Friday, August 14, 2015

2025 Cafe Targets.

An interesting post on GreenCarReports suggests that 9 car models already meet the 2025 EPA standards. Frustratingly, however, the nine cars are not listed. The original report does have another graph with a little more insight (page 434).
  Two of the nine cars are the Toyota Prius and the Ford Fusion hybrid, not surprisingly.  But the other cars remain mysterious.
   The graphic also shows that the Mitsubishi Mirage is not one of the nine.

Thursday, February 12, 2015

Scatter Chart Test

This is a test

Wednesday, August 6, 2014

EV sales projects

Mark Larsen is projecting 1,000,000 cumulative by 2017.

This is based on 5% monthly increase based on the Cumulative Number, which I feel is a mistake.  The cumulative rate of increase has been steadily decreasing, as one would expect when working from a higher installed base.

2011 42%
2012 12%
2013 8%
2014 5%

So I tried 5% increase per month based on the not cumulative number.  That is roughly 60% increase per year.

This obviously results in more modest projections.  And because inquiring minds want to know, here is the same data in log form.

I've spoken with Mark about this and he does not agree with me.

Friday, February 7, 2014

Efficiency of EVs and Hydrogen Powered Vehicles.

If you wanted to power your car on renewable energy, would you be better off with an electric vehicle (EV), like the Nissan LEAF, or a hydrogen fuel cell vehicle (HFCV) like the Honda FCX Clarity?  There seems to be two different opinions on this.  Among the car companies, Nissan and Tesla seem to believe that electric vehicles are the way to a green future, whereas Honda and Toyota are firmly planted in hydrogen fuel cell vehicle camp.

To be sure, both technologies have advantages and disadvantages. For me the best part of hydrogen is a quick fillup and a long range, 240 miles in the case of the Honda FCX Clarity.  The best part of electric cars is their highly efficient simple operation. Battery. Electric motor. Done.  On the downside, hydrogen seems to have an infrastructure problem and probably very high costs.  With EVs, the problems are all about the battery limitations causing issues with cost, range, weight, and life.

But let’s set the larger picture aside for a moment and focus on efficiency.  Let’s narrow the focus still further and talk about powering both vehicles from solar panels mounted, say, for example, on the roof of a home.  How does the efficiency of an EV compare to a HFCV?

The Vehicles

Well the EV part is straightforward because the EPA lists the efficiency of each model sold in the USA.  Let’s make the Nissan LEAF our exemplar for this discussion.  The EPA says the LEAF requires 30 kWh/100 miles.

The HFCV is more complicated and comes in two parts.  The first is the efficiency of the HFCV at using hydrogen.  The second is the efficiency of making the hydrogen by electrolyzing water using electricity.

The efficiency of the HFCV is easy.  Let’s make the Honda FCX Clarity our exemplar for this discussion. The EPA lists the efficiency of the Honda as 60 miles/kg of hydrogen.  So if you purchase 1 kg of hydrogen, you can go 60 miles.

The Electrolyzer

The difficult part is how much electricity does it take to make a kilogram of hydrogen.  Let’s take a couple of different approaches to answering that.

First Try:  In 2010 Honda introduced a new version of its solar powered hydrogen generator, shown in the picture.  It is a very cool piece of technology that uses a high differential pressure PEM electrolyzer that can make high pressure hydrogen directly without the need for a compressor (Gizmag, “Honda’s next gen solar-powered hydrogen fuel station for home use”, 2010).  That is a big deal because it saves on both electricity and noise.  The station slowly makes 0.5 kg hydrogen overnight (8 hours) from grid electricity and transfers it to the car, i.e. no hydrogen storage in the home, saving on tanks.  It really sounds like overnight home charging of EVs more than anything.  But that 0.5 kg made overnight is only going to make the car travel 30 miles, compared to a full overnight charge on the LEAF EV allowing it to travel 84 miles.  But I digress, ...back to efficiency.

