Efficient generator needs minimal iron

A novel generator, conceived to improve the efficiency of pedal-driven generators in remote places, is nearly 90% efficient and has none of the laminated iron magnetic circuits that are normally necessary. This makes it very thin and lightweight, and potentially very cheap to manufacture. It was recently demonstrated by Alexander Bushell – proprietor of Global Medical Systems, which has developed a field operating theatre system that it is supplying to African countries – and Ray Laws. Our first reaction on seeing the generator was that it should not be at all efficient – but in action it managed to light up three 50W 12V bulbs without any problem. The idea is the brainchild of Dr Malik Awad, who lives in Belgium. Bushell told us: “He came over a with concept and we got a patent on it.” The development machine has a stator in the form of six iron-cored coils mounted between two sheets of plastic. The rotor was in the form of two crosses – one rotating in front of the stator connected to another rotating behind it. Each is equipped with flat, rare earth magnets on the insides of the extremities of each arm, facing the coils. There are North poles on the magnet faces of one rotor and South poles on the magnet faces on the other rotor. No laminated iron is used to complete magnetic circuits outside the rotors. Bushell continues: “It is more cost effective to manufacture than a conventional dynamo and the efficiency of even this crude model is 80-88%.” It has an offer of funding from SEEDA, and intends to fit a device to one of its own Wind Star wind turbines at the Kent Science Park in the next three months. Describing its development, Ray Laws explains: “We had no physical drawings. One thing wrong with the first design was that it had a couple of steel ball races in it. When we ran it up, the magnets affected the ball races. The current model has nylon ball races. We will probably go onto glass or ceramic ball races.” The magnets are held mechanically on the iron cross carriers – which must be slightly narrower than the magnets, so there is no interference from the mild steel that the carriers are made of. “We are currently producing 60W to 80W, but soon expect to be producing 150W by getting the magnets closer to the coils – mounting the coils in a nylon assembly and doing away with the thick plastic plates,” says Laws. Bushell concludes: “We hope to secure a micro grant and employ a few specialist engineers to improve it – then build about five test units. We then want to transfer it to our bicycle generator, because it can be built in line with the pedals without a gearbox. We also have a proof of concept that we can attach directly to our wind turbine shaft – also without a gearbox.” Global Medical Systems (Europe) Email Alexander Bushell Pointers * Efficiency so far is 80-88% as compared with around 65-75% for a conventional generator of similar size * It is very light in weight – using no mass of laminated iron – and inexpensive to manufacture