Magnets aren’t US anymore

The permanent magnetic is a quiet, unobtrusive work horse in so many applications that it, like many things that are mechatronics related, is mind bogglingly (is that a word?) pervasive.  Magnets are the key material technology to enable high efficiency and power dense electric motors.  And electric motors are everywhere.

The particular magentic material that has enabled the CD, DVD, Hard Disk Drive, high performance speakers, magnetic resonance imaging and many other technical wonders, is Neodymium Iron Boron.  Based on General Motors research on magnet materials (in the 1980’s), scientists found a particular molecule of these materials which exhibited extremely high magnetic strength.  And, of course, one of the immediate benefits would be reducing the size of starter motors in cars by 30% and the weight of the motors by even more.  Great stuff!

But making the molecule wasn’t exactly a picnic.  Alloying was easy, but it turned out you had to cool the material down suddenly in order to get just the right molecule to form in a powder and then sinter and magnetize the result.  A whole new process had to be developed, called spin casting, to cool the material quickly enough to generate high quality raw material for NeFeB magnets.   I’m sure there are a lot more technical details, but I don’t remember much from my tour of the GM Magnequench facility in Indiana.  It’s been several years.

NeFeB alloy has been dramatically improved and as demand has increased, fortunately, the price has dropped from the extremely high levels during it’s introduction.  As prices have declined it is estimated that 16,571 tons of Neodymium were used in magnet making in 2009 and 24,635 tons will be used by the year 2014.  That’s an increase of 48% in five years.  That’s huge.

The reason for all the increase is the fact that NeFeB magnets make really efficient motors.  So the new generation of appliance motors and air conditioning compressort that include NeFeB magnetics to increase the flux of the rotor combined with electric and hybrid car motors are driving demand more more magnets.  And now some emerging technology in the wind power marketplace, direct drive generators, will require many tons of additional material.

But what about our friends at GM Magnequench?  They’re gone!  The great future, full of potential for a US manufacturing company, lost to the sale of the company and closing the manufacturing facility.  GM sold the company to New Materials Technology in Toronto which is owned by China.  But the new owners couldn’t run the US factory at a profit.  Even at $20/hour for labor.  All the manufacturing jobs, gone.

There is currently no NeFeB magnet manufacturing in the US.  Which is kind of crazy when you think of all the applications we have for the stuff.  Even worse is the fact that a lot of advanced military hardware is dependent upon the magnets for guidance motors on missiles and a host of other applications.  And according to one source China now owns 97% of the world’s Rare Earth Elements sources.    Which is why there are now hundreds of companies in China selling magnets.

On the positive side, this has lead to overall declining prices for these magnets.  But will that continue to be the case?  The Chinese government is expecting to decrease their exports of magnets by 34% next year.  This could spell trouble for many companies.

But there is hope. The USGS has reported that the Mountain Pass Mine in Southern California is one of the largest and richest deposits of Rare Earths, including Neodymium, in the world.  And Molycorp is ramping up to fill the gap with new mining and manufacturing capacity.  Go get ‘em guys! Free enterprise at work.

Big Wind Machines

Recently I had occaision to discuss the merits of wind power with a colleague.  In particular there is a controversy between horizontal axis wind turbines, the giant propeller driven systems you see in advertisements, and vertical wind, which does not have much presence in the marketplace.  The premise is that horizontal systems can take advantage of the large swept area of the propeller blades to generate a great deal of force.  I’m not sure if this is supposed to imply that large swept areas intrinsically convert more kinetic energy from the wind into electricity.  And it is easy to conclude that this is the benefit of horizontal wind turbines.

Except that there is a fundamental mechatronic system at work.  The large propeller turns at low speeds, typically around 18 rpm on average, and there is a massive gearbox that is used to increase the speed of the output to turn a generator at high speed, which is typically where generators are most efficient.  The gear increaser has the effect of also increasing the amount of torque required at the input (propeller) by the gear ratio.  So if the gear increase is 100:1, then the propeller must be size 100 times larger in swept area in order to produce the needed torque to turn the generator.

