Last week, a technical consulting company called Ricardo, based in the UK, issued a press release on its Kinergy concept for a “high-speed, hermetically-sealed flywheel energy storage system concept with a highly innovative and patented magnetic gearing and coupling mechanism“. What immediately drew my attention to the concept, is the use of a permanent magnet gearing system in order to convert external torque into internal speed within the system. To my knowledge this is one of the first apparently commercialized uses of magnetic gearing for this type of application [if you know of others, please add a comment below].
Flywheels work on the basis of imparting energy into a rapidly rotating mass, which can then be tapped for later use. They are a well-established method of providing back up power for commercial power utilities, and more recently, they have started to see use in regenerative braking applications for vehicles, where the energy from braking is transferred into a flywheel [instead of the alternative electrical generator approach].
It is to this latter application that the Kinergy is apparently being applied. In Figure 1 we can see a cutaway model showing the insides of the device. The blue-and-yellow components represent the magnetic gear system.
The Ricardo Web site says that:
[t]he range of potential Kinergy applications is significant not least due to its comparatively very low projected production costs. The technology is thus ideally suited for use in road vehicles where regenerative braking and torque assist is employed as a means of improving efficiency and hence reducing fuel consumption and CO2 emissions. Such potential applications range from small, price-sensitive mass-market passenger cars to large luxury SUVs, buses and trucks. Across all of these vehicle categories, Kinergy offers the prospect of enabling effective hybridisation extending into market sectors where the use of conventional electro-chemical battery systems technology would be prohibitively expensive.
They go on to say that:
Further potential Kinergy applications also include low-cost, compact energy management and storage systems for use in industrial and construction equipment, elevators, railway rolling stock, and local electrical substations and power distribution systems.
Magnetic gears of this type are relatively new, and there are not too many commercialized applications for them as yet. The systems generally consist of three concentric sub-systems which allow for the conversion of speed into torque and vice versa, without contact between the sub-systems. They can also be combined with electrical motors and generators to form some very interesting electrical machines.
Ricardo says in the excerpts above that they anticipate “very low projected production costs“. Magnetic gears are not cheap to build, because of the labour involved, so one would have to surmise from this statement that in relation to the system as a whole, the gear sub-system is not a major cost driver. Certainly there are some significant advantages to magnetic gears over and above mechanical gears, to make them worth considering.
Ricardo is working on the use of the Kinergy concept in a demonstrator FLYBUS vehicle based on an Optare Solo bus, as shown in Figure 2.
I’ll be posting more on magnetic gears in the near future, and I will be presenting a review of magnetic gears and related electrical machines at the Magnetics 2010 conference in Florida, next January. In the meantime, you can read the rest of the article on Kinergy here.