March 15, 2010
Smart Charging Stations For Electric Cars

Smart charging stations are coming to market for for recharging electric cars (e.g. Nissan Leaf) and pluggable hybrid electric cars (e.g. Chevy Volt).

This spring, GE will start selling a line of "smart charging stations," devices that communicate with utilities to optimize charging, for electric vehicles. The technology could be key to ensuring that electric cars don't strain the power grid, and it could cut down on consumer electricity bills. Eventually, because the charging stations could help stabilize the grid, they could allow utilities to rely more on intermittent renewable sources of energy such as solar and wind power.

Electric cars recharged with smart charging station will especially make wind more viable since wind is less predictable than sun. For many people once they come home for the evening they might have 12 hours before they start driving again. A smart charging station can communicate with the local electric power utility's load balancing computer and its recharging of a car plugged into it could be started up whenever the wind blows harder. A sudden slow wind period could be compensated for by temporarily halting the recharging of hundreds of thousands or millions of electric cars.

Since most electric car charging will happen at night during the lowest demand period electric cars will also increase demand for the lowest cost baseload electric power generators. If 4th gen nuclear power turns out to be cheap then more nuclear baseload capacity could be built because more demand could be shifted to the off-peak hours by controlling when electric cars get recharged.

What's needed for smart charging to take off: Cheaper electric cars and electric utility regulation that enables a dynamic pricing environment to incentivize interruptible off-peak electric power use.

Share |      Randall Parker, 2010 March 15 10:49 PM  Energy Electric Cars

Brett Bellmore said at March 16, 2010 4:06 AM:

Going to need more than just the power plants, though. It wouldn't take too many electric cars charging in your average neighborhood to overwhelm the last portion of the grid. Which is sized on the theory that most of those houses won't, at any given moment, be drawing more than a tiny fraction of their rated load. Doubtless a smart enough charging station could keep the wires from sagging and the transformers from blowing, but if they did so at the cost of people setting out to work on partially charged batteries, they're not going to be very popular.

grumbles said at March 16, 2010 5:32 AM:

What's needed for smart charging to take off: Cheaper electric cars and electric utility regulation that enables a dynamic pricing environment to incentivize interruptible off-peak electric power use.

And, true to form, we see incumbent power providers starting to bitch about wind power just as it begins to approach economic sense.

Among the cows in Iowa said at March 16, 2010 12:50 PM:

At the end of 2009, Iowa had 3760 MW of wind capacity ( which provided about 15% of the electricity consumed in the state. 879 MW of this was added in 2009.

Iowa has about 1.7 million registered cars and 1.3 million registered trucks ( If all of them were plugged into the grid and could take as little as 1 kW each, they would be able to manage almost any sort of variation in the output of the wind farms. It seems safe to say that this would allow wind generation to go from 15% to 30% without causing problems for the grid.

Brett Bellmore said at March 16, 2010 3:36 PM:

Yes, that would work, if people conveniently charged their cars on a schedule dictated by when the wind was blowing, rather than when they intended to drive their cars. Why do you see that happening? Because electric car owners don't actually plan on USING their cars?

Among the cows in Iowa said at March 16, 2010 6:34 PM:

I do not care how much fuel my car has in it as long as it is enough to get me where I want to go today. If my car filled itself up while I was parked and always had a minimum of 30 miles worth in the tank, I would concern myself with the fuel gauge about once a month. The rest of the time, some fuel-management agency could use the extra capacity in my tank as a buffer for oil deliveries to the terminal.

Doing that would solve a lot of problems. Eliminating underground fuel tanks at gas stations would cut out a lot of cost as well as environmental problems from leakage. The total of the fuel tank capacity of US vehicles, on the order of 4 billion gallons, is much greater than the supply at gas stations. The old story is that if everyone filled up their fuel tank on the same day, every gas station in the nation would be dry. It's true. If the oil companies could deliver directly to people's cars as cargoes of various grades came from the pipeline, they could eliminate all the storage at gas stations and nobody would care.

An electric car that's plugged in can get delivery of electricity at any time. An electric management company can deliver power first to people who need it right away, and not worry about people who have more than their immediate needs. They can charge cars minute by minute as the power comes from the wind farm, and worry about deficits some hours in the future (like overnight). The people willing to wait can get discounts. It is all the same except that the USA has a lot more ways to generate electricity than gasoline, and almost none of them have to be imported.

Brett Bellmore said at March 17, 2010 3:47 AM:

Electric cars don't HAVE excess battery capacity. They won't have it in the future, either, any more than you've got people driving around gas powered cars with 1000 gallon gas tanks: It would be inefficient to carry around the excessively large battery, and expensive, too.

Nope, doesn't work. Not for wind. Maybe, for some people in the right schedule, for solar. But not for wind. Nobody is going to volunteer expensive energy storage they bought for another purpose, just to level load for windmills.

