You need to be more specific! Don't think along the lines of "I want to make the world a better place using technology", that's too vague! Come up with something that suits your talents/resources. If you're good at programming, then come up with some ideas that utilise that talent (like working on an artificial intelligence project, for example).
I am working on something very very innovative and cheap.
Unfortunately, innovation isn't usually cheap. If you look at a product such as the arduino uno, for example (dear me, it's innovative all right!
), you can see that it's pretty cheap, at only $30! However, if you look into the cost of designing such a product, creating all the framework around it (like the arduino programming environment and 'language'), designing the board, sourcing the components, finding bugs and fixing them, coming up with new revisions, etc, etc, etc, that's a HUGE cost! In fact, if arduino wasn't so open-source based, I would imagine the same board would fetch you at least a hundred bucks or so!
If by cheap, you mean you want the consumer to pay less, and you don't mind investing some capital to fund your project, then ignore the above rant
I want to make everything myself from circuits to body(but not motors and wheels xD)
Circuits and body of what? Don't rush ahead, first get an idea of what you want to do! Right now, it seems as if you don't really know at all (you're suggesting things from renewable energy to blind peoples' aids to metal detectors to motion sensing lights)! I suggest making a list of all these possibilities for your project (don't spend ages on it though), then eliminate them based on what's realistic. For example, do you have any background in the field of biofuels? If not, then strike that off:
converting bioenergy-->electrical energy
Do this until you find something suitable! You can worry about all the details like where to make your PCB much later. Don't cross a bridge until you come to it...
No no, I dont mean to waste anyone's time, all I want is a good idea
You aren't wasting anyone's time! Nobody has to help you if they don't want to.
Good luck with your project