This actually gets a bit worse since the mass, and it is very substantial, of the gear box itself represnts inertia that is resisting the turning of the blades.  And there is a generator rotor at the end of the gearbox whose mass (massive mass) is now resisting the turning of the propeller by the square of the ratio.  So if the ratio is 100:1, the inertia is increased by 10,000 times.  Even magnetic drag, or the residual attraction of the rotor to the stator, will get amplified in the same fashion, making it a significant force to contend with.

Add to this situaion a list of systems losses for overall fricitional loss of the bearings and gearbox, parasitic losses for steering and blade pitch adjustments.   Efficiency losses due to long distance transmission of power, that is a by-product of the remote sites that have favorable wind conditions.  It’s a pretty difficult situation to engineer.  And they keep proposing to build them bigger and bigger, hoping that the scale effect will overcome the problems.

All of the vertical wind systems I have seen so far are much smaller due to the fact that smaller rotors can turn at higher speed and power electric generators directly.  The flax axial generator is very popular in do-it-yourself designs that people are experimenting with in their back yards.

But vertical wind can also scale up.  And there are a few companies doing it.  With convertional wind power costing $2/watt, vertical systems could bring that price down very quickly and allow systems that can be installed close to the point of use or in offshore arrays where generation takes place almost 100% of the time.  Unlike the average 31% on the large land based systems.

Now that’s progress, 300% increase in energy generation at lower cost.  Hope it comes to market soon.

Batteries of the Future

Battery technology has been getting a lot of focus in the last couple of years.  After all, you can’t have a decent electric car (or hybrid for that matter) without having the right kind of battery.  And, just one more time, battery technology is what prevented the marketing of the electric car after the oil embargo of the seventies, at least as far as the necessary technology goes.

So it isn’t surprising that almost $2B in cash is being invested to start 4 new manufacturing plants in Michigan to make lithium ion batteries.  The State of Michigan is giving tax incentives totalling over $500 million.  The DOE has put grants and development contracts in the hundreds of millions of dollars in the hands of some of the same companies.  So it looks like we have picked the winner, and we are taking steps to make sure that there is capacity available to make the product.  Or at least assemble it.  Some of the battery supply is supposed to be coming in from Asia.  No surprise there.

There are two major issues in any battery.  The basic chemistry and materials that go into it, and the manufacturing processes that go into making it.  The basic chemistry sets the boundaries for what is possible.  The materials side is important in terms of raw materials cost.  You don’t want to build something that is dependent on strategic metals.  And making sure that the primary materials are readily available.  Recent reports indicate that the lithium needed for the emerging battery market is available in the US, but there is even more in South America.

On the manufacturing side, it’s all over the place.  Mechatronics everywhere.  From manufacture of the primary cell in either a cyclindrical cell or a prismatic shape to the assembly of the final package.  Temperature sensors, fans for air cooling, voltage or current sensors for monitoring charge and output, non-conductive housings, high power density connector terminals.  It’s pretty busy getting it packaged right.

I was involved in the manufacturing processes for the Optima sprial wound lead acid cell.  Great piece of technology.  Really difficult to get the mechatronics right.  Winding multiple 4 foot long layers of lead mesh, separater membranes and stuff that looks like toothpaste into a perfect roll the size of a can of soda isn’t a process that gets worked out overnight.  So there’s probably quite a bit of work to do to get the volume up where it needs to be.

Battery technology, regardless of chemistry, depends on the amount of surface area available.  Same issue for fuel cells, or even combustion of gasoline.  In a sense, when fuel is atomized, the surface area of the fuel is increased.  So it’s not surprising that most of the improvements forecast in battery technology are a result of research in nanoparticles and other unique physical arrangments of the constituent parts.

And unlike the decades that it took to manage lead acid battery recycling, there is already a major effort to manage recycling and disposal of lithium.  The DOE is currently providing funding to a private company to expand it’s disposal capability to include lithium technology.

Energy Density and the Real Cost of Driving

Energy density by itself is not a sufficient measure of anything.  It is only useful in a specific context.  For example, one can refer to the energy density of battery technology.  And that is an extremely useful comparison because the weight of the battery in an electric car is critical to its success.  The General Motors EV1 was abandoned because the battery technology was too heavy.

