I've seen an amazing little system that goes along the ridge of your roof line. Not sure whether it's in full production, or the cost, but it looks like it has potential.
Just done a quick check, Ridgeblade. The website sucks balls, but the product seems to be brilliant.
This isn't the ridgeblade website, but it gives you an idea of how it would look.
http://peakenergy.blogspot.co.uk/2009/10...arket.html
Was thinking about these, but again, it's something for a rainy day fund, or when I have spare time.