Posted by Max Dunn
Thu, 03 Dec 2009 16:26:54 GMT | no comments
The Nissan Leaf electric car is making a 22 city tour and stopped at Stanford yesterday for a lecture and viewing of the car (although we didn’t get to drive it). The car looked – well, like a car – and the most of the information was standard electric car stuff. For instance, a 24kWh Li-ion battery pack with a 80 kW (106 HP) motor will propel it up to 100 miles with a top speed of about 90 MPH. They covered the usual stuff about 95% of all trips in the US being less than 100 miles and 80% of the charging will be at work and home. The also estimated that it will save about $1,400 a year in gas costs, which just about covers the cost of the battery over the 10-year life.
They are working hard to be the first affordable EV. They expect to start taking orders in Spring of 2010 and start delivering cars later that year.
For me, the most valuable information from this lecture is that they are collecting zip codes of people interested in the Leaf on the web site and sharing these statistics with the electric utilities and some utilities are starting to upgrade the transformers in the areas that will likely have a lot of EVs. They also mentioned that some places can be very difficult to get permits to install the charging stations in personal garages. They said that the Mini-EV program gave up trying to setup the electric car program in New Jersey because of these problems. The reason this was interesting to me is that it points to a possible business opportunity!
For more information, see my detailed notes.
Posted in Electric Vehicles
Posted by Max Dunn
Mon, 03 Aug 2009 16:57:33 GMT | no comments
What would you think is the safer car to drive – the Toyota Camry at 3300 pounds or the Ford Explorer at 4800 pounds. Would you believe the lighter Camry?
Safety statistics show this to be true. For every million Camrys on the road, 41 Camry drivers perish in crashes and an additional 29 people die in accidents involving Camrys. However, for every million Ford Explorers on the road, 88 Explorer drivers die and it kills 60 other people. So driving an Explorer is twice as dangerous as driving a Camry!
Why is this? The bigger Explorer can’t avoid accidents as easily as the nimbler Camry and is more prone to rollovers.
So next time someone says they feel safer in a big car, point out that the smaller car is actually safer.
References:
Posted in Electric Vehicles
Posted by Max Dunn
Sat, 25 Jul 2009 15:08:16 GMT | no comments
A friend of mine recently got a 400cc Suzuki Burgman scooter and loves it. He gets 53 MPG which is pretty good, but realized that it was about the same as a Prius that gets 48 MPG. “Why is this?”, he asked. The Prius weighs about 3000 lbs while the scooter is only 400 lbs.
Let’s look into this.
Regenerative Breaking
Even though the scooter is a lot lighter, the Prius captures about 50% of the energy when breaking and uses it to accelerate. So this brings the effective weight of the Prius down to 1500 lbs.
Wind Resistance
Even though the scooter has a frontal area 4 times smaller than a Prius, a scooter is not very smooth going through the air. It has a coefficient of drag (Cd) of about 0.9 versus about 0.26 for the Prius. Adding this up, the total drag coefficient (Cd x A) for the Prius is 6.24 and the scooter is 5.4. This means that the scooter takes almost as much energy to overcome wind resistance as the Prius!
Motor Efficiency
Small engines are not very efficient, while Prius engines are very efficient.
Conclusion
Add them up: the extra weight is not as significant because of regenerative breaking, the wind resistance is about the same and the motor is much less efficient. Given all this, it is not surprising that the scooter and the Prius get about the same gas mileage!
Posted in Electric Vehicles, Sustainable Energy
Posted by Max Dunn
Mon, 29 Jun 2009 16:17:01 GMT | 1 comment
One of the factors that we often forget when comparing Electric Vehicles (EVs) to gas powered cars is that it takes a lot of energy to extract and refine oil into gas.
For instance, in California it takes about 14kWh of electricity to get a barrel of oil out of the ground, and about double that to refine it. About half a barrel of oil gets refined into gas, which means this 20 gallons of gas takes about 21 kWh of electricity.
It also takes a lot of natural gas to refine oil, and if this natural gas was used instead to produce electricity, it would produce about another 20 kWh of electricity.
Therefore in a typical gas car that 20 gallons will last 400 miles. But if we just left that barrel of oil in the ground and used the electricity and natural gas for an EV instead, we could go about 120 miles or about 30% of the distance of the ICE car.
So the next time a comparison is made between the efficiency of gas cars and EVs, remember even before the gas gets into the tank, we are already giving up 30% of the energy that we could have used to power an electric vehicle.
Posted in Electric Vehicles
Posted by Max Dunn
Thu, 19 Mar 2009 19:48:45 GMT | no comments
I admit it – I am a numbers geek. I love to play around with numbers and think about them, and no more so than with electric vehicles. So imagine how happy I was too see some fantastic numbers about the Tesla Roadster!
The first of these graphs shows how much energy it uses at different speeds. The fact that energy goes down to a certain point is not surprising – all cars have a sweet spot where they operate most efficiently – but what is surprising that it is about 20 MPH versus about 55 MPH for gas cars. Another interesting point is that at 65 MPH the Tesla uses about 280 Wh per mile. This is measured from the battery to the wheels, so adding in the charging losses will decrease it to about 3 miles per kWh, which is the figure I normally use.
