Monday, February 18, 2008

Oil Drum Debate with Nick on Intermittency

I tend at times to get involved in online dabates. At the very least dentes are methods of self education. I do listen to what the other side says, and sometimes I change my mind, if confronted with a question to which I have no good answer. I have, for example, modified prior views on the genetic basis of behavior, although the issues are far more complex than the genetic determinist would allow for.

My oil drum debate with Nick, was triggered by claims of another commenter, Chris. Chris claimed that renewable power sources were inherently more efficient than nuclear. Part of my responce was to point to the problem of intermittency with renewables.

Nick responded to that comment with a statement that began:
"Intermittency is greatly exaggerated as a problem for renewables. That said, I have to say I find this argument silly, and intellectually dishonest on both sides."


"Nuclear advocates point to non-problems (like intermittency) . . ."

I responded to Nick:

In my book claiming that intermittency is a non-problem is where the intellectual dishonesty lies. Intermittency is a non-problem, only for supplemental power. Intermediacy becomes a problem once renewables are offered as base or even peak power. There are three methods of coping with the problem of intermittency, back up generation with fossil fuels, energy storage, or massive renewable generation redundancies. Each method requires the building and maintenance of duplicate facilities, in order to cope with the intermittency.y.

Nick responded back by apologizing for saying that my point about intermediacy is intellectually dishonest, He then stated that:

There are more, and better, methods of coping than that. First is connecting grids at the edges in order to reduce the variance (aka intermittency) of various generation sources. If you make your grid effectively large enough, variance becomes manageable. This is relatively low cost, as you don't need the kind of earth-girdling cables envisioned by another TOD post recently, you just need to connect grids at the edge.

2nd is demand management: if you make meters dynamic and time-of-day sensitive, and have a large % of demand which is flexible and schedulable, generating variance becomes much easier to deal with. For instance, if you have 100M EV's (as we will in the US, in one form or another), you have a very large demand which can be shifted at essentially no cost.

3rd is location and source tuning: using both the predictable patterns of certain negatively correlated wind locations, and the negative correlation of wind and solar to reduce system variance. This costs nothing but the time spent in planning and regulating installations, something system operators should be doing now. - Nick


I responded to Nick:

Nick, I am pleased that you are willing to dialogue about this. Let me address you your preferred methods of coping with intermediacy. I will take them out of order. You suggest demand management as a coping method. Demand variation is something of a problem for nuclear power, so I have looked at the issue from that viewpoint. There are flexible demands, that is demands that can be shifted to other times, and methods of altering consumer behavior, however some demands will remain inflexible, For example the demand for power for air conditioning in the summer. Texas is as you are probably aware quite hot in the summer, and the heat is actually a health hazard. There is no why you can get people at home to turn off their air conditioners on hot summer nights in Texas.

You suggest connection to the grid as a means of providing electricity, but how is the power going to be generated. The sun is down so solar sources are out of the picture. Texas summer wind potential drops too. I believe that the capacity factor for Texas wind generators is below 17%. But worse, the wind is highly variable, and wind output may drop to zero all over the state. Thus wind generation would provide Texas with the worst of all possible worlds, high generator redundancy plus unreliability. If your wind system is built to compensate for a capacity factor of 17%, you will build so many windmills that it would be far cheaper to just build all nuks. Thus the grid seems to provide no solution to the problems of renewables.

Finally you suggest location and source tuning. I assume that in my thought experiments on renewables. I assume that wind generators will be located in the best locations, and that solar generation will be located in the Southwest. But putting solar in the Southwest will not stop the sun from going down. And building windmills in the Texas Panhandle is not going to give you the power you need to keep Texas Air Conditioners running all night long on Texas Summer nights.

My argument for charging the energy input of backup fossil fuel plants to renewables is this. A renewable power system, as I believe I have just successfully demonstrated, is not capable of always meeting electrical demand. Ergo, it requires alternative sources of electricity, lets call them the green crutch, as backups. Now if you went with an all nuclear system, the crutch would not be needed. We can throw the crutch away, by recognizing the limits of renewables, and not expecting more than they can deliver.

