Top Ten Challenges – Energy Storage

Thinking about the top challenges we face in mechatronoics there is one that’s connected and not really obvious.  It’s energy storage.  The energy storge problem takes many forms based on the application.  Our tendency is think in terms of batteries because that’s most likely 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 their 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.  Carry 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.   Solar power only happens when it is daylight and there are no clouds.  Wind power only happens when the wind is blowing.  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.

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.

Top 10 Mechatronic Challenges

I recently wrote on the mechatronic challenge of wind power.  Converting wind into mechanical power that can be harnessed for man’s use has been going on since the 9th Century according to Persian historians.  Certainly wind powered grinding of grains has been around in Europe for several centuries and, lest we forget, wind power pumping of water in the United States.  So there is some irony to the cultural “buzz” about wind power at home and abroad, as if the technology were entirely new.  There’s a lot of history, we’re just updating the technology to produce energy in the age of electricity.

Water has been used for power generation as well.  Following a similar path, we learned during the early part of the industrial revolution how to locate manufacturing plants near waterways so we could convert water flow into mechanical power using the water wheel.  This is, in fact the root of all modern motion control.  All the belts and pulleys, cams, gear reduction systems follow from the work done in mechanical engineering from this period of time.  All of the electronic analogs of the mechanical behaviors found in mechanical systems are the functions which we refer to in mechatronics today.

Wind power and water power gave way in the 1800’s to steam power as the improved steam engine of Watt became the standard of energy efficiency, or should I say “cost effectiveness”.  Because the absolute value of technology is in its cost effectiveness.

Still, wind energy poses a huge technology challenge, as witnessed by the number of vairations that exist and new versions that are emerging.  And hopefully improvements will continue to come from the creativity and  imagination of engineers and inventors all over the world.

But what are the other big mechatronic challenges that come to mind?

Transportation certainly ranks in the top 10.  We have seen hydraulic, pneumatic and electric vehicle solutions touted for a variety of uses, personal transport, delivery vehicles etc.  Ballard Energy and General Motors have both been building hybrid and pure electric buses for city transportation systems for several years with some success.  Interestingly, the electric bus is easier to engineer, which seems unreasonable, but the bus has more interior space to put things like batteries and a methanol converter for generating hydrogen for fuel cells.

But there is a great lesson in what appears to be an almost chaotic string of choices in the transportation arena.  One solution will not work for all requirements.  There are many people for whom a 40 mile per day drive cycle is perfect.  The NEV, Neighborhhod Electric Vehicle, is a golf cart type solution that is rated for street usage, and because of its relatively simple performance requirements, is relatively easy to achieve and lowe cost.  As we categorize cars with greater range, the problems get more difficult, and because of the storage limitations of batteries, have only been achievable as hybrids.  But with some hybrid designs reaching 50 and 60 mpg (estimated), these vehicles may be great solutions for other users.  Although, we must consider their cost effectiveness.  If they cannot be introduced at prices well below $50,000 the absolute value of the technology is not very good.

So forget the 15 second soundbyte that will solve the world’s problems.  It doesn’t presently exist.

I would like to hear from any readers about their picks for the Top Ten Mechatronic Challenge.

Mechatronics on the Trail of Global Warming

By Donna Sandfox

Omron Electronic Components, LLC

A new highly portable mechatronic system to measure harmful pollutant relies significantly on a MEMS flow sensor

Figure 1. Stationary Aethalometers are used throughout the world, but have been too heavy to be truly portable until now.

Carbon dioxide is well known as a major contributor to global warming, and there are many ways to detect and measure it. But it is not the only culprit. Scientist have found that the second most significant contributor is soot, or black carbon. Not only does black carbon contribute to environmental degradation, but these tiny particles also cut short the lives of seniors and sicken children. A recent economic impact study in California’s San Joaquin Valley (The Benefits of Meeting Federal Clean Air Standards in the South Coast and San Joaquin Valley Air Basins, November 2008) has identified the cost of air pollution and estimated it at more than $1,600 per person per year.

Black carbon doesn’t stay in the atmosphere as long as carbon dioxide, so controlling it has the potential to achieve major benefits in the short -term. Some of the major emitters of black carbon are diesel engines plus wood- and coal- burning fires. However, to analytically determine the source of black carbon and recommend effective changes to correct the problem, scientists require instruments capable of measuring black carbon in the field.

Manufactured by Magee Scientific of Berkeley, CA, the Aethalometer, is an instrument that uses optical analysis to determine the mass concentration of black- carbon particles collected from an air stream passing through a filter. However, until recently, these instruments were too large and bulky to be easily moved to a suspected point of origination for black carbon; the smallest device (the AE42) weighed approximately 25 lbs and measured 11 x 12 x 8 in. The instruments collect data from installations located around the world (Figure 1), but these only give scientists local samplings.

To get a complete picture of the black-carbon problem, scientists required a very small portable Aethalometer to easily determine black- carbon readings in almost any location. A reduction in size required some clever engineering and component sourcing.

Figure 2. The AE51 Aethalometer’s designers took advantage of the flow sensor’s port placement by designing the manifold to interface to them directly without tubing.

