[sparky]

.
that's the whole issue of base load , peak supply and intermittent supply
while , for the grid , "alternatives" are an engineering abomination ,they can be quite useful in some circumstances

1- in very expensive remote location the right of supply make costs hugely expensive , like running a 10 miles of poles and wires for one little ol lady and her tea kettle .

2- during the summer afternoon peak , solar in Australia present some interesting potential ,

if the world was perfect demand would be the same all the time , one can only dream
while less efficient , some quick turn on auxiliary capacity is needed to cope
think of an assembly line with trucks , there is the permanent pool and , as needed ,the rented ones
nominally more expensive

There is also load shedding , some industry , like mine , can drop production during peak ,freeing some of their cheap electricity requirement and selling it at peak price , we did it a few times and made money while cutting down production

the operators were bitchy as hell , getting a large chemical plant to go up and down like a yo yo make their life more stressful

[KaiserJeep]

OK, the topic seems to be switching to what are called "peaking power plants" such as the gas turbines Newfie mentioned. There is a CALPINE gas turbine peaking plant a little less than two miles from my home. When it is in use there is a vapor plume coming from the stacks, and the smell is barely perceptible - but only when you are straight downwind of the plant. I don't mind it at all.

With the power grid, you really are using the grid as the energy source - but that energy which is both generated and consumed not too far apart geographically is more efficient in the sense that the resistance losses (aka joule losses or ohmic losses) are minimized. The utility interconnects only see the losses due to the surplus of power that one utility is buying or selling from another. The more closely they can match the local demand to the local power production, the less grid power they need buy, thus the investment in those peaking gas turbines.

Of course, the utility-controlled solar PV roofs are also (in a sense) peaking power plants, in that when electric demand peaks, so does solar power production.

[MD]

This has been a great thread, and thanks to Dusi for starting it.

KJ has added some great insight re the grid, and its vulnerabilities. Although I agree that there is an emerging risk of a "grid crash" sometime in the future, I do not agree that it means that power will go off forever after the fact.

More likely we will see segments of the grid decoupling from the whole. Some segments will be down, and remain down. Others will decouple from the super high voltage lines, and go regional.

Getting into some details, and hopefully KJ will chime in here, power transmission occurs in voltage tiers. In simple terms voltage times current equals watts (which is the basic measure of power), and when you are moving power over distance you want voltage as high as possible because current is limited by the diameter of the wires. Voltage is only limited by its ability to jump to ground. The highest level is almost a million volts today. Think of voltage as water pressure. The higher the pressure the more flow you can get, but if it gets too high the pipes burst. (lightning!)

Your household voltage is 220 volts (nominal... 208 to 240... detail gets into delta wye transformation which gets way too gritty for this forum)

Next up the line is 480 3 phase, which is what you find in industrial buildings, and many large buildings. (Canada is 575 volts). One "leg" (a single segment of three phase referenced to ground) of this makes 277 volts, which is used for lighting... more detail.

Then you get 4800 and 7600 volt transmission lines.

It keeps multiplying above that.18000 volts, then 180000 volts, then a half million volts or so. Generally speaking the bigger the towers and the longer the connecting insulators, the higher the voltage.

in order to connect the grid together, each distribution node needs to be synchronized exactly with all the rest. Synchronization is a difficult and highly technical process.

If the grid goes down though, it is very possible for smaller generators to power segments of the grid, by "simply" decoupling key transmission points.

KJ, your turn. I'm done for now.

anyone want to hear about three phase generators and rotating field theory?... I thought not.

ps: three phase rotating electromagnetic fields are amazing. Just amazing. Seriously. The math isn't even that hard. A little algebra and trig, combined into a little vector analysis, and you are good to go.

[MD]

So getting back to Desu's original question: As an end user there is some real value in being fairly close to source power. In the northeast that means Hydro power. In texas that means oil. In the mid Atlantic that means coal. Every where else in the world you need to look at the localized primary source.

78% ff supply as an average across a continental grid means little when faced with grid fracturing.

Grid fracking. Nicely ironic, eh?

Think about it.

[sparky]

.
Think of the grid as a pooling of resources for one area ,
as the voltage of the grid increase the pooled area increase too
any contribution is at their level of voltage , alternative are contributing at the lower single phase 240 Volts
as such they contribute to the very local area
wind is mostly for the local tree-phase distribution
gas turbine generators feed the 10 Kv network
the real heavy plant , basically coal , hydro and nuclear are the backbone , they are very slow to ramp up and down

This is not strictly accurate but this layered cake picture give you a grasp of the problems
for information ,the grid balance hundreds of Giga Watts in 20 milliseconds time frame
a million elephants dancing in step , if more than one go off tempo , everybody crash ,
it take a while to restart

I've watched our High voltage feed fluctuate in the morning as people wake up switch on appliances and lights and take showers , the voltage drop until a new unit is brought on line , in Australia there is a rule that there must be a running backup of the same capacity as the biggest unit on line .

