Electric vehicles could stabilize large disturbances in power grid

November 24, 2014 by Lisa Zyga, Phys.org feature
The stability benefit of additional PEVs increases up to 4%, but degrades rapidly after 7% penetration is reached. Credit: Andrej Gajduk, et al. (CC by 3.0)

(Phys.org) —Today when an electric vehicle is plugged into the grid, it's almost always in charge mode, meaning it consumes power. But it's also possible for an electric vehicle to operate in discharge mode, in which it acts as a giant battery and injects power into the grid when needed. Several recent studies have shown that plug-in electric vehicles (PEVs) operating as vehicle-to-grid (V2G) devices can offer advantages for the grid such as backup power for renewable energy sources, power regulation, and load balancing.

Now in a new study, researchers have found another potential advantage of using PEVs as sources of for the : they can improve stability when the grid is subjected to large disturbances. Large disturbances are caused by a wide range of problems, such as abrupt load changes and line tripping. Among their negative effects, they can damage sensitive appliances and, if not cleared within a specific time, the system may be unable to resume stable operation.

The researchers, Andrej Gajduk, et al., at the Macedonian Academy of Sciences and Arts in Skopje, Macedonia, and other universities, have published a paper on their findings in a recent issue of the New Journal of Physics.

As the researchers explain, the last century saw the rise of two very large energy conversion systems: the electric utility system and the light vehicle fleet (cars, vans, and light trucks). Although the two systems were developed separately, the increase in electric vehicle use means that they will merge at some level in this century. In a sense, all vehicles can be thought of as mobile storage systems, and have a total power capacity that is about 24 times larger than the power capacity of the entire electricity generation system in the US. By 2020, PEVs are expected to account for 1-2% of all vehicles in the US, potentially offering unprecedented benefits to the grid, which itself has essentially no storage.

"The power grid and electrical vehicle fleet are exceptionally complementary; in particular, the electric vehicle fleet can enhance power gird transient stability, which could represent a huge problem as will dominate the future electric power grids," coauthor Ljupco Kocarev, Professor at SS Cyril and Methodius University in Skopje, Macedonia, and at UC San Diego in the US, told Phys.org.

In the new study, the researchers developed a control strategy in which PEVs regulate power to the grid by rapidly responding to large disturbances. In a simulation of the New England power system, 50,000 PEVs (representing 1% of all light vehicles in New England in 2020) each has the ability to exchange electricity with the grid at a maximum rate of 10 kW.

With the use of dedicated, high-speed, high-bandwidth Ethernet cables, the PEVs can receive information from generators within 10-20 milliseconds. A decrease in the turbine speeds at the generators signals a power shortage, and so the PEVs are instructed to feed additional power to the grid, essentially acting as small back-up generators. An increase in the turbine speeds indicates surplus power in the grid, causing the PEVs to consume the excess power. In order to be effective, the PEVs should respond as quickly as possible without overreacting.

The results of the simulations show that PEVs can improve stability in two ways. First, they can reduce the speed and voltage fluctuations resulting from large disturbances by up to 80%. And second, they can extend the critical clearing times (after which the system will be unable to resume stable operation) by 20-40%. In general, the PEVs can begin to stabilize the grid within seconds of a large disturbance.

While the PEVs provide benefits to the grid, they are not negatively affected themselves. This is because large disturbances are relatively rare, occurring about several hundred times per year. Further, the regulatory actions that follow large disturbances usually last only a few seconds, so that the effects of power regulation on the PEVs' energy reserves are minimal.

Surprisingly, the researchers found that increasing the percentage of PEVs in the simulation improves the stability benefit only up to about 4% PEV penetration. After this point, the benefits level off and then degrade rapidly after reaching 7% PEV penetration. This negative effect is likely due to the PEVs overacting to the disturbance and injecting or withdrawing too much power from the grid. The results suggest that there is a limit to how much improvement can be achieved with this type of control. The researchers plan to investigate further improvements in the future.

"My future plans include developing and testing different control strategies, developing a rigorous framework to study both the steady-state and transient stability of the combined system and electric , and extending research methods to include the electricity market," Kocarev said. "I believe that the V2G concept will enable a paradigm shift with synergistic benefits for the transportation and electricity sectors. Several V2G demonstrations are expected to be finalized in the near future, for example, by 2015 at the Los Angeles Air Force Base."