The press release doesn’t give the energy efficiency of the station directly, so we need to do a little inferring.  The 6 KW array is supposed to supply enough power to produce 0.5 kg/day.  Well a 6 KW array will produce about 24 kwh/day (more in the summer, less in the winter).  So that means it takes 24kWh/0.5 kg or 48 kWh/kg.

Second Try: A 2009 report from NREL (National Renewable Energy Laboratory) entitled “Hydrogen Resource Assessment” by Milbrandt and Mann researched the efficiency of commercially available electrolyzers.  The number NREL uses in their analysis is 58.8 kWh/kg which is based on the average of four different electrolyzers.  The number does not seem to include the energy needed to compress the hydrogen to, say, 5000 psi, which would raise the number higher.  The number is about 25% more than the approximation from the Honda Solar hydrogen generator which is interesting because Honda claims their 2010 system is 25% more efficient than their previous model. So perhaps the 48 kWh/kg is a good approximate number.

Third Try:  From chemistry, it is possible to calculate the energy needed to convert liquid water into hydrogen and oxygen gas.  The details of the process are described in a book called  “Solar Hydrogen Generation: Toward a Renewable Energy Future” on page 57.  It takes 39 kWh/kg to convert liquid water into hydrogen and oxygen gas.  This value is known as the higher heating value.  But when a fuel cell in a car converts hydrogen gas back into water, the water comes out in the form of steam.  So it is only possible to recover the so-called lower heating value of 33 kWh/kg.  So even with no losses in the system, this process is only 85% (33/39) efficient just because we start with liquid water in the electrolyzer but end up with steam coming out of the tailpipe of the HFCV.  So 39 kWh/kg is the lowest possible amount of electricity that could be used to by the electrolyzer.

And the Final Answer Is

So we have three values, 39, 48, and 58.8 kWh/kg.  Let’s give the benefit of the doubt to the HFCV and choose the middle number of 48 kWh/kg.  The actually number is probably a little higher, closer to the NREL number, but perhaps Honda has built a better mousetrap.

Armed with that number, it is now possible to calculate the efficiency of the HFCV.
48 kWh/kg / 60 miles/kg = 0.8 kWh/mile =

HFCV 80 kWh/100 miles
BEV   30 kWh/100 miles

That means it takes a whopping 2.6× more electricity to power a HFCV than an EV.  If both are powered by the sun, the HFCV would need 2.6× more solar panels.  As a practical matter, if you own two HFCVs, the 12 KW solar array will be much too large to place on the roof of a typical home.

So given this difference, why are the car companies and the EPA still interested in HFCV?  The efficiency is poor. The cars are shaping up to be very expensive (even by EV standards).  Oh, and there is this infrastructure problem.  Sure, EVs have a little bit of infrastructure to deal with too, but for less than  $2000, you can at least install an EVSE (“charger”) in your home and drive to and from work.  Filling up with hydrogen will likely need to be done in the old gas-station model.  Hydrogen stations will need to build in clusters starting, say, in South California, and working their way out.

Hydrogen does have its advantages.  In addition to being able to make it from water, it can be made from steam reforming of natural gas.  It can even be made from coal, if need be.  So there is some flexibility there that helps address the energy security needs.

Exiting from the tailpipe of HFCV is nothing but water, so local pollution issues are not a problem.  That is definitely a good thing.

An if, and it’s a big if, the hydrogen infrastructure could be put in place, a HFCV could be operated in the same way as a gasoline car.  Drive 240 miles and stop at the nearest hydrogen station to fill up again.

And perhaps if gasoline cars are used as a baseline for comparison, rather than EVs, the HFCV doesn’t look so inefficient.  Of course it isn’t much of a step forward either.

Efficiency for the Win

In the end though, in matters of energy, efficiency generally wins out.  For each little bit of improvement in efficiency, there is just that much less coal to dig up, or oil to pump out, or solar panels to buy, making the more efficient system worth paying little more for up-front.  Of course, in the case of EVs versus HFCV, maybe the more efficient EV system is actually less expensive, but we will not know for a few more years once HFCV start being sold, perhaps in 2015.

