Have a look at MNE - Some of it's largest holdings are wind related but it also offers useful diversificiation across the sector. Here is a link:
(You'll need to accept the usual terms of access but the info is a worthwhile read - if you don't fancy the investment trust there are equivalent unit trusts too - the top 10 holdings may be worth research if you prefer direct investment, though beware of liquidity in some of these stocks).