Technology is the term we use for things that don't quite work yet.
Category: 'Electric Vehicles'
Monday, August 23rd, 2010
Good design! Low unsprung weight while retaining direct drive benefits.
Bad hub wheel motor design.
I’m not going in to the details on particular attempts at hub motors, but even if executed perfectly they are bad.
Unsprung weight means terrible handling and reduced road-holding capabilities!
Done, end of story, move on.
Good news: There is an alternative.
In-board electric motors: You place the motors in the center of the vehicle and use standard short drive shafts to bring the power to each wheel. The downside? Space… you need to fit two motors (remember you no longer have a differential) as close the center of the vehicle as possible and either have the entire motor pivot or have short angled drive shafts from each one.
By placing the center of gravity of each motor almost completely off the wheel you mitigate the unsprung weight to almost nothing.
There are a couple other problems with wheel motors, you need a massive amount of current and a motor that is efficient over a wide range of RPM’s. Modern high powered IGBT’s and MOSFET’s are probably up to the task and when integrated in to intelligent power controllers, they can drive various forms of electric motors at high levels of efficiency and power.
The second problem ‘massive current’ is a bit harder. Battery chemistry is changing rapidly, but it is still difficult to find chemistries than can supply large current, long cycle life, reasonable price, weight, size, safety and the ability to be mass produced.
All said, drop the stock differential, the stock drive shaft, the motor, the transmission, exhaust, emissions equipment and all the other ICE components that become redundant and then you might have a chance of building something that has a reasonable power to weight ratio and efficiency level.
One last thing, as an alternative you could place the motor where the transmission is on a RWD vehicle, keeping the existing differential and drive shaft (a 100 year old design). This adds additional weight, but you no longer have the space restrictions and gain a bit of gearing which might lower your peak power needs.
This Detroit Electric design is ancient but a good compromise.
Monday, December 15th, 2008
Top Gear is by far the best television show about cars ever aired. They can be quite opinionated and occasionally wrong, but they do their best from their perspective. Today’s episode 12×07 unfortunately, in my opinion, they got it wrong. While they loved the performance and looks of the Tesla roadster they made it clear they believe fuel cell powered electric vehicles (FCEV) are superior to battery electric vehicles (BEV).
1. They implied the fuel for recharging battery electric vehicles is from “dirty” power generation and that the alternative is a small wind powered recharger that would take 600hours to charge it.
They neglected to mention that any hydrogen produced would be powered by the same “dirty” power generation that any electric vehicle would be recharged by. They also neglected to mention that in doing so would require more power and would be less efficient. Meaning more pollution with hydrogen than battery electric.
2. They also implied that owners would be charging their vehicles with a “normal 13 amp” outlet which would take 16 hours (or 600 with the silly windmill).
They neglected to mention the Tesla is designed to be recharged with a much higher output connection included with the vehicle that charges it in 3.5 hours. That’s a massive difference and likely a dealbreaker for many people if they didn’t know the truth. Also, battery technology is improving at an incredible rate at the moment. There are already batteries from several manufacturers that will be able to be recharged in under 15 minutes.
3. They also complained about the price and went on to explain how hydrogen fuel cell powered vehicles would NOT cost more than a “normal car” and “possibly less”.
Now with the US exchange rate as it is, the Tesla is overpriced, but the overall implication is that hydrogen fuel cell vehicles will be cheaper than battery electric vehicles. As far as I know there is no evidence that shows this will happen. Hydrogen fuel cells are still a pipe dream and battery electric vehicles while expensive now are at least available now and very likely could be cheaper than hydrogen fuel cells when they first arrive 5-10 years from now.
4. The most minor gripe was with the range. They mentioned they only got 55 miles on their track vs. the 200mile rated range.
That’s an unrealistic expectation. The Bugatti Veyron holds 26.4 US Gallons and at its rated 14MPG it will go 371 miles. But at top speed it will run out in 12 minutes or 50 miles. But is this fair to say it only goes 50 miles? Obviously, I chose an extreme example but I also believe driving around the Top Gear test track is also an extreme example.
So why do I like BEV more than FCEV? It’s the EFFICIENCY stupid!
Power generation -> Liquid Hydrogen -> Electric Motor = 17%*
Power generation -> Gas Hydrogen -> Electric Motor = 22%*
Power generation -> Battery -> Electric Motor = 66%*
Power generation -> Capacitor -> Electric Motor =79%**
*From a report FROM the European Fuel Cell Forum.
