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Doty WindFuels is a subgroup of Doty Scientific - a small company founded by my father 30 years ago. We are currently developing a new energy paradigm - a process for using variable renewable energy to convert CO2 into liquid hydrocarbon fuels and chemicals. The products would be called... More
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  • Vehicle To Grid Makes Absolutely No Economic Sense Whatsoever. 26 comments
    Jun 8, 2012 1:32 PM

    A hard sell:

    To begin, we need to determine what the purpose of an electric vehicle is. If that purpose is to operate as a vehicle, then the critical issue must be the versatility in one's ability to move from one place to another. That means maximizing the distance that could be traveled on a moment's notice. For instance: the Leaf can only go 60-70 miles on a full battery, so if someone is called from work to go on a family emergency and then return to work… they probably won't be able to go home. This lack of flexibility from the standpoint of middle-of-the-day options is one of the largest problems facing EV marketing and sales.

    Hence EV advocates are crying out for the ability to plug in their cars at work - not because they want to donate some of that precious stored energy TO the grid, but because they feel anxious from the lack of flexibility in their driving options and want to increase those options, so they demand more energy FROM the grid.

    If the EV owner were participating in V2G, and got some kind of emergency phone call during a time frame when the battery had been discharging energy to the grid - leaving the battery further discharged then when he/she had gotten to work to begin with - then that would further reduce the EV's capacity to function as a vehicle at precisely the time in which it was most critical that the vehicle be able to function as a vehicle. This fact will absolutely reduce enthusiasm for the concept without significant financial incentives.

    The idea behind V2G is that owners will happily allow their vehicle to cycle the battery: fast charging and fast discharging half of the battery while the car remains parked. The impact on the battery life for rapid cycling may not be well characterized, but we know that it is 100% negative - it absolutely will decrease the longevity of the battery, though we don't know how quickly it will decrease the life of the battery. If the battery costs ~$15,000, how much will the power company have to offer the prospective owner of the battery to cut 30% of its lifespan? What about 40% of the lifespan?

    For a Leaf owner, if you assume the natural battery longevity is 10 years, and this V2G insanity will shorten the lifespan to 7 years, we can run the following assumptions:

    The average Leaf owner will show up to work having depleted 30% of their battery from their commute, meaning that they have 20% left to donate back to the grid for half-V2G. That's 4.8 kWh. For reasons that we'll get into later, it's highly unlikely that any given vehicle will charge or discharge energy at a rate greater than ~3 kW from work, and less from home.

    Raw Economics:

    Assuming they contribute 4.8 kWh, recharge 10 kWh, and then again contribute 10 kWh to the grid every weekday, and contribute 12 kWh during the highest demand every weekend day for 7 years, you have the following completely unrealistic scenario where a Leaf owner will donate critical excess capacity during ultra-peak demands on weekdays totaling 27.01 MWh, while drawing a less critical 18.25 MWh from the grid during peak hours on weekdays; and on weekends the total amount donated to the grid during peak periods would be ~8.76 MWh during that 7 years.

    Economically, the price of "Super Peak" (summertime) critical need energy in CAISO can be as high as ~$300/MWh, while the price of the "peak" energy in CAISO averages ~$100-150/MWh, and the price of off-peak nightly energy hovers ~$50/MWh. (These are hub prices, not final consumer prices - the point here is to analyze the potential gain from the perspective of the power companies). CAISO is far and away the market with the greatest profit potential for V2G.

    If we assume the energy drawn overnight has a value of $50/MWh, the energy drawn during non-critical peak hours on weekdays has a value of $100/MWh, the energy contributed during peak hours on weekdays has a value of $300/MWh, during 4 months of the year and the energy contributed during "peak" times on weekdays for the rest of the year has a value of $150/MWh, then assume that the energy contributed during the peak times during the weekend has an average value of $100/MWh… we get a total value of the vehicle's contributions equaling $6,276.00, and a total value of the withdrawals equaling $2701. That leaves a profit of ~$3575.00 for the power company… which seems like a tough profit consideration if they have to convince an EV owner that will lose some use of his/her vehicle and lose 30-40% of the lifespan of a $15,000 battery. But this very sloppy back-of-the-envelope calculation was done assuming that every kWh that was sold for free and every kWh received was contributed for free AND ASSUMING THERE IS NO CHARGING LOSS OR LINE LOSSES.

