On Sunday, 27 March 2016 12:41:53 UTC+1, philgurr wrote:

The question is what is their working life?

Planning applications usually give a working life
of 20 years and some are now already more than
half-way through this. What happens in 20 years?

Logically they will be replaced when improvements are most profitable/money is available/****wits let them.

****wits being the people who mistakenly forced the closure of nuclear power plants in Southern California not long ago.

The obvious improvements being less unsightly (although I think they are impressive) and less noisy, although siting them alongside a motorway is not a bad idea.

I imagine enclosing them inside a casing, rather like jet engines are, would increase their performance at the expense of increasing their weight but they will be significantly less noisy.

Such a design might be beneficial if it could make them useful in strong winds currently they have to be switched off and parked in high winds so all that energy is lost.

But is that a bad thing?
What does wind do besides blow?
God doesn't design things like that for no other purpose than to see it happen.