Breaking News
Comments
Newest First | Oldest First | Threaded View
<<   <   Page 2 / 3   >   >>
Wilco1
User Rank
CEO
Re: EVs and the grid
Wilco1   9/11/2013 7:05:45 PM
NO RATINGS
Bert, you are confusing GW (power) and GWh (energy). You can't do 250GWh / 50GW = 5x - those are completely different things! Lets restate my figures using GWh only for clarity:

Actual daily use is about 1050GWh. I assumed 350GWh (33%) extra generation for EV based on existing spare capacity. That allows you to recharge every 8.2 days and drive 11100 miles per year assuming 250 miles per 100kWh charge.

So yes that extra 33% electricity needs to be generated and will of course require extra gas/coal depending on the power generation mix. However the interesting thing is that even if the extra electricity was generated from coal, that still generates less overall pollution and CO2 than using petrol.

When you say "get rid of the battery altogether, as the energy storage medium", what exactly do you propose we use instead? The energy needs to come from somewhere, be sustainable and low carbon, what options are there besides electricity from nuclear, wind and solar? If you use a different storage medium, electricity will need to be converted to that and back. For example generating hydrogen from electricity and then burning it in an ICE is one of the most inefficient things you can do.

Bert22306
User Rank
CEO
Re: EVs and the grid
Bert22306   9/11/2013 6:40:45 PM
NO RATINGS
Oh, as to range, yes, take a look at most claims made by EV manufacturers, and actual tests, and it ends up being in the range I stated. For instance, the relatively new Ford Focus, a claimed range of 76 miles.

And these are all small cars, let's not forget. Compacts, in US terminology. So yeah, I don't buy calculations that depend on your average-sized road hog running 250 or 300 miles on one battery charge.

Bert22306
User Rank
CEO
Re: EVs and the grid
Bert22306   9/11/2013 6:32:59 PM
NO RATINGS
This is what you said:

"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."

And then, you went on to compute how to distribute that 250 GWh to all cars on the road. And concluded that it could be done by "refueling" each electric car just once a month. That sounds like 5X the amount of electricity to be generated, and limiting everyone to one battery charge per month to achieve that.

I understand that all the proponents of battery-powered electrics like to obfuscate the picture, by harping on this "no extra distribution systems needed." That's what I was objecting to. That extra energy comes for something. It's either more coal or natural gas being burned, or more nuclear spent fuel, or more windmills where people complain about them, and so forth.

On the other hand, get rid of the battery altogether, as the energy storage medium, and then we can be rid of all the gimmicks and apologies. EVs don't have to be just battery powered.

Wilco1
User Rank
CEO
Re: EVs and the grid
Wilco1   9/11/2013 6:31:49 PM
NO RATINGS
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.

Wilco1
User Rank
CEO
Re: EVs and the grid
Wilco1   9/11/2013 6:18:10 PM
NO RATINGS
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.

David Ashton
User Rank
Blogger
Re: EVs and the grid
David Ashton   9/11/2013 6:05:53 PM
NO RATINGS
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.

rick merritt
User Rank
Author
Re: EVs and the grid
rick merritt   9/11/2013 6:05:27 PM
NO RATINGS
@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?

Wilco1
User Rank
CEO
Re: EVs and the grid
Wilco1   9/11/2013 5:54:33 PM
NO RATINGS
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!

Bert22306
User Rank
CEO
Re: EVs and the grid
Bert22306   9/11/2013 5:51:09 PM
NO RATINGS
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
User Rank
CEO
Re: EVs and the grid
Wilco1   9/11/2013 5:32:09 PM
NO RATINGS
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!

<<   <   Page 2 / 3   >   >>


EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Glen Chenier

Engineers Solve Analog/Digital Problem, Invent Creative Expletives
Glen Chenier
Post a comment
An analog engineer and a digital engineer join forces, use their respective skills, and pull a few bunnies out of a hat to troubleshoot a system with which they are completely unfamiliar. ...

Max Maxfield

What's the Best Traveling Toolkit?
Max Maxfield
13 comments
A few years ago at a family Christmas party, I won a pocket knife as part of a "Dirty Santa" game. This little scamp was a Buck 730 X-Tract. In addition to an incredibly strong and sharp ...

Rishabh N. Mahajani, High School Senior and Future Engineer

Future Engineers: Don’t 'Trip Up' on Your College Road Trip
Rishabh N. Mahajani, High School Senior and Future Engineer
10 comments
A future engineer shares his impressions of a recent tour of top schools and offers advice on making the most of the time-honored tradition of the college road trip.

Larry Desjardin

Engineers Should Study Finance: 5 Reasons Why
Larry Desjardin
41 comments
I'm a big proponent of engineers learning financial basics. Why? Because engineers are making decisions all the time, in multiple ways. Having a good financial understanding guides these ...

Top Comments of the Week
Flash Poll
Like Us on Facebook
EE Times on Twitter
EE Times Twitter Feed

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)