About 25 years ago Utah inventor Gary Lee was growing frustrated with his snowmobile’s gearbox. Far too often when he was out riding the transmission would get really hot and burn out the rubber belt inside the gearbox. This got Lee thinking about how to design a more durable transmission. After years of work he’s designed a prototype of a recently patented transmission that he claims could make wind power profitable and help the industry move away from subsidies.
The poor reliability of gearboxes is a challenge for the wind power industry and the high cost of replacing busted gearboxes is a chief expense, according to the American Wind Energy Association. While wind turbines are designed to operate for 20 years, estimates for the life of an average gearbox are in the six-to-10-year range, although this can vary, Jeroen van Dam, an engineer with the National Renewable Energy Laboratory’s Gearbox Reliability Collaborative, said in an email. The collaborative, which includes wind turbine manufacturers, owners, operators and research institutes, has found that gearbox problems are an industry-wide issue and not tied to a particular wind turbine or gearbox manufacturer, he added.
The fixed gearboxes currently used in wind turbines are vulnerable to spikes in wind speeds, Lee said in a telephone interview. High-speed gusts apply a lot of torque (the force that spins the turbine’s shaft) to the transmission, placing it under stress. Sometimes, the wind doesn’t hit the turbine straight on and might catch just one of the blades, which can bend the gears, Lee said.
“If you look at windmills, you’ll see quite often that several of them are not turning and that’s because they’re broken,” he said.
Lee’s invention, the Universal Transmission, has the capacity to absorb the shock of variable winds and keep the turbine’s generator, which creates electricity, spinning at a constant speed, explained Dick Wilson, CEO of VMT Technologies, the 12-person Provo company, where Lee works, that holds the patent for the Universal Transmission. The company has built and tested a metal bench-scale prototype of the transmission, which has not yet been tested inside a wind turbine or vehicle.
The Universal Transmission could improve wind turbine efficiency by five to 20 percent, said Wilson. This figure is based in part on the expectation that turbines will not need a power converter (which converts the fluctuating electrical frequency generators that work at variable speeds produce to a frequency compatible with the electric grid) if fitted with the Universal Transmission. The transmission would also be pared with a synchronous generator, which improves efficiency, he explained.
The Universal Transmission would bring down maintenance costs for wind turbine operators, Lee added. Removing the problem of torque spikes would allow turbines to produce more electricity and with individual turbines functioning more efficiently operators would have to put up fewer wind towers, he said.
There’s a very good chance the technology can make wind power profitable so that the industry can function without subsidies, Lee said.
As the name suggests, Lee designed the Universal Transmission with a broad range of uses in mind. The technology could be used in trucks, SUVs, vehicles with diesel engines, tractors, and farm and mining equipment, Wilson said.
How It Works
The Universal Transmission is an adaptation of what’s known as a continuously variable transmission. Standard transmissions, such as those found in cars, allow drivers to shift between a fixed number of gear ratios, with each gear change being like a step up or down a set of stairs. A continuously variable transmission, however, is more like an escalator in that it can change between an infinite number of ratios that fall between a minimum and maximum ratio, Lee explained.
Traditionally, these systems use a metal or rubber belt between two pulleys. In a car one pulley is connected to the engine, while the other is attached to the drive shaft, the part that spins the drive wheels.
Continuously variable transmissions use friction to transmit the engine’s torque, Lee explained. The Universal Transmission, however, uses a metal chain with teeth that is always engaged with the gears to which it’s attached and is therefore always engaged with the engine. It does not rely on friction, which means more torque can be applied to the transmission without it heating up and melting, he said.
Continuously variable transmissions are already used in some cars, but unlike VMT’s product cannot be used in bigger trucks because they can’t handle high torque, Wilson said.
If a trucker were driving up a hill with the Universal Transmission, the trucker would not have to push in the clutch and drop gears, which makes the truck lose power, Lee explained. The Universal Transmission, which works without a clutch, would automatically keep the engine working in its “sweet spot,” which improves fuel efficiency, he said.
VMT is a research and development company that is looking for partners to manufacture and commercialize the transmission. These partners would assist in funding so that the Universal Transmission could be tested inside wind turbines and vehicles, Wilson said. While marketing the Universal Transmission in the U.S., VMT is going to promote the technology to the wind power industry in China, which last year surpassed the U.S. to become the world leader in wind power, Wilson said. VMT also has a representative in Korea, where one company has agreed to engineer a prototype of the Universal Transmission and another company has agreed to build and test the prototype in vehicles, at a cost of $500,000 to each company, he said.
Electric vehicle manufacturers have shown interest in the product and VMT has received purchase orders from two manufacturers: Vision Motor Cars, based in Kentucky, and Leo Motors in Korea. Vision, which manufacturers an electric small pick-up truck, smart car and sports car, has put through $348 million in purchase orders for the transmission system.
Vision’s vehicles, which are sold in Europe and are awaiting Federal Motor Vehicle Safety Standards certification in the U.S., are fitted with manual transmissions, said Brooks Agnew, president of Vision Motor Cars, in a telephone interview.
Traditional automatic transmissions are not suitable for electric cars because they’re inefficient and require fluid pumps, which drain the batteries, Agnew explained. In future, the Universal Transmission will allow Vision to offer drivers an automatic transmission that meets his company’s design criteria, he said.