This is one more attempt to kill a zombie myth: the notion that local generation of renewable electricity can substitute for long-distance transmission. I can see where this comes from -- the sun shines almost everywhere, and the wind blows strong within a few hundred miles of most places where it doesn't, right? If we are going to use renewable electricity at all, it's hard to understand why we wouldn't get it from rooftops, parking lots, or at worst surrounding rural areas.
But if we generate renewable electricity locally (locally being anything from your own rooftop to a wind farm a few hundred miles away), we end up with a huge monthly variation. Even in one of the nation's best solar sites [PDF] you end up with slightly over half the power available in the worst months compared to the best. Wind sites can be worse. For example, the Northfield, Minn. school district recorded a more than a 3 to 1 ratio between best and worst months.
In contrast, if you connected all existing U.S. wind farms [Excel] in a national transmission grid, in 2007 the ratio between best and worst months would vary by no more that 1.7 to 1. Add solar electricity (which tends to be high in months wind is low) and that ratio would be reduced to a 30 or 40 percent difference between best and worst production months. Long-distance transmission can reduce daily variation as well.
In short, a mostly renewable grid without long-distance transmission will cost at least double one that includes such transmission. Note that this applies to rooftop generation and giant solar or wind farms alike.
Q&A
Aren't long-distance transmission lines even more expensive?
Not than doubling or tripling generation. Also very high prices quoted for transmission installation and maintenance conflate transmission and distribution. In the U.S., long-distance transmission costs are about half of distribution. Maintenance is even a smaller percentage. For example, a few years ago Western Washington suffered a major outage where wind storms took down both transmission and distribution. Long-distance transmission was mostly up within 24 hours, whereas distribution was fixed over the course of almost two weeks. Even though transmission is much more expensive to build and repair per mile, distribution requires many times the line miles. Transmission is point to point, or perhaps a few points to a few points. Distribution has to branch out to ever county, municipality, unincorporated area, and ultimately to every home.
Don't long-distance lines reduce reliability?
Not if they are modern High Voltage Direct Current lines. The most common HVDC type installed today actually can help guard against spikes and improve power quality.
Aren't HVDC lines an environmental disaster?
Not compared to coal and natural gas generation. But they can be installed in a much more environmentally benign way than at present. It has been suggested that we use existing railroad rights of ways for long-distance HVDC transmission -- both as part of electrifying freight rail, but also as a way to create a true national grid without harming wilderness. Ultimately we need to remember there is no such thing as zero impact electricity. There is no Kilowatt fairy, no BTU bunny. Efficiency and renewables, including transmission are the lowest impact energy sources we know of.
Won't demand shifting in a smart grid make long-distance transmission unnecessary?
Demand shifting for a few hours or even a day won't compensate for monthly variations in production. Even on a day-to-day basis, long-distance transmission is probably needed to produce a smooth enough production curve for smart-grid demand shifting and electricity storage (including vehicle to grid) to match.
Don't most such variations match local seasonal peaks? That is, isn't wind strongest in winter in cold climates, and sun strongest in summer in hot ones?
If we were just changing electricity supply this would be valid. But climate control has huge potential for both efficiency improvements and non-electrical renewable supplies. Improved insulation, weather sealing, air circulation, along with ground source heat pumps can reduce demand. Direct solar heating (in commercial buildings and multi-unit residences cooling) also has significant potential. Dollar for dollar, these save or provide more energy than renewable electricity. This does not mean we don't need renewable electricity. By the laws of physics, doing more with less won't ever extend to the point where we can get something for nothing. But it does mean that renewable electricity only makes sense in a context where we are also massively investing in efficiency improvements and direct solar heating. These efficiency techniques will reduce seasonal variation in electricity demand.
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Comments View as Flat
Sean Casten Posted 5:13 am
17 Sep 2008
The strawman isn't quite right
I'm not aware of any credible person who argues that the choice is between central and local. Rather, there is a recognition that a regulatory model focused on lowest-cost, lowest-carbon generation would have a substantially larger local bias than the current system, wherein about 92% of all our power (in the US) is generated in remote central plants.
But even if it were possible and/or desirable to build all generation at the load (it isn't), we'd still need a grid to connect those generators together, since a grid of interconnected generators is vastly more reliable than a system where all generators are separate, for obvious reasons. So we still need wires.
If I understand your point right, many renewables (wind, hydro, geothermal and solar) are optimally sighted where the renewable resource is rather than where the load is, and therefore they need wires. On this, I completely agree. The costs of those wires are not insignificant - nationally, they add about $1400/kW of delivered power for transmission + distribution, and even more once you factor in reliability and reserve margin considerations. As such, they need to be factored into the cost of any renewable-intensive grid as we evaluate policy options. But it doesn't de facto mean that we must build wires, or diminish that cost. E.g., we should not start from the assumption that the grid will be 100% renewable, but rather from the presumption that we will clean up our power system as rapidly as is possible given all constraints - financial and otherwise. Where that means that we need to invest in wires to facilitate renewables, let's do so. But let's not simply rush into wires on an "if you build it, they will come" model.