Explore further: Researchers examining electric vehicles and the power grid

More information: Andrej Gajduk, et al. "Improving power grid transient stability by plug-in electric vehicles." New Journal of Physics. DOI: 10.1088/1367-2630/16/11/115011

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gkam
2.5 / 5 (10) Nov 24, 2014
Cue the skeptics.

Many folk are unaware of the benefits of the new technologies. But they are not really that new, we have been using them in our grid in the West since the late 1970's.

Unable to use electric vehicles, we had a program using the emergency generators in the facilities of our customers, dispatched directly by the utility. In the 1980's.

You folk can do it,too.

Eikka
5 / 5 (6) Nov 24, 2014
Unable to use electric vehicles, we had a program using the emergency generators in the facilities of our customers, dispatched directly by the utility. In the 1980's.


That's really not the same thing.

It takes a minute to spool up a generator, whereas the article is talking essentially about transient instabilities lasting seconds, that would usually not be dealt with because it hasn't been a major problem up until now with the increasing share of renewable power.

They're talking of the kind of disturbance that happened in 2006 in Germany, caused by an overload condition from wind power in the grid, that produced a domino effect by tripping automatic breakers. If there had been some distributed positive/negative capacity to respond within a second, the blackout wouldn't have spread across borders all the way through France and Italy.

Eikka
5 / 5 (5) Nov 24, 2014
Cue the skeptics.


The added complexity and cost to electric vehicles and their charging systems is really unwarranted if the system has the diminishing returns as described in the article.

It's ridiculous to assume that every car owner would also pay to install 10 kW fast charging systems, nor is it likely that the utilities could give them to everybody in the first place.

And since the grid needs much much much more energy storage capacity than electric vehicles can provide, the system would become redundant anyhow.
gkam
2.7 / 5 (9) Nov 24, 2014
Look up the German facility that uses batteries for load and reactance control. It already works, and is cheaper and faster than other methods using rotating equipment.

We could use ultracapacitors and other technologies. But large-scale drops in voltage are very unusual events on transmission lines. You brought up one instance in the use of our technologies. Did Fermi I stop nukes?
gkam
2 / 5 (7) Nov 24, 2014
"And since the grid needs much much much more energy storage capacity than electric vehicles can provide, the system would become redundant anyhow."
--------------------------------------
Show me. Are you assuming we will get all our power from EVs???

gkam
2.5 / 5 (8) Nov 24, 2014
Eikka, do not be afraid of connecting to the utilities, fear this:

http://www.brenna...rn-thing
imido
Nov 24, 2014
This comment has been removed by a moderator.
gkam
1.9 / 5 (8) Nov 24, 2014
"It will not cheap to use car batteries for balancing of grids"
--------------------------------------------------

Compared to what? The engineers and accountants are well aware of the costs, and the costs of other alternatives.

Please understand we will not use a few massive plants in the future, we will use what is available and has free fuel. Customers can be producers, too. It is the ultimate in Capitalism, where you can buy or sell at will and ability, and therefore get the cheapest stuff available, as well.

It also realizes the adage "From those according to ability to those according to need."
imido
Nov 24, 2014
This comment has been removed by a moderator.
gkam
2 / 5 (8) Nov 24, 2014
"We wouldn't need to distribute and store energy at all."
--------------------------------------

When and if that happens we will all celebrate. Meanwhile, we have to work with what we have. And it is sufficient for now, and better as we go, as needs and technologies change.
imido
Nov 24, 2014
This comment has been removed by a moderator.
gkam
2 / 5 (8) Nov 24, 2014
" the cold fusion was found before ninety years already.."

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

Then, do it.
gkam
2.5 / 5 (8) Nov 24, 2014
One of Eikka's complaints was that wind power produced so much power, the system could not handle it. Lots of folk would like to have that problem.

The issue is proper integration.
Shootist
2.3 / 5 (3) Nov 24, 2014
Better if every new home, or housing development came with its own PEM fuel cell, say 15Kw/hr per dwelling. No new large power plants would ever have to be built again.
gkam
2.1 / 5 (7) Nov 24, 2014
Okay, PEM cells need pure Hydrogen. Got a small, cheap and efficient reformer?

