(Caveat lector ... I'm grumpy today...) It seems to me that supercaps are the first thing which needs to be developed for this to have half a chance of going anywhere.
Michel Jullian wrote: > A quick search revealed that the concept of cars selling energy to a > grid already exists --at a wider scale, that of the electrical power > grid, which makes even more sense of course!-- and is called > Vehicle-to-grid (V2G): > > http://en.wikipedia.org/wiki/Vehicle-to-grid > > << > Vehicle-to-grid (V2G) describes a system in which power can be sold to > the electrical power grid by an electric-drive motor of a hybrid > vehicle that is connected to the grid when it is not in use for > transportation.[1] If the car uses batteries for storage it's very hard to believe pushing the power into the car and then sucking it back out again could make sense. The charge/discharge process is far from 100% efficient. Just feel a battery pack which is getting a rapid charge some time -- "cool as a cucumber" doesn't describe it. Supercaps would change this, of course. > Alternatively, when the car batteries need to be > fully charged, the flow can be reversed and electricity can be drawn > from the electrical power grid to charge the battery. Given the ranges of practical battery packs today, the driver's desire to have a fully charged pack is mostly likely going to be "almost always". I don't see that a lot of drivers are going to want to have their battery pack run down, particularly when they've driven down town for the day and will need to drive home again in the evening -- and that's exactly when it'll happen if the socket next to the meter sucks out power from anybody with a full pack. Better batteries, which pushed the range from 100 to 150 miles (for a good current pack) up to, say, 300 or 400 miles (comparable to a gas car with a smallish tank) would change this. But with today's batteries it doesn't seem reasonable to me. > Vehicle-to-grid can be used with such gridable vehicles, this is, > plugin vehicles (this is, electric vehicles as Battery Electric > Vehicles (BEV) or Plug-in hybrid electric vehicles), with grid > capacity. Since most vehicles are parked an average of 95 percent of > the time, their batteries could be used to let electricity flow from > the car to the power lines and back, with a value to the utilities of > up to $4,000 per year per car.[2] Sure, the utilities would find it useful (but note carefully the "up to" clause there -- that implies this is an upper bound, not an expected value). But how about the car owner? When the driver came back to the car and found that it had flat batteries because the utility had need of the power, I don't see that the value to the driver can be anything but negative. And it would seem that that scenario *must* happen from time to time, if the batteries in the cars are actually to be used this way -- driving needs are rarely completely predictable. "But wait!", you say. "How about commuters? They're totally predictable!" No they're not. They're *mostly* predictable, which is very different. Joe signs up for the V2G program, and the Tuesday after that he decides to go out for lunch with a client. Oops, his batteries have been drained, because he wasn't supposed to need the car until 5 PM that day and that morning was a hot one and the utility needed his power ... oh, well, call a cab. > One notable V2G project in the United States is at the University of > Delaware, where a V2G team headed by Dr. Willett Kempton has been > conducting on-going research. Their goals are to educate about the > environmental and economic benefits of V2G and enhance the product > market.[3] Other investigators are the Pacific Gas and Electric > Company, Xcel Energy, the National Renewable Energy Laboratory, and, > in the United Kingdom, the University of Warwick.[4] > ... > Three versions > > V2G is a version of Battery-to-grid power applied to vehicles. There > are three different versions of the vehicle-to-grid concept: > > A hybrid or Fuel cell vehicle, which generates power from storable > fuel, uses its generator to produce power for a utility at peak > electricity usage times. The ICEs used in hybrids are pretty horrible compared to a central generating plant. Do we want to go that route? Ignore the question of whether it's practical; is it a good idea, pure and simple? I would doubt it. If the hybrids were all external combustion closed-cycle steam, or even gas turbines, the story might be different, but reciprocating ICEs are not 'way up there in efficiency and cleanliness. Remember that catalytic converter under the floor -- it's just *throwing* *away* the fuel which the engine failed to burn, because it's easier than getting a reciprocating ICE to burn it "right" to start with. (There's no thermodynamic justification for a catalytic converter!) > Here the vehicles serve as a distributed > generation system, producing power from conventional fossil fuels or > hydrogen. > > A battery-powered or hybrid vehicle which uses its excess rechargeable > battery capacity As I already observed, "excess" rechargeable capacity is a problem the EV manufacturers and owners would love to have. > to provide power to the electric grid during peak > load times. These vehicles can then be recharged during off-peak hours > at cheaper rates while helping to absorb excess night time generation. > Here the vehicles serve as a distributed battery storage system to > buffer power. It isn't off-peak charging that seems unreasonable here; it's the notion that the driver would be happy to have his batteries run down during the day, during *on* peak hours. A consequence would seem to be that you'll need to "sign up" in advance if you want to use your own car, which doesn't seem reasonable. Sunday: "We won't need the car this week, so let's let Edison drain it during the day." "OK, sounds good to me, they'll pay us an extra 50 cents over and above what we paid for the electricity so let's do it!" Following Tuesday: "I'm exhausted; let's go out to a restaurant tonight." "Sure, I hear the Blue Strawberry is really good, let's try that." "Great! Let's go" "Uh, oh, the car's run down, we didn't sign up to use it tonight..." > A solar vehicle which uses its excess charging capacity to provide > power to the electric grid when the battery is fully charged. Here the > vehicle effectively becomes a small renewable energy power station. This seems to me to be the only scenario here which really makes sense. Unfortunately solar panel capacity on an EV is likely to be too limited to be of anything other than academic interest for a system like this. And, of course, if you want to garage the vehicle when it doesn't need to be charging itself (to protect those expensive solar panels, for one thing) that kind of limits the time it'll be spending out in the sun feeding power to the grid. > Such systems have been in use since the 1990s and are routinely used > in the case of large vehicles, especially solar-powered boats....>> > > Going back to the specific EV recharging problem, in such a scheme > what would be needed would be a mains socket at every possible parking > spot, where a car in need of power could draw it from the grid, which > would itself, especially during daytime, be mostly powered by the > other EVs nearby playing the role of distributed buffers. The need for > recharging stations as such disappears, as the cars interface directly > with the grid. > > Of course, smart sockets with bidirectional power metering means and > secure identification means will be needed, this seems to be the first > thing to develop. > > Michel > > 2009/8/14 Michel Jullian <[email protected]>: > ... >> How about a grid wiring all spots on the parking lot? This way (riding >> my soapbox again) the cars with extra energy could sell it back, not >> to individual buyers in this variant, but to the parking lot's grid. >> Wouldn't this be a nice way to implement the huge local storage >> required? > ... >