A final point - the need for wires is not the same as a need for new wires. One of the great benefits of any shift towards local capacity is that it frees up capacity on the existing wires infrastructure, and does so in non-linear ways. Putting a kW at the load not only displaces the need for a kW of upstream generation, transmission and distribution, but also reduces the line losses in the system (gaining another 9.5% kicker on average, 22% on-peak) and reduces the reserve margin requirements on the system, since many small generators are more reliable than a few large ones. As such, a combination of a shift to local and renewables is possible with a de minimus investment in T&D.
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Gar Lipow Posted 5:43 am
17 Sep 2008
Renewables
Sean, as far as I know whether we have renewables or not is a choice. No I'm not in favor of building wire without the renewables: otherwise they might be used for transmitting coal or nuclear generation. But if you take seriously the need to reduce emissions by 80% in a 20 year time, then we need to do everything - huge efficiency increases and renewable both. Efficiency by itself is not going to reduce emissions 90% or more. Neither will a renewable dominated grid by itself. So yes, I think we CAN and SHOULD decide we need a renewable dominated grid. The goal is not to get any old reduction, but to get big enough reductions fast enough. And nobody has pointed a way to do that without decarbonizing the grid - at least not without giving up the industrial infrastructure needed for things like antibiotics, lightbulbs and computers.
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Jon Rynn Posted 5:49 am
17 Sep 2008
If the utilities were nationalized, I suppose
this would make it all much easier, no? I know Sean has implied before that nationalizing the grid would make sense, but would be politically impossible. If only the utilities had poured money into subprime mortgages, and were about to collapse, the Feds could take them over!
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Duggles Posted 5:54 am
17 Sep 2008
As an aside...
What does it take to connect a low-voltage DC source to a high-voltage DC transmission line? I'm kinda curious as to how you distribute the power output of a solar array that's putting out sub-1kV power?
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Jon Rynn Posted 6:09 am
17 Sep 2008
Hopefully a propos...
...an interesting article on wind power, geothermal heat pumps, and peak loads, at oildrum, "Wind and Heat pumps: A winning combination"
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greentiger Posted 7:19 am
17 Sep 2008
High V Low Distance DC Lines
Hey Gar,
Do you know any data on the efficiency of these lines (as compared to your typical high tension lines we see all around at present)? (I'm looking for a figure like x% power loss over 100 or 1000 miles)
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Gar Lipow Posted 8:22 am
17 Sep 2008
Efficiency losses
Big picture first. AC lines are more efficient over short distances. HVDC lines are used to push electricity long distances. Over the distances HVDC lines are typically run losses average about 10%, but can vary a lot. Also, as Sean says there is a difference between average, and peak. When you aren't using a line to capacity, when you run much lower voltage than the maximum it can hold, losses are smaller. Over the lengths you actually run HVDC don't think you will ever have average (as opposed to minimum off peak losses) of less than 5%. And as an average that will be rare. Over really long distances you might get long distance losses as high as 20%. That would be doing stuff like moving concentrating solar power from Libya to London. It is unlikely you will every have long distance transmission averaging more much than this, if for no other reason than past that point there are really strong arguments to be made for trading off more generation for less transmission.
====Seperate question - DC to DC.
OK two circumstances. It is very unlikely that rooftop generation will ever be fed directly to long distance lines. Where renewable electricity goes directly into long distance lines it will be wind farms or solar farms or large scale geothermal or whatever. So what if you have a whole bunch of rooftop generation? Well it will be converted to AC and fed into the local grid as now. If there is more than the local grid (and other local grids connected by AC transmission) then the excess power will be converted to DC and fed into DC Lines. This is all hypothetical. And the moment no place in the U.S even approaches the level where that is neccesary, and there are only a handful of DC transmission lines here.
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Colin Wright Posted 9:32 am
17 Sep 2008
If we build it, will they come?
I'm wondering about the chicken/egg problem here. Even Al Gore is only talking about an upgrade to the grid for his 10 year transition.
I wonder too where the most urgent corridors are needed. Pickens of course wants to bring Texas wind north. Could solar in the SE supply and supplement Texas/Dakota wind in the NE? Etc. Do we have that kind of information yet?
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Gar Lipow Posted 10:53 am
17 Sep 2008
where to run the grid
The answer is that the most urgent needed for new wire is as part of railroading.
