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Sometimes (EV & PV) Dreams Really Do Come True

The fact is, I’ve been pining for an EV for 30 years, since I was in grad school in the “Energy Systems” program at Caltech. When my wife and I bought our first car together (1979 Toyota Corona), I swore it would be “the last gas-powered car I’ll ever get.” Boy, was I wrong about that! So when my daughter took me to the Tesla Gallery in Boulder CO in May (2010) and I test drove the Roadster, I swooned. Two weeks of agonizing soul-searching and finance juggling followed, and I ordered a Roadster. The truly fiscally responsible thought of waiting another two years before I could get a Model S, when I might be able to get a Roadster now – was simply too much to bear.

So 13-1/2 days ago, Roadster (#1014) - *my* Roadster - arrived. Turns out it was one of the first 2.5’s off the assembly line. I’d ordered a 2.0, and they announced the 2.5’s a couple of weeks later. Much to my amazement, in response to my inquiry on supposed improvements in the power management system in the 2.5 (improving performance in “high temperature operating environments”), my Service Rep informed me that my order was being "upgraded"! Maybe it's just me, but Phoenix sounded like a "high temperature operating environment," and I breathed a huge sigh of relief.

The 14 weeks in between – that was really a lot like waiting for a new baby: You’ve got to get everything ready, and you want it all to be perfect. Between when I placed my Roadster order and when it arrived, I wired in the 240V/50A receptacles, had the garage repainted, and had a new epoxy floor put in. (As an aside, I’ve got to admit I was so eager to get ready, I installed the receptacles about two days before the Universal Mobile Adaptor arrived. Remembering incorrectly, I made the mistake of putting in NEMA 10-50’s instead of 14-50’s, so I actually had to do that job twice.) Better than all that, however, just prior to ordering the Roadster, I'd put in motion the installation of a 5 kW photovoltaic system on the house, which also came to fruition during the wait for the Roadster. It went online about two weeks before the Tesla arrived, and immediately started producing about 24 kWh/day of electricity. In fact, my decision to install the PV system was part of my rationalization process in making my Roadster decision: I already owned two Prius’s, had an energy-efficient house, and felt pretty green. How could I possibly spend so much “mad money” on a car like the Tesla, however environmentally cool it seemed, unless I could say that I actually eliminated its carbon footprint (at least, operationally)? I’ve been following various discussions in the last few months about the hidden carbon costs of electric vehicles, and was afraid I’d feel guilty about getting yet another “green” vehicle without first putting some of my other money where my mouth was – namely, start producing a substantial amount of my own energy directly from the sun. Installing a PV system would be far more economically justifiable, so if I did it first, I could then rationalize the Roadster. And why not simply wait another couple of years for a Model S, at maybe half the price? My California-girl wife was quick to point out, “but we can’t drive it to LA either – not enough range; why wait?” So I sold all my BP stock to cover my $9,900 reservation fee (a great investment move, as it turned out – I’m afraid we all know the sad story behind that), and subsequently all my Exxon, Chevron, and Shell stock to make my substantial down-payment on the Roadster. Sure I was earning nice dividends from Big Oil, but not quite enough to make up for the lost capital over the previous two years and the global economic woes. I figured: I can lose money in the stock market easy (almost guaranteed, in fact) – why not instead lose it in depreciation on a (really cool) car? At least I’m not kidding myself! (And who knows, I may have a real collector’s item soon!)

And did I mention - we live in a very energy-efficient "monolithic concrete dome" house. In our area of Arizona, we’re served by a public utility that offers a time-of-use rate plan. If I can shift at least 30% of my energy to off-peak hours, I pay less. Most people do that by compromising a little comfort: higher thermostat setting during the peak hours, putting the water heater on a timer, and intentionally avoiding baking, laundry, and so forth, during on-peak hours. But our dome home has a huge thermal mass which naturally load-shifts its cooling requirements – the single largest power consumption in Phoenix for half the calendar year - to the off-peak hours. It’s almost painless, and is why our on-peak consumption was already less than 15% or better. To be honest, I was actually afraid of going negative on-peak with the PV system (which turns out to pay very poorly), so we somewhat intentionally positioned the panels to produce more off-peak than on-peak energy. (Most central Arizona photovoltaic installations aim for mid-afternoon peak generation, which coincides with peak demand and the most lucrative payback ratio.) Even so, amazingly, we came very close to going negative – this first month of operation is going to show only about 2 kWh/day of billable on-peak consumption. Compare that with our average summer off-peak consumption of about 70 kWh, before the photovoltaic system went in (and the Tesla arrived).