Better yet is to use neighborhood-sized solid oxide or molten carbonate or other self-reforming fuel cell technologies.
gkam
1.7 / 5 (6) Nov 24, 2014
But the basic idea of shootist is what will evolve, to augment local PV and wind, leading to self-sufficient "cells" in the grid, able to isolate from common grid problems if needed, but stay connected for normal inter-support.
Enviro Equipment Blog
not rated yet Nov 24, 2014
If the media did a better job of reporting this aspect of electric vehicles then perhaps they would have significantly higher sales. Just a thought.
kochevnik
not rated yet Nov 24, 2014
Better if every new home, or housing development came with its own PEM fuel cell, say 15Kw/hr per dwelling. No new large power plants would ever have to be built again.
Yes there are fuel cells for RVs but the fuel must be very pure. Also do they impede transients as rapidly as chemical batteries?
gkam
2.1 / 5 (7) Nov 24, 2014
Enviro, nobody is set up yet to use them for this. When they do have commercial penetration, we will find a system of charges and balances.

I like it when I am part of my society, part of the grid, part of making things happen, and not just a lump on the couch, dependent on everybody else, usually a Big Money corporation.
gkam
2.1 / 5 (7) Nov 24, 2014
" Also do they impede transients as rapidly as chemical batteries?"
----------------------------------------------

They are not robust, and would use transient protection. The fuel cell would probably be protected by the output stage, the regulator or other stabilizing function. If not, Zeners, spark gaps, MOV's capacitors, or other devices do well.
gkam
2.1 / 5 (7) Nov 24, 2014
Transient protection is an established science. For commercial devices, usually a simple pi filter can be used, two capacitors to ground separated by an inductor. The caps short out any high frequencies, while the inductor impedes changes in current.
gkam
1.7 / 5 (6) Nov 24, 2014
"Transient protection" has been turned into a high art by the guvmunt. When I taught it, we had the folk who protected the equipment at Alice Springs. They were very interested in signal security, and the passing of information through powerlines by equipment use.

At Sandia National Labs in Livermore, the electrical panel covers were welded on, to keep people out. We had to have some welds cut to do measurements the Power Quality and Harmonics class wanted to do.

It takes more than just a shielded isolation transformer.
24volts
not rated yet Nov 24, 2014
I do have one question about doing this. When you buy power from the electric company to charge your car you pay retail for it. Normally when you feed power back into the system from a solar setup etc... The power company does not pay you back retail but only a fraction of it. How is that going to work with this setup? I hope they will pay full retail back or people won't be doing it very long regardless of how much is helps the grid. Nobody is going to want to pay for the same charge multiple times..... I know this sounds a bit silly even asking but I'm sure there are power companies that would try it anyway.
gkam
1.7 / 5 (6) Nov 24, 2014
24V, the real problem is just the opposite. Right now most power companies have to buy it at full retail, making no money on it at all, but having to maintain the system.

What usually happens is the PV-produced power offsets the power coming into the house, until it exceeds it then it makes the meter run backwards. If it is an electronic meter, it will measure kWh produced and that consumed each month, and if you owe, you pay. There is a monthly meter charge. If you make more that month than you use, we all thank you.

I think the power companies can pay less than full price, with some to offset the cost of the system.
gkam
1.7 / 5 (6) Nov 24, 2014
Why should we like PV on rooftops? Because they replace the most expensive and dirty power we have to use, called Peaking Power. That is why it makes sense for societies, and why they originally made utilities pay full retail for it. I expect that to change.
malapropism
5 / 5 (3) Nov 24, 2014
... the cold fusion was found before ninety years already..

I followed your link and read the article. Perhaps you missed (or did not wish to see) the part that read, "After substantial criticisms and further studies, the two researchers [Fritz Paneth and Kurt Peters, who were "first claim to have observed the fusion of hydrogen under pressure to form helium"] withdrew the claim of helium synthesis."
Eikka
5 / 5 (4) Nov 25, 2014
So much banter here.

What usually happens is the PV-produced power offsets the power coming into the house, until it exceeds it then it makes the meter run backwards.


What actually mostly happens is, the PV-producer gets a second meter for the PV system alone and buys the power back from the utility, because the FiT rate at which they have to buy it is higher than the regular rate.

If the power co paid actual market rates for the power, it would fall below profitable because all PV in the area produces at the same time, and increasing supply while the demand stays the same will only lead to decreasing prices - PV becomes unprofitable. Hence the subsidies.

