A year in green tech: It's not the hover car we were promised, but it's really close

Connexions.org

Ever since the invention of the wheel, humans have known that our ability to do work will always encounter resistance.  In most cases, we know this resistance as friction - the force that opposes movement between surfaces.  I bring up the wheel because in that case, we finally understood that we could take advantage of friction and put it to use.  Prior to the wheel, moving an object meant lifting or sliding, with sliding preferred for its ease.  In each case we have to expend significant effort to overcome either the weight of the object or the friction from the surface.

School of Champions

The wheel takes advantage of this resistance to motion.  When we turn a wheel, the rotation wants to force the surface of the wheel to move relative to the ground, the friction resists this motion, and responds with a force the propels the wheel forward.  The energy required for motion still takes some loses due to friction, but much less so than sliding along the surface does.

This brings us to a technology that has its roots in centuries of research, but which has only gained market penetration over the last decade: frictionless bearings.  Much of the equipment that runs our life uses rotational systems.  We use fans to move air for ventilation and cooling, we use wheels and axles to move people and freight over long distances, and we use compressors to drive air conditioning systems.  In order for a rotational system to work, something must hold the rotating shaft in place while allowing it to spin and perform its service.

If we simply hold it in place, the friction between the rotation shaft and the surface of what holds it (also known as the bushing) will create significant waste heat and eventually result in the wearing out of either one or both surfaces.  To significantly reduce this friction, we return to the concept of the wheel and introduce bearings to the system.  A series of smooth balls arranged in a collar around the shaft comprise the bearing system (many may know these as "ball bearings" or BBs...famous for their other application in toy guns for kids).  When the shaft rotates relative to the support surface, the bearings roll to provide the structure needed to hold the shaft in place, but with a minimum of friction between the shaft and support.  They provide the same function that the wheels do in a car, and with the same result...more motion with less wasted energy due to friction.

As well as they perform, bearings still cause the loss of anywhere from five to ten percent of the input energy.  Although they minimize friction, they do not eliminate it.  In order to minimize or eliminate the remaining losses, we need a technology that removes contact altogether, and with a minimum of energy input.  Thankfully, such a technology exist....

Hovercrafts.

Ok, so maybe not hovercrafts, per se, but the same idea...magnetic bearings.  A rotating system uses metal shafts and metal bushings, and the property that provides strength also creates the wear.  Metal also reacts in a magnetic field.  If we can create a magnetic field of sufficient strength and stability, we can support the rotating shaft, allow it to move freely, but not have surface contact.  The rotation without friction virtually eliminates the energy loss, and the only cost comes from the input energy to keep the magnetic field stable.

Magnetic bearings come in three varieties: active fields, passive fields, and hybrid (a combination of active and passive).  Active fields use an electric current to create and control the field.  This requires the use of electrical energy, thus eating into some of the savings, but usually somewhere in the range of twenty percent of the friction losses.  Passive fields use specifically chosen magnets to create the field without electrical input.  In the latter case, the material availability of the proper magnets drives up price, a condition not created in the former where more standard materials create the field when the system applies electricity.  The hybrid case combines both in a balance that reduces both energy and material cost.  The bearings must account for support in both the rotating direction and the direction parallel to the shaft (to prevent the shaft from shooting straight out through the bushing).

Magnetic bearings will not change the world and eliminate the need for energy.  They make an incremental change over the previous technology.  When added to other incremental changes, however, we can create a technology base that requires less and less energy.  With lower energy needs, we increase the likelihood that renewable energy will handle the loads, and create the platform on which we can build a zero-cost energy future.

Plus wouldn't it be cool if this led to the invention of a working hover car?