Among the cows in Iowa said at March 17, 2010 8:18 AM:

If the electric car has 100 miles of battery range (GM EV-1), and the driver only needs to go 20 miles before parking and plugging in again, the 80 miles is "excess" for that trip. Even if you keep another 20 miles for emergencies, that's 60 miles of capacity that can be used as a buffer. An EV-1 using 250 watt-hours per mile and holding 40 miles minimum charge level before going out would have 15 kWh of buffer.

Compare this to wind power production. If 1.7 million vehicles averaged even half of 15 kWh of buffer on an average day they would total about 13 GWh, or almost 4 hours of Iowa's wind farms cranking at their full nameplate capacity.

Who said anything about "volunteering"? People who participate will be compensated. Do you have a shopper reward card? Same thing.

RBL said at March 17, 2010 8:53 AM:

Iowa does not get 15% of its electric power from wind. Do not confuse installed capacity with actual Kwh generated. In 2007, for instance, Iowa's windmills only delivered 27% of their nameplate power. Iowa's electricity is mostly generated by coal, which reliably ran at 58% of capacity.
Iowa's one smaller nuclear plant delivered 76% of its rated capacity, although another source claims it's much better.

Among the cows in Iowa said at March 17, 2010 10:15 AM:

You are looking at the wrong page. See

Wind generation in Iowa in 2009: 760 GWh
Total generation in Iowa in 2009: 4272 GWh
Fraction from wind: 17.8%

Iowa's nuclear fraction is well below the national average, and the hydro resources don't make much either. Maybe that can be improved. There is a dam in the middle of town which I am told used to generate electricity, and if there is one I am sure there are more.

Randall Parker said at March 17, 2010 6:16 PM:

Brett Bellmore,

Think about people who go on vacation. They won't drive their 20-50 mile range EV. So it'll stay home for weeks. Well, why not effectively rent it out for load balancing while you are gone?

But even if your EV never provides power to the grid it can help do load balancing by allowing the electric utility to control when it recharges. Other sources of demand fluctuate. Available generation capacity fluctuates - especially if wind provides a significant fraction of all electric power. More EV cars plugged into the grid means more sources of dynamically controllable demand.

Among the cows in Iowa said at March 19, 2010 9:01 AM:

Winds here are 14 knots this morning, and I'm not even in the windy part of the state. Maybe wind farms couldn't supply all of Iowa's lighting, heating, hot water and gasoline-substitute all the time, but they certainly could today.

Nick G said at March 20, 2010 12:24 PM:

Randall, a small quibble:

wind is less predictable than sun

Wind actually has less variance than solar: clouds can have sharp edges, and solar electric output can drop very quickly, much more quickly than wind farm output. I'm not sure about predictability - that's a different animal - but I think you're really thinking about variance here.

Randall Parker said at March 20, 2010 7:12 PM:

Among the cows in Iowa,

You live in a pretty good state for wind. Do you happen to know when it blows strongest and weakest by time of day and time of year?

Nick G,

I take your point. Clouds: Solar has more variance in, say, Florida than in Arizona. States with more clouds will have more variance. Also, the variance depends on time of year. We are coming to the end of the rainy season in SoCal. My guess is we have much less solar variance during the summer months.

Do you happen to know how much insolation varies due to clouds? Very cloudy days can be very dark. But I've never seen it quantified. What percentage drop will there be in PV output?

Another thought: Concentrating solar power is going to show less variance than PV. The rate of conversion of heat to electric power can be controlled in order to buffer the ups and downs.

Nick G said at March 22, 2010 9:52 AM:

Yes, Solar has a lot more variance in Florida than in Arizona - most people don't realize how much cloud cover Florida gets in summer - it's not nearly as sunny as you'd think. One of the reasons so many new immigrants to Florida leave quickly, and why so many people are "snowbirds".

Do you happen to know how much insolation varies due to clouds?

I haven't seen good numbers. It varies by wavelength, by type of PV, and between PV and CSP. Some PV handles indirect/diffuse light better (thinfilm is better than traditional silicon), and PV generally handles indirect/diffuse light much better than CSP.

It's true that thermal storage will help mitigate CSP's disadvantage there.

Among the cows in Iowa said at March 31, 2010 5:48 PM:

No, I don't know the details of the seasonal winds in Iowa. I can tell you that March winds here live up to their name, and winter snowdrifts are also impressive.

The new wind power maps were very favorable to Iowa. Look at the spreadsheet:

Iowa's potential is more than 2 million GWh per year. Iowa generates a bit over 4000 GWh per year. Maybe Iowa could use 5 times as much if it replaced natural gas for heating water, lots of oil for vehicles, and made fertilizer from electricity, and it would still have 100 times as much potential as it can use. It looks like an export market to me.

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