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THE Power Grid Thread (merged)

Discussions of conventional and alternative energy production technologies.

Re: What fuels our power grid?

Unread postby morph » Mon 08 Jan 2007, 11:17:33

if your from the US then
look here

or many european countries
you can look at the spreadsheet on this page
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Re: What fuels our power grid?

Unread postby JRP3 » Mon 08 Jan 2007, 12:10:07

Yes, I'm in the US. Thank you, that's just what I was looking for.
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Re: What fuels our power grid?

Unread postby NeoPeasant » Mon 08 Jan 2007, 12:34:04

I would like to see the results of a poll that shows where Americans think electricity comes from. Too many times I have heard someone speculating that we could solve greenhouse gas problems by running things on electricity instead. I think most people here think electricity is benign and harmless stuff that comes mostly from dams.

Anyone got an idea how many pounds of coal get burnt to produce a kilowatt/hour?
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Re: What fuels our power grid?

Unread postby NTBKtrader » Mon 08 Jan 2007, 13:09:07

Anyone know what the outlook is for nuclear energy? How many plants are being built in the US right now?
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Re: What fuels our power grid?

Unread postby morph » Mon 08 Jan 2007, 13:17:28

$this->bbcode_second_pass_quote('NeoPeasant', 'I') would like to see the results of a poll that shows where Americans think electricity comes from. Too many times I have heard someone speculating that we could solve greenhouse gas problems by running things on electricity instead. I think most people here think electricity is benign and harmless stuff that comes mostly from dams.

Anyone got an idea how many pounds of coal get burnt to produce a kilowatt/hour?


theres a bit on wikipedia about energy density of coal
http://en.wikipedia.org/wiki/Coal#Energy_density
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Re: What fuels our power grid?

Unread postby JustinFrankl » Mon 08 Jan 2007, 14:28:28

$this->bbcode_second_pass_quote('morph', '')$this->bbcode_second_pass_quote('NeoPeasant', 'I') would like to see the results of a poll that shows where Americans think electricity comes from. Too many times I have heard someone speculating that we could solve greenhouse gas problems by running things on electricity instead. I think most people here think electricity is benign and harmless stuff that comes mostly from dams.

Anyone got an idea how many pounds of coal get burnt to produce a kilowatt/hour?


theres a bit on wikipedia about energy density of coal
http://en.wikipedia.org/wiki/Coal#Energy_density

According to the information at Wikiipedia, and some calculations, it takes 0.958 pounds of coal to produce 1 kWh at 30% efficiency (typical for a coal plant). 1 kg of coal yields (net) about 2.3 kWh.
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Re: What fuels our power grid?

Unread postby pea-jay » Tue 09 Jan 2007, 03:08:48

$this->bbcode_second_pass_quote('NTBKtrader', 'A')nyone know what the outlook is for nuclear energy? How many plants are being built in the US right now?


Roughly about zero. When I worked for a utility several years back I asked the same question and followed it up in 2005 when I was in the planning sector. Apparently there is a liability provision that nuclear generators would like to see improved upon before sinking hard cash into getting a permit. Then there is the whole issue of waste disposal. California has banned any nuclear expansion so long as there is no final resting place for radioactive wastes. Cant speak for the other states.

We'll see over the next few years. I'm betting this industry will get a real boost only when the natural gas powered generators blink offline for a want of methane molecules. THen and only then will we get serious about nukes. If ever.
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Re: What fuels our power grid?

Unread postby Loki » Tue 09 Jan 2007, 03:43:17

$this->bbcode_second_pass_quote('NeoPeasant', 'I') would like to see the results of a poll that shows where Americans think electricity comes from. Too many times I have heard someone speculating that we could solve greenhouse gas problems by running things on electricity instead. I think most people here think electricity is benign and harmless stuff that comes mostly from dams.

That's a much better question than the original post, which erroneously assumed a "national grid." We have regional grids, all powered by different combinations of fuels. Here in the PNW, it's mostly hydro, with a mix of gas, coal, nuclear, and a tiny bit of wind and other "renewables" thrown in for good measure. We're also tied into the SW grid, which has a different combo of fuels (mostly nuclear, coal, and hydro I believe).

I'm sure most people have no idea whatsoever where their juice comes from. I asked my mom once---she had no idea. I certainly had no idea when I was growing up. I only know my regional situation because I happened to write my master's thesis on hydropower. I lived here for many years without giving a second thought as to where my juice came from. I flicked the switch, the lights turned on. That's all I knew.
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Re: What fuels our power grid?

Unread postby JRP3 » Tue 09 Jan 2007, 11:51:16

$this->bbcode_second_pass_quote('Loki', '
')That's a much better question than the original post, which erroneously assumed a "national grid." We have regional grids, all powered by different combinations of fuels.


You're talking semantics, as it's often referred to as the national grid. My original question was exactly what I wanted to know, what percentages of what fuels are used to generate power in the U.S. I wasn't interested in the regional differences.
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Re: What fuels our power grid?