As it turns out, I’ve actually consumed darned near every kWh of solar power generated by my PV system, over the last 13-1/2 days, in my Roadster – on and off peak combined. In other words, much as without the Roadster, the PV system would have lowered my net metered energy consumption, the Roadster ends up being a battery that effectively moves (in more ways than one) all that solar energy I’m generating on-peak, to off-peak. Or looking at it another way, I’m shifting my daily gasoline based energy consumption from a Prius, that I used to drive every day, to the off-peak consumption of the house, courtesy the Roadster. This was a synergy I hadn’t actually thought through ahead of time, but I’m not complaining about how it’s working out.

On the down side, I can already tell I'm going to have to watch my mileage, as I've already put over 800 miles on the Roadster. Before it came, I'd planned on using it for my daily commute. That would account for less than half of those miles. Instead, I've used it for every non-commute-specific trip that didn't need more than two people along. The problem is, it’s too cool to not drive! (Maybe I should confess, since we're talking about the down side for a moment - summer afternoons in Phoenix *might* actually be just a tad too hot to drive - but even when the A/C cuts out to favor the PEM and battery, I just sweat it out. And I figure I'm going to have 9 months to drive with the top off, cooler in every possible way.) I think maybe my mileage (definitely my energy/mile) *will* taper off. I mean, I've only given about 40 "test rides" to friends so far, and wouldn’t you think the novelty might eventually wear off – at least for me?

As for the "My Car/Our Car” aspect, as another blog has put it, I have to say: my wife definitely likes the Roadster, but for the most part, she seems to be just as happy to ride along as drive it herself. Don’t get me wrong - there's no doubt she has fun driving it (if I can keep my mouth shut about how she’s not getting up to the speed limit as quickly as she could)! I guess she's just not a performance junkie. Me, though - I'm a mechanical engineer, and revel in first-hand experience of the physics and engineering of this incredible machine. 30 years later, it’s really a dream come true.

I don't understand why you would not drive it as much as possible. In the year I've had mine, the gas guzzler has been driven only about once per month... sometimes just to keep the battery charged, mostly when I need more seats.

Greg.

Fantastic post! Love the dome-homes, too; they're great for any challenging environment, whether hot, cold, tornado/hurricane prone, whatever.

Love to have you comment and post at another site I support: www.focusfusion.org . It's a research project now getting down to the "short strokes". If the hoped-for "scientific break-even" is achieved this year, another few years of engineering could result in licenses being sold to makers on the open world-wide market for small 5MW generators, at about 1/20 current best capital and operating costs. How'd you like 0.1¢/mi. energy cost for your Roadster?

For the techy stuff, start with this page: http://focusfusion.org/index.php/site/category/C30/

Anyhoo, I agree with Greg: why not maximize Roadster use? Think of all the negative "opportunity cost" per mile! ;)

great post redsnapper.
i have to wait for my model s which is supposed to arrive in july 2012 (can't afford the roadster and need the room of a model s).

anyways, one part of your post is particularly interesting to me:

"Maybe I should confess, since we're talking about the down side for a moment - summer afternoons in Phoenix *might* actually be just a tad too hot to drive - but even when the A/C cuts out to favor the PEM and battery, I just sweat it out. And I figure I'm going to have 9 months to drive with the top off, cooler in every possible way."

I live in scottsdale and therefore have the same extremes in temperature that you do. Is it really true that the A/C will shut off entirely? I was told by a company representative that having max A/C would likely increase power consumption by 10% but that it would still work.