[MD]

$this->bbcode_second_pass_quote('sparky', 'a') million elephants dancing in step , if one go off tempo everybody crash , it take a while to restart

[sparky]

.
Not really , the demand and supply must match , some give and take between zones is necessary , that's one of the big problem in restarting .....synchronicity

[KaiserJeep]

Getting back from shopping and cooking dinner, a couple of things I would add:

1) MD was correct about voltage - the higher the voltage in a transmission line, the lower the losses. But the transmission voltage is a constant once the design is done, as you must purchase and install multi-million dollar transformers for both ends. The transformer near the energy source "steps up" the voltage to the transmission line voltage, the matching transformer at the other end "steps down" the voltage to a lesser value for the smaller, lower voltage transmission lines that radiate away from the "power substation" transformer yard. The practical limits are set by the large ceramic and glass insulators that support the power cables, at some point these begin to suffer from "coronal discharge" which is visible at night as electricity leaks over the surface of the insulator. (Hats off to the iron-willed helicopter pilots and dangling linemen who clean such insulators, not a job I would want.)

2) The power distribution grid is designed to be the entire area-wide grid, and no consideration exists for running grid segments independently. Entire interconnects (one color area on chart #1) are run from central control rooms, via remote controlled high voltage switches, mainly installed at the substations. The system does not easily adapt to being broken into smaller segments, as there exist no control rooms to monitor and operate the switchgear. Yes it is theoretically possible to supply the local area around a power plant with power from that plant, but this is never done - you would first have to sever all interconnects to the larger grid, then take manual control of the switchgear, and then make darned sure that you are not contending with the central control room that will be attempting to bring back the grid as a whole.

Bottom line is that you might live within sight of a functional power plant, but still be denied electric power until the grid is restored in it's entirety - within one of the local colored regions in my first illustration. To make the grid behave differently would cause so much chaos it is unlikely to be attempted.

Best advice: plan to make your own electricity, if you are skeptical that the grid can persist. Residences are certainly the lowest priority loads which means that residences would remain online the least amount of time. Higher priority loads would be hospitals and other emergency services, police, food distribution warehouses, your local supermarket, and major trucking hubs (electricity pumps all fuel at all retail fuel stations).

This is why I am setup to isolate my home from the grid via a "T-bar switch", then power my critical loads via a small generator of 1000w. Five minutes after I do that, if the sun is shining, my rooftop solar PV comes online - after that happens, I can run anything in my house including the furnace and pool pump. Then I do what I need to do while the sun shines, and run my "critical" loads all night on the generator. For me in warm central California, "critical" is my refrigerator, a single electric blanket for me and the wife, and my HDTV. I will let the generator run out of fuel, then get up (wind up alarm clock) and refuel it for preparing breakfast.

I have generator fuel for a week. Never have had a real power outage over 11 hours, and even that was a rare exception event, the 9.0 Loma Prieta earthquake in 1989. Nothing since then has lasted more than three hours.

If I lived in a much colder area, such as the state of Wisconsin where I plan to retire next year, I would still have a generator - a larger LPG-fired water-cooled unit, and you can make darned sure I would have the extra plumbing to run the hot generator coolant through an air handler that would heat my home, versus heating the outside air in the generator's radiator. Waste not, want not.

When I buy my retirement home next year, I will be making plans for an entire season of heat and power and water and sewer, independent of local utilities. The details will vary depending upon where I buy, the goal is as much self-sufficiency as I can reasonably afford.

[sparky]

.
there has been an abundance of example of countries running with a defective , dysfunctional or rationed grid
KJ is right the individual consumers are at the bottom of the priorities , Lebanon during the civil war , bulgaria post communism ...etc ...was heaven for individual generators salesmen ,
for the users , lighting and fridge were the most important , hot water and cooking much much less so
hospital and critical infrastructure have diesel emergency generators as a matter of course and often Uninterrupted power supplies system to bridge the gap until the diesel crank up to full load

[Newfie]

HVDC, eh!