** Assuming 20% better for not losing anything in the batteries.
Even assuming those numbers are a little biased towards BEVs, no matter how you look at it BEVs are at least twice as efficient at a minimum. They both require a power source so you can’t argue about the source of power. But BEVs requires half the power! So that’s twice as good in my opinion.
I also don’t like to argue about distribution because both of them require infrastructure upgrades, but in my personal opinion it’s much easier to add high-powered (<15mins) charging stations at existing refilling stations and medium powered (several hours) outlets at homes. Remember you won’t often need a full charge at refilling station. Most of the time if you run low in electric vehicle you probably only need a quick under five-minute charge to get you where you need to go. Normal charging will happen at home. In the rare circumstance of long range driving, you’ll probably actually appreciate a 15 minute recharge every few hundred miles just to stretch your legs out.
The other thing which is great about a 5-15 minute recharge is the economic benefits to the stations. Remember most refilling stations don’t make substantial profits from selling fuel. They make their profits from selling ancillary items such as cigarettes and snacks. If you’re there 5-15 minutes you’re going to buy more on average.
The two points they legitimately make are that
1. Batteries are too expensive at the moment.
2. The batteries in the Tesla make it weigh too much.
I believe both of these problems will be solved with evolutionary (not revolutionary) improvements in battery chemistry. I can only hope someone from Top Gear actually reads this and might be swayed in the right direction…
Wired chimes in…
Tree Hugger weighs in…
P.S. Before anyone thinks I don’t get Top Gear, I do. It really is one of my favorite programs. They are hardly fair to ANYONE and for an Electric & American *gasp* car they really did give it a positive (for Top Gear) review. But, for some reason or another, I just wish they would have added in a few counter points and then when they oversold the Hydrogen thing…well…that was the final straw!
Tuesday, September 30th, 2008
Hydrogen Is Overhyped
There are at least three basic parts to powering a motor vehicle.
1. An energy source
2. An energy carrier
3. A motivation system
A natural resource that we can exploit in order to generate work. Without trying to get too cosmic, all energy sources in the universe that we are aware of are finite and will eventually run out. It is important that we choose our energy sources carefully in order to not pollute the environment (heat, carbon, radiation, etc…) and to not run out.
Examples: solar power, geothermal power, fossil fuels, wind, hydroelectric, nuclear fission, nuclear fusion, etc.
A method that allows stored energy to be moved from its energy source to its destination where work needs to be done.
Examples: electrochemical conversion (batteries and fuel cells), fossil fuels, flywheel, polonium, the electric grid, etc.
A device that turns energy into kinetic work.
Examples: electric motor, internal combustion engine, pneumatic pump, turbine engine, rocket engine, etc.
Fossil fuels and radioactive materials such as uranium are somewhat unique in that they are both an energy source and an energy carrier. The disadvantage of using these sorts of resources are obvious. They will run out sooner than later (10’s or 100’s of years vs. millions’s of years for other resources), they often cause pollution and they often cause political turmoil because of their geospatial location.
Hydrogen falls into the second category, it is an energy carrier. Many people who are used to dealing with fossil fuels often mistakenly believe Hydrogen is an energy source. Also unfortunately, since fuel cells operate most efficiently with pure hydrogen and because there are virtually no environmental byproducts when using Hydrogen it has been identified and championed as the future energy carrier. But, it’s a really terrible energy carrier. It requires an energy source to produce, energy for transportation to move it locally, and energy and expensive containers to store it.
Hydrogen is the LEAST dense element on the periodic table. There are no other elements with a lower density, why would we choose this as the ultimate way to store energy?
Regardless of which energy source we use, what we need is a technology that can store energy with very little loss, in a compact package, repeatedly, and with low or no environmental impact.
Energy Carrier Candidates
- Kinetic energy – flywheels, springs, etc.
- Burning liquid fuels – fossil fuels
- Burning gaseous fuels – fossil fuels, hydrogen
- Electro-chemical conversion:
- Batteries – NiCd, NiMh, LiFePO4, Limn2o4, Licoo2, Lipf6, etc…
- Fuel cells – hydrogen
- Radioactive decay – uranium, polonium, etc…
- Pure electricity – capacitors
Best Long Term Solution
If we are to pick a technology with the most promise and the most long-term benefits personally I think capacitors are the way to go. Little or no losses, extremely high power (how much energy you can use per unit of time), quick charging (<5mins with the right hookup), virtually unlimited cycles (long lasting), and density on par with 2x modern lithium ion (think 450+ mile range). EEStor claims to have ultra capacitors with the density equivalent to twice lithium-ion batteries. If this is true it is truly game changing.