I'd love to hear your thoughts on that and if there were other owners out there who had A/C issues. I wear a suit to work on most days and the prospect of not having working A/C in 110+ temps is frightening.

Thanks for all of your replies.

grimmer
Even before I learned any tricks (I'll explain more in a minute), the A/C has worked fine even on hottest days in the mornings on the way to work, and in the evenings on the way home (of course, I didn't have it until Aug 27, so I can't speak for June & July and most of Aug). We even drove a 165 mile round trip to Picacho Peak in the middle of the afternoon when it was 110F, and at 75mph into the wind never even noticed any lapse in the A/C. The return trip, with a good tailwind, A/C seemed to fade about half-way back. That being said, my commute is only 15 miles one way, and 20-25 minutes in traffic.
Again, before I learned any tricks, I'd noticed that midafternoon trips (e.g. Phoenix to ASU Polytechnic and back) the A/C worked great for the first 15 miles, then faded. (I can't say it shut off completely - fact is, the fans still run, and the air's no doubt cooler than outside; but when it's 110F you do notice the lack of *cold* cabin air!)
But there are a couple of tricks my service rep passed along since then. One I've tried, the other I haven't had the need for, yet (takes a little more planning): as background the Roadster has different "charging" modes (which also correspond to "driving" modes). Normally, you charge and drive in "Standard" mode, which, among other things, controls the battery temperature. My understanding is that if the battery is running at the upper limit of what the cooling system can control, it will sacrifice cabin temperature to favor the battery. So, once you're out on the road, and sense that the A/C is fading, you kick it over into "Performance" mode, which allows the battery to go to a higher temperature. That, of course, gives you some extra minutes because the cooling power can again be temporarily redirected to the cabin. (Naturally, they don't recommend you drive in Performance mode a lot, because it does reduce the life of the battery.) This is the trick I've tried, and it definitely works. The second trick is to plan ahead, and if possible, plug it into the charging system in "Max Range" mode 15-20 minutes *just* before you hit the road. The point isn't to add more charge to the battery (though it will, if you had only been in Standard mode prior to that), but rather, Max Range mode actually pre-cools the battery (for more efficient charging). So again, it gives you an extra few miles/minutes at the beginning of your trip, where the battery starts out cooler, so the cooling power can be directed to the cabin for longer. Between the two tricks, I could see I might double the duration of full-power A/C operation from 15 miles to 30 miles. But as I said before, I have only had trouble in the midafternoon, even on the hottest days. I also expect, just like anything else fun, that the faster and harder I drive, the more cooling has to be directed to the battery; it's likely that there's probably some "sweet spot" of speed where the cooling system works most efficiently thanks to forced air over the heat exchangers, coupled with modest power consumption from the motor. Sitting in stopped traffic in 110F is probably worse than driving at 30mph.
Optimistically speaking, I'd like to think they will have made additional improvements in the power management system by the time the Model S is on the road - especially when they get reports like these from "extreme environments." Further, the Model S has a hard top, and is probably better insulated than the soft top of my Roadster. I can only imagine that the Model S is going to have the same set of charging/driving modes, but obviously whether some of these "tricks" will work on the Model S depends on lots of things.
Having said all that, if my job required lots of driving in the afternoons, I'd think seriously about letting the Roadster have a rest during July and August, and drive my Prius. My wife's commute is a lot shorter than mine, too, and I'm sure she wouldn't complain if I said, "OK, you've got the Tesla for a couple of months."

thanks so much for that detailed information! i'll definitely cut and paste that and re-read it once i get the car. since they're predicting july of 2012, i'll need those techniques "out of the box." i also have an even shorter commute than you so between your strategies, and a short commute, I hope not to be a dripping mess.

One point that might not be clear is that the A/C does not fade in order to reduce energy consumption. Rather, the A/C is still running at maximum rate, but the cooling is diverted to the job of extracting heat from the battery. The water + anitfreeze coolant circulates through the battery and a heat exchanger with the freon circuit near the right rear wheel. When the battery temperature reaches a threshold, then the chilled freon is diverted from the heat exchanger in the cabin to this battery heat exchanger. I don't know whether the flow can be partial through each path or just time multiplexed between the two. Also, regarding this:

"We even drove a 165 mile round trip to Picacho Peak in the middle of the afternoon when it was 110F, and at 75mph into the wind never even noticed any lapse in the A/C. The return trip, with a good tailwind, A/C seemed to fade about half-way back. That being said, my commute is only 15 miles one way, and 20-25 minutes in traffic."

