In order to get enough energy for the fridge (and ice for Coke'n'rum in the evenings) I installed a hydro generator on my SO30i :-)
Due to the needed construction for a wind generator, it's noise and the low performance I decided not to go that way.
I have a photovoltaics (solar) panel which is fine to get charged batteries while not being onboard.
The product I installed is called "SailingGen".
I found a comparison of hydro generators on: www.mergerandfriends.de/technik/strom-an-bord/strom-erzeugen/31-schleppgeneratoren
It can easily be removed and put into the locker:
I can confirm the given numbers of above weblink.
In my configuration it works well until 20° declination.
At 30° declination the charge current strongly degrades due to the fact that the prop isn't deep enough in the water anymore.
My SailingGen has a length of 70cm between the two pivotal points (standard is ~60cm).
Going with 5kn speed through water will still charge my battery and supply all electric consumers including the fridge.
I've made my own mounting as stated in the pictures due to fact that I do not want to have holes nearby the waterline. Therefore I asked the manufacturer for a longer shaft.
Also it's worth mentioning that according to the prop shape the SailinGen want to turn to the port side.
That's why there is a supporting line to the starboard side. With this line you can control the position and you can get it out of the water in case your batteries are fully charged.
The video below shows my unit in operation.
There are more comments on this installation on the Jeanneau Forum page:
Hansi - SO30i - SevenEleven - Germany