A second alternative to invest in wind energy is given by stocks and ETFs of companies in the energy.
There are many “renewable energies” ETF and a bunch of solar ETFs.
However the choice for wind ETF is much more limited.
There used to be one ETF form Invesco (PWND) specialized in pure wind players but it has been delisted due to very low trading. Yes, that is not a good sign.
So, as far as I know today (2018) the only wind ETF is First Trust ISE Global Wind Energy Index Fund (FAN – a very appropriate name).
Not all the companies in this ETD are 100% wind: for instance, the biggest share (almost 10%) is Ørsted (or Dong, if you prefer the old name like me: Dansk Olie og Naturgas).
You will, however, find the big players, including Longyuan Power (probably the biggest wind power producer in Asia) and all the usual suspects such as Vestas, Siemens Gamesa, etc.
What you will buy is very high volatility today, but probably also long term growth.
An alternative is to do some cherry picking and select the stocks one by one. Almost all players are traded (with some exceptions, for instance Enercon).