US Energy Flows

February 16, 2007 2:12 PM

Lawrence Livermore National Lab produces fascinating charts of energy flow in the US (more). More energy use statisitics can be found at the Energy Information Administration.
posted by pombe (30 comments total)

There's a slightly more attractive version of the flow diagram in a recent piece in Science, if you have access to it. I'm really impressed with the information content in the diagram - for instance you can see that most oil (~75%) is used for transportation, and that almost none is used for electricty production. Also fascinating is that energy lost via inefficiencies is slightly greater than useful energy produced from these feedstocks.
posted by pombe at 2:18 PM on February 16, 2007

+-60% of energy is _lost_ ? In distribution ? That's mighty inefficient. Also interesting the 21% of loss coming from transport
posted by elpapacito at 2:23 PM on February 16, 2007

elpapacito -- I wonder if 'electrical system energy losses' reflects the losses through waste heat, not distribution.
posted by JohnFredra at 2:36 PM on February 16, 2007

I assume the electrical system losses are mostly due to waste heat; i.e. the loss is the difference between the energy content of the coal, for instance and the total amount of power reaching the consumer. Similarly, transport losses are probably mostly due to inefficiencies in internal combustion engines.
posted by pombe at 2:45 PM on February 16, 2007

I wonder if 'electrical system energy losses' reflects the losses through waste heat, not distribution.

That dosn't make any sense. How much "Waste heat" does my computer produce? What about a vaccum cleaner, or a fridge?
posted by delmoi at 2:47 PM on February 16, 2007

That dosn't make any sense. How much "Waste heat" does my computer produce? What about a vaccum cleaner, or a fridge?
posted by delmoi at 5:47 PM EST on February 16

Notice how your computer gets hot? Even with the heat sinks, a CPU can get up to 90F. That's not because it's concentrating really hard. Likewise power adapters and motors all get hot.

But a lot is lost in transmission. Power transmission cables do not have zero resistance, and the 50 amp neighborhood transformers that pull the 19kV+ down to 240V gerante some heat and waste too. No free lunch.

I do not think the chart is referring to efficiency of generation, but rather the lost electricity after generation, although those aren't the easiest charts in the world to read.
posted by Pastabagel at 2:57 PM on February 16, 2007

Disclaimer: i am not an engineer, I play one

delmoi: if one machine needs 1 unit of energy to produce 1 unit of work (for instance lifting 1kg one meter away from a surface) and if the said machine actually consumes 1,2 units of energy to do that job, clearly 0,2 have been used in something that isn't the required job.

The 0,2 of energy wasn't "lost", but was transformed in heat (due, for instance, to resistance of the circuit) and you can't get that heat and transform 100% of it back into electricity, which is the kind of energy you need to do the job. Ok you can use the heat to do something else like..heating your room, but you couldn't convert it back with 100% efficiency, so part of it (or all of it) is considered lost.

Similarly consider the wooden chips and pieces from a production..you can recover 100% of it and use it for something else, but you can't convert it back to original wood. So for wood working purposes, it is wasted. You could say "but it still is wood" but you still would need to invent a process to reassemble it back without losing one atom of wood.
posted by elpapacito at 3:05 PM on February 16, 2007

Another way to think about it: Do you expect your (computer/ vacuum cleaner/ etc) to primarily produce heat? No; you expect it to compute, or clean or whatever. Light bulbs are the most notorious example of this; IIRC, 90% or more of energy going into a regular filament light bulb is wasted as heat, with the minority of energy being used to generate light.
posted by boo_radley at 3:07 PM on February 16, 2007

Delmoi raises an interesting point, though -- how do you actually enumerate the amount of energy that's wasted? Is it lots of averages and hand-waving, or is there a better method? Doubly-tough with transportation sector, which is even less of a closed-loop. I'm an engineer, but not a power engineer, so this kind of stuff both intrigues and befuddles me.
posted by JohnFredra at 3:20 PM on February 16, 2007

That's mighty inefficient.

I was waiting for someone to say that.

Folks, there's this little problem. It's called the Second Law of Thermodynamics. It's a real bitch, but we're stuck with it.

