A design for a 12 volt supply in rural communities of Cambodia.

I am designing a system for rural communities in Cambodia who are totally off-grid and unlikely to be in the near future. (Starting with a singular power-plant, which may well lead toward a ‘Micro-Grid’ by adding and linking other power-plants).

Appliance load would initially be just 12 volt LED lighting at night and 12 volt fans during the day and night. Plus charging of mobile phones. Luxury option would be to run a 12 volt TV. (The option to use inverters and 220 volt appliances would not be offered which simplifies things). This will be distributed to households.

As yet the demand amount is not known but it would be better to back-engineer and restrict the consumption dependent upon the supply.

I have built a swivel and tilt pole which supports the solar panel array. The apparatus restriction would be merely that of weight and windage. So let’s presume 4 panels of about 650 mm x 1200 mm dimensions (and the relevant weight); maximum.

So depending on the output of the panels comes the Amp rating of the Controller and whether to wire as 12 volt or 24 volt.

Question: If the panels and controller are wired at 24 volt, can 12 volt supply be taken from the battery bank? (I may be showing some naivety here, please excuse me).

Having produced X amount of amps from the panels, given that Cambodia has abundant sunshine even during the ‘Rainy’ season (which due to Global Warming isn’t happening dramatically) How many amp- hour/batteries are needed?

Distribution:

The communities chosen will be as dense as possible so that cable runs can be kept to a minimum. However houses could be 500 feet or more away from the batteries, what would a reasonable cable length and size be to carry the load without too much voltage drop?

Question: Can a large cable be connected between batteries and house and then a smaller size cable be used inside the house. (let’s say feeding a load 4 x 3Watt LED lights per household plus occasional phone charging and 12 volt TV use).

The solar controller could be set to deliver power until say 11pm and start up again at first light. That way nobody can leave a power demand on.

Question is there a device which will shut off the supply when the batteries have reached say 60% discharge? (or whatever you recommend).

I understand I am asking many questions and this is a multi-faceted topic, however I have confidence that you can help me build a rugged, perhaps over engineered power supply for rural communities.

Your help is assisting me in my humanitarian efforts to help people who have never experienced good quality lighting, which so often we take for granted. I thank you in advance of your reply.