Aethalometer operation

Aethalometers function by measuring the amount of particulate deposited on a fiber filter by a specific amount of air passing through the filter for a predetermined amount of time. This mechatronic system needed to incorporate mechanics, electronics, and computing in one compact package. One of the major size reduction obstacles to overcome was finding a small, lightweight, highly accurate flow sensor with low power consumption. Having worked with Omron in the past, the engineers from Magee Scientific again called on Omron for a solution to their requirements, and the company recommended its D6F-P MEMS mass flow sensor for gathering the required air samples.

Figure 3. D6F-P flow sensors are individually calibrated before shipping to deliver excellent repeatability results.

Size and power constraints

The body of the D6F-P measures just 10 mm high by 23.3 mm wide by 27.2 mm deep, and with a weight of just 8.4 grams, it fell within the size and weight restraints set forth by Magee. Designed for easy installation, the D6F-P has both the input and output ports on the same side which facilitates the connection of tubing.

Magee engineers made clever use of this feature, designing their new AE51 Aethalometer so that the sensor ports would mate directly to their manifold, without the need for tubing (Figure 2). Since this miniature Aethalometer was to be battery powered, current consumption was a concern. The D6F-P proved to be very efficient, drawing a maximum of only 15 mA while operating on 5 Vdc.

Accuracy and repeatability

The AE51 relies on calculating the exact amount of air, driven by a blower incorporated in the device for a given time. Therefore the flow sensor would have to be very accurate. The D6F-P’s flow range/ pressure range of +1.0SLM (+0.84 in H2O) with an accuracy of ±5% F.S. maximum and ±2% F.S.

typical would deliver the precise flow readings Magee required to obtain reliable measurements.

Additionally, since the sensors are individually pre-calibrated at the factory for high repeatability, Magee Scientific’s finished device adjustment and test time was kept to a minimum (Figure.3). Durability was also a concern since the AE51 would have to take multiple readings, but the sensor’s MEMS technology has been proven to deliver a long life with excellent repeatability.

Figure 4. A patented dust segregation system with dual centrifugal separators ensures that the sensing chip remains clean.

In the real world

Since the AE51 is designed to measure black- carbon particulate in areas of known high concentration rates, the sensor had to be reliable in these dirty, real- world environments. Measurements would need to be taken at busy traffic intersections, bus stops, industrial sites, and coal-burning power plants.

The AE51 would also be used in remote areas of the world where use of wood fires to cook and heat is common. Although the filter used to measure the density of the black carbon is in front of the sensor’s inlet, if any particles that got past were to effect sensor operation, measurement accuracy would be compromised.

Figure 5. The reduced size of the hand-held AE51 is obvious when compared to the rack mount AE22 Aethalometer behind it.

To prevent that occurrence, the D6F-P design uses a patented dust segregation system (DSS). The DSS in the flow path incorporates dual centrifugal chambers, in which particulate matter follows in the outer path away from the MEMS sensor chip regardless of the flow direction. Thus there is practically no degradation in sensor performance over the lifetime of the system.

Keeping the MEMS sensor chip clean lets Magee guarantee a long life for their Aethalometer without worry about black-carbon build- up harming the device’s performance (Figure 4).

The A51 Aethalometer (Figure 5) is so small that it can be strapped to a user’s belt, enabling the user to become the instrument’s legs and freeing the user to do other work while the meter is gathering information. It can also be tethered to weather balloons for upper atmosphere readings. Another potential application would allow the device to be carried by those whose health might be affected most by inhaling large amounts of black carbon. The AE51 would alert them to areas that have high concentrations of this toxic material.

Omron Electronic Components, LLC

www.components.omron.com

Wind Energy and Mechatronics

By Steve Meyer,
CEO/Senior Consultant
Solid Tech Inc.

What would you put on a “Top Ten” list of the toughest mechatronic applications of all time? The electric car, plug-in or hybrid is certainly on the list.

One application that needs to be on the list is the Wind Turbine. It is a mechatronic challenge because it combines the aerodynamics of rotor design, the mechanics of a gear reduction system, the electromagnetics of an electric generator and the power electronics system for output power conditioning and synchronization to the utility grid system, all of which is designed in the range of 1000 to 4000 hp.

Each portion of the system must be designed in conjunction with the other systems to achieve the overall goals of efficient net power conversion.  Plus, wind turbine hardware has constraints that are different from other forms of equipment.  In addition to efficiency, another top priority of wind power turbines is life expectancy. The manufacturing constraints those priorities create are a nightmare.

Since most wind turbines sit on top of 150 ft tall masts, the systems are also weight constrained.  Other constraints include a second axis of motion that pivots the nacelle that houses the gear reducer and generator.  It can weigh more than 5 school buses. Then, the whole assembly must steer into the wind.  Sounds like fun.

The efficiency of the rotor at a variety of wind speeds is totally an aerodynamic issue. While this not my area of expertise, even with my limited background, it is clearly a problem since wind speeds vary constantly.  The consequence of this dynamic is that the rotor speed cannot be predicted.  Therefore, the electrical system must take a varying input and convert it to dc and then back to
synchronous ac, or control the speed of the rotor and waste some of the input energy.