Context is very important.  Comparing the energy density of the battery to the energy density of a fuel is completely useless.  And this is an argument that some people use, incorrectly, to defend fuel based vehicles.  Gasoline may be 80 times more energy dense than a lead acid battery, but what does that really mean?  Of course, gasoline has far greater energy density than a lead acid battery.  That’s an absurd comparison if not taken in its full context.

What is the efficiency of the energy conversion process?  Internal combustion systems generate a lot of heat which is loss and highly inefficient.  Taken with its frictional losses and parasitic loads like the alternator, water pump, etc., input to output efficiency for internal combustion vehicle systems is estimated at 40% or less.  The same comparison for an electric car can result in measured efficiency of 90%.   So the comparison of system efficiency for internal combustion engine passenger cars and pure electric passenger cars is that the electric system is more than twice as efficient.  Lithium batteries are 4 times as energy dense as lead acid and will reduce the required payload of 1800 to 2200 pounds of batteries to a much more reasonably 450 to 600  pounds.

What is the absolute value of the technology?  That’s the really important question.

One basis for comparison would be cost per transportation mile.  In both cases, the system efficiency is directly affected by the cost of input energy.   When gasoline is $2.50 a gallon, a 20 mile per gallon car costs 12.5 cents a mile.  When gasoline is $4. a gallon, a 20 mpg car costs 20 cents a mile.  Pure electric cars are impacted by the cost per kilowatt hour, but generally are documented as costing about 3 cents a mile.

A more complete comparison would incorporate the maintenance cost in addition to the energy cost per mile.  Again the electric vehicle has significant advantages.  There are no annual maintenance costs, although some value might be assigned to amortize the cost of the battery pack.

Further, one can include the purchase price of the vehicle.  A $20,000 gasoline powered car will cost about $15,000 to operate over 5 years at 12,000 miles per year.  An electric car will cost about $1800 to operate over the same period.  So if a comparable electric car cost $33,000 the total cost of ownership over 5 years would be the same.  Not surprising when you think about it.

It will be interesting to see what comes out of Detroit over the next two years.

Top Ten Challenges – Energy Storage

Thinking about the top challenges we face in mechatronics there is one that’s connected and not really obvious.  It’s energy storage.   Our tendency is think in terms of batteries because that’s the form of energy storage that we are most familiar with.  Cell phones, laptop computers and many other portable gadgets of the Internet Age are very dependent on energy storage systems for their size, weight and hours of service.  But of course, these are all battery applications.

So  our first reaction to energy storage as a mechatronic challenge  might be that it’s really just a chemistry problem and not mechatronic at all.  But energy storage comes in many forms and applications.  Energy storage is a requirement of almost every form of energy and control systems.  Hydraulic and Pneumatic systems require accumulators to store energy so that short term loads don’t use up enough power to make the system unable to respond to demands placed on them.  Energy rate over time is a governing principle in all these systems.

The initial linkage in my thinking was the electric car.  As someone who worked in the electric car field many years ago, it was that the battery that killed the electric car.  Carrying 2200 pounds of lead acid batteries to make a car go from here to there simply didn’t make sense.

There has been a lot of debate on that subject and a LOT of incomplete information offered which clouds our understanding of the social or political problem.  But the cost and energy density of the battery pack is making sufficient progress to insure that quite a few new vehicle options will be available in 2010 and 2011.

In normal batteries energy densities of 30 Watt hours per kilogram of weight are common.  Nickel metal hydride doubled the energy density to about 80Wh/kg.  But the real improvements are coming from the lithium chemistries at 130+Wh/kg.  There are more dense chemistries around, but they are typically very high temperature or otherwise very expensive, and so not practical for widespread use.

But the energy storage problem is not limited to chemistry.  The flywheel energy storage system has been a topic of engineering development for decades.  Energy density in these systems is in the range of 100 to 130 Kilowatt hours per kilogram, a thousand times more power.

So why aren’t we working on that for cars?  It’s been done several times and never quite works out.  Chrysler had a prototype K type car with a Garrett flywheel system.  Couldn’t make it small enough to be cost effective.  And there were issues of life expectancy and failure modes due to the fact that flywheel was operating on magnetic bearings in a vacuum housing.