Because they replace the most expensive and dirty power we have to use, called Peaking Power.


Peaking power isn't the dirtiest there is. It's just expensive, and solar power doesn't even coincide with the peak all year round.

You're falling back to your old pattern of hyperbole again.

Eikka
5 / 5 (4) Nov 25, 2014
Look up the German facility that uses batteries for load and reactance control. It already works, and is cheaper and faster than other methods using rotating equipment.


Well, there's newer high speed flywheel systems. Then there's fuel cell and battery systems in Japan, and utilities even in the US have been installing "power conditioners", or battery stations of a couple MWh in trouble areas. The idea itself isn't new and it works - the main problem is just the cost of it, which is why they're hoping to leverage electric cars for it.

You brought up one instance in the use of our technologies. Did Fermi I stop nukes?


Problems in prototype systems aren't really comparable to faults in production systems. Prototypes are expected to fail, which is why you don't put a prototype straight into production.

Our renewable systems however are still prototypes with lots of unsolved issues, like the lack of proper balancing and control, yet we're pushing them out.
EnricM
not rated yet Nov 25, 2014
Cue the skeptics.


The added complexity and cost to electric vehicles and their charging systems is really unwarranted if the system has the diminishing returns as described in the article.

It's ridiculous to assume that every car owner would also pay to install 10 kW fast charging systems, nor is it likely that the utilities could give them to everybody in the first place.

And since the grid needs much much much more energy storage capacity than electric vehicles can provide, the system would become redundant anyhow.


Even if you count the use of such vehicles to power the user's own home and therefore reducing the demand on the general power grid?
Eikka
5 / 5 (3) Nov 25, 2014
Show me. Are you assuming we will get all our power from EVs???


No. I don't know why you would think that?

The grid needs power reserves in the scale of Gigawatt-hours to balance out daily variations in power use and production with renewables, and Terawatt-hours do the same on a monthly scale. Petawatt-hours do to the yearly scale to account for year-to-year differences in renewables output.

Electric cars can provide a couple kWh each in neg/pos balancing without affecting their primary use as vehicles, so given 250 million of them (all cars in the US), the available capacity for balancing is in the GWh scale.

The other problem is, with the average age of vehicles being 11 years, it would take at least 22 years to get to that point even if 100% of new cars sold -today- were electric. It just isn't going to happen in the next 50 years, unless something dramatic and unpredictable happens.

Eikka
5 / 5 (3) Nov 25, 2014
Even if you count the use of such vehicles to power the user's own home and therefore reducing the demand on the general power grid?

The effect is the same regardless of where you inject the power. Reduce consumption or meet demand, same thing.
One of Eikka's complaints was that wind power produced so much power, the system could not handle it. Lots of folk would like to have that problem.


You fail to understand the problem. It's not that the system produces too much power on the whole because on the whole it makes too little, but what it produces it does in unwanted ways.

Imagine if your car's throttle would jam on full about 15% of the time while you're trying to drive it down the highway, and you'd just have to make do with that.

What we currently have is analogous to swerving on to the passing lane at 160 mph just to swerve back to the shoulder a minute later, while everyone else is going a steady 65.
The issue is proper integration.

Indeed.
antialias_physorg
not rated yet Nov 25, 2014
And since the grid needs much much much more energy storage capacity than electric vehicles can provide

They're not talking long term storage. They're talking load balancing.

This part...
In a sense, all vehicles can be thought of as mobile storage systems, and have a total power capacity that is about 24 times larger than the power capacity of the entire electricity generation system in the US.

...would indicate that there is ample room to play with.

The advantage here is that this could be used to bridge the gap between slow reacting storage methods which can be brought online if a drop is for longer periods (e.g. backup powerplants which need some time to rev up)
Eikka
5 / 5 (3) Nov 25, 2014
Electric cars can provide a couple kWh each in neg/pos balancing without affecting their primary use as vehicles


More on this point:

The renewable systems need more negative balancing than positive balancing due to the tendency to produce power in fits and spurts, so they demand a battery system where you can shove lots of energy in quickly, and then drain it out slowly over time.

To that end, you'd need to dedicate a portion of the EV's battery to be kept empty, let's say 10 kWh off the top, but in doing so you're really just hauling around dead weight most of the time. It will be more cost effective to have that capacity as stationary instead of expensive EV batteries.