Alan Drake's proposal
Basically spend 450 billion dollars to upgrade our freight rail system to the point where most trucking traffic can be switched to it. Electrify the most heavily used 20% of this system. Problem for this to happen you need to electrify long swatches of rail which are nowhere near any grid. Solution - use the railway rights to way to add transmission lines. You can make this into a true national grid for not much more than it will cost to just bring electricity to the railroads.
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Jon Rynn Posted 11:16 am
17 Sep 2008
Great! Rail/renewable electricity positivefeedback
Now we can link expansion of the rail network, a critical part of decarbonizing transportation, with decarbonizing (sp?) the electrical grid. They both need to happen together.
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Duggles Posted 11:18 am
17 Sep 2008
Thank you for your answer, Gar.
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vakibs Posted 9:29 pm
17 Sep 2008
Speak out on the real alternative, Gar
Aren't HVDC lines an environmental disaster?
Not compared to coal and natural gas generation.
But this is not we should be comparaing them against ofcourse. The alternative is nuclear energy, especially new models of small reactors such as LFTR.
What is the lesser evil ?
Mining a lot of iron and copper, and dumping all the money of the government to produce an electric superhighway, and forever wasting 15% of the produced energy in transmission losses.
Or some nuclear radiation spill (which is theoretically ruled out by the reactor design, and practically never observed in the USA) lurking somewhere deep in the figments of your imagination.
Let's think in terms of eco-dollars.
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amazingdrx Posted 11:33 pm
17 Sep 2008
Choice
"...a zombie myth: the notion that local generation of renewable electricity can substitute for long-distance transmission."
The fact is that we have no choice. Go local/distributed or don't go at all. Even go individual home or not at all, over the next 10 years.
Do we have the national will or the capital anymore to expand the grid? With distributed smart grid generation and storage the present grid has many times the capacity needed.
And the beauty of renewables combined with distributed smart grid is that individuals can start up the energy revolution. Wait for the collective will to do it or just go for it?
We have no choice. Just go for it. It's nice to think of am HVDC buried super grid follwing electric rail lines and commuter rail in freeway medians, but that maybe decades away.
A few HVDC lines from say the great plains wind farms and southwest solar areas to areas with large industrial loads? That could happen quicker. And maybe start the super grid up.
On the other hand, there is nothing wrong with thinking big Gar, just don't try to claim that thinking small won't get there quicker. Vak's nuclear idea as distributed backup needs a decade or so of testing.
But biogas from waste and local storage doesn't. It'll reliably power backup a renewable home or local or regional grid right now.
And why is superconducting electromagnetic energy storage overlooked? This has huge potential on a shorter time frame than a super grid or distributed nuclear power.
Sean's favorite, cogeneration, using natural gas/biogas could fill in nicely given solid oxide fuel cell/turbine efficiency and local heat use. Every big building or group of buildings could have a cogeneration distributed backup system.
Dies a smart grid mean every home or business will automatically have a backup system? No, but it will make backup systems in individual homes have a short payback period and that will impell investment in them.
Especially for small businesses that can't afford months long power outages, as with Ike. For them it is literally, go with backup or go out of business.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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amazingdrx Posted 11:54 pm
17 Sep 2008
Local would double or triple costs?
Well if you are looking at a 100% renewable energy economy, maybe.
But as the revolution proceeds this is not a problem. As much electricity as any renewable source can generate will gratefully be absorbed by the utility grid, and maybe even payed for if regulation is reformed from net metering to actual payments for investors in renewables.
It's easy to fall into the old "snapshot" fallacy. The notion that somehow the grid could be switched to renewables/conservation overnight.
It's a popular fallacy underlying many anti-renewable talking points.
Instead, this conversion proceeds slowly over decades. And in that reframing to a more realistic transitionary model, homes, businesses, local and regional grids going renewable, in steps and phases, there is more than enough absorption capacity and backup for renewables.
Remember the AWEA claim, up to 20% penetration, wind causes no insurmountable grid instability. Combine wind and solar, which tend to compliment each other seasonally, and smart grid storage and supply demand managment, and conservation removing 40% of present demand... you end up with a stable grid anyway.
But add HVDC by all means, even better. But it's over a decade out because of government dithering and lobbyist resistance.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Michael Hoexter Posted 11:37 am
18 Sep 2008
Good work Gar
Gar,
Much appreciate the explanation and support for a renewable supergrid.
DrX,
The smartness of the grid will not make up entirely for variations and shortfalls in the primary energy that may occur locally or regionally. A smarter grid is going to be a necessity but I believe you put too much faith in the smart-grid as a kind of "holy water" where we are talking about a basic First Law problem of not being able to create energy out of nothing. Removing coal and natural gas from use by the grid is going to use a big hole in that primary energy. Linking supply and demand, which the transmission grid as described by Gar will do, will enable us to fill in that gap, and/or use the scalable energy storage capacity of thermal energy from CSP.