The national power grid has exactly the same problem at orders of magnitude more power.  If there is to be any hope of an intelligent national power grid, storage systems of this kind are needed to act as a buffer between demand and supply..   Solar power is only available when it is daylight and there are no clouds.  Wind power only happens when the wind is blowing.  This means that supply is intermittent over time.  So if there are big fleets of electric cars charging overnight, there have to be storage systems that can manage the energy storage requirement.

So mechtronic challenge #4 – Energy storage. Large and small, high efficiency and long term.

Control, Motors and Efficiency

I was talking with some friends about control technology and made the observation that over the last decade the progress in the control field has been really amazing.  Particularly, the processor technology that is available for controlling electric motors is operating 1000 times faster than the control platforms of a decade ago.  We look at events in nanoseconds, not microseconds.

Increasing the control system’s frequency response is not signficant in itself.  But it does mean that software can be applied to problems that are more subtle in the operation of a particular system.  Observation of the phase relationship between the rotor and stator in an electric motor is now commonplace in 3 phase systems.  Algorithms for optimizing this relationship dynamically are also commonplace to adjust the power factor or reduce energy consumption in inertial loads like fans.

But this is not where the big energy gains will come from.  These improvements are smaller and more incremental.

Variable speed motors are systems that are made up of electric motors and power electronic systems.  Both are subject to losses in the form of heat.  In the motor bulk magnetizing of the stator, phase loss due to load, and copper losses due to the construction methods used are common.

Better metallurgy is needed to reduce losses associated with magnetizing the stator core.  The steel industry has attempted to address this issue, but the high cost of exotic alloy laminations prevents the advanced materials from becoming widely used.

Copper loss is improved in the segmented stator, but this manufacturing technique is most often found in more expensive servo motors, even though analysis suggests the cost is lower.  This may have to do with scale effect, since the servo motor world runs at much lower volumes than the AC motor world.

The other major dependency in the speed control is the power semiconductor.  The costs for power devices are falling and performance is improving.

So where are the big efficiency gains going to come from?

The control system strategy.  If the application is not well regulated you might be able to get a big increase in efficiency by measuring things more carefully.  In a cooling tower changing from a +/- 10 degree thermostat to a +/- 1 degree thermostat allowed me to implement a control system that reduced the energy consumption sufficiently to pay for the equipment in less than two years.

No new technology motor, nothing special about the variable frequency drive.  Just what was available at the time.  The big difference was the strategy.  Measuring what was important and organizing everything in the control system to achieve our objective.

Energy

Everyone has an opinion about Energy Policy.  Just ask.  They’ll tell you!  And I am glad for the fact that there is a lot of discussion taking place.  We need good dialog and good information.

We might be a little lacking on the information side.  Nuclear power for generating electricity is not a popular topic, but worse yet, no one seems to want to talk about pebble bed reactors.  Pebble bed reactors have been around for over 25 years and represent the most stable path for producing electricity without burning fuel.  Small spheres of an enriched radioactive material are encapsulated in a ceramic insulator so that the nuclear fuel cannot accidentally achieve critical mass.  The same property of the geometry causes the “pebbles” to achieve high enough temperature to heat steam and generate electricity, but reaches thermal equilibrium at 800 degrees remaining stable without coolant.  So there can’t be a meltdown.

This makes atomic energy safe enough to locate in a major city without fear of a metldown or a chain reaction, the two weaknesses of conventional nuclear powerplants.  The fuel is encapsulated in carbide and graphite materials with processes that are very difficult to circumvent.  And because of the simplicity of the design, these reactors are lower cost than the water cooled reactors.  Could we save the environment and satisfy our energy needs at the same time?  Maybe so.

But this conversation is not part of the energy plan for the US.  Neither is drilling off the US coastlines and putting American workers back in the business of supplying our oil and gas needs in the US.  That makes no sense. The oil industry chose to import gasoline directly from the middle east 30 years ago because it was cheaper.  But we have done nothing to update our supply chain since then, and now we have to buy oil from countries that don’t like the US.