Eikka
5 / 5 (3) Nov 25, 2014
They're not talking long term storage. They're talking load balancing.


Yes, but think about it. Once we do have long term storage capacity, we also have so much transient input/output capacity anyways that the electric vehicles are simply not needed for the job, and it makes no sense to go out of your way to equip them with the capability.

These things go hand-in-hand.

We also need the transient capacity to serve a whole fleet of electric cars, otherwise they don't have a hope for quick-recharging en mass without bringing the grid down, and without the ability to scale up the quick-recharging infrastructure there's no hope for electric cars to take over.
Eikka
5 / 5 (3) Nov 25, 2014
..would indicate that there is ample room to play with.


They're referring to as "capacity" the engine/motor power of the vehicles combined, which is a slightly misleading metric.

The advantage here is that this could be used to bridge the gap between slow reacting storage methods which can be brought online if a drop is for longer periods (e.g. backup powerplants which need some time to rev up)


Again, they're talking of sub-second reaction times with a dedicated data infrastructure with a latency below 50 milliseconds to treat extremely fast failures.

The 2006 European blackout started with utilities trying to route excess power from North Germany windmills to South Germany consumers around a cut power line, and in doing so triggered a cascade failure that spread a distance of about 3000 km in just 28 seconds.

Once it enters your grid borders, you have just milliseconds to react to it, and by the time your other backup is online it's no longer needed.
gkam
2.1 / 5 (7) Nov 25, 2014
I have quit debating Eikka on this. But his 50 ms statement is troublesome. Large transmission lines can clear in less than one cycle, which is 16.7 milliseconds. I will explain one instance of a problem. When the lightning strikes the transmission line in Texas, the robots would stop in Louisiana in the GM plant.

Transmission lines at that time used sparkgaps, which are crowbars instead of MOV clamps. that means the voltage is dragged down to zero to quench the flashover. This drags the voltage down on the line, and if any systems are susceptible to it for that short period, they stop. It became a political problem of great magnitude, and SWEPCO called on outside help.

Usually most systems can ride out short losses, before the contactors drop out, as the inductors send power into the circuit as the fields collapse.
gkam
2.1 / 5 (7) Nov 25, 2014
The "fix" for the Urethane Robot in the GM plant was extremely simple once they let me talk to the designer. We increased the ride-through ability of that one machine with a simple change.

The point is, we understand powerline dynamics. We know how to do these things. Please stop bringing up things to complain about.
TheGhostofOtto1923
3.7 / 5 (6) Nov 25, 2014
" the cold fusion was found before ninety years already.."

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

Then, do it.
You make it sound as easy as becoming an engineer. Just 'do it' and poof! youre an engineer.
The "fix" for the Urethane Robot in the GM plant was extremely simple once they let me talk to the designer. We increased the ride-through ability of that one machine with a simple change
-Or poof! a robotics engineer.
Eikka
3.7 / 5 (3) Nov 26, 2014
I have quit debating Eikka on this. But his 50 ms statement is troublesome.


The figure follows the article itself, which speaks of 10-20 millisecond latency for the data infrastructure. I simply assume it takes slightly longer than that to coordinate concerted action.

You should read it.

Of course such a system cannot compensate for lightning, because such effects travel down the line at a speed constrained only by the impendance of the line at a fraction of the speed of light. It doesn't necessarily take even one cycle to propagate, so information of such events cannot transmitted before the event is already over.

What it's good for is rapid transient power changes generated within the power system, by itself, such as large wind farms dropping out of line, or advancing cascade failures.
gkam
1.7 / 5 (6) Nov 26, 2014
Keep on complaining, and we will keep on making the necessary changes to the power systems to get us off most of the dirty fuels. I actually do understand power systems, but do not want to have to explain to you every negative you dig up.

BTW, you come-lately folk to the renewable club are still learning how to control the new technologies. Do not blame it on the technologies.
Eikka
5 / 5 (4) Nov 28, 2014
I actually do understand power systems, but do not want to have to explain to you every negative you dig up


Oh, so you've switched from making ridiculous claims of personal accomplishments to claims of hidden knowledge that is too esoteric to explain.

If you can explain it to me, then I will change my mind. I have no personal attachment to the facts I hold.

BTW, you come-lately folk to the renewable club are still learning how to control the new technologies. Do not blame it on the technologies.