Let’s put it this way, if you can get a 6 KW solar PV array on the roof of your home, it can be used to power either one HFCV, or two EVs plus the house itself.  That makes EVs a very big win indeed.

Sunday, January 26, 2014

Vehicle Particulate Emissions

{Author's note: this post is about ICEs not EVs}

Atmospheric particulate matter are tiny particles suspended in air.  The particles can be both naturally occurring (volcanos, dust storms) or man-made/anthropogenic (vehicle emissions, power plants, concrete manufacturing).  Anthropogenic atmospheric particulate matter “is consistently and independently” are related to the most serious health effects including lung cancer and and cardiopulmonary deaths.  (Wikipedia, “Particulates).

Various government agencies have been working to reduce particulate emissions from a range of sources, chief among them are cars and trucks.  The classic source of particulate emissions is the older diesel cars and trucks that can be seen puffing out black smoke.  Modern diesels use particulate filters and frequently emit fewer particles than many directed injected gasoline engines.

Emissions regulations are an array of acronyms, bins, phase in dates, and other confusing jargon.  In the USA, this is further complicated by there being two different sets of emissions regulations, one created by the EPA, the other created by California but followed by many other states that can choose between either EPA or California rules.  It is slightly bizarre that the state of Massachusetts (for example) is subjected to California air quality laws.

Below are the particulate emissions limits created by the EPA which uses a “bin” system of which bin 5 is generally considered the most important because that is the median number that vehicle manufacturers must meet.  Note that emission will be reduced by almost two orders of magnitude (200 down to 3 mg/mile) from 1991 to 2025.
1991 200 mg/mile (Tier 0)
1994 80 mg/mile (Tier 1)
2004 10 mg/mile (Tier 2)
2017-2025 3 mg/mile (Tier 3)

California has a similar system (with different acronyms of course) that concludes with 1 mg/mile particulate specification by 2028.  I wonder if there will be fewer particulates coming out of the engine than going in at that point in time
2004-2007 80 mg/mile LEV1
2015-2019 10 mg/mile  (LEV2)
2017-2021 3 mg/mile (LEV3)
2025-2028 1 mg/mile (LEV3)

The Europeans have been on top of this problem as well, which is probably more important over there because of the high penetration of diesel engines in the passenger vehicle market.  Interestingly, 2014 will be the first year when they implement particulate emissions requirements on DI (direct injected) gasoline engines reflecting the tendency of DI engines to produce more particulate emissions than modern particulate filtered diesels.
1992 PM=140 mg/km,  diesel,  (Euro 1)
1996 PM=100 mg/km, diesel,  (Euro 2)
2000 PM=50 mg/km, diesel,   (Euro 3)
2005 PM=25 mg/km, diesel,  (Euro 4)
2011 PM=4.5 mg/km, PN=6e11 particles/km, diesel,  (Euro 5b)
2014 PM=4.5 mg/km, PN=6e11 particles/km,diesel+gasoline,  (Euro 6)

Emissions regulations are very complicated and the above numbers should be taken as general trends.  Undoubtedly an expert would talk about the phase-in dates and the percentages of vehicles that need to meet a given specification on a given year, or that the number only need to be achieved as a “fleet average” not for an individual vehicle, or that certain changes in gross vehicle weight will change the specification.  All that is true but the above numbers are intended to give a quick overview of the requirements, something that is desperately needed in the emissions literature.  This could be a book writing opportunity.  Who wouldn’t want a copy of “Particulate Emissions for Dummies” under their Christmas tree.

Wednesday, October 23, 2013

Driving Tesla Model S as fast as you can with Supercharging.

With Tesla adding an Autobahn tuning package, it made me wonder if driving fast in a Model S would just leave you hanging around the SuperCharger more often.  Perhaps a little bit of calculation can shed some light.