Someone might infer from this description that the A/C is more likely to fade with a headwind than with a tailwind. That would be wrong, because the energy consumed to move the car is greater with the headwind. Furthermore, assuming that Picacho Peak is at a higher elevation than home, gaining potential energy also takes more energy from the battery, while on the descent less energy is required from the battery to move the car. (I, too, love the fact that this car is a rolling physics demonstration.) The actual reason is that the battery probably started out cool at home, and the heat in the battery built up during the trip out could not dissipate before the trip back, so the aggregate heat buildup along the total trip only hit the threshold to require taking over the active cooling on the return leg.

Steve,

Picacho Peak (not the peak itself, but the freeway exit, where we turned around) may be a tad uphill from Phoenix; if so, less than 1000' (and that over 82 miles, so hardly a factor). [Let's do the math: 1000ft/5000s = 0.2fps; gross weight about 3000lb, or 600lbf-ft/s, or about 1 hp, or 750W. Thus, the climb itself adds about 1kWh to the 82 mile trip, or less than 0.01kWh/mile. At 75mph, I think we might expect about 0.5kWh/mile without a headwind or climb, so I conclude the elevation change is noise.]

Because the A/C worked BETTER on the way TO Picacho (headwind and uphill), my theory was that due to the headwind, the heat exchanger had better airflow than on the return trip. It's no doubt true that the battery also started cooler heading that direction, but all things considered and other experience over the days driving around Phoenix these first couple of weeks suggests that it usually only takes about 20-30 minutes before the battery (actually usually the PEM) hits its temperature limit. (Again, this has been when outside ambient is 105F or higher.) The drive to Picacho was more like 90 minutes each way.

One other factor, however, is that the drive to Picacho is mainly SE, and in the early afternoon, we had the sun over our right shoulders; on the return trip, later in the afternoon and driving NW, we had the sun in our faces (well, ahead and on the left) - so the cabin probably also had additional heat load, plus direct insolation on the skin always makes it feel hotter even when the air is cooler.

The main conclusion, I think, is that midsummer midafternoon in central Arizona qualifies as a high temperature operating environment, and we're running on the edge of the cooling system's capacity. But if even in that extreme environment, it manages to keep the vehicle itself "safe", it's doing a very respectable job!

redsnapper,

The other factors you mention are good ones to consider.

One should not infer battery temperature from PEM temperature or vice versa. They behave quite differently. The PEM has little thermal mass, and just air cooling. When several of us were driving on the track at Laguna Seca, the PEM limit was definitely the first to get in the way, followed by motor temp. The battery was not a problem.

Steve,

Yes, it's been quite clear that the PEM usually runs hottest and hits some kind of temperature limit first - there are, after all, three different temperature indicators on the temperature display, so one would reason that they're not intimately linked. *You're* the one who said, in your initial response: "The actual reason is that the battery probably started out cool at home, and the heat in the battery built up during the trip out could not dissipate before the trip back, so the aggregate heat buildup along the total trip only hit the threshold to require taking over the active cooling on the return leg." So are you saying the thermal mass of the battery is so large that it might take a couple of hours before it got to a limiting temperature? I was told that you only need to keep the charging system on for 15-20 minutes (in Max Range mode) before the battery is cooled to charging temperature - not, however, that cooling time is necessarily related to heating time.

redsnapper,

The load on the battery with normal freeway cruising speed is pretty small, like 15-25kW depending on speed and load. So, yes, it might take a couple of hours to heat up. On the other hand, the active cooling can pull heat out at a higher rate.

I have not been in a situation yet where I wanted A/C for the cabin and didn't get it because it was all taken for cooling the battery, so my conjectures are not from direct experience. I have had the fans come on when I was not running the A/C, though (and while driving, not charging).

