Hydro to compliment my solar

Kia ora! About time I joined a forum after 10 years of trouble free solar gathering.

Using a generator really bugs me so I have fixed the 1000 cubic metre dam that's 20m above our house with the hope of running a very small turbine in bad weather to top up the 24v battery set up. Aiming for about 200w.

I'd love to hear from anyone who has done this as information on the googletron mostly relates to bigger systems. 

Thanks! Josh