As EGS comes online over the next few decades, we may be able to pare down the density of grid interconnections we will need, as EGS may allow local renewable baseload power generation almost anywhere.
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amazingdrx Posted 11:02 pm
18 Sep 2008
"Holy water" smart grid
If that grid could adjust demand to meet supply and store excess supply, would that be a "holy water" smart grid?
How about if the smart grid had an emergency power mode, that powered lights and electronics?
How about if each home or building connected had a few batteries for backup power in that emergency mode? And one out of 10 buildings had a backup generation system of around 10kw? That could power those buildings in emergency mode.
Or one out of 100 buildings had a 100kw backup generator, or some range between those.
Say a natural gas/biogas powered solid oxide fuel cell/turbine generator at 70% efficiency, with the waste heat used for hot water and building heat. Maybe a farm, municpal sewage, and processing plant biodigestor could feed the fuel cells, instead of natural gas?
Or maybe along rivers, current power generators. On farms or in parks wind, or offshore wave/ wind or tidal or ocean current generators.
And maybe 3 out of the 10 buildings could have solar cogeneration, with battery storage they charge up whenever the sun shines, regardless of
Pray, Michael, pray for the "Holy" smart grid. Hehey.
(Could it be like the SEC banning short selling? They just did that. That way markets can't go down. Eureka!)
Yes, ban power outages! a wireless internet signal using the backbone of the grid as a tranceiving anttenae would jump any breaks in the lines related to storms. No more loss of communication in emergencies.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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amazingdrx Posted 11:05 pm
18 Sep 2008
Oh, one more
How about an emergency cable that you can plug into your neighbor's smart grid power system in case of storm outage?
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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MAD MAC Posted 3:49 pm
19 Sep 2008
Amazing makes a very good point here
Our existing nuclear power plants will continue in operation for some time. Additionally more can be built - at least they are pretty clean. That gives you a steady base supply.
What is really needed here, however, is continued government support to:
a. Under-write with tax incentives renewables.
b. Ban the construction of new Coal and Oil fired plants.
The market will take care of the rest. You make it profitable, and it will happen.
Victory in Pattani
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Gar Lipow Posted 4:31 pm
19 Sep 2008
Smart Grids and Market
Note that DRX's "backup generators" are still run by fossil fuel generators. Basically he is advocating upgrading renewables to the less than 20% of power you can provide without a transmission upgrade, and supplying the rest with advanced fossil fuels. And as to the "free market" we have seen the "free market" doesn't handle everything, even with the "right incentives.
A per kWh subsidy will give us exactly what DRX sescribes - an increase in renewables, but but still leaving them a niche market. If we are serious about phasing out fossil fuels, we need public investment - in a grid, and in deployment.
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amazingdrx Posted 5:25 pm
19 Sep 2008
Gotta start with a niche Gar
"...an increase in renewables, but but still leaving them a niche market. If we are serious about phasing out fossil fuels, we need public investment - in a grid, and in deployment."
Right now only a private company, Xcel is investing in a smart grid. Not all backup needs to be fossil powered. Biogas from waste offsets a lot of GHG. 20 times the fossil natural gas, for instance.
That's a lot of backup. But of course as a larger HVDC grid is installed and maybe some solution like superconducting storage is introduced. The grid can go 100% renewable, in the long run.
Meanwhile patchwork will work, and prove the concepts and technology.
This direct subsidy really is public investment. But I agree, build out the smart grid with HVDC for power transmission from high source areas to high load areas. Just don't delay the local, state, and regional startup.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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MAD MAC Posted 9:05 pm
19 Sep 2008
I disagree
"If we are serious about phasing out fossil fuels, we need public investment - in a grid, and in deployment."
Generally speaking, the fewer business under government control, the happier I am. There is no reason this can not be accomplished via incentive to the private sector.
General rule of thumb: That done by the private sector is done better than that done by the government sector.
Victory in Pattani
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amazingdrx Posted 12:45 am
20 Sep 2008
Careful re-regulation
That will have to happen MAC.
Government just bought up the latest bad debt to emerge from a sea of debt. 90% of the bad debt iceberg is still invisible, underwater.
Targeted public investment, applied very carefully, night just get the economy going in the right direction.
This is a world wide disaster, and like the last world wide disaster, WW2, needs to be addressed with government leadership.
The auto makers have announced that they need 25 billion to stay in business, government has to mandate the production of standardized conversion of present car models to plugin hybrid, before it goves them that cash infusion.
the jeep, various aircraft, amd liberty ships were standardized in designed and then inmdustries across the nation were required to build them. That is necessary now. Capitalism must be directed in times of great human turmoil, like war and war-like scale disaster. like that we are now facing.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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MAD MAC Posted 1:54 am
20 Sep 2008
Government leadership yes - ownership, no
I have no problem with government steering the ship. I just don't want them to own the ship.
Victory in Pattani
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