First, I started with a graph from Tesla of battery consumption versus speed.  Unfortunately that graph only went up to 80 mph, so I had to extend it (yes I know that exponential is probably not exactly correct, but it's close).
Having that data, I needed to make some assumptions about the Superchargers.  If they are 120 KW, they can charge an 85KWH battery in 0.708 hours.  Sure, I know it would take much longer than that because the last 20% of charge is slow, but I'm just trying to get a rough estimate here.

So with some simple math, we can figure out the "running time" and the "charging time" and compute an "aggregate MPH".

Running Charging Total
range Time Time Time Agrregate 
miles/hour WH/miles (miles) hours hours Hours MPH
10 220 386 38.6 0.71 39.34 9.8
15 195 436 29.1 0.71 29.77 14.6
20 190 447 22.4 0.71 23.08 19.4
25 190 447 17.9 0.71 18.60 24.0
30 195 436 14.5 0.71 15.24 28.6
35 200 425 12.1 0.71 12.85 33.1
40 215 395 9.9 0.71 10.59 37.3
45 225 378 8.4 0.71 9.10 41.5
50 245 347 6.9 0.71 7.65 45.4
55 265 321 5.8 0.71 6.54 49.0
60 285 298 5.0 0.71 5.68 52.5
65 315 270 4.2 0.71 4.86 55.5
70 340 250 3.6 0.71 4.28 58.4
75 365 233 3.1 0.71 3.81 61.1
80 400 213 2.7 0.71 3.36 63.2
85 429 198 2.3 0.71 3.04 65.2
90 463 183 2.0 0.71 2.75 66.8
95 501 170 1.8 0.71 2.49 68.0
100 542 157 1.6 0.71 2.28 68.9
105 586 145 1.4 0.71 2.09 69.4
110 633 134 1.2 0.71 1.93 69.6
115 684 124 1.1 0.71 1.79 69.4
120 740 115 1.0 0.71 1.67 69.0
125 800 106 0.8 0.71 1.56 68.2
130 865 98 0.8 0.71 1.46 67.1

That puts the optimal speed (in a time sense) at an impressive 110 mph.   Realistically, optimal speed will probably be a slower than that due to charging issues.

Unfortunately, the aggregate speed is only 69 mph considering the charging time.  It will mean driving for 1.2 hours and then charging for 0.71 hours.  That might be slightly painful.

The only thing worse, would be to go for optimal efficiency and drive at 25 miles./hour which would be 17.9 hours of driving and 0.71 hours of charging.  Bathroom break anyone?

Friday, September 6, 2013

table test

This is a test of exporting from Excel
EV Monthly Sales

EV Monthly Sales

2013 Chevy Nissan Toyota Ford Mitsu Toyota Honda Honda Ford Ford Smart Chevy Fiat Tesla Monthly
Mon Volt Leaf PiP Focus i RAV4 Fit Accord C-Max Fusion ED Spark 500E Mod. S Total
Jan 1,140 650 874 81 257 25 8 2 338 0 2 0 0 1,200 4,577
Feb 1,626 653 693 158 337 52 15 17 334 119 0 0 0 1,400 5,404
Mar 1,478 2,236 786 180 31 133 23 26 494 295 0 0 0 2,300 7,982
Apr 1,306 1,937 599 147 127 70 22 55 411 364 0 0 0 2,100 7,138
May 1,607 2,138 678 157 91 84 15 58 450 416 60 0 0 1,700 7,454
Jun 2,698 2,225 584 177 39 44 208 42 455 390 53 27 0 1,350 8,292
Jul 1,788 1,864 817 150 46 109 63 54 433 407 58 103 150 700 6,742
Aug 3,351 2,420 1,791 175 30 231 66 44 621 600 182 102 160 1,300 11,073
YTD 14,994 14,123 6,822 1,225 958 748 420 298 3,536 2,591 355 232 310 12,050 58,662