Unread postby SchroedingersCat » Tue 09 Jan 2007, 13:38:26

EIA Stats

The EIA is a great resource for all things related to energy.
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Re: What fuels our power grid?

Unread postby jbeckton » Wed 10 Jan 2007, 11:55:33

I don't think people understand at all. How many people think that electric cars would be great becasue they don't pollute the environment? They never stop and think where the electricity comes from.

The bottom line is that the cheapest source is almost always used. That happens to be coal for most of the US.
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Re: What fuels our power grid?

Unread postby morph » Wed 10 Jan 2007, 12:11:12

$this->bbcode_second_pass_quote('jbeckton', 'I') don't think people understand at all. How many people think that electric cars would be great becasue they don't pollute the environment? They never stop and think where the electricity comes from.

The bottom line is that the cheapest source is almost always used. That happens to be coal for most of the US.


agreed, they just think electricity = pollution free

and then when you say where the electricity comes from they say 'oh just put some solar panels on the roof of the car, that could easily power it'
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Re: What fuels our power grid?

Unread postby Starvid » Thu 11 Jan 2007, 11:23:58

No nuclear reactors are currently being built in the US. But there are about 35 being planned.
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Re: What fuels our power grid?

Unread postby Starvid » Thu 11 Jan 2007, 11:28:35

$this->bbcode_second_pass_quote('jbeckton', 'I') don't think people understand at all. How many people think that electric cars would be great becasue they don't pollute the environment? They never stop and think where the electricity comes from.

The bottom line is that the cheapest source is almost always used. That happens to be coal for most of the US.
Even if the electric cars were powered by coal plants they would still be cleaner than the current breed of diesel and gasoline vehicles.

This due to the higher efficiency of the electric car well to wheel life cycle.
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Re: Nation's grid could power almost 185 million electric ca

Unread postby yesplease » Sun 01 Jul 2007, 00:27:11

Whoa, whoa, whoa. First off, the grid is only at ~50% capacity on average, because it's built for peak demand, not consistent demand over a 24 hour period. For instance, even during a summer day that isn't very hot, demand fluctuates from about a half to three quarters of peak capacity. This implies we can supply a significant number of EVs charging at night, since a good chunk of the grid is idle at that time anyway.

Second. We wouldn't need or want to replace even 150 million vehicles with pure EVs. The ones we do want to replace with EVs are those in the city, idling away, using kW's of energy, where just W's would do. ;) In other words, we would target the most inefficient ICE operation, dense urban commutes, for replacement with EVs. So, we replace an inefficient use of oil with an efficient (relatively) use of electricity. The energy needed for the average EV in the city isn't nearly what a ICE powered car uses. Something like ~200Wh/mile from the charger. For instance, while a ICE powered Toyota RAV4 may get 25mpg city, and use ~35kWh to go 25 miles, i.e. 35000Wh/25miles=1400Wh/mil, while the same RAV4 with an electric motor and battery pack only needs ~200Wh/mile. It's much more efficient because gasoline engines are much less efficient during low load operation.

Otoh, there's no point in getting an EV if we have a 100 mile per day highway commute at ~80mph. Just just a Honda Insight and be done with it. :)
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Re: Nation's grid could power almost 185 million electric ca

Unread postby whereagles » Sun 01 Jul 2007, 05:23:30

Actually, efficiency of electricity all the way from steam turbines to outlets is like 35-40% only. While this is still better than an ICE, it isn't so by such large a margin.
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Re: Nation's grid could power almost 185 million electric ca

Unread postby patrick_b » Sun 01 Jul 2007, 06:18:27

$this->bbcode_second_pass_quote('grabby', 'o')ne gallon of gasoline is about 35,000 kilowatt hours I think, if I remember right.
we use 9 million barrels of gasoline a day in the USA
this is about 400 million gallons of gasoline a day.
how many more killowatt hours is that?
400 million time 35 kilowatt hours


More or less ok...

$this->bbcode_second_pass_quote('grabby', 's')o the grid would have to give us 14,000,000,000 more kilowatt hours PER DAY extra to run all our cars.
AND this will come from burning 9 million MOPRE BARRELS OF OIL to supply this electricity...


No, sorry this is wrong... You neglect the fact that electric cars are much more energy efficient than their internal combustion engines equivalents.

If a US citizen scraps its utility vehicule (SUV, sic) and replaces it with an electric sedan, there would be perhaps 3, 4 or 5 times less energy consumed for the same distance driven, specially when doing and go driving. (regenerative braking, no engine idling).

With the amount of money spared on fuels, I think many Americans would install solar panels on their homes simply to lower their electricity bills.

Also electric cars tend to be now less convenient than their internal combustion engines equivalents, meaning that Americans would drive less...

So yes, such a plan would work and I think this is a false accusation to pretend that it was crafted by oil executives.

The problem I see is the following: lowering oil consumption would lower the price of oil which would encourage more oil use elsewhere. But if we assume that supplies will diminush in the future, this is a good plan to avert serious disruptions...
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Re: Nation's grid could power almost 185 million electric ca

Unread postby patrick_b » Sun 01 Jul 2007, 06:49:52

$this->bbcode_second_pass_quote('LGW', 'S')o your gallon of gasoline equals 132 / 3.6 = 37kWh.
Now, put in account that electromagnetic motors have effectiveness grades of 85%+. The internal combustion engine 40%+ if done well.