During July's heat wave, we had 40C temperature and high humidity, and I was driving my brand new Roadster. In the afternoon after the car was good and warm, the cabin air conditioner became, uh, ineffective, and I had to open the windows. And this is in Canada. But to be fair the car arrived during a record heat wave...

I find the fan often turns on when you are moving slowly, which makes sense since there is less air flow. And it runs a lot more if the A/C is on.

Steve,

Do you know if the PEM benefits from the active cooling system? I assume the motor itself does not, but based on your comments, it sounds like the cooling system is shared exclusively between the cabin air and the battery. So the lower thermal mass of the PEM might affect whether I get a "Power limited" warning quickly under high temperature conditions, but wouldn't have anything to do with A/C in the cabin.

PEM and motor are air cooled. Only the battery and cabin are air conditioned.

Back to generating power, here's a new combo:
http://www.cogenra.com/why-solar-cogen/

Leaches the heat from the PV to also heat water. Claims much higher overall efficiency.

Redsnapper, Just read your original post and was going to say "what a good post" but it seems everybody else has beat me to it. Way to go{little play on words here}.

You mentioned you were a mechanical engineer, just wanted to say there is a genuiness and congeniality that just seems to come through from many of the "real deals".

Thanks for investing in this car it will help us all eventually, hope you take that into your account for justifications to buy the car. We are going to figure out how to deal with this energy thing with the help of the diety and people like you.

What are you doing up at this time of night? Gotobedarreddy.

Over 30 years of bank data processing, of which the bulk gets done in the evening and night. Post all the days work. Night is where the action is in bank data processing. Has made me rather nocturnal{seriously} however this process really started while I was in college. Got my best studying in the wee hours.

I noticed your post was three thirty eight am, what are you doing up so early, fixing to go jog or something. I hate getting up early. Last three years of work had to go to bed with the chickens and get up at five am, hated this.

Retired and living on Web Time. F'rinstance, right now it's 7:20 tomorrow morning UT. Following the sun west, I get about halfway there, which makes it about 3:20 pm tomorrow afternoon.
Got it? I know it's confusing.

Redsnapper,once on vacation trip AC went out on I40 just as getting into the Mojave desert in Chevy Nova, think it was unseasonably cool even for June. Thought we were in real trouble, let all windows down and not to bad at all, fairly comfortable as perspiration imediately evaporated and wind coming through windows kept us relatively comfortable. Guess this area is reffered to as upper Mojave or high plains. AC came back on as we got out of the desert around Barstow. Came back on lower route AC ran perfectly rest of trip. Stopped at a service station on lower route somewhere in the Pheonix or Tuscon area, wind blowing like a blast furnace and soo hot. Sure glad AC didn't go out comig back. Pheonix and Tuscon were terribly hot althogh I love the low humidity. The lower the humidity the better I feel generally. Loved your part of the world, would love to live and explore there some, although I understand that it can get dangerous for the unexperienced. Explore the northeast quadrant of Alabama if you ever get the chance, beautiful mountains, lakes,swift running streams,beautiful flora, quaint towns and lots of new nice homes as well as beautiful old homeplaces.

ifilm77: Please don't post your website plug in 10 different threads.

ifilm77, am now flagging all your posts as spam.

Redsnapper, Didn't mean to get so caught up in the tourism thng but you and your wife sound like you like to explore.

Since you are a mechanical engineer will you take at my question about the wheel regenerating juice without interferring with ongoing thermo dynamics laws of the wheels. I am driving the more technically inclined nuts with this but just just can't seem to turn this concept loose, not just yet. As i stated before I will get some engineers at Auburn to look at my concept but of course I am trying to get input from whoever I can. Just seems like devices wouldn't be too difficult to devise that would do this without breaking any laws of thermo dynamics. I am just thinking turning wheels and turbines? Be frank in you assesment, I wont be offended in the least. My skin has gotten quite thickened on this issue,ha.