[Pops]

$this->bbcode_second_pass_quote('KaiserJeep', 'W')ith the power grid, you really are using the grid as the energy source - but that energy which is both generated and consumed not too far apart geographically is more efficient in the sense that the resistance losses (aka joule losses or ohmic losses) are minimized. The utility interconnects only see the losses due to the surplus of power that one utility is buying or selling from another. The more closely they can match the local demand to the local power production, the less grid power they need buy, thus the investment in those peaking gas turbines.

[yellowcanoe]

$this->bbcode_second_pass_quote('Pops', '')$this->bbcode_second_pass_quote('KaiserJeep', 'W')ith the power grid, you really are using the grid as the energy source - but that energy which is both generated and consumed not too far apart geographically is more efficient in the sense that the resistance losses (aka joule losses or ohmic losses) are minimized. The utility interconnects only see the losses due to the surplus of power that one utility is buying or selling from another. The more closely they can match the local demand to the local power production, the less grid power they need buy, thus the investment in those peaking gas turbines.

[MD]

$this->bbcode_second_pass_quote('Pops', 'I')sn't it the nature of electricity that those electrons make it to me in larger measure than those from the Columbia? (I realize they don't actually "flow" like water).

Prolly a distinction without a difference.

[Pops]

Yeah, I knew that analogy would confuse things, lol. But lets say that in my little portion of the grid around the hydro station we are more or less supplied. Flip the switch that connects to the grid and nothing changes because we don't "need" that pressure we make our own.

Obviously just theoretical since the interconnects that enable the balancing between producers, transmitters and consumers is part of what make the whole thing work.

[KaiserJeep]

Remember that wires have electrical resistance, measured in units called "ohms". Every energy source on the entire interconnect area is simultaneously producing power, and you are consuming that power in a single location. The lowest resistance circuit is the closest power plant, the second lowest resistance is the one slightly further away. The furthest generator from you has the greatest electrical resistance because of the cumulative total of all the wires in between source and load.

The distribution of the electrical current from all these generators is inversely proportional to the electrical resistance. The source that supplies the most current to your electrical load is the closest one, the source supplying the least energy to the load is the furthest one with the highest resistance.

Since even the major interconnects (the single color areas) are tied together and are busily selling power to each other on the open market, technically the power running your PC or charging your mobile device comes from every generator on the grid - even a few electrons from the furthest hydropower dam that Quebec has online. But you get the most energy from the "closest" generator.

I put "closest" in quotes because the power plant you can actually see in the distance just two miles away might be connected to your house over say a total fifty miles of wire, while one you cannot see might be supplying power through only fifteen miles of wire. From an electrical perspective, you are actually "closest" to the generator with the shortest wiring and the lowest electrical resistance. Even the concept "closest" is not a simple one - a fat wire with twice the cross section of another smaller wire has a lower resistance than a shorter but smaller wire. Copper wires have lower resistance than do aluminum wires. (I better stop talking about the exceptions before I really confuse the audience.)

But YES, you are technically using every active generator in every interconnect, as long as the connections between each area are online, every generator in North America that is connected to the grid is supplying some portion of your power. One of the functions that those control rooms that I mentioned perform is to synchronize all the sources to be "in phase", so that this power sharing is possible.

If we ever have the centralized control of the grid that the "Supergrid" goal calls for, the entire grid will be under a single hierarchy of computer controls, everything from Hoover dam to the reactors on Three Mile Island to the Solar PV panels and electrical inverters at your house. The computers will be dynamically adding and subtracting electrical loads using the "Smart Grid" controls, everything from large manufacturing plants to your individual storage battery or water heater at your home. You would have to look at a monitor - probably run an app on a PC or mobile device, to tell whether you were connected to the grid or consuming power from your own storage battery.

That is, if we have time to implement all this before the lack of fossil fuels trips us up. The greater the interconnections, the greater advantage we gain from power sharing, as long as we can do so in a fashion that makes the entire grid less vulnerable to sabotage, and more - rather than less - resilient.

Edit: These basic concepts are embedded in the two basic formulas of electricity, which are called "Ohms Law" and "Watt's Law". Then there are simple algebraic calculations of parallel and series resistors in circuits, and the way that electrical currents flow in inverse proportion to the resistance. When you touch the probes of a voltmeter to two points in an electrical circuit, you actually are adding another circuit loop, with a very high resistance, through which a minute current flows that you use to "measure the voltage". The meter deflects in a way that is proportional to the total current flow through the high resistance of the instrument, because of Ohm's Law.