I agree with your numbers, but this 40% is the peak efficiency of an internal combustion engine. This number is right for a power station that usually runs at a constant optimal speed and load.

But internal combustion engine cars are much much less efficient:
1) Iregular speed and load.
2) An engine in a car almost never runs at peak efficiency.
3) There are big losses in the (automatic) transmission and gear shifting.
4) ICE cars cannot use regenerative braking -> they even consume gas while breaking.
5) ICE used in cars are not designed for maximal efficiency but to have decent power on a wide range of RPM. So their peak efficiency is lower than the ICE of a power station.
6) Much time spent in stop and go traffic.

SO. As far as I know, the real energy efficiency of a normal car is around 10%. We have used ICE cars because gas was extraordinarily cheap compared to other solutions. But these types of cars have the worst efficiency.

Now if you consider a SUV the energy efficiency is even much worse because of the uselessly wide tyres, the terrible aerodynamics and their inefficient and oversized engines.


Then there is another important point to see:
It's easily possible to use the heat generated by power stations to heat homes a few miles around it simply be heating water and making it circulate. Many power plants in Europe do this since the first oil shock in the 70's and buildings around power stations typically don't have a central heating system. Heat from an ICE in a car is always definitely lost.
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Re: Nation's grid could power almost 185 million electric ca

Unread postby yesplease » Sun 01 Jul 2007, 07:38:18

It's actually closer to 15%, but that's kind of a cop-out, because it examines the engine's thermal efficiency w/o looking at the system's efficiency. I.e. we could have a V8 engine in a full size SUV that works way more than a V6 in a full sized sedan, so the average engine efficiency is higher. Otoh, since it's so much larger and not nearly as aerodynamic, it gets worse mileage, but since we're just looking at thermodynamic efficiency, we don't factor this in. An extreme example of this would be comparing a Chebby Corvette at ~70mph to a Chebby Tahoe at ~70mph. Eve though the vette will get nearly twice the mileage, the SUV will have better well to wheel efficiency since it's engine is working so much more. Probably doing the same thing, transporting one to two people with minimal luggage, too...

Hell, we could all drive fully loaded semis to work, and the well to wheels efficiency of our fleet would be ~20-30% compared to the ~15% now. But we'd average ~5mpg versus the ~20mpg. :roll: Otoh, the limited energy capacity batteries have tends to encourage efficient vehicle design, at least from the perspective of range, since it's way more appealing to make a low CdA.Crr vehicle than it is to double the battery pack size/weight/cost.
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Re: Nation's grid could power almost 185 million electric ca

Unread postby PolestaR » Sun 01 Jul 2007, 13:11:18

$this->bbcode_second_pass_quote('Starvid', 'R')ead the link I posted. Plenty of calculation there.

edit: So sorry, posted the wrong link. This is the right one: http://www.peakoil.com/fortopic17736-0-asc-15.html

edit2: I might as well post the core of the argument right here. Enjoy.

$this->bbcode_second_pass_quote('', 'C')onsidering the amount of power needed to run electric cars I think you are a bit off. Let's look at the energy flow diagram posted by jimk.

Image

As you can see transportation is almost entirely powered by petroleum and NGPL. Transportation is 26,5 quads out of which only 5,3 quads are converted to useful energy (ie propelling cars and trains, the rest is waste heat) mirroring the roughly 20 % efficiency of the infernal combustion engine (5,3/26,5=0,2).

Ok, transportation require 5,3 quads of useful energy. Let's say batteries become good enough for electric cars. Then we need 5,3 quads of useful energy to power these cars. Since an electric car has an efficiency of roughly 75 % we will need 5,3/0,75= 7,1 quads of electricity, and since a nclear power plant has an efficieny of roughly 33 % we will need 7,1/0,33= 21,4 quads of nuclear energy.

The current production of nuclear energy in the US is 8,1 quads, so we need roughly 21,4/8,1= 2,64 times as much nuclear energy to supply the electric cars with power.

Since nuclear power supplies 20 % of the US power needs, this would equal a total increase in power generation capacity of 20 %*2,64= 52 %.

A big increase yes, but not at all impossible.

I'd like to add that the above calculation covers all oil powered transportation, including cars, trucks, trains and planes.

It adds up to something like 200-250 new reactors. If we say that we only want to replace cars and light trucks and guesstimate they use half of all transportation oil it means 100-125 new reactors. Not a trivial effort, but very possible as China did twice that in the last three years, except with coal and hydro.


I think you should also factor in battery replacement because they only last a year or two don't they before they need replacement? And we are talking about what, 200-500kg of batteries? Also the growth of transportation to keep "business as usual" is rather interesting, I mean in 2005 the quads for transport were already at 28.1, up from the 26 figure in your calcs.

Either way, the battery tech isn't here yet, so we can't even begin to replace anything but a small portion with EV.
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