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Wanted: Link Between EVs & the Grid

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junko.yoshida
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EVs and the grid
junko.yoshida   9/10/2013 8:38:19 PM
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The State of New York is asking that they are looking for "technologies and strategies that can integrate EVs into the electric grid," 

What sort of specific technologies are needed to integrate the two?

Bert22306
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Re: EVs and the grid
Bert22306   9/11/2013 3:55:29 PM
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Here's a worthwhile project. I haven't seen these numbers cited, but it would be instructive to have them available.

Assuming that all automotive machinery were converted to battery-powered EVs, by how many times would demand on the electric grid be increased?

junko.yoshida
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Re: EVs and the grid
junko.yoshida   9/11/2013 3:57:46 PM
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Hmm, that's a damn good question, Bert. Need to check that out.

Wilco1
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Re: EVs and the grid
Wilco1   9/11/2013 5:32:09 PM
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Well, let's do the calculation. In the UK there is approximately 100GWh spare capacity during the night low. If you use all unused capacity (max is about 55GW, say we use 50GW 24/7), then there is an additional 250GWh per day. This is all existing capacity, no extra power stations, links, storage or anything will be needed - we just use what we already have installed more effectively.

Assume we all have a Model S with a 84kWh battery. Charging it from totally empty to full requires about 100kWh (charger and distribution losses of 16% total). That means you could charge a million cars on the spare night capacity or 3.5 million with the total spare capacity.

There are 28.7 million cars on the road in the UK, so all cars could recharge once every 29 days if only charged at night, or once every 8 days if charged using unused day capacity. Assuming you get 250 miles per charge (instead of the 300 advertised), this implies 3100 and 11000 miles per year respectively. Estimated annual mileage for all 4-wheeled cars in the UK was 8430 in 2010 (this includes business vans so mileage for cars will be lower).

So despite using very conservative estimates, the current UK grid as is can easily handle all cars being converted into EVs. Perhaps a surprising answer - but a result of the much higher efficiency of electric power!

Bert22306
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Re: EVs and the grid
Bert22306   9/11/2013 5:51:09 PM
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Sorry, you missed the point.

Even if there is supposed "capacity" in the grid, that doesn't mean the extra electricity needed comes from nowhere. So what I was asking is, how many times the the current load on the electric grid, would be created if all automotive machinery fed off it?

You claim 5X times as much demand, and even then, this only holds if vehicles recharge once a month!

Oh, I don't buy this 300 mile range propaganda. That might be true, for a handful of types, under absolute ideal conditions maybe. The real-world tests end up showing anywhere from 35 to 60 miles or so. Not quite enough to credibly run your car for a month, at the cost of quintupling the amount of electricity has to be generated.

Anyway, that's the computation people need to see. Not so much these claims about "if everyone plugs in at night only," as if that can be the complete solution.

Wilco1
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Re: EVs and the grid
Wilco1   9/11/2013 5:54:33 PM
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A related question: could I use solar panels on my roof to recharge my car?

The standard size is a 4Kwp panel which in the UK generates about 3000kWh per year. That's 30 recharges of a Model S battery, so you can travel at least 7500 miles using solar power alone. That's very close but not quite enough to cover the average UK annual mileage of 8430. You'd need 4.5Kwp in the UK or live in a country with 10% more sun!

rick merritt
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Re: EVs and the grid
rick merritt   9/11/2013 6:05:27 PM
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@Wilco: I thinbk there is more"energy" going into broad standards and policies for being able to sell rooftop solar energy back to the grid.

Doesn't charging your car from your solar require significant extra costs of energy storage?

David Ashton
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Re: EVs and the grid
David Ashton   9/11/2013 6:05:53 PM
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The fact is that solar power comes just when EVs need it - when most of them will be in company parking lots.   Subsidise companies to install lots of PVs on their roofs and bingo - green EVs.

I appreciate that this is a bit simplistic.  Not all companies have vast warehouse type buildings suitable for PV.  And sales reps, for example, are always in their cars during the day.   But it's horses for courses, and there are some horses for which this course will be very suitable indeed.

And electricity can be easily transported, on existing infrastructure, to where it is needed.  Can someone do the sums to work out what power would be generated if every roof in the country was covered in PVs?  The only challenge is how to use it efficiently - which to a large extent means storing it, in EVs or otherwise.

Wilco1
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Re: EVs and the grid
Wilco1   9/11/2013 6:18:10 PM
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Nowhere did I say 5 times! The extra electricity you need to generate is just 33% for 11100 miles per year for all cars in the UK. However my point is that you don't need to build any new generation capacity for this - it already exists, but as yet is unutilised. This is where a smart grid doing load balancing using EVs becomes interesting.

Any claim that real-world tests show you get only 10-20% of the claimed range requires some serious evidence to back that up - I presume you do have credible links that prove this rather than just making that up?

This is exactly the sort of FUD that one often gets when discussing wind/solar/EV. If you have more accurate numbers (which you can back up with links) then please go ahead and improve upon my calculations.

Wilco1
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Re: EVs and the grid
Wilco1   9/11/2013 6:31:49 PM
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Rick, the way it works is that when your panels produce power, and you are not charging your EV, the electricity will be used by your neighbourhood. As a result power stations do not need to generate what your panels generated. If you recharge at night, extra power needs to be generated. Overall power stations use slightly less gas/coal then they would if you recharged during the day peak. So you can use the grid as "storage" by changing the timing of when electricity is generated. This doesn't cost anything extra, in fact it is cheaper.

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