Monday, June 14, 2010

The Electric Car Resurrection V: Charging Stations

The biggest issue with electric cars is "range anxiety". Electric cars have a range that is more limited than ICE cars. That would not be an issue if electric cars could be charged up as quickly as ICE cars can be filled with gas. People are used to being able to wait until they are just about out of gas before stopping at a conveniently located gas station, unless they are cruising through Death Valley. With an electric car, it can take anywhere from 25 minutes to 8 hours to recharge, depending on the voltage and current available from the charging station. Most people aren't going to be able to wait 8 hours after running down their 100 mile range Nissan Leaf to zero charge. This will likely take a level of planning most people are unused to, even with iPhone apps with maps of charging opportunities and apps in the car that tell you how much range you have left and whether you could make it to the nearest charging station if you went somewhere.

The simplest solution to the problem is to recharge the car at home. What I do is to simply plug my PHEV Prius into the 110v socket at night, like a cell phone, and let it recharge on cheap, off-peak power. In the morning, it's ready to go again. This type of recharging also works at other places, like a friend's house or overnight at a bed and breakfast, or even downtown at the public library where there are a couple of 110v electric sockets scattered around the garage. After a while, you get proficient at identifying where there are sockets. My wife's employer has two sockets specifically for electric cars that she uses to recharge the Prius. At my employer, on the other hand, the facilities department sent security after me when I plugged the car into an exterior outlet, then put a small sign on the outlet stating that it was not to be used. Oh well.

While overnight charging at 110v 15 amps works for my 5 kwh battery, with a larger battery, such as the Nissan Leaf or Chevy Volt has, the amount of time to recharge on 110v 15 amp would be prohibitively long. Which is why these cars come with a 220v 30+ amp charging station that is installed in your garage when you buy the car (and for which you pay extra). Note that not all houses can support the current load of a high current recharge of this type. If your grid feed is only 100 amps, as many houses are that were build in the 1970's or before, then you won't be able to get an all-electric car without upgrading your grid connection. With the additional current available, an all-electric car like the Nissan Leaf or an gas-assisted electric PHEV like the Volt should recharge in about 5-8 hours, so, again, overnight charging at home works.

This pattern is fine for commuting. But if we want to get away from just using an electric car for commuting, then charging stations need to be essentially everywhere: parking lots, downtown on the street, you  name it. You need to be sure that a station will be available whenever you are in a civilized parking spot (we can leave out Death Valley for now). Not only that, but the car must be able to draw enough current to recharge in a conveniently short time, since people on a 500 mile trip are not going to want to wait 8 hours after driving only part of the way. Making the recharge time the same as it takes to fill a tank with gas is probably too much to hope for, at least initially, but maybe a half hour at most would probably work for many people, especially if the range were high enough, say 200-300 miles like the Tesla. How high would the voltage need to be and how much current are we talking about? Try 400+v at 400 amps, but straight DC instead of AC, and the car would only about half charge in 30 minutes. The conversion to DC happens in the charging station, not the car.

There are a couple startups working on this technology. One is Coulomb Technologies. Their business model is to sell charging stations and the owner then sells the power. Because only utilities, as regulated monopolies, are allowed to sell electricity by the kwh, the charging stations sell power by time. This is a convenient dodge to avoid having the customers of Coulomb be regulated like utilities are. Another startup is 350Green. Their business model is to own the charging stations, install them for free, and cut the property owner in for 5%. Their charging stations also sell power by time, but take time of day and season into account.

Coulomb's model suffers from the chicken and egg problem. As long as there are not lots of electric cars, property owners and municipal governments won't see the economics of buying charging stations. Maybe some gas station owners will install them near areas where there are lots of electric cars, as is the case with E85 fuel. 350Green's model has better economics, though their incentives are a bit slim. Electricity, even during peak times, is about 1/3 the price of gasoline for the same amount of range, so the property owners won't be making much. In any case, there is a technical problem with these fast charging models. Unless the charger contains a large bank of capacitors that charge up slowly to almost the amount of power the car requires, the load on the grid from trying to draw down so much energy over such a short time may cause some failures in transformers and other equipment.

In my opinion, an easier way to solve the problem would be to take advantage of the infrastructure we have. Every street light pole has a small plate near the base the provides access to the wiring. You can see an example here:

What if, instead of installing fancy charging stations, every street light pole was installed with a 110v 15 amp and 220v 30 amp socket? Naturally, this wouldn't take care of drivers going long distances, but it would sure help when you are out driving around on a Saturday afternoon doing errands and need a quick recharge while getting a haircut. The main issue, though, is how to collect money for the power. One obvious way is to put a credit card swipe connected through the cellular network on the pole, and make  people swipe their credit cards. Another would be to have some kind of wireless-based recognition system on the car and pole, and have the pole then charge the car owner through a post-paid plan, like a cell phone plan. There are lots of ways to arrange the charging, municipalities could even sell yearly passes to residents for unlimited power use.

There are probably lots more ways that charging stations could be arranged, but initially, home charging looks like it is most likely to be the initial pattern. This isn't actually so bad, since many families have at least one car that they just use for commuting. If a large majority can be convinced to replace that car with an electric, the impact on carbon emissions will be huge and we'll be well on our way to permanently reducing our collective carbon footprint to where it doesn't threaten the planet.

No comments:

Post a Comment