Read more...
Posted in Electric Vehicles
Posted by Max Dunn
Thu, 05 Mar 2009 18:12:54 GMT | no comments
A lithium air (Li-air) battery with a novel structure is looking very promising for use in battery-powered vehicles.
One problem with battery-powered vehicles (and an argument for hydrogen fuel-cells) is that it takes a while to recharge the batteries. While this is fine for city driving (since the batteries can be recharged overnight) it makes it tough to drive a long distance, like driving from San Jose to ski at Lake Tahoe.
This Li-air battery could solve the problem of long charge times by allowing service stations to replace the liquid electrolytes and metallic lithium cassette, allowing battery-powered cars to be driven continuously.
Then the metallic lithium can be electrically regenerated from the used liquid electrolyte making the process sustainable.
This Li-air battery could prove very useful in making battery-powered vehicles more practical.
(Reference: AIST Develops New-type ‘Li-air Battery’)
Posted in Electric Vehicles
Posted by Max Dunn
Wed, 25 Feb 2009 00:20:21 GMT | 4 comments
Natural Capitalism is a terrific book. But it got one thing wrong – its hope for hydrogen cars. Dan Neil at the LA Times put it well: "Any way you look at it, hydrogen is a lousy way to move cars." (Ref) Here are a few of the reasons why hydrogen won’t work:
- Hydrogen is only an energy carrier. It is not an energy source. (Ref)
- Hydrogen is made from fossil fuels. And this will likely be the case for the next several decades. (Ref)
- Hydrogen production produces CO2. (Ref) For instance, the Honda FCX Clarity hydrogen car indirectly produces 176g CO2/mile while the Toyota Prius hybrid produces less CO2 at 167g CO2/mile. (Ref)
- Hydrogen cars are very expensive. The FCX Clarity costs several hundred thousand dollars and it will take many years to even drop below $100,000. (Ref)
- Hydrogen leaks. A hydrogen car left in an airport parking lot for two week could lose 50% of its hydrogen. (Ref )
- Hydrogen isn’t very efficient. (Ref) Only 20% to 25% of the energy needed to make hydrogen can be recovered. (Ref) Even using renewable energy, battery powered vehicles can still go 3-times further on the same electricity than hydrogen vehicles. (Ref)
- Hydrogen cars fill up slowly. It currently it takes about 30 minutes to fill up a hydrogen tank. (Ref)
In the long-term, maybe the challenges with hydrogen cars will be solved. However, it is also likely that the few remaining problems with battery powered vehicles will be solved too. Physics will then remain firmly on the side of battery powered vehicles and it will be easier and more efficient to just transfer renewable electricity over power lines to charge battery vehicles than to convert the electricity to hydrogen, ship it, and convert it back into electricity again.
Posted in Electric Vehicles, Global Warming
Posted by Max Dunn
Tue, 03 Feb 2009 05:36:12 GMT | no comments
There has been some worry that there wouldn’t be enough lithium production to meet the rising demand for Li-ion batteries for electric vehicles. However, a recent study has concluded that due to the recession, demand for lithium will drop and there will be adequate supplies at least through 2020.
(Reference: TRU Presentation Lithium Supply & Market)
Posted in Electric Vehicles
Posted by Max Dunn
Fri, 23 Jan 2009 16:07:43 GMT | 1 comment
There are some questions about whether electric vehicles (EVs) actually reduce the amount of CO2 emitted, especially when electricity is produced by coal. However, we have seen that EVs in clean energy states produce only 1/6 as much CO2, and even in the worst case, produce no more than a regular gas car.
Providing more evidence of this, a new study by Boston Consulting Group not only shows how much less CO2 electric vehicles produce, but also puts a figure on how much this costs:
While this report shows that the cost of reducing CO2 with electric vehicles is not cheap, costing between $7,000 and $14,000 to reduce CO2 in half, the CO2 savings far surpass anything possible with advanced gas (ICE) engines. And the CO2 emissions caused by electric vehicles is only going to get lower as electric power generation becomes cleaner and the premium for electric cars will continue to fall as batteries become cheaper.
(Reference: The Comeback of the Electric Car)
Posted in Electric Vehicles
Posted by Max Dunn
Thu, 08 Jan 2009 18:37:16 GMT | no comments
The prices that people are paying for RAV4-EVs are a little crazy. Last year, several sold on eBay for over $45,000.
Today there was an auction for a 2003 RAV4-EV with 97,000 miles – which means the battery pack will need to be replaced at a cost of about $15,000. Nevertheless, the sale price was $32,600, so the total cost will be over $47,000 – crazy!
I mean the RAV4-EV is a great car, but it makes more sense to wait for another year or so when the new electric vehicles like the Chevy Volt will be available and will likely be less than $40,000.
Posted in Electric Vehicles