    Once you factor in a 10% charging loss for all charging overnight, an 8% discharging loss for all discharging, and a 6% line loss for all power sold to the point-of-charge and a 6% line loss for all power received from the point-of-charge… We start getting into real trouble.

    Using the above line loss and charging loss assumptions, now we only have $5427 worth of energy contributed back to the system, and we require $3149 worth of power, for a net profit of only $2278… and we're still sacrificing 30-40% of the longevity of a $15,000 battery.

    Last Mile Transmission considerations:

    The big problem here, however, is last-mile concerns on transmission. It's easy to make big-picture assumptions about the grid as though it had infinite input/output capacity at any point… but that is not the case.

    Most people work in large office towers that have "cubeland" space dedicated to them. If someone in one of those "cubes" decided to bring a dorm-style refrigerator to plug in within their cubical, they would be sharply reprimanded. If 4 people decided to do so on the same floor in the same day, they'd trip the breaker. I have friends who are not allowed to plug in CELL PHONE CHARGERS (~3W) at their cubes due to restrictions on energy draw. This makes sense to people that understand the wiring schematics of the buildings, and know how close any particular breaker runs to the maximum energy transfer level it is allowed. Regardless of how absurd it seems, anecdotes are endless of how a new worker ended up bringing down an entire floor of cubeland by plugging in a coffee pot or radio or something. It's not as though the building had been wired with #30 gage wire or something, but the breaker system had been designed for a certain maximum load, and as more and more desks were squeezed into a space, that load was more quickly approached and surpassed.

    Scale that exact same type of system up, and you get the grid. The power lines running down the street to Doty Scientific Inc have a rated capacity, as do the transformers, and the much smaller lines that connect DSI to the larger lines running down the road. With 4 CNC machines, 10 regular machines, several hundred fluorescent light bulbs, 5 ovens, 2 furnaces, a plug-flow reactor, 1 GC, 2 high-powered magnets in a spectrometer lab, 8 large AC units, 20 computers, and dozens of other low and mid-level power draws, there are many times we may run 50-80 kW (Yes that's a LOT for a small business. Our research is incredibly energy intensive, and we fund that research by manufacturing equipment that is sold internationally.) But even with as much power as we run, a single vehicle being charged at 3 kW would require ~ 6% of our total draw. If we had 5 such vehicles being charged at any given time, we WOULD trip the service limit for the building - something we've never done before.

    A typical small commercial enterprise (say a small clothing store in a small strip mall) might have lights, cash registers, a TV, a fan, and maybe a cell-phone charger for the person behind the register… but have parking for 20+ cars. It's easy to imagine one of these stores might operate comfortably with only an average draw of less than 5 kW. 1 single charging car out front may double their load. If the grid is analogous to a cubeland floor of an office building, then each of these businesses and stores is analogous to a single cube, and each of those EV's might be analogous to something between a personal dorm-style refrigerator.

    In order to adapt to this, the power company will have to re-wire the connection from the buildings to the transmission lines, upgrade the building's service, then upgrade the transmission line capacity for the street and some of the transformers.

    So if your initial reaction to my monetary calculation was "but if we use the cars for frequency regulation (FR) they can cycle hundreds of times during an 8 hour period!), consider that the actual maximum power deliver from the battery of a Nissan Leaf is more than 80 KW… then imagine what that would do to last-mile transmission considerations if several dozen vehicles tried to dump 80 kW back through the meter to the local transmission lines on the same street all at once.

    The transmission upgrades in established regions are so expensive that in some cases that power companies have opted for fixed muli-MWh battery stations to accommodate higher loads just to delay upgrading the transmission capacity!

    Think about it.

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Comments (26)
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  • Clearly explaining the obvious, incomprehensible to trolls. Good job. :)
    8 Jun 2012, 05:28 PM Reply Like
  • > half-V2G... 30%... 20%


    Half V2G doesn't mean half the kWh energy. It means that the vehicle would vary its rate of charging (kW) following a frequency regulation signal -- never discharging, only charging, but varying the rate to benefit the grid.
    8 Jun 2012, 05:48 PM Reply Like
  • Author’s reply » Marketquant,


    V2G has always been a concept of using the batteries in the vehicles to use as a charge/discharge battery for grid storage. Every single paper that I have read on the subject (six papers and countless articles) has mentioned preserving half of the battery for driving functions, while using the other half of the battery's capacity for charge/discharge frequency regulations (hence the name "vehicle-to-grid"). When you used the phrase "half V2G", I therefore assumed this was merely a name change to clarify that half of the battery's capacity would be preserved for driving the vehicle.


