LONG BEACH, Calif. — Plug-in electric cars could destabilize the distribution of power, a utility executive cautioned at a conference here this week.
Ed Kjaer, director of Southern California Edison’s electric transportation advancement program, said plug-in manufacturers, designers and component makers are poised to capitalize on a “perfect storm” that could push electric cars into the mainstream…
But Kjaer warned that consumer demand for electric cars is still unproven. He also said he wants infrastructure planners to focus on how a flood of plug-in cars would drain the power grid at the most local level…
Chief among those challenges is how thousands of power-hungry vehicles would tax distribution transformers at the local level. Such transformers have historically handled electricity load for about 10 average-size homes each.
Adding a plug-in car to the grid is equal to about a third of a house, Kjaer said. And because early adopters are likely to spring up in geographic concentrations, that could mean overloaded transformers at the distribution level or plug-in cars potentially causing power outages.
“The worst imaginable situation you could have is your neighbor yelling at you because you blacked out the neighborhood,” Kjaer said.
Kjaer is less concerned about transmission or generation being overtaxed, as long as consumers are taught to charge their plug-in cars at night, during off-peak demand periods, to smooth the load. Kjaer said improving distribution is the key infrastructure challenge for utilities, aside from creating a network of charging stations.
“We’re talking about the last 10 feet” between the house and the transformer, he said. “It’s the last 10 or 20 feet that we’ve got to work on. We’re got to work on it really hard, really quickly, because these cars are coming…”
I think you will need to mirror the battery packs in plug-in electric cars with a battery pack in the household garage. That household battery would also help with levelling the load from the household and for downloading off-peak electricity. But all that is a lot of infrastructure. Another alternative is to see if you could design an inductive charging system where the car is parked over a charging coil. You might also consider short term energy storage in an array of ultracapacitors. Perhaps you could include such dual-charge designs for cars if it was feasible.
If you have short term storage in ultracapacitors with a reasonable capacity and a way to charge them inductively while a car is parked over the recharge coils, you could have a series of recharging points on the shoulders of roads and in special parking spots and behind traffic lights where cars typically stop for a short amount of time. The ultracapacitors could be charged very quickly and they could be used either as energy for the journey or they could be used to charge the battery for longer term storage. Recharging accounts could be set up electronically to bill a car owner when they download energy. A car may stop a number of times over these recharge points for a typical trip. GPS systems and onboard computers could let a driver know if they need a quick recharge and where the next opportunities for a recharge will be. Such a recharging regime will avoid many of the problems with plug-in electric vehicles and over time once recharge points are installed everywhere, a car with flat batteries could either be given a shot of charge from a service like NRMA or RACV road side assistance so that they could drive to the next recharge point, or it may be possible to roll the car to the next recharge point. Batteries do deteriorate over time. Such a recharging regime would better suit high capacity transfers of energy rather than having most of the recharging being done domestically. It may be a problem for travelling large distances, but even there, if you decided to have a recharge point every x kilometers on a major highway you could still have a national road system going electric. The recharge points would be static subsystems that are part of the road/road shoulder systems and if they are well designed they should not need regular attendance by service technicians. It should be possible to monitor their quality of service remotely through the smart grid. Such a system would be perfect for the European Union.
The point about inductive charging, if it is feasible for electric cars, is that the driver will not need to leave the car while recharging. With a large short term storage capacity in ultracapacitors it should only take a few minutes for a recharge to take place. Another thing to think about is that once we move to electric vehicles, there will be major efficiency incentives to design cars that are very light and that might have lightweight but strong materials to build the chassis and panels from. A lighter car will have a greater acceleration and will travel a further distance on the same amount of energy compared to a heavier car with a steel chassis and panels.
As an example of what inductive charging is about, the new Palm Pre has an optional inductive charger. I don’t know how suitable it would be for charging EVs but here is another example from Wikipedia.
16 August 2009
Silver Lining Redux
One obvious place to store the ultracapacitors for an electric vehicle is so obvious that it may have been overlooked. The storage capacity of a capacitor is related to the surface area of the plates. Typically, capacitors have a couple of conducting plates very close to each other and with a dielectric to separate them. One way to have a large surface area for the conducting plates is to make them very thin like foil and then roll them up into cylinders. Another option that could work uniquely with electric vehicles, and that was hinted to in the post called Silver Lining, is to have thin layers of flat conducting plates built into the outer panels of the car. You could have many thin layers built up over a large area of a few square meters. You would have to design it so that the stored charge and moving currents do not interfere with anything and it would have to be built with specially designed fuses to neutralise the charge should a panel be ruptured or exposed in an accident. It might be built in a similar way to older integrated circuits with the production consisting of adding layers over layers and having the circuits (or insulating boundaries) etched into the layers. This might hold a surprising amount of energy, and when fuses blow in sync with each other it would ideally be designed so that it would not burn, but so that the fuses would short out the circuit between the oppositely charged plates at many places within a panel simultaneously.
You could also imagine panels used within buildings with a similar storage capacity, and how about having panels of layered ultracapacitors fitted to the base of solar panels. The controlling hardware and software could be an external unit with the solar panels and storage, and other components, plugged into the controller. It would not take up much more space than the solar panels themselves but it would really increase their usefulness to have a local storage capacity. Temperature might be a problem if they were fastened under solar panels.
You would expect these capacitor panels to contain a large number of capacitors that can be charged and then isolated individually and then discharged individually in a controlled way. It could be compared to RAM in a computer, while batteries are more like a form of long term storage like for information on hard disks, if you want to use a computing analogy.