The limits are these. Wind will never be reliable enough to serve as base or peak power. Therefore wind of of very limited utility outside reducing CO2 emissions. Wind can only serve as a supplement to fossil fuel power, If fossil fuel power needs to go away, there is no rational for wind.

Solar is good at providing daytime power. But solar power imposed penalties and expenses related to materials demand, land use and security. At present the capitol costs of solar exceed that of nuclear, and the cost of materials for building solar facilities are rising. Therefore solar is a candidate for daytime peak power, but may never fulfill its expectations. Furthermore, if solar power is marginal in the Southwest, its performance will be far worse in other parts of the country.

My conclusion then is that at present, only nuclear power can fully substitute for fossil fuel power sources. Furthermore, without some significant breakthroughs in the generation and storage of solar power, the substitution of nuclear for fossil fuels is inevitable.

Afterward: I by no means think that Nick's remedies are bad in themselves, it is just that they don't do for renewables, what renewables advocates say they will. Interconnecting the grid is already working for much of the United States. For example the Southeast exports power to the North in the winter, while importing power from the North during the summer. That helps both areas get by without adding seasonal capacity to meet peak demand. Such a swap is not so easy for Texas. Much of our peak generating capacity is from natural gas. Texas consumers are burning gas in the winter to keep warm. The gas producers would rather sell gas to consumers in the winter, than to sell it to electric companies. The fact that the gas producers have a surplus of natural gas in the summer means that gas is on the market for power production during the summer in Texas. Adding an interstate grid connection to the Texas power system does not help Texas meet peak summer demand. Summer is a peak demand time for the most likely exporters of power to Texas, while power generation by wind drops all over the country.

Update: “What we know, is the wind blows sufficient for these windmills to be producing about 35%, perhaps 40% of the time. So the paradox of building windmills is that you have to build a lot of ordinary power stations to back them up and those are going to be almost certainly gas in the short to medium term and that’s what’s required. If you ask the question who’s making sure that there’s enough gas stations out there to back up the windmills the answer is nobody.” - Dr Dieter Helm, Energy Economist and Fellow in Economics, New College, Oxford

8 comments:

Sovietologist said...

One of the things that I don't understand about the "supergrids make intermittency irrelevant" arguments is that I thought that, on some level, all grid stability issues are local. If demand exceeds supply locally, resources have to be freed up somewhere on the grid to make up for it- and most renewables simply can't do this. Expand this to a massive international grid, and the level of complexity rapidly reaches unmanageable levels. It seems obvious to me that even with substantial energy storage, a national power grid with a substantial reliance on solar and wind would occasionally run out of stored energy under abnormal weather conditions- resulting in a regional or nationwide blackout that could not be fixed without enough reserve generation to make up for the shortfall. Imagine the long-term economic and social consequences of the ever-present possibility of such a disaster! It would hobble our entire civilization. Since you need enough reliable, on-demand generation to cover all demand anyway, it makes much more sense to build a predominantly nuclear power infrastructure even if a renewable infrastructure could be made to work nearly all of the time. The risk/benefit ratio for renewables just isn't acceptable without a mind-boggling amount of energy storage- at which point it's so much more expensive than nuclear that there's little use bothering.

Charles Barton said...

sovietologist, you are quite right. First, there are two ways to even out power generation variation from renewables, Connect them to batteries, or connect them to a grid that also is connected to load following power sources. If all of the power sources have variable and unpredictable power output - and this would include solar power - then the grid itself will be unstable.

Load following works best locally, thus load following sources need to be located all over the country.

Advocates of a wind based super grid won't tell you that 9% of the time the system will be off grid for periods of up to 12 hours, that about once a month the system will be off line for from 12 to 24 hours, and that at least 3 times a year the system will be off line for more than a day,

The assured capacity factor for the system during the the 87% of the time when the system can be expected to operate is something like 15%. Such a low capacity factor would require as many as several million windmills to supply us with assured power 87% of the time. Install fewer windmills and the amount of time you are going to have assured power drops even more.

