Would tend not to get stuck into Renewable ETF's.
Why?
Because the ETF's end up owning stock of laggards which underperform. I am a firm believer in a focussed portfolio and ETF's (at least most of them) dont give you this.
Diversification is a hedge against ignorance if you ask me. There are plenty of top notch stocks out there that if you are willing to do a bit of research can yield results far exceeding that of an ETF.
This is just my opinion, take it for what it is worth (nothing really as far as stock prices are concerned!!)
GEX on the NYSE is a good renewable (though highly wind oriented) ETF that is still reasonably underpriced with limited downside. It is one of the better ETF's for wind exposure as most of the companies invoved trade on obscure exchanges. Vanguard have a few aswell.
Solar ETF's are ten a penny. Be careful with these as there are a lot of dud/laggard solar stocks out there and these ETF's own them. I would tend to pick stocks (not ETF's) off research (not tips) in the solar sector as every stockholder of the typical solar is screaming their stock is headed for the moon. Not going to happen as has been demonstrated the last two weeks (earnings season for solar's).