[h2]

KaiserJeep, thanks for your very clear explanation. For others who want to get a good overview of how all this stuff works, I suggest:
When the Lights Went Out: A History of Blackouts in America
http://mitpress.mit.edu/books/when-lights-went-out
http://www.amazon.com/When-Lights-Went- ... 0262013746

I came across this a few years back and found it one of the most generally useful books I've ever read to help understanding how large complex systems like grids fail, and why. I believe the overall principles apply just as well to complex systems like computer networked 'clouds' running virtual servers (which function in a very similar way to electrical grids, and also fail in similar ways), as well as probably many other highly complex networked systems we rely on.

KaiserJeep, I knew there was something sensible about you, like Rockman, now I see why.

[KaiserJeep]

One parting thought for all of you.

Today, with an uncomfortable but relatively small number of unemployed people, the cost of copper is rising steadily on the average. People are climbing high tension towers and cutting active high voltage circuits and stealing the copper, which has other uses such as plumbing.

Tomorrow, when the grid goes offline, it will only be a matter of days before there are so many missing wire segments that the grid cannot be restored, ever. As useful as it is, the power grid is a manifestation of relative abundance and cheap power. In tomorrow's world where power is neither cheap nor abundant, the grid goes down and never returns.

We will then be in a sense in a 19th century world again. Need a factory? Build the power plant first. Factories end up next to rivers, wind farms, dams, and very large central solar arrays. The very expensive products that they produce end up costing even more after they have been transported to the consumer.

Residences without their own power sources are dark. You may have power for one or two hours per day as is common in the third world, but only because you and the local law enforcement shoot copper thieves, as the signs plainly say. Recharge all your mobile devices when the power comes on, and your storage batteries that keep your less than 100w of LED lighting going. Dream of the rooftop solar panels that you were not clever enough to purchase TODAY when they are cheaper than they have ever been, and before they get more expensive than they were in the 1960's when refined silicon was worth more than gold.

The best power source you have is conservation, something that pays off in both today's world and tomorrow's. Tear off your old roof, and add 6" of foam insulation before your next re-roof. Don't paint your clapboards again, take them off and add 4" of foam over your already insulated walls, and put them back, with wider corner boards to cover the gaps. Insulate your basement. Upgrade to triple-glazed low-E windows. Tighten up your home against air infiltration. Get your seasonal heating bill down to 1/10th what it costs today, so that you can still afford central heat in a world where energy costs 10X what it does today, and understand that you might have to make all the energy you use yourself.

Fail to take these basic precautions, and you will end up spending the Winter in a tiny space that you can afford to heat. Perhaps it was once a garden shed, or a storage room in your basement. All of your clothes and most of your bedding are jammed in about two feet between the outside wall and a plywood shell you built, makeshift insulation. In the house above, a three foot heap of clothes, mattresses, or dry leaves on the floor above your tiny shelter also insulates. Think of spending six months in about 100 square feet, and cooking and using the bathroom in there as well. Meanwhile, around you unguarded firewood piles vanish, centuries old shade trees are being felled, and vacant houses are being torn up and burnt.

Get the picture? The timing may not be great for you. It probably sucks, in fact. But this is your only chance and I DID WARN YOU.

[Newfie]

Think of it this way, you are sitting on the corner of a chair. Most of you weight is on the left front leg. So the left front leg is mostly holding you up.

Now cut off one of the back legs, you get all wobbly, then if you giggle arouund just a bit, you fall over?

It's a system that pretty much requires all of its parts to function.

[Pops]

You guys are funny. This question is simple, does more of my power come from next door or across the country? I'm not convinced as yet that I get as much from NYC as from the dam next door (even if the power needs to take a 50 mile detour getting here). If I get more from next door is that more than I get from halfway across the country? Outside my NERC region?
LOL, doesn't matter.

Anyway I just found a cool EIA GIS map showing generation plus a bunch of other energy stuff
http://www.eia.gov/state/maps.cfm?src=home-f3

[KaiserJeep]

Indeed, we did PRECISELY answer your question. The answer was that ALL of the generators on the grid contribute power, and those furthest away contribute the least. Beyond that simple concept, you must utilize the simple arithmetic of Ohm and Watt, and the simple algebraic relationships that model parallel circuits and series resistances.

If that doesn't mean anything to you, don't worry, you are in the majority. One of my Physics professors once told me that many people intellectually understand Physics, and did well on many tests. A far smaller group actually applied what they had learned to understand the world around them. From that group come all the Scientists and Engineers and Physics professors.

His exams were all "Real World" word problems that required you to understand, mathematically model reality, and then calculate a solution. The people who did well on these tests were indeed a select minority.