Electron with 2 or more renewable charging sources how can you do it?

Hi everyone.

I have a Particle Electron which is happily gathering sensor data every 20 minutes and publishing to the cloud. I’ve used an Arduino mini before with an RTC, voltage regulator and GSM board and have found the Electron much more reliable and much less prone to unexpected behaviour. It will be off-grid in its final location so I have a 6V 4.2W solar panel hooked up via a diode through micro USB to charge it (easier to detatch etc!) and I’m using the software mods to charge at up to 1000mA and prevent it doing anything strenuous if the battery is below 20% SOC.

Given I live in the UK, Solar isn’t that great in the winter, so I was wondering if there was a way of having multiple renewable energy sources so that when the sun is not out and either it is windy or rainy (or both) then I could harvest whichever renewable is performing best. Also, what is the best way to get photovoltaic solar to provide at least some power when not in direct sun? Would it be a case of going for a 9 or 12V panel to keep it well above 5V even in bright but cloudy conditions??

I have purchased a mini 5V regulated water turbine and I’m hoping to harvest rainwater and siphon it out when the tank is full - similar to flushing the toilet via a siphon flush. This would give a burst of power thanks to the head of water being released all in one go rather than dripping through.

Is it just a case of connecting them with diodes and in parallel?

Any ideas?