In his post on the potential of our current grid to support electric cars, John McGrath mentioned V2G in passing.
Electric cars (either hybrids or full EVs) have the potential to be a real-life silver bullet. Anyone who advocates for increased use of renewables is inevitably confronted with the problem of intermittency. With wind, the rule of thumb is that if grid energy supplied by wind grows to more than 25-30%, utilities need to spend prohibitive amounts on "spinning reserve" to even out supply.
Well, a nation driving plug-in hybrids makes for a spinning reserve of amazing proportions according to one estimate (PDF), the U.S. fleet would power the U.S. electrical grid seven times over.
What these estimates neglect is the capital costs of the batteries themselves. The assumption seems to be that since car owners have the batteries anyway, the economics can be calculated based on operating costs -- electricity and inconvenience.
But battery cell lifespan is measured in cycles -- charges and discharges. If utilities start drawing on car batteries, they will shorten the lifespan of the battery cells. At current battery prices and cycles, this adds 25 to 80 cents per kWh -- before electricity prices are considered!
Surprisingly, this does not make V2G uneconomic; it just limits V2G value to spinning reserve only, while ruling it out as a practical means of peaking or evening out day-to-day variability by renewable sources.
The key is that both peaking and day-to-day shaping draw on storage capacity frequently. Where the lowest cost extended batteries suitable for electric cars (NiMH) cost about $300 per kWh of capacity and last 500 cycles, for $350 per kWh you can buy large scale Vanadium flow batteries that will last 10,000 cycles. Over those 10,000 cycles you would have to buy 20 NiMH batteries (or 10 LiON at $1,000 each, or 35 lead acid cells).
However, pure spinning reserve is not taken advantage of frequently. It is drawn on in case of failure. So renting capacity infrequently, even at a very high price, makes more sense than owning capacity you almost never use.
In other words, use flow batteries (and pumped storage) for day-to-day shaping of variable renewable electricity, and to replace fossil fuel peaking plants. Use V2G to compensate for equipment failures, seasonal peaking, and unexpected shortages of renewable power beyond what such dedicated storage can compensate for.
You still won't want to use it to compensate for extended shortages. The study cited suggests a fleet of PHEV could provide about eight hours of backup for an entire grid. But part of the fleet is on the road at any one time; you can't draw too deeply on any car, because you compromise the ability of the owner to travel. And even before you reach that point, if you draw down an owner's power so deeply that she starts recharging again in a few hours, you have not gained much -- if the shortage is ongoing.
So V2G would only be useful as true spinning reserve -- to keep the power going in certain types of emergency until a backup, off-line operating reserve can be brought on-line.
This is definitely useful. But it is not the key to making renewables fully dispatchable.
There is a fascinating side point in the V2G article that may well be that key; it proves me wrong about something I'm really happy to be proven wrong about. I will write about it in my next post.
Do we need nuclear and coal plants for baseload power?
Cash for Clunkers brought us ... more clunkers!
Comments
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John McGrath Posted 5:28 am
13 Dec 2006
My immediate thoughts are that a V2G system would have much less lifespan impact on a car's batteries than the actual act of driving it. But on these matters, I do defer to you.
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sunflower Posted 5:44 am
13 Dec 2006
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Biodiversivist Posted 6:02 am
13 Dec 2006
In the end, it all comes down to biodiversity. Help acquire and protect ecological hotspots, give to a conservation organization: http://www.saveourbiodiversity.com
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Biodiversivist Posted 6:11 am
13 Dec 2006
If the PHEV is a design that allows the driver to use batteries or gasoline, then the driver would just have to drive on gas if the battery is too low. A Plug in hybrid would likely have three batteries: one for the 12 volt system (as is the case today), one to assist the hybrid system drive train, and one for pure electric.
In the end, it all comes down to biodiversity. Help acquire and protect ecological hotspots, give to a conservation organization: http://www.saveourbiodiversity.com
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Gar Lipow Posted 6:52 am
13 Dec 2006
More or less proportionally. If draw less power from more batteries you draw down less of battery life, but for more batteries. If draw power from larger cells, you draw down less of battery life, but for more expensive batteries. 25 cents per kWh is really the lowest price you will get drawing from car batteries; with advanced batteries (which you want to use in an electric car) the price can rise above 80 cents per kWh for battery use. (I don't want to think about what the cost would be for drawing down the $20,000 - $30,000 battery pack you have in the Tesla.)
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Gar Lipow Posted 6:55 am
13 Dec 2006
In which case on top of using up the batteries you are indirectly powering your grid on 15% to 20% efficient IC engines. At any rate the main point is you don't want frequent drain of expensive automobile batteries to power your grid.
