The Promise of Ultracapacitors - Part 1
By Josh Landess
Editor's note: There have been a number of promising developments recently in the use of ultracapacitors to improve the performance of hybrid electric and battery electric vehicles. Considered by many the leading US manufacturer of ultracapacitors, Maxwell Technologies, located in San Diego, California agreed to let EV World's corresponding editor, Josh Landess visit their operation and talk to them about their technology. Here is part one of Josh's in-depth interview.
I spoke recently with Richard Smith of Maxwell Technologies about the ultracapacitors that his company makes. Maxwell has almost a half-dozen competitors, but only one (Panasonic) makes ultracaps large enough for vehicle use and some people think Maxwell makes the best ones. GM, for one, seems to be very serious about using Maxwell's product in their busses (about a 50% mileage improvement from a non-regenerative-braking bus!), heavy trucks and in a few years even in some consumer trucks and SUVs.
Ultracapacitors store and release electrical energy quickly, efficiently and reliably. They perform well in harsh weather conditions. Their cycle-lifetimes are orders of magnitudes greater than those of batteries, so they do not need to be replaced as often and thus they are able to drive down the total cost of ownership of a vehicle. They are particularly suited to delivering a lot of power very quickly, and it has already been demonstrated that their costs can be brought down nicely once mass-manufacturing kicks in. The idea of an ultracap is not to replace batteries: they cannot store nearly enough energy to be the sole source of electric energy in an electric or hybrid vehicle. Rather, ultracaps seem to be the ideal complement to batteries and other energy sources, doing the job of very temporary storage and high-power discharge.
JL: It's Monday April 30 and my name is Josh Landess. I'm speaking with Richard Smith the Senior Vice President, Strategic Business Development with Maxwell Technologies.
Ok, let's just jump right in.
I've noticed at your web site you make some tech papers available for download, I didn't get registered for that yet. It's just as well... could you synopsize for our readers what is it about the ultracapacitors that makes them particularly suited for fuel cell vehicles, I think there was a whole paper on that.
RS: Ok, First of all Fuel Cells are basically a energy-generating system, and all fuel cells create electricity by some method the most common being Hydrogen and Oxygen in a PEM type cell. When the fuel cell is actually operating, it creates electricity, but it is not very dynamic, ..by that I mean if you need a high inrush of current to accelerate a car, for example, then you might have to build a fuel cell that is quite large just to handle that acceleration load. What you'd rather do is balance the capacitors, which store electrical energy and can dump it very quickly as power, with the fuel cells so that you can accelerate the car for 10 or 15 seconds while the fuel cell is ramping up its power.
JL: I've heard that there is a 10 or 15 second delay, that number came up in a conversation I had with somebody. They're better at this than, say, flywheels or batteries [where] they have advantages?
RS: The capacitors?
RS: Yes, well the capacitor is better than batteries or flywheels in that it's... better than flywheels in that you're in electrons and you stay in electrons. It's better than batteries in that it's a power component. In other words it will give you very high current very quickly without much loss. Batteries will generally be able to do very high current, but only for a few times, so the batteries die pretty quickly if you draw real high power from them. Batteries are good for long-drain like flashlights.
JL: Are you working on putting these into forklifts? I noted [in listening to the corporate reports] there was some conversation about industrial applications as well as automotive....[note: I asked this question partly because there are dozens of thousands of heavily-used EV's throughout the warehouses of America and the world, if we count forklifts.]
RS: In the industrial world there are a number of applications, and actuation is one of the primary markets that we go after. Actuation can be forklifts, they can be like airport lifts. They can also be tailgate lifts on trucks that use electro-lifts instead of hydraulic. Again, there are a couple of reasons for that. One is you can generate high power for a very short period of time, 10 or 20 seconds, which is generally the time that a lift has to operate. And then during the idle time, while it's up or down, you can charge that with an alternator, or trickle-charge it from the battery so that the capacitor is ready to work again whenever it's needed.
In the whole industrial sector though we also look at actuation right down to the very small devices. We're being designed in and used in control valves, for example, and a lot of these control valves used to use springs to determine the safe position. So, if the power is lost, then the valve goes to "safe" which may be open or shut depending on the condition of a pipe or a gas-pipe, or a vent in a air-line. So, capacitors are used as that power function because you can store the electrical energy and then when power is disrupted the capacitor then uses its electrical energy to turn the valves to a safe position. The valves are smaller, quieter, which turns out to be an attribute that's important in some applications, and also faster to respond, because they don't have to drive a spring in a gear-train, so you can load the motor at direct speed.
JL: So, it sounds like also in cars beyond the large ultracapacitors for regen braking, [there could be] a lot of different uses for little tiny ultracapacitors.