    I'm sorry for the misunderstanding.


    If the concept you were proposing was actually just using a smartgrid charger to fluctuate charging rates, much of this post still applies, because in the end you have to get 16-20 kWh into the battery. With slow charging, that takes 8-10 hours. So you can't fluctuate the charging rates without losing the total amount of charge acceptance for the battery during the night.


    If you ramp up the charge rate so that you can fluctuate that charge rate as needed for FR, then you'll run into serious last-mile issues with the power grid, and you'll dramatically increase your battery charge losses.


    So the post still applies, even if I incorrectly defined the concept you were considering. But I am sorry about the misunderstanding.
    8 Jun 2012, 10:43 PM Reply Like
  • > fast charging and fast discharging


    I haven't seen any proposals for doing fast charging or fast discharging in V2G.
    8 Jun 2012, 06:04 PM Reply Like
  • Glen, good to see you publishing. Also, good to match a face to the many comments...
    8 Jun 2012, 06:17 PM Reply Like
  • V2G-half (half of a bi-directional connection) is an awkward and not very popular term -- you'd think that there would be a better name. I don't know if there is another term for it (are they avoiding the "demand response" label?). Nonetheless, the concept of a grid operator controllable distributed load with complete variability between 0% and 100% charge rate seems to be an ideal grid asset.


    The V2G researchers in PJM claim that upgrading from a 25 kVA pole mounted transformer to a 75 kVA would cost around $2000 in their service area (Pepco), and the customer side cost would be around $800 to accommodate a 19 kW car.


    Separately, Aerovironment has presented that 6 ultra-fast 250kW (1.5 MW total) chargers operating simultaneously on a typical 26kV 600-900A local line would use only 5% of the local line capacity.


    Interest in full V2G has faded, probably due to low nat gas prices killing the A/S revenue potential. But the folks involved in analyzing EV deployment seemed to consistently present solutions to potential problems.
    9 Jun 2012, 08:27 AM Reply Like
  • I think they're avoiding the 'demand response' label because they want to pretend that EVs are somehow special and different. In some ways they are (dynamic response, flexibility), and many they're not (ease of integration, basic control guidelines).


    Most of the early work on V2G assumed selling into the primary reserve/FR markets, with totally different economics to what's shown above. The problem is that this market will saturate fairly early. The interesting thing is that you can actually address this market with a uni-directional power flow anyway.


    Grid integration of fast charging infrastructure in most areas where you'd actually want to put one is pretty trivial. The trickiest will be highway rest stops, where it probably makes most sense to just add another MV/LV transformer to serve the new load. At distribution voltages (26kV, as in your example above) an additional MW is almost never a big deal. You don't want it to be the straw that breaks the camels back, obviously, but in most cases it won't be.


    3 Jul 2012, 01:56 AM Reply Like
  • Author’s reply » Nick,


    Along major transmission lines - as perhaps in some cases you'd find following an interstate highway - a MW is doable. In a neighborhood or business park, adding an additional MW of demand would be incredibly difficult to accommodate.


    To put this into perspective... a giant Walmart supercenter big box (>100,000 ft2) averages less than a MW power draw during the day, and less than 1.5 MW during the night. This is more difficult then you are taking into account.


    It is doable off of major transmission lines, but any leader feeding neighborhoods, business parks, shopping centers, whatever... would have a big problem with the sudden addition of a few MW of demand.
    3 Jul 2012, 09:15 AM Reply Like
  • Perhaps the answer is the "Better place" solution in terms of range and ensuring it can be sold back to the grid.
    Do I agree that you could push the breaker for the building? Yes, anything is possible. Should your work provide that if it is going to push the breaker for the building? Absolutely not
    You also have to consider the customer base. If you are an EV owner and have a choice to go to store A (no charge stations) or store B (has a charge station) to get something, You would go to store B because they have an incentive to bring you into the store.
    With that being said, I don't think every single store should have EV chargers, it does not make sense both from the store or from the EV user (i.e. it would be more time consuming to go to McDonalds, Wawa, or Dunkin Donuts, plug in, get the coffee and come back out). I would say the only places of businesses where it would be good would be malls, restaurants, movie theaters, or the like.
    With regards to EV cars using the batteries to provide power during peak, it would be a really tough sell to get any EV owner to do. That's not what the batteries were designed to do. Yes, you can deep cycle and quick charge, and the 85 kwhr Tesla does seem to hold up even after 150,000 miles doing that, but it's very abusive. Asking someone to abuse any of their possessions, for your company's monetary gain is wrong.
    11 Jun 2012, 01:17 PM Reply Like
  • Author’s reply » Dan,


    We clearly agree on vehicle-to-grid. I think several stores and restaurants will have charging stations - in an attempt to lure fans rather than worrying about actual EV owners (the ultimate niche market)... But all of these "charging stations" will be slow, low-power charging - for reasons outlined above.