But there's also a different principle involved, one I have observed myself as an engineer but never seen formally stated anywhere. It's a pair of truisms (or actually one plus its contrapositive):

All robust systems are inefficient.
All efficient systems are brittle.

And this means that engineers deliberately incorporate inefficiency into critical systems, as a side effect of making them robust. (Not all inefficiency leads to robustness, but all robustness involves inefficiency.)

You can have greater efficiency in our energy system if you're willing to put up with common catastrophic shutdowns of the system. (For instance, widespread multi-day electricial blackouts several times per year.) But most people would not consider that acceptable.
posted by Steven C. Den Beste at 3:34 PM on February 16, 2007 [2 favorites has favorites]

The waste energy is primarily due to the Second Law of Thermodynamics and the limitations of a Carnot heat engine. The best coal fired plants are at best 35% efficient. The distribution losses are small compared to the losses at the generating plant. Automobiles are about 25% efficient. The rest is waste heat to the environment.

What is not shown on the charts is the fact that a significant amount of the useful energy output on the right is directed into the production and transportation of the feedstock fuels on the left. So there should be another arrow that peels off some of the useful energy on the right and feeds back to the left. This means that the net useful energy is even less than depicted.
posted by JackFlash at 3:44 PM on February 16, 2007

I think those electricity losses are counting thermal losses in generation. See the carnot theorem... essentially limiting efficiency of thermal cycle plants to around 60% maximum - often much less than that for peak-operation gas turbines.
posted by anthill at 3:51 PM on February 16, 2007

D'oh!

Who'd have thought a Carnot double post would ever happen...
posted by anthill at 3:51 PM on February 16, 2007

Notice how your computer gets hot? Even with the heat sinks, a CPU can get up to 90F. -- pastabagle.

It gets hot weather or not you have a heatsink. The heatsink helps transfer the heat to the air. It would still be produced without it, just that it would stay in the chip until it melted, or ceased to function.

But that's not the point. With the light bulb, some of the energy is converted into light, and some to heat. With a computer some is converted into heat and some into... what exactly? Nothing, all of the electricity that enters your computer is turned into heat, except for a small amount that is used to signal things, like network packets or video output, but that's a very small amount compared to what's converted into heat.

So the question is, how much of that heat is wasted, and how much of it is "used"? It's not an easy question to answer.

delmoi: if one machine needs 1 unit of energy to produce 1 unit of work (for instance lifting 1kg one meter away from a surface) and if the said machine actually consumes 1,2 units of energy to do that job, clearly 0,2 have been used in something that isn't the required job. -- elpapacito

Right, but what work does a computer do? What work does a vacuum cleaner do? I mean, moving a few grams of dust from the floor into a bag does not require several watts of power? Doing computing, etc. How do you quantify how much of the energy was wasted and how much was "used"?

Electronic devices produce Light (EM), heat, and kinetic energy. But most devices produce only by the time their done. How do you separate "good" heat from "waisted" heat?
posted by delmoi at 4:25 PM on February 16, 2007

How do you quantify how much of the energy was wasted and how much was "used"?

That's my question as well.
posted by JohnFredra at 4:57 PM on February 16, 2007

I was waiting for someone to say that.

Ok you can breathe now ! Damn I saved a life !

Not all inefficiency leads to robustness, but all robustness involves inefficiency

High reliability strictly implies low efficiency , but low efficiency does not imply high reliability ?

That sounds true for system that must produce a continuous, consistent product/service , like providing energy ; there is probably some level of redundancy and increased cost in extra structures needed to make each layer work with at least another.

Somehow roman aqueducts come to mind : gravity is an highly reliable motion "source", but the evaporation process needed to bring water on top of mountains needs an energy source such as the Sun.

Also bike chains, or chains in general : I remember reading somewhere chains transfer most of the energy applied to the front gear to the back gear (and also some new method , not the same as a chain, but more efficient and applied in bikes..damn memory!)

So in theory if we need a work done we could use a very long chain and bring energy from A to B..which would be very reliable, and quite efficient (even if longer chain = greater weight and I guess more energy to move the increasing mass of chain) ; yet by devising methods to "transfer" electricity we realize an "electron chain" that is quite more flexible, probably more reliable and maybe more efficient (when measured against ordinary chain)

----------------

How do you quantify how much of the energy was wasted and how much was "used"?