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Biodiversivist Posted 7:33 am
13 Dec 2006
In the end, it all comes down to biodiversity. Help acquire and protect ecological hotspots, give to a conservation organization: http://www.saveourbiodiversity.com
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scatter Posted 11:11 pm
13 Dec 2006
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Jianguo Xu Posted 12:30 am
14 Dec 2006
Your conclusion, however, is based on the current NiMH battery. Progresses are being made in this direction. As Scatter pointed out, Altainano disclosed that their batteries can last over 15,000 cycles. I am not going to judge Altairnano's credibility. Nor am I going to say that their battery is good enough for PHEV applications. My point is: your point is a very good one on the need for a long cycle life battery. However, we cannot judge future based on the current technology, assuming we will not make the necessary progress.
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Gar Lipow Posted 2:46 am
14 Dec 2006
No, we also can't build infrastructure now based on future breakthroughs. V2G is offered as a proposal for squeezing storage space out of existing technology. Future breakthroughs, though probable, are not relevant to deciding what we should do now.
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amazingdrx Posted 3:02 am
14 Dec 2006
And storage is a minor factor compared to the possibility of using the solid oxide fuel cell/microturbine as both backup generator in electric cars and a distributed generation substitute for baseload power plants.
Check out the fuel cell/turbine and microturbine vehicle power systems in development for the last few years.
http://thefraserdomain.typepad.com/energy/2006/12/why_a_h...
These systems combined could be the inexpensive backup for renewables we really need.
Each vehicle a tiny power plant. Trains, trucks, cars, farm, and construction equipment when parked and plugged into the grid and a biogas or natural gas source could do the job.
100s of millions of distributed, zero emission (with a return line for exhaust gases to cogenerate building heat and feed algae in solar systems) tiny power plants waiting for a computer signal from the local utility company to heat up and go online, with the vehicle batteries only providing a 15 minute backup, with very little discharge and resulting battery life shortening.
Gotta get up to speed Gar. Your negative assesments of renewables based on dated information is not helpful for the changes in energy policy we sorely need.
http://amazngdrx.blogharbor.com/blog
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amazingdrx Posted 3:13 am
14 Dec 2006
What if that were the attitude in the WW2 war production effort? Instead of jeeps, US soldiers would have gone to war with mules?
All the developments that helped win the war radar, computers, nuclear weapons and on and on would not have been pursued. (Well maybe the bomb was not such a great idea)
The fact is that world saving technology is being starved for capital intentionally by monopoly corporate/government influence.
Much of it already proven technology, like the nanotech li-ion batteries and solid oxide fuel cell/microturbines and full spectrum solar PV cells and offshore floating wind/wave power platforms.
http://amazngdrx.blogharbor.com/blog
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Gar Lipow Posted 11:41 am
17 Dec 2006
I want to get away from the false dilemma of waiting for costs to come down, or moving now at horribly high prices. There are cost effective things we could be doing now. Lets start moving on those.
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Jianguo Xu Posted 4:34 am
18 Dec 2006
Assume at mass production the battery cost can be $400/kWH (mass production cost of $250/kWH has been quoted by EPRI for NiMH batteries for EV applications), and we need 20 kWH of capacity. This gives a battery cost of $8,000 per car. At $3/gal fuel cost, this is competitive. Plus, if you use the vehicle for V2G applications, you will have give some credit to the vehicles.
My point is we are not far - all we need is to make the battery long lasting enough. And that may be within our grasp. All what it takes is time and money for the development of the technology.
My understanding is this is a forum for alternative energy solutions. Most of what we are talking about are not yet economical. Therefore, R & D money is needed in areas that are promising. We need to identify them. Besides, the current pricing structure does not price in the environmenal impact of eneryg use. If in future pricing of energy will correctly reflect the true life time cost that includes the environmental and health impact of fuel use, then we will see the economic numbers for these alternative energy solutions much better looking.
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Engineer Posted 10:49 am
21 Dec 2006
Electricity 'grids', such as the Western Electric Coordinating Council (WECC, one of seven such entities in the US), develop operating rules for interconnected transmission systems that all Control Area (CA) operators abide by.
These rules govern such things as reserve capacity. Operating reserves are those generating resources that can be brought on line to take the place of other generating facilities taken off line for scheduled maintenance.
Scheduled, since from a 'cold start', a coal plant (I know, I know, but like it or not, they are out there for some time to come) can take as much as 48 hours to reach full output. Natural gas combustion turbines are faster, but can still require as much as 8 to 12 hours.
Operating reserve requirements are 5% of the overall system capacity for hydropower, 7% for thermal generation.
For unscheduled outages, there is the spinning reserve requirement, which is 50% of the operating reserve, or 2.5% of hydro capacity, 3.5% of thermal capacity.