If you "professionals" actually solved all the problems back in the day, then why didn't you share the information? Is it some sort of secret?

Or is it that none of you actually had any experience of these problems because what you were doing with renewables in the day was like a drop in a pool.
gkam
1.5 / 5 (6) Nov 28, 2014
"Or is it that none of you actually had any experience of these problems because what you were doing with renewables in the day was like a drop in a pool."
----------------------------------------

Well, we developed and employed all those technologies, proving the ones which were good, and finding ways to make them better.

What have you done?
kochevnik
not rated yet Nov 28, 2014
The "fix" for the Urethane Robot in the GM plant was extremely simple once they let me talk to the designer. We increased the ride-through ability of that one machine with a simple change
-Or poof! a robotics engineer.
More exactly an EE. EEs work at the circuit level, and often don't know anything at all about the integration efforts in a good robot
gkam
2.1 / 5 (7) Nov 28, 2014
"More exactly an EE. EEs work at the circuit level, and often don't know anything at all about the integration efforts in a good robot"
-------------------------------------

Do you REALLY believe that is true of someone you do not know? Want to discuss the stepper motors and shadow masks? I solve problems of integration, in systems.

In this case, the problem was a four to five-millisecond drop in transmission voltage, which only affected certain sensitive operations, such as the plastic bag plant in the same city, with its DC Motor Drives.

With the bag plant, the remedy was to serve the controls with a ferroresonant transformer to ride out quick drop-outs, keeping the safety systems alive and the systems up. Ferros operate in saturation, rounding out the square wave with large capacitors in the secondary. The large magnetic field feeds its fields into the line when the in put voltage drops, and can sustain a full load for about 4 mSecs.
kochevnik
1 / 5 (1) Nov 28, 2014
Do you REALLY believe that is true of someone you do not know? Want to discuss the stepper motors and shadow masks? I solve problems of integration, in systems.

In this case, the problem was a four to five-millisecond drop in transmission voltage, which only affected certain sensitive operations, such as the plastic bag plant in the same city, with its DC Motor Drives.

With the bag plant, the remedy was to serve the controls with a ferroresonant transformer to ride out quick drop-outs, keeping the safety systems alive and the systems up. Ferros operate in saturation, rounding out the square wave with large capacitors in the secondary. The large magnetic field feeds its fields into the line when the in put voltage drops, and can sustain a full load for about 4 mSecs.
No I don't believe. I directly worked with EEs and they told me exactly what you wrote, which is strictly EE circuit engineering. There were hard problems in robots: integrated motion, vision, grappling
gkam
2.1 / 5 (7) Nov 28, 2014
Wow! REAL EE's???

Look into a computer-operated integrated circuit test system and get back to us.
gkam
1.7 / 5 (6) Nov 28, 2014
An old test system like we used in the early 1970's had an 18-bit M-365 computing Controller, Voltage and Current Sources, and a Measurement System. They were connected to the handlers and probers in a token-ring network using Kelvin connections.

We "spoke" assembly and machine language through them rows of Blinkinlights and their pushbuttons. It was made by Teradyne.
TheGhostofOtto1923
3.3 / 5 (7) Nov 28, 2014
Wow! REAL EE's???

Look into a computer-operated integrated circuit test system and get back to us.
Unlike yourself who was never any kind of engineer. By your own admission.
With the bag plant, the remedy was to serve the controls with a ferroresonant transformer to ride out quick drop-outs, keeping the safety systems alive and the systems up. Ferros operate in saturation, rounding out the square wave with large capacitors in the secondary. The large magnetic field feeds its fields into the line when the in put voltage drops, and can sustain a full load for about 4 mSecs
-The remedy generated by professionals whom you only assisted in some capacity. Is this not true?
gkam
2.1 / 5 (7) Nov 28, 2014
All that above is old stuff, and I am retired. A has-been, perhaps, . . but much better than an onlooker, someone carping from the sideline, the voices from the holes in the fence around construction sites, the critic who never worked with the technology.
TheGhostofOtto1923
3.3 / 5 (7) Nov 29, 2014
All that above is old stuff, and I am retired. A has-been, perhaps, . . but much better than an onlooker, someone carping from the sideline, the voices from the holes in the fence around construction sites, the critic who never worked with the technology.
-But the ditch digger, the maintenance guy knows more about how the building is designed, is that it? You are SO full of shit.

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