Getting reliable power in some areas of rural India has been such a problem for schools that they need to search for another solution. These schools and businesses in India were featured on BBC Click (click below for that and skip to 19 minutes in) and use an innovative solar charge pack as a backup for the hours when power fails.
This is an innovative solution but a cheaper and equally effective solution would be to purchase a projector with a long battery life, like the Pico Genie M550 Plus, that can last long enough to cope with long power outages, while still being bright enough to project clearly even in bright light conditions.
You can also load all your content onto the projector itself and project files from its onboard document reader, so you don't need to worry about supplying power to an external source to use it.
If you're in a part of the world where power isn't reliable or you work in a job where you travel to remote areas without power, a portable projector could be the economical solution to your problems!