Let' say you need one gram moved from A to B, all you want is that and nothing more. We don't know how much energy/work is needed to do only this task, but we know that heat is not wanted, as the vacuum cleaner isn't conceived as an heater.

If we can figure out how much energy is needed to "produce" the heat generated by the VC (another form of energy), we can by difference obtain a closer approximation of how much energy is needed to move the gram of dust (knowing the total energy consumption, of course).

That would be an approximation by reduction.

Maybe it's easier to figure out how much energy is needed to move one particle of dust from A to the surface of a screen..and maybe the "closer" we get by subtraction to the amount the more difficult it becomes..maybe it really is like lim (x->+inf) A-x1-x2-x3... = 0 ..but of course we first need to be able to measure such small non-null quantities.

Fascinating subject.
posted by elpapacito at 5:22 PM on February 16, 2007

This chart primarily looks at energy flow in the macro sense. That is, the efficiency of the energy producers -- electric and gas utilities. The assumption as that most of the energy delivered to the customer's home or factory is used for useful purposes inside. If you plug in the numbers from the chart you will see that they make the assumptions that 75% of residential energy is useful and that 80% of industrial energy is useful. It is hard to know how they came up with those assumptions but it is probably a rough guess based on the fact that home furnaces are 60 to 80% efficient and electric motors and refrigerators are 80 to 90% efficient. Things like computers and vacuum cleaners are small contributors.
posted by JackFlash at 5:26 PM on February 16, 2007

All robust systems are inefficient.
All efficient systems are brittle.

LEDs are very efficient and robust.
Incandescent bulbs are very inefficient and brittle.
posted by euphorb at 5:29 PM on February 16, 2007

Someone should dig up the ask.mefi post about the flashlight inside a perfectly reflective sphere. Thermodynamics, again.

A computer consuming power converts ALL of that power to heat. Ditto for light bulbs and TVs. What do you think happens to that light after it leaves your video screen, or lightbulb, or TV? The light impinges on something (mostly your walls and furnitures) and transfers a tiny amount of energy to each. All becomes heat. The only exceptions are those forms of energy leaving the room/house, like light through a window or the aforementioned network signals out your net connection. All insignificant and getting turned into heat outside anyway.

Vacuum? Heat. Clock radio? Heat. Refrigerator? Oh, that's a LOT of heat. If the power's coming into your house and not leaving, or being used to literally raise the altitude of something, it's ALL getting converted to heat.

Thanks pombe for the post. I've seen this before, back in my power generation days, but it's still fascinating to see again.
posted by intermod at 6:03 PM on February 16, 2007

Cars are 25% efficient? I thought the figure was much closer to 1%. Damn, now I have to go and find my cite.
posted by maxwelton at 6:06 PM on February 16, 2007

flashlight inside a perfectly reflective sphere
posted by elpapacito at 6:08 PM on February 16, 2007

these are beautiful diagrams. I have nothing else to say, and I'm sure none of you care that I think this but I feel compelled to say it anyway.
posted by silence at 6:11 PM on February 16, 2007

oh. I thought of something else to say.

Mr. Steven C. Den Beste I think this :

"You can have greater efficiency in our energy system if you're willing to put up with common catastrophic shutdowns of the system. (For instance, widespread multi-day electricial blackouts several times per year.) But most people would not consider that acceptable."

shows a terrible lack of imagination. For instance, here in France we have a system whereby you can sign up for electricity at a discounted rate if you're prepared to put up with a number of "red days" per year. On these red days a little light comes on in your house to warn you that electricity on that particular day is going to be a LOT more expensive (can't remember exactly how much more, but a LOT). So on those days you turn off as much as you can, don't use a washing machine or electric kettle etc. In this way the power system doesn't have to build too much wasteful redundancy into the system because they can limit the demand. It seems to work really well.
posted by silence at 6:39 PM on February 16, 2007 [1 favorite has favorites]

Does anyone know of diagrams like this for other important things, like food, or manufactured goods, or raw materials for goods?
posted by weston at 6:41 PM on February 16, 2007

EuphorB: an LED is not a system.
And all generalizations are subject to minor and unimportant exceptions.