The logic seems to be about reducing our energy consumption instead of increasing our energy production.  Using less is fine until it cuts into our ability to produce necessary goods like electronics.  We don’t need to hobble the largest sector of the economy by telling semiconductor companies that we have to turn off electricity to their plants during the summer months.  They will have no choice but to locate to other countries.

You can’t “save” your way out of a recession.  You can’t save enough money to keep a company in business if it stops selling it’s products.  That’s all there is to it. And our policy leaders need to understand and apply that logic to the current situation.  The best thing to “stimulate” the US economy is to get it’s businesses producing.  Produce more energy with the resources that we have.

And when the car companies can make a competitive electric or hybrid vehicle, we will produce less gasoline and make more electricity.   There are plenty of opportunities to sell new cars to stimulate that industry too!

Electric Vehicles and Electric Motors

A friend of mine finally got delivery of a Tesla Roadster.  This prompted discussion of the drive train and the fact that Tesla has had to go from two speed transmissions which were failing to a transmissionless drive train.  The ultimate mechatronic challenge, the electric car, is also a challenger in terms of the precise  application of electric motor technology.

But it has to be said that the motor and drive solution for the electric car is not where the problem has to be solved.  Any motor can be made to run an electric car.  What is critical is how you apply it.  The starting conditions require high torque at low speed and the running conditions require low torque at high speed.  So, typically, what looks like a small 5 to 15 horsepower running requirement at full speed, becomes a 150 horsepower starting requirement depending on how quickly you would like to start.  If you want to keep up with a Corvette, it uses 450 HP to start.

And this produces a lot of confusion.  Why not use at 2 speed transmission to help the situation.  Fine, but the ones that are available can’t handle the dynamic response of the electric motor.

Can electronics help this situation?  Interestingly, yes.  There is a control algorithm generally called vector control which allows you to manage the rotor torque and stator torque separately.  By varying the phase angle between the two, like advancing and retarding the timing of a mechanical distributor cap on an internal combustion engine, you get different speed torque curves out of the motor.  COOL!  Is there any downside to this?

Yes.  You need more current to produce more torque.  That doesn’t change.  So you have to be able to supply the current, and you have to be able to manage the heat.  The heat is transitory since you only need the high current during starting, but it is best to have sophisticated software running to keep track of the RMS temperature of the motor.  Lower operating temperatures mean longer life and reduced risk of demagnetizing the motor.

So, yes, you can run an electric car with a garden variety AC motor, and with good electronics, you can make it run fairly efficiently.  With higher efficiency motors, the benefit is increased driving range from a given power source.  High efficiency motors are frequently smaller and lighter weigh, but a weight savings in the motor of 50 or even 100 pounds is not that big a factor in the driving range when the curb weight of the vehicle is 3000 pounds.

Basically, its F=ma.  If you can reduce the mass of the vehicle, you reduce the battery payload required to power the car.  Aluminum space frames, like on the Prowler, have been studied by the car industry and can reduce curb weight by 400 pounds and reduce cost by 10% at the same time.  We need to bring all the mechatronic leverage to the situation that we can, if we are going to make electric cars that make sense.  Before its too late for Detroit.

Energy Equivalence or Not

Among the many issues facing us today is the cost of personal transportation.  To a large extent, modern American manufacturing was built largely on making cars and all the steel, carpet, glass and all the other products that are required in a car.  Interestingly, the electronics sector of our economy, far bigger than automotive, has increased it’s contribution to the modern automobile, but that’s another topic.

There is a lot of material being published about our use of cars and our dependence on foreign oil.  Oil and Gas companies made the decision some years ago that it was cheaper to send tankers of gasoline refined on foreign soil than to ship the crude oil and refine it here.  That was the beginning of the current problem.  Now after many years of disuse, our refining capacity has been mothballed.  What you don’t hear much about is the fact that a lot of that capacity can be brought back within a  year by recomissioning old plants.  Yes, new plants are needed.  Yes, in the short term we need to drill for oil.