    There are some fast-charging stations being wired in, but the power is so great for these stations they have to be specifically wired off of major trunk lines in order to not crash the grid. One of those stations would draw more power during peak time frames than the average large neighborhood. So that kind of charger will never be found at your local Walmart. The wiring would be too much of a headache.
    11 Jun 2012, 02:30 PM Reply Like
  • Dan5, since the Tesla S-85 has not even started selling, it is a bit premature to state the battery holds up for 150,000 miles of driving. The battery is warrantied for only 100,000 miles.


    I have not seen any responsible evidence of a Roadster exceeding 100,000 miles. A year or so ago, a German driver was publicized because he had reached 100,000 km.


    I thought I had read he had to replace the battery before reaching 100,000 miles, but can't find the the link. Not much publicity on that.....
    11 Jun 2012, 03:37 PM Reply Like
  • Actually the Model S has in the endurance test. Musk was tweeting about it a while ago. 150,000 miles is alot to do in a few months, so they had to be fast charging it OR have someone there 24/7 (unlikely)



    The warranty for the battery for the 85 kwhr pack is 8 years unlimited miles, and I believe the cut off threshold is 80% of the original charge.

    I believe the warranties are all 8 years and the following


    40 kwhr/ 100,000 miles
    60 kwhr/ 125,000 miles
    85 kwhr/ unlimited miles


    The rumors about it what type of battery is the certain Panasonic cell, which I looked at and can withstand 500 deep cycles and still have 80% charge left**. After 1000 deep cycles it looks like you'll have about 60% left. (note on the 85 kwhr that's around 300,000 miles, and that's if you abuse the batteries). Try running you car to empty and repeating that for 300,000 miles
    ** Caveat is that it is deep cycles and constant "fast charging" which I can not stress enough is very, very very abusive. I expect it to have alot better than 80% after 8 years/150,000 miles
    11 Jun 2012, 05:35 PM Reply Like
  • Have you related the survival rates of the Prius nickel metal hydride batteries as something that migh constitute "responsible evidence"?


    You could probably "find the link" on that.
    2 Jul 2012, 03:34 PM Reply Like
  • So, 120v runs my toaster, 240v my dryer, but 480v EV stations will "crash the grid"?
    2 Jul 2012, 03:39 PM Reply Like
  • Author’s reply » Cogwheeler,


    Line capacity is a concern of total power on the line. Power is measured in Watts (W).


    W = V*A, where V is the voltage, and A is the current.


    The only reason that 480 V was used was to reference the hype revolving around the new 480 V charger, which is supposed to charge the Leaf's 24 kWh battery in 15 minutes - which means the charger is operating at ~100 kW, implying an amperage of ~200 A.


    A TV is usually ~250-400 W, a computer is ~200-500 W, an oven or microwave might be ~1200 W, a large air conditioner might be 1500-2000 W, and a dryer is ~4000-5000 W. Plugging in several 100,000 W chargers into a small region (where we assume current energy demand would not be reduced to accommodate this additional draw) would absolutely overtax line capacities for those regions. Causing local brownouts and blackouts among the residences and businesses that are on the same leader.
    2 Jul 2012, 04:33 PM Reply Like
  • Author’s reply » Cogwheeler,


    Here you seem to misunderstand the significance of the differences between the batteries. Just because the nickel-metal hydride battery has proven itself to be robust, that really offers no information on a completely different battery chemistry and assembly. Not to be rude, but that would be like stating that an LED and an incandescent should have similar life-spans because both technologies use electricity to make light. Different designs will have a serious impact on longevity.