It is called spinning reserve as it is supposed to be running, ready to be switched into the grid within seconds in case of a sudden, unplanned outage with another generator. Could be fuel problems, mechanical problems or even the loss of the transmission line feeding from the generator, but it needs to be on line, ready to go, not 'gee, maybe we ought to see if this is available'.
Just a little information/clarification.
In theory there is no difference between theory and practice, but in practice there is!
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Gar Lipow Posted 11:37 am
28 Dec 2006
However extensive wind use needs more than spinning reserves; it needs actual storage or backup to subsitute for frequent drop which occur on a daily basis. With PHEV or HEV based on today's batteries this latter use would consume expensive battery cycles.
I'll agree with Jianguo that if V2G was based upon either cheaper batteries, or batteries with so many cycles they would outlast the life of the car then this would not be a problem. And in fact there are many ways such a breakthrough is likely to happen. In the meantime, I hope Jianguo will agree that if we had eggs, we could have ham and eggs, if we had some ham.
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marcus Posted 4:02 am
02 Jan 2007
http://www.udel.edu/V2G/KempTom-V2G-Fundamentals05.PDF
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ffletcher Posted 6:29 am
02 Jan 2007
Planning reserves are now called Reserve Margin and it the amount of capacity needed above that required to meet peak load. Reserve Margin is calculated using probabilities associated with the maximum hourly load in ten years compared with the expected hourly capability in ten years. If one wishes to learn more about this it is called Loss of Load Probablity (LOLP). In general this is about 15%, but can vary considerably. Planning reserves address the capacity associated with planned outages.
Operating Reserves is composed of two types of reserves: Regulating Reserves and Contingency Reserves.
Regulating Reserves are based on the ability of a generator or a group of generators to response to load changes using a standard called the NERC Control Performance Criteria. The actual regulating reserve requirement is determined based on the maximum load change expected on a system within one minute. Regulating Reserves must be under the control of the Control Area computer that balances generation to load on a continous basis.
Contingenecy Reserves are reserves to be applied to the system in the event of a major failure. At least one half of the requirement must be on line and operating, up to one half can be off line but capable of being on line and operating in ten minutes. The spinning portion of Contingency Reserves must automatically respond to a frequency dip. The rate of response to a dip is measured in MW/.1 Hz Deviation and is called frequency basis. The frequency basis is a matter that is still unsettled. Responses are typically measured in time lines based on cycles, where each cycle is 16.67 milliseconds.
During a disturbance the grid generally undergoes a frequency dip, but it is possible for some areas, where there are many generators, to experience a frequency increase. Most inverters can not withstand a frequency deviation and when exposed to a frequency deviation over a certain tight bandwidth shut down.
Because of the complex issues associated with remaining connected to the grid during a major outage I would consider a V2G response that isolates the local load from the grid and serves only the necessary loads in the home the customers choses using the vehicle battery.
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marcus Posted 4:13 pm
03 Jan 2007
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ffletcher Posted 3:15 am
04 Jan 2007
The complex issue is staying connected to the grid during a regional generation and transmission failure. The electrical waveform during such disturbances can be very non-linear and impossible for an inverter to attempt to match. The engineering associated with this issue is called stability analysis. I would not say it is too complex to engineer, just that it is complex.
I see what I forgot to say was that the non-spin portion of the contingency reserve requirement can be met with load reduction. Therefore, by tripping off the load and serving the local home with the vehicle rather than the grid there is a value associated with reserves. It just is not the spin portion. I am not sure going for spinning reserve recognitiion rather than non-spin is worth the extra equipment and engineering that each installation will require.
In a parking structure with 300 to 500 cars I think I may well go through the engineering required.
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sunflower Posted 3:26 am
04 Jan 2007
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Gar Lipow Posted 9:13 am
04 Jan 2007
Yes for spinning reserves, and occasional peak power - exactly what I said.
>http://www.udel.edu/V2G/KempTom-V2G-Fundamentals05.PDF
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Carlos Posted 6:48 pm
22 Jan 2007
I'm a little worried that while we debate the high tech, the low tech may be overlooked.
Firstly, who will ensure that all the BEV's released using no memory effect batteries will all support the same V2G plug? Remember that we need these cars plugged, no matter where they stop. If drivers need to fiddle with adapters, that could be the last straw.
Secondly, I see a small chicken/egg problem. There is no return on the V2G overhead, until V2G is active. V2G won't be active, till there are enough V2G cars in the grid to make it viable. Does anybody know a politician who will actually understand the potential of V2G sufficient to sponsor the kickoff period?
Thirdly, we want users to profit from their battery investment. They are after all, saving the planet. To make money, we need to ensure standard comms protocols between all players - globally! Without standard comms, utilities will be able to lock in owners to a contract for pittance. Think back to when phone numbers were not portable between carriers - same situation.
Make this work!
Carlos, Sydney, Australia.
(Partners in crime, we didn't sign Kyoto either)
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