The gear system requires large-scale, precise machining.  Not so much because there is some accuracy required in the load, but for efficiency and minimal wear.  Only a few companies in the world are able to produce these systems, and the current orders are backlogged to 2011.

Manufacturers have found that wind turbines are more cost effective the bigger they are.  This makes sense on the motor side because power increases with the square of the radius.  But it sure makes everything more difficult.  The mast and cantilever load of the turbine and propellers is huge.

But all that engineering has to be done inside a cost envelope.  According to the Danish Wind Energy group, a typical 600 kW system costs around $450,000.  Installation costs will be $135,000, making the initial cost $585,000.  If the unit produces 1,500,000 kWh hour a year at 0.05/kWh it generates $75,000 that year minus an average maintenance cost of $6,750.  At a cash flow rate of $68,250 a year, it will take 8.4 years to break even, not including discounted cash calculations.

You can play with the numbers on line at the Danish Wind Energy website.  The US utilities are regulated in how much they can get for power.  At 0.10/kWh the payback is 4.2 years.  But what if the wind estimates are too high?  That’s a lot of money.

The public policy question is how much government funding is going in to this arena?  Is the Federal or State government offering subsidies to facilitate the adoption of the technology?  If so, shouldn’t we be getting a discount on our electric bill if taxpayer money is used?

Footnote: The Global Wind Energy Council in Brussels reports that installed capacity for wind power worldwide was up 28.8% last year with the US increasing its base by over 50% and edging out Germany as the leading user of wind power in the world.  Interestingly, China, often accused of being one of the most environmentally irresponsible countries, is the No. 4 user of wind power in terms of installed base with similar growth over last year.  Maybe some things are headed in the right direction.

The Absolute Value of Technology – Part 2

So continuing on a theme, there are many ways to describe value.   In order to measure the value of technology, we must measure it’s cost performance.  There are many elements of the value proposition that need to be considered, such as cost to acquire the technology, installation costs, maintenance cost and life expectancy.  And the benchmark for cost performance is the market price for the old technology.

So taking electricity, for example, any comparison of new technology to deliver electric power must be compared with the present cost to deliver power.  If coal fired powerplants can deliver power, with all of the costs already accounted for, at 10.6 cents per kWh, then any new method must achieve that cost performance or customers must be prepared to pay more for electricity.  If CO2 reduction or eliminating coal combustion pollution are sufficiently high priorities in the consumer’s mind, then electricity will simply have to cost more.   Read more

The Absolute Value of Technology

I read constantly on a variety of subjects.  I am interested in electric cars, wind energy, industrial productivity, electric motors, lots of stuff that would seem to be disconnected.  As someone who is involved in the development of technology, it is important to me to look to the future.  For my consulting clients I must often identify the barriers to entry of markets.  What are the hurdles and how do we overcome them?

In case you haven’t read any of my posts, I am a bit skeptical when government gets involved in developing technology.  I don’t think we the taxpayer have ever gotten a good deal in that regard.  I am particularly concerned by the billions of dollars per year spent by the Department of Energy considering the very few benefits gained for the extraordinary sums that are spent. Read more

Energy Stimulus Debate

As “We the People” wait for Congress to do something to stimulate the economy we are flooded with information about “Green Initiatives” as part of the stimulus strategy.  And its really easy to get dragged along with the tide of enthusiasm.  After all, the electric car has languished in the shadows for over 70 years since the Baker company closed its doors.  So the idea of re-inventing even a small part of the automotive industry in the US is very appealing during a difficult period in our history.

We all share the concern that unemployment is up and many areas of the economy are slow.  But let’s be sure that when the government says its going to spend our money, that the decisions are based on sound strategy.  Maybe government spending money that it doesn’t currently have isn’t such a great idea. Read more

SKF Solutions for Increased Productivity and Sustainability Benefits

SKF has a wide range of technology that can be applied in the Agriculture Industry to increase productivity, lower operational costs and deliver sustainability benefits.

Solutions are typically aimed at extending machine component service life and reducing maintenance, both of which contribute to less stoppages, more reliability, and more machine availability. All of this results in longer operational hours for tractors, combines and attachments in the agriculture industries. Emphasis is also put on designing solutions with minimal lubrication needs. Read more

Solar Power, Mechatronics and Economics

At the recent Semicon show the big buzz was about the emerging Solar Energy industry. Lots of “new” products, lots of buzz. The big semiconductor machinery manufacturers who view crystalline solar cells as a stimulus to the demand for machinery and silicon have put in a lot of effort. The main goal? Get the cost of the solar cells down to where electricity produced with silicon is comparable to the cost of electricity generated by fossil fuel.

And, in fact, the industry is getting there. The current estimates are that solar power is costing about the same as peak demand consumer power, $.23/kWh. And with the current wave of investment and scale up, something which the semiconductor industry has always done well, there is serious forecasting that the cost of solar electricity will continue to fall. Read more

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