    To be fair, I don't think there's nearly as much of a concern about premature battery failure as others... and I typically factor in the assumption of a 10-year lifetime of moderate use in my calculations, merely because - so long as I'M not the one buying the product - I am happy to assume that it will function as designed. (When I buy the product I expect quite a bit of evidence to that effect, but there's no chance that I would consider an EV within the next two decades regardless... I have not interest in increasing my pollution profile.)
    2 Jul 2012, 04:42 PM Reply Like
  • When you say "station" do you mean "50kW fast charger" or "large cluster of 50kW fast chargers"?
    3 Jul 2012, 02:03 AM Reply Like
  • Author’s reply » Nick,


    In the case of the comment above, I'm talking about single charging platforms in front of each business and/or store.
    3 Jul 2012, 08:48 AM Reply Like
  • The way I understand it is that fast charging is something to be avoided. Once in a while it's ok, but if you do it every day it really does degrade the batteries. Some lithium chemistries you can "cook" the battery over long periods of time, others are worry free, it depends on who makes them, but the average consumer isn't going to know.
    I really don't expect a "fast charging" network to be heavily utilized. I would expect 99% to charge at home and during trips to use camp grounds/other chargers. I believe someone marked out a US coast to coast trip with a Model S which would take 5 days without using superchargers. I would prefer if using a 220 V/40 A draw instead of a 480 V/ 100 A draw because its more gentle on the batteries.
    There is one that can charge in 10 minutes by Lightning car company, which requires a 480 V, 500 Amp draw, probably using a DC and super capacitor configuration (really don't know what they are using) to achieve the kwhr and that chemistry is solid as anything- that battery will last over 100 years
    That's one of the most compelling arguments to get a battery lease agreement with Better Place (1 minute battery swap) for the Leaf, MiEV and Tesla Model S and Model X. Kind of like owning the car, but not the engine in a normal car
    11 Jun 2012, 03:53 PM Reply Like
  • No supercaps - Lightning GT uses LTO batteries. The charger is just a simple AC//DC converter with a fairly high power rating.


    You're on the money with your comment re: limited utilization of fast charge infrastructure. It has to be there for peace of mind and occasional use, but it will be used rarely - except on highways for long trips where you need to size for different duty cycles. Betterplace know that too - that's why the economics of their system still works even with $500k battery swap stations; they don't need to build anything like sufficient for the entire vehicle fleet, just enough to get geographic coverage.
    3 Jul 2012, 02:08 AM Reply Like
  • If your vehicle has a 200-300 mile range and you do the typical less than 40 miles a day of travel I don't see where the big sacrifice comes in letting a small portion of your pack be available for FR and grid support.
    14 Jun 2012, 09:56 AM Reply Like
  • Don't forget about uni-directional V2G. Shedding loads has the same effect as added generation. I don't care if utilities take my charging EV off-line. As long as it is done charging by the time I specify, I don't care when they charge it.


    SAE has added a PLC protcoll to their J1772 recommended practice for EV charging, making implemention of uni-directional V2G pratical and inexpensive.


    16 Jun 2012, 01:28 PM Reply Like
  • GSP - While you said "uni-directional V2G", I think you meant centrally controlled charging, or G2V. V2G seems highly unlikely to be viable; intelligent vehicle charging that can generate regulation income to the owner could be practical.


    "Practical" in the sense of "less-stupid" charging, although I don't believe any charging system on the market has sufficient communications built-in to make it work. "Practical" does not mean EVs themselves will be practical for the overwhelming majority of Americans.
    17 Jun 2012, 09:51 AM Reply Like
  • Many do. Possibly not for the FR market (though I could write the necessary code in two days) but for the secondary reserve timeframe most of the 'decent' system providers - especially Coulomb Technologies - are building in demand management portals for local utility integration.


    The mode 3 charging protocol already has a really elegant method of controlling the precise power level of the onboard charger from the LVL1/LVL2 charger side.
    3 Jul 2012, 02:11 AM Reply Like
  • What about simple network access to charger throttling? Car owners can already remotely access their cars wirelessly, power companies can have the same access to the charger parameters and throttle them up or down as needed. That feature could have an override if the consumer doesn't want to participate and has a need for a certain amount of charge at a specific time. Cost incentives would provide payback for allowing charge throttling.
    17 Jun 2012, 11:55 AM Reply Like
  • It already exists and is deployed with some providers systems. It might not be used today because EVs are still such a small fish from a grid perspective, but it works and will increasingly be used to ensure EVs are operating in valley filling mode when their grid impact becomes significant.
    3 Jul 2012, 02:13 AM Reply Like
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