Here’s a cool solar-powered sound system!
The sola-system’s parts were chosen in order to build a device that would be a one time buy. This means that after the original purchase the owner would not have to buy any other linked products (like batteries or adaptors) to use the speaker. This allows for much less waist economically and environmentally. The speaker system does not ever need new batteries, cords or disks, what you pay for is what you need.