be quite good as the alternative is diesel. Flying planes into yachts leads to early acquantance with Bournemouth beach, irrespective of who is at fault.
We are not far from the day when the technology transfer may start being from turbine blade designers into wing designers rather than vice versa. They are becoming very interesting from both a structural and an aerodynamic perspective.
Offshore large turbines are required only because onshore planning is a nightmare. O&M on offshore turbines is going to be a bundle of fun. Watch out for sme humungous met masts going up offshore, hopefully on charts and with collision lights.
Fly safe please folks