El Papacito: Somehow roman aqueducts come to mind : gravity is an highly reliable motion "source", but the evaporation process needed to bring water on top of mountains needs an energy source such as the Sun.

"Efficiency" is a multi-dimensional concept. Energy efficiency is not the only aspect to it. The Roman aqueducts were energy efficient in operation, but they were designed to carry more water than was absolutely required, and water usage was inefficient. (Some of the water leaked away, and water in excess of need was flushed.) The construction techniques used to create the aqueducts involved substantial overdesign, and thus they cost more than they really needed to. (The fact that some of them are still standing today means they were overbuilt.) And there were other ways in which they were inefficient. Energy is not all there is to it.

Delmoi: Doing computing, etc. How do you quantify how much of the energy was wasted and how much was "used"?

For that we have to make reference to Claude Shannon. Information represents order and order is energy. There's a small but irreducible amount of energy associated with information and the processing of it. Part of Shannon's genius was to realize that this meant that the Second Law of Thermodynamics was a factor in calculating reliability of information processing and communications systems.

To increase reliability you have to use more energy. The less energy you use, the greater the chance of errors -- because errors are Second Law entropy creeping in.

I read somewhere that modern computers operate at several orders of magnitude greater energy levels than is theoretically required. Cellular DNA and RNA processing is vastly more efficient and IIRC is within a factor of 10 of the theoretical limit.
posted by Steven C. Den Beste at 7:08 PM on February 16, 2007

Cars are 25% efficient?

Car engines are maybe 25% efficient. Then there are losses from friction in the drive train and tires, and air resistance. Then you might reasonably consider that transporting the passengers is the intented use, so all the energy spent accelerating the car itself is wasted. Then I suppose you might consider the energy used in building and maintaining the car, refining and transporting the fuel. I wouldn't be surprised if the actual work done was closer to 1% than 25% of the total energy used.
posted by sfenders at 9:15 PM on February 16, 2007

thanks Steven C. Den Beste that was the answer I was trying to formulate.
posted by pointilist at 9:45 PM on February 16, 2007

For instance, here in France we have a system whereby you can sign up for electricity at a discounted rate if you're prepared to put up with a number of "red days" per year. On these red days a little light comes on in your house to warn you that electricity on that particular day is going to be a LOT more expensive (can't remember exactly how much more, but a LOT).

Reminds me of a phenomenom I've heard about. Say you have a factory that produces widgets and requires a lot of electric power to do so - dozens of megawatts. So you build your own generating facilities since at that point it's cheaper than buying from the power company, but you still have a connection to the power company for when your generators break. Then summer hits, and the marginal price of power increases twentyfold. If you're a smart factory, maybe you realize that by shutting down your factory floor for the day and just selling all the electricity you can generate, you make more money than the day's production of widgets would net you.

What I mean by marginal price: most of the power needed on any day is contracted for in advance at some normal rate. When it gets really hot or there's problems on the grid, they'll start trying to buy more power at higher rates. The power contracted for in advance stays at the same price, of course, but the additional power can really cost ten or twenty times more to encourage generating companies to run more expensive peaking units, run base load plants at higher loads at the price of more wear and tear, and the factory thing I just mentioned. The price also depends on the location of the generating facility - a facility in NYC is more valuable on a high load day, because all the wires coming into NYC can't carry anything like NYC's full load. Facilities on Long Island can carry even higher prices, because generally power coming in from outside would hit the congestion both entering and leaving NYC. There's been political wrangling over a cable between LI and Connecticut .
posted by TheOnlyCoolTim at 11:00 PM on February 16, 2007

Folks, there's this little problem. It's called the Second Law of Thermodynamics. It's a real bitch, but we're stuck with it.

Nice cognitive divergence from the point that our domestic transportation system is horribly enegy inefficient in moving stuff around, both notionally and comparatively.
posted by Heywood Mogroot at 11:04 AM on February 17, 2007

And is it really wasted heat? 'cause it's, y'know, inside my house, where I want to be warm.
posted by five fresh fish at 8:17 PM on February 17, 2007