RS: If we look at the cars and the direction cars are heading, they're turning into moving electrical plants. They have silicon everywhere. Your car doors, your trunks, underneath the hood, a lot of your systems are controlled by actuators and electrical power, and the reason for 42 volt systems on cars of the future is simply because the amount of power that you need is growing way beyond the 2000 watts that the maximum alternators can produce today. You need sometimes 6 to 18 thousand watts to drive everything that's electrical on a car: heated seats, defrosters, power windows, headlights, 1000 watt stereos, so in that case you need a higher voltage system on the car. But when you do that you also need distributed power within the car. And so the ultracapacitor can be used to actuate door mechanisms, for example, and you would think why would you want to do that.
Turns out in the modern car you have a up-and-down power window, you have side-crash bars in the door, you have airbags in the door, very soon you have very little room for mechanical mechanisms like door handles, so you need them to be driven electrically. You need a lot of power to drive the solenoids in the door to open the door essentially, and so you could do that with Powercache series of small capacitors in the door.
JL: Let me get to the nitty gritty a little bit about electric vehicles. The press releases last fall regarding the Solectria project were pretty impressive. I think there was a 32% improvement in range figure. I'm not precisely sure how that was defined. Can that be taken as a measure of how much an ultracapacitor, properly outfitted into an electric vehicle, can improve its regenerative braking?
RS: Actually, you're on the right point. It's really a matter of efficiency. The same amount of energy is required to drive over a certain profile, highway profile, braking, accelerating, going up and down hills. The difference between 100% and 132% of range comes from being more efficient in using that electrical energy. When you regenerative brake on a car, the batteries can't absorb all that energy, so a lot of it is still given off as heat, whereas the capacitor can absorb that energy much more efficiently. So instead of absorbing 60% of that energy with the capacitors we can absorb maybe 95 to 98%. So that's better... so we've recaptured more energy with the same braking.
JL: Can you actually recycle something in the neighborhood of 80 or 90 percent?
RS: The design point of our capacitor for automotive use is to accelerate for 10 seconds and then regen for 10 seconds at several hundred watts, and there's a number of different specifications automotive companies use, and do that round-trip at 90%. In other words, you accelerate at 95% efficiency, electrical power being dumped into the motor, 5% given off as heat, as a I2R loss - a resistance loss, and in regenerative braking the same thing, you're drawing current in and recharging the capacitors. Most batteries under that same scenario drop to anywhere between 50 and 60 percent efficient. In other words they give off huge amounts of heat, and very little electrical energy.
JL: There were some guidelines at the Department of Energy site for proposed rebates for rebates for regen brakes, and they were at 20, 40 and 60 percent thresholds, and it sounds like you're just kind of blasting through that with this approach.
RS: Right, most of the people if you listen to the conferences on 42 volt systems with regenerative braking, almost all the battery people say that regenerative braking is an oversold concept. What they mean is that for their batteries, they're not very efficient. But if they were efficient, like the capacitors are, then it's not an oversold concept. It actually is a very practical concept. A lot of energy can be recaptured for re-acceleration.
JL: Well, my personal feeling is every time I hit the brakes I'm throwing away as much energy as quickly as possible with getting nothing back in a regular car, in the midst of an energy crisis. It seems like bad design, and what I like about the ultracapacitor is that, regardless of whether we're talking about electric or hybrid-electric, it doesn't matter, because you're recycling the energy of braking as much as possible.
RS: Right. If you look at that from your perspective that you described, in that in order to stop a car it takes the same amount of horsepower to go from sixty to zero as it does from zero to sixty, exactly the same amount of horsepower.
JL: Right, by physics.
RS: But what you're doing is creating heat with that by friction against the brake shoes. If you could capture most of that energy then you have a reservoir to re-use. So it's a recycling effect of this energy that was spent accelerating to some speed, and it doesn't matter whether your engine is gasoline, diesel or a fuel cell, you still need to brake on a car....
RS: ...So you always have that challenge of capturing that braking energy. And the most efficient method of capturing it right now is ultracapacitors. Batteries and other devices are ok, but they're not as efficient.
JL In the fairly well-publicized debates with the California Air Resources Board, a really big factor has been cost... the cost of the proposed electric cars, the cost of proposed hybrid cars, and anything that could bring the cost down has to be regarded as super-important, especially if you're slightly replacing some of an advanced battery pack that's extremely expensive, and I note a lot of your literature emphasizes that it saves on battery life. [Do you] extend battery life?
