1. Engines, not generators. Higher tier engines put out more power.
2. Conductive pipes transfer power. Phased conductive pipes transfer it without a connection. Tessreact's also transfer items, liquids and power with no connections.
3. Redstone energy cells are charged the same way the machines are. If you can power a machine with an engine, you can charge an energy cell with one. If you can power a machine with a conductive pipe, you can charge an energy cell with one. They can also be picked up and moved without losing their charge.