I have by now invested into various solar funds in Spain, Italy and France.
In total these investments have been leading to photovoltaic systems which are producing enough electricity for 18 households. This is due to the high irradiance level in these countries and the fact that the capital is increased by a factor of 4-5 based on bank credits. In other words, only 20 % of the investment is payed by people like me and the other 80 % are financed through banks with an interest rate of 3-4 %. The bank receives full securities and the equity investor (which would be me) takes the financial risk but in consequence one can trigger a 5 times larger investment. Such closed funds are high risk and I can not recommend to spend your most precious money. But if you want to make a long term investment and maximize your contribution to the deployment of renewable energies, then these funds are a good choice. It is a bit of a gamble but interest rates can reach 10 % per year.