RS: Yes, if you're in a cycling application, most batteries have a limited life, depends on the depth of discharge, and a lot of the advanced technology batteries, they're very expensive and they don't last very long in heavy cycling. So, what you'd like to do is to say, "What is the economic solution?", the heart of the question, what is the economic solution. It's strongly our belief that the economic solution is to take the simplest battery that is very acceptable today, [..] the standard lead-acid battery, which is very low on cost, and use it for the energy drain portion of either a hybrid or an electric vehicle, but to pair it up like the Solectria experiment with capacitors. And then the capacitors do all the power function.
It turns out in another research project that was done in University of Hawaii under DARPA funding, we basically took a starting battery, a standard lead-acid battery, put it with capacitors and then cycled it many, many times and we found that we not only got the extended range, a fact that Solectria also demonstrated, but we got about two and a half times battery life. In other words, the batteries lasted.... If they would have lasted 2000 cycles they lasted 5000 cycles....
RS: ...So it's a significant impact on the cost. And also you're replacing a very low cost battery instead of a very high cost battery. And you get all the benefit of some of the exotic chemistry batteries. And actually you get more benefit because we'll work at a broader temperature range and we'll be more efficient at very low temperatures than the batteries will.
JL: Are you packaging your product with batteries at all or that's just not feasible?
RS: Our strategy is pretty straightforward. We believe that in order to be successful we have to have somewhat of a battery model, and that is that we need to make cells as cheaply and in as high a volume as we can. So, first and foremost we have to make the best cell out there, and then we have to make it as low a cost as we possibly can, and then we have to make it by the millions. So our focus has been on the operations and materials science side, to get the cost per cell to the lowest possible number of anybody out there, at the same time keeping our performance higher than anybody out there. We've managed to do both of those things so far, and we have plans to continue to do those things.
The second part of our strategy is to team with people such as Solectria, and General Motors Allison Division... which they will actually integrate our product into drives which then can be purchased as systems or subsystems, that can actually drive trucks and busses in the case of Allison, and in the case of Solectria it could drive cars, small trucks and busses on the 40 passenger type busses. So Solectria has whole family of drives that they're putting together with our ultracapacitors. We're in a long-term strategic relationship with Solectria. And they're going to be building hybrid drives, using ultracapacitors for small busses and trucks, as well as passenger cars.
JL Wow, ...that's really exciting.
RS: And that's going to be...that's part of our strategy. We can supply them with the cells, they'll do the integration up to the drive level, and then the car manufacturers can integrate them into the car part of the business.
JL It's been emphasized to me before, getting a really good electric vehicle or hybrid electric vehicle together is not about just one part, but the motors and controllers, as mundane as they may sound, and the Solectria press releases talked about Solectria's proprietary technology being also very important...
There was a comment at your annual meeting a few days ago that I thought was really interesting. I think it was [Maxwell CEO] Carl Eibl speaking. And he discussed your competition in ultracapacitors, and I didn't realize there was any until he mentioned this... somebody asked him, I think it was said there are about five competitors, quote-unquote one "serious" one, Panasonic...
JL: ...and that, I'm not sure if I understood correctly, but nobody at this point is really doing the large ones that you are.
RS: The closest competitor in the large cell is Panasonic. They have a product they announce as 2000 Farad Product. It's been tested by ourselves and many other people. Using the same criteria that we use, we would rate it at 1600 Farads, not 2000. And our capacitor we rate at 2700 Farads, and using that same criteria, if we measure 2700, they would measure 16.[?] So, although they have a spec that claims to have close to our capacitance, it's still substantially smaller. If that's of total importance, then we still make the largest capacitor by far.
What's even more important I think is for that same capacitor we actually make it at or below the same price-point per cell that they do. And then we also know that if it's cycled at a high number of times, if it's cycled thousands and thousands of times, which most automobile manufacturers say that we have to be able to do hundreds of thousands of cycles...
JL: ....Yeah, we're talking about hundreds of thousands of cycles...
RS: ....Yes, and then the bus applications and truck applications could be millions of cycles, ...their part deteriorates very rapidly under those conditions. So the fact of the matter is that so far we've not had any serious technical, price or availability competition. I think equally important in the component world for electric vehicles, hybrid vehicles and all of these to take place is mass production has to happen, and we've been able to build a factory where in the case of General Motors they asked for 10,000 parts last December. We shipped 10,000 parts in December.
RS: No one else could even come close to delivery of that kind in that short period of time.
JL: 10,000 of those big ones?
RS: Big, big cells, right. Our capacity today is around 8,000 cells per month, but obviously we can ramp up if needed. The total volume required in large cells is still very moderate. In our small cells, we have the capacity to do 50,000 cells, or 1.7 million cells a month, so in our smaller cells there's more demand right now.
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