I have been looking for some similar projects to invest about 10BTC in each myself.  One I have been trying to get the numbers worked out for is a solar powered mining rig.  I am comfortable with the first block paying 12.5BTC to cover my investment.  Any blocks solved after the first, would be mostly profit.  Its been a little tough getting the research completed to see if this is even worthwhile, but I'm still working on it.  I'll happily share the information if this is something you would be interested in too, but it may take a little while for me to complete it.