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Just to feed into the points and advises that have been made on the pros and cons of DC as opposed to conventional AC. Using PV panels to supply the type of building you have mentioned can be problematic. Using DC you can limit power theft and discourage unapproved cable connections which will drain batteries and make the system less sustainable/costly and higher servicing costs. However if you go with 36-48 volt DC then you can keep cable sizing for the type of room sizes you have highlighted down to 4-6mm which can be easily purchased in the countries you have listed and at a normal price.

When installing DC lighting systems you should seriously consider no cutting back on installation costs, 1-2 lights per light switch maximum, as you want to be able to achieve maximum energy efficiency and with DC circuits at 36-48 volts DC circuit breaker current will be very high so 2-3 lights per breaker. For each room having independent systems is important so that if a room is over used this does not lead to the draining of an entire battery bank. Isolate the potential to bring the whole system down by breaking the system into 2-4 smaller systems. 2 class rooms plus an office and external lighting ideally should be 4 separated systems.

If you decide to use the PV, DC to AC (inverter-charger systems) then you need to consider the losses in energy (cable losses and DC-AC conversion losses) and oversize the system accordingly. Using any existing wiring systems will increase losses and battery drainage issues so best to install new wiring to assure the system is efficient. Keeping circuits and system small is still a good design, when using this system so that sustainability and rehabilitating failing loading designs is easy.

Battery drainage is vital with both types of systems so getting a company to install a system which is programmed to disconnect and protect batteries at 50-40% drainage is vital. Depending on the type of batteries this will assure that lifespan will be 3-5 years as opposed to 12-18 months.

The AC system will be the easy system to buy materials locally, for example lights, but the DC system will require ordering materials and having spares plus correct training and M&E but have better sustainable characteristics.

The option of having a DC lighting system with an AC inverter-charging setup should also be considered as buildings often serve a multiple of tasks and lighting may be required for literacy requirements.

Best of luck

Paul