Best Short Term Solution
If we want to pick a solution for the interim to improve over fossil fuels I’d have to choose batteries. Fuel cells are merely batteries that instead of recharging (storing chemical energy) they re-fuel the cells with additional liquid chemical fuel and the cell is merely a catalyst (hence fuel-cell). Unfortunately, they are not ready for commercial production and sales yet. So it has to be standard chemical batteries for the time being. In the past 5-10 years there have been huge technological improvements in lithium-based batteries. There are at least half a dozen commercially viable lithium-based battery chemistries available today that can charge quickly, last much longer, are much safer, and are cheaper than traditional lithium cobalt.
It is more than likely that there will be a mix of technologies used for various modes of transportation for the foreseeable future (hybrids, biodiesel, CNG, ethanol, pure EV’s, etc). Hydrogen is often touted as some sort of panacea energy solution when in fact it’s expensive to produce, difficult to store, and difficult to use. Existing oil companies and automobile manufacturers who have vested interests in the status quo like hydrogen because of these reasons. It favors the usage of fossil fuels for the time being and it also favors the same large companies who will build the large infrastructures needed to support the hydrogen economy.
Monday, September 22nd, 2008
Energy storage technologies are improving. There is no denying that. Whether it’s batteries, ultra-capacitors, or kinetic energy systems (flywheels) improvements are being made across the board. With that, every few weeks or so someone says “my energy storage will allow electric vehicles to be charged in under X minutes” (Typically 5-10). This is usually followed up with something about how the electrical grid will never be able to handle that and how you could never do that at home.
I also periodically run into someone who starts talking about swapping batteries out of the cars for freshly charged ones. This is obviously being pursued most famously by Shai Agassi’s Better Place. As intriguing as this may sound for some people it is totally unrealistic for the consumer marketplace. Besides all of the obvious possible ways to try and cheat the system for profit, the practical limitations are also overwhelming. Imagine how many batteries a refueling station would need as technology improves with multiple chemistries and vehicles of various sizes need different capacities and voltages. Packaging alone will not allow quick replacement for all vehicles. Thus this technology will ultimately be limited to fleet vehicles.
Does anyone really believe people are all going to want to drive the same vehicle or even the same line of vehicles or even vehicles that can only have batteries exchanged from the same company?
The reality is this, batteries will charge faster, the power for these batteries will come from the grid. Most homes will not be equipped to do fast charging. So where will it come from?
Let’s see, who has the existing real estate, the resources for the necessary equipment, and the economic incentive? Duh… Refilling stations.
We already know the majority of income from existing refilling stations comes from ancillary products (cigarettes, snacks, etc.). Stations will slowly allocate additional space for charging electric vehicles using existing parking areas and other under-utilized space. The local electricity providers will work with them on meeting requirements of both maximum draw and potentially energy returned to the system at peak needs. This could potentially also help offset costs of on-site storage of electric energy. Whether they use Kinetic, Capacitor or Batteries, refilling stations will have the ability to store this energy on site and dispense it to vehicles as needed. They could even have electric signs that say things like “Full charge* in 7 Minutes for $5!” (*and tiny print for 30kw maximum [insert additional legal disclaimers here]) that changes based on their current available energy.
Electric vehicles will not appear all at once out of thin air. Most arguments for electrical grid issues make the assumption that all vehicles will need to charge off the existing grid all at once and today. the reality is, it will take years for the vehicles to get on the roads, years of standards committees working out the system ( charging rates, voltages, connectors, etc.) and years for the filling stations to upgrade. No, they will probably not charge in under five minutes day one, no it won’t be free, and yes you will still be able to charge slower at home.
Electric vehicles are coming, fast charging stations are not going to be free and they will be available at refilling stations. It’s so obvious that no one seems to say it…
Update: A prime example, at least one intelligent commenter pointed out if you charge at home you actually SAVE time because you don’t have to spend time at the gas station.
Update 10/2: According to this study by the US Department of Energy If 84% of the cars, pickup trucks, and SUVs in the US were Plug-in Hybrids they could be supported using the EXISTING generating, transmission, and distribution capacity (if vehicles are charged during the least used hours at night). This would also result in a 27% reduction overall of the total greenhouse gasses in the US.