But the really strange discussion is around the energy equivalency of various conservation techniques, and the number of barrels of foreign oil that it will save.  Most of the time, these equivalencies are purely theoretical.  The only thing that will save barrels of foreign oil is more fuel efficient cars and driving less.  And by the way, American consumers have been demanding higher efficiency cars since the first Oil Embargo in 1974 when I bought my first Moped and my wife and I went to school and back on a gallon of gasoline a week. Anything else is a political statement, and one that should really be ignored.

It is dis-information to say that using compact flourescent light bulbs is the equivalent of so many barrels of crude oil.  Yes, there is an energy equivalence, but there is no direct connection between the two because light bulbs consume generated electricity.  So there might be a valid statement about how many pounds of carbon dioxide the compact flourescent saves in our national energy picture based on emissions from coal fired power plants.  But even that’s difficult to measure, what percentage of our national energy supply is nuclear?  Doesn’t that mix require that we calculate the CFL bulb CO2 savings as a percentage of the fuel mix that goes into the national power supply?

Similarly it is a common to talk about the energy equivalence of a battery’s energy storage capacity compared to the energy density of gasoline.  This too, while appearing to be very scientific and logical, is very lopsided.   It ignores the fact that we are really talking about transportation.  The proper context would be that an electric car has an efficiency of 80% to 95% of input energy converted to output of the moving vehicle and an internal combustion engine is only 25-40% efficient in converting gasoline’s stored energy to mechanical motion of the car.  So comparing the energy density of gasoline with the energy density of batteries is out of context and misleading.   And yes, batteries are still not where we need them to be.  But the Lithium technology is a good first step, and it’s being aggressively engineered to improve density even further and bring costs down at the same time.

If the IRS allows 50.5 cents per mile, and the emerging electric cars cost .04 cents a mile to operate, that’s the real cost of technology comparison that counts.

Super Size my Motor?

There is an interesting problem with applying electric motors that is a constant source of difficulty, the nature of peak power versus continuous power.  The problem is that few systems operate at a statistical average power demand.  Frequently, this causes equipment designers to oversize the motor for the application.  At the same time, however, this can put the motor in a very low efficiency operating range.

So what’s the right solution?  Right sizing.  Yes, just like Goldilocks and the Three Bears, not too big, not too small, but just right.

There are some great DOE publications on motor sixing that can be very helpful on the AC motor side, so make sure to give those a look.  But the implications of how to deal with varying loads are complex, each requirement having its own unique conditions that need to be considered.  Is an underpowered application actually safer?  Sometimes, yes.  I recently noticed that a particular orbital sander had been designed so that if the unit became momentarily overloaded, it stalled.  Perfectly safe.  In fact, this design is to be preferred because it prevents accidentally damaging a work piece by burying the sander in the wood and removing too much material.  Who’d have thought of it?  Certainly not Tool Time Tim.  More Power!

In fact, most of us view more as better.  More power means more production.  Or does it.  In an increasingly energy conscious community, more power means more cost.  And that’s really what its all about.  The value of the motor is not just in the purchase price, but also in the operating cost.  Especially if the motor is expected to run for 8 years, 24/7.  (That’s what the life expectancy of large AC motors is)

There’s another trick to the power requirement problem.  How much time is spent at full load and how much time is spent at average power, or, what is the duty cycle?  If the system is starting and stopping frequently it puts different constraints on the motor.  If the system is typically starting only once an hour, then we can consider the thermal duty cycle of the motor.  The momentary peak power requirement is insignificant and the vendor can usually tell from their modeling and testing of their products how much impact the peak current will have on the motor’s average temperature.

After all, its Thermodynamics 101 in the final analysis.  Every energy transformation produces heat as a byproduct.  How much heat a given system can tolerate is the key to its operating life.  In electric motors, the key values are the insulation system’s temperature rating, usually in the range of 150 to 180 C and in the case of steppers, brushless dc and permanent magnet dc motors, the magnet’s ability to resist high temperature and high coercive magnetic fields that can be generated in the motor.  Both sets of limits are generally well considered by suppliers when electrically controller motors are shipped as motor/drive combinations.  This can get a little tricky when pairing motors from one vendor with controls from another vendor.

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