First, make wheels turn by sprinkling with pixie dust ...

redsnapper, one thing that just caught my eye on re-re-reading your excellent post (best ever on the site?): is that 70kwh/day figure for real? What're the big draws that use so much?
I'm curious, too, what your on/off peak rates are there. Here, we're on a flat rate of about 6.7¢.

P.S. To those not familiar with the home style redsnapper has, check out domeofahome.com .

A decimal error? 7kWh sounds more like it. 70kWh is more than ten times what I use in entire average day.

If "wheel regenerating juice without interferring with ongoing thermo dynamics laws of the wheels" were even remotely possible in the near future, don't you think some company would already be working on it or have a product on the market?
If ifilm77.com keeps posting, he may become the new king of this forum.

dsm363, I have suggested that you not let this wheel thing bother you so much. You and BrianH seem to be answering a question I am asking someone else. I already know your answers and thank you very much for your input but this is being asked of somewone else entirely and you seem eager to put your dubious opinion in to perhaps make Redsnapper hesitant to want to enter such a fray.

No I do not necessarily think a company would necessarily be involved in it if it were remotely possible. All the companies don't know everything and I bet even the laws of thermodynamics might even have a few creases and nooks that we don't even know about. Bet laws of theromodynamics possibly has some fluidity in it as am almost sure a lot of laws of physics, electricity, and other scientific area do. Things may exist in these disciplines that we dont know about yet, will you grant that? When were the "Laws of Thernodynamics" established and by who. Or do you concede they might be being established daily as other disiplines are when the boundries are being pushed. Do you think perhaps Tesla pushed a few boundries of known and established disciplines. So once again {how many times have I expressed this?} with utmost respect do I have in the way you handle yourself on this website. I apppreciate your professional, congenial mannner. I have utmost respect for you technical knowledge and professionalism. But I ask of you plese, if it's folly just please try not to let it upset you so. After all what has been considered folly in the past has turned out not to be so in some cases. You have responded to my post often in a professional and congenial manner and I have enjoyed reading many of your post. So please consider this as a plea for a little slack and nothing more. Kindest regards, Searcher

Google the difference between a law, a hypothesis and a theory to start. Could a law possibly be disproved? Yeah but then everything in science based on that law would fall apart.

With all due respect, you have started to drive actual owners away from this forum. After months and months of posting the same stuff over and over again, you're starting to wear on peoples nerves which is why you're starting to see more and more negative comments directed at you.

dsm363, I have attempted to discuss a wide variety of subjects on the website as well as I can based on my limited technical knowledge. Actually I have felt less negative comments directed at me, perhaps some have given up, ha. Likewise, with all due respect, I have seen even you and others act in a strident way to newcomers to the website who may not have been familiar with how things work, example recently the person from Romania I believe who was excited about the Tesla car he had test driven. He obviously was trying to reach out to like minded persons who liked the Tesla cars to. He was posting on all the threads with the same messege. You very politely explained to him that most everybody reads all the posts thus not necessary to post same messege on all threads and I am sure this was probably politely sufficient but then everybody had to get all stident and start slamming the poor fellow "new kid on the block syndrome". Not good group behavior{ which for the most part I don't like} as it often brings out the worst in us. But I have been the "outsider" before when it comes to group behavior and I am actually thankful for these bad experiences as I think it has made me more aware hopefully and not be as prone to engage in such behavior and at the same time have a feeling for people that have to endure this type behavior often for no fault of their own, maybe just that they were born unattractive and in some parts of the world people may be far less sensitive than they are in others. I think of what some of these people have to endure daily as they have to go out and face the world, go to school, go to work, etc. and truly keep them in my heart. If I had not endured being the "outsider" at times I probably wouldn't give this a second thought.

As far as people leaving the website because of me, all I can respond to with here is sincere regrets.

I was trying to contact Redsanpper because of his obvious congeniality and the fact he was a mechanical engineer. But as I said before bear with me awhile longer. I will contact the engineers at Auburn and discuss the "wheel" thing with them offsite and maybe I will soon shut up about it.

I sincerely hope you have not found anything offensive to you personlly in this post. Again, kindest regards. Searcher


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