Anonymous said...

Dear Charles Barton !
Let's look at the following scheme.
* we are promoting a new technology - hemispheres ( 12-30 diameter )attached to wind ring generators turning around a central steel tower. The hemisphers' backs covered with solar thin film modules. The only available wind-sun power generation scheme.
* hemispheres as slow runners ( 0,75 x wind speed / turbines 15 x wind speed ) can go in altitudes up to 300 m - with wind energies of ~ 16 / in 80 m (turbines) ~ 5.
* capacity factors of 80-90%
efficiencies of 75%
that's all the difference.
* attached a hydrogen plant and a fuel cell plant - to cover wind slow downs.
* then the system has BASE LOAD CAPACITY - capacity factor 100%.
* investment costs ~ 2.600 $ per KW - production costs ~ 3 C ($)per KWh.
* a 100 MW wind farm needs 7 towers each on 5 hectars of land -
output 100 MW. 100 towers replace a 1500 MW coal plant or nuclear plant.
we are open for any dialogue.
< aquaculture@eurotel.co.za >
Johannesburg - Hamburg

Charles Barton said...

Has this technology beer described in any peer reviewed technical journal yet?

randal.leavitt said...

It is astounding that anyone could think that intermittent energy sources will be useful. A disruption of one thousandth of a second in the grid can cause massive damage for electricity users. Huge, sudden surges from one part of the grid to another can melt the transmission lines themselves. This was the cause of the massive 2003 blackout. And who wants all these transmission lines with all their inefficiency and dead birds? Put the nuclear reactors underground, right in the middle of the cities, and reduce the number of transmission lines.

We are entering an era of much more dynamic weather. We want weatherproof energy sources. Deliberately linking our energy production to weather variable sources is just suicidal.

David Walters said...

Let's examine this. First, wind. Wind is only good for one reason: when it blows, we can use less coal or fossil. When it blows. We burn less coal, but not turn off, a coal plant. this is a good thing, not a bad thing. But it makes the coal needed for the obvious reasons. And, wind is expensive, and more so at 20% real availability.

Solar is no intermittent. It is, more or less, predictable, but can never exceed the maximum 8 hours or so of high solar availably. And it's expensive.

On the grid. I work with the grid everyday. I monitor it for my power plant. There ARE some amazing advances in grid balancing going on these days, including the idea of using extra-high voltage DC transmission cables (756kv or higher)
.

The first one is being built in SF from the East Bay. It's a 500Kv version. But the grid is a far more complex animal than most people will ever realize. The Northeast of the US got an inlinking for that a few years ago when the whole region went black. Regardless of the efficiency of the grid...you need STEADY power, on demand, to handle balancing it out...to make sure it runs at the right voltage in your house 115V and at 60 Hz.

Yes, these new EHV DC lines can effectively wheel power from Maine to Texas but it can't deal with things like capacitor bank failure, loss of local generation, loss of local load, etc. VAR flow in the US is only getting worse, largely because there are fewer and fewer generators being located NEAR the load. It's all getting moved out from where it's needed. This is a problem.

As ANY independent system operator what they think of wind and you will get the official "yes it's part of the mix" AND, from the same ISO, a huge roll of the eyes. They can't stand it because it is so intermittent and the wind generators...get this...are trying to make wind available without the needed equipment to flatten out the voltage or make it steady (say a wind farm is rated for 500 MWs. It is predicted to giave about 150 over a 12 hour period. the ISO then wants..."only" 90 MWs because they know at least that much will be steady from where the wind farm ties in to the grid..but Nooooo...the wind brokers want ALL the power...up and down...to be sent to the grid. You can imagine what this does to the voltage and VAR flow!).

David

DV8 2XL said...

You all might be interested in this website/blog on the issues with wind power.

Blowing Our Tax Dollars on Wind Farms

As I think you can tell from the title it's not a big booster of the idea.

Charles Barton said...

Thanks for the heads up.

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