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Unintended Consequences

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zdas04

zdas04

Mechanical
Jun 25, 2002
10,274
I just got a link to a New York Times article from NACE Corrosion Press.

The basic idea was that when the sun goes down or the wind stops, then the large-scale renewable energy sources stop producing any power and the fossil fuel plants have to ramp up to fill the gap. One guy contended that because of inefficiencies inherent in start-up and shut-down, the plants put more NOx and SOx into the air during the start-up than they saved during the shut-down--resulting in MORE regulated emissions with the wind farm than there would be without it. The wind association refutes this conclusion, but it looks to me like they are citing pretty weak sources.

David
 
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Steady state, with everything at equilibrium temperature, emissions control uses mainstream technology to reduce the currently regulated gases to astonishingly low values. The key is reaching steady state and equilibrium temperature. While on that voyage, the emissions can be quite significant. Since plants are designed for 99.99% up time, the focus on emissions technology is absolutely expecting normal operating temperatures. Now if I have to start the plant up every afternoon, shut it down when the sun comes up, and then start again during the day if the wind dies down, I have the potential for a lot of low temperature transients. I'd be surprised if anyone has those extra emissions in their permits.

David
 
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The only "renewable" that comes close to natural gas or coal plants in cost is hydro. Hydro power production goes on around the clock, and can easily be ramped up or down.

Output from wind and solar plants is actually fairly predictable, so ramping up/down production from conventional plants to balance the grid demand is not too problematic. But as noted, the traditional plants must be kept "idling" during the off-peak hours, which is somewhat wasteful.

There are several approaches to large scale storage of wind and solar power for load balancing. The most cost effective are pumped storage hydro, and possibly underground pneumatic. Wind and solar will only become practical when the cost of these technologies becomes cost competitive with traditional sources.

Modern natural gas plants are extremely efficient and have low emissions. These combined cycle plants can achieve thermal efficiencies exceeding 60%, and their NOx emissions are very low.

In most of the US, coal is about 6 cents/kW-hr, NG is about 12 cents/kW-hr, wind is about 20 cents/kW-hr, and solar is over 30 cents/kW-hr. Coal is widely available (the US has the world's largest domestic reserves with over 100 year's supply), and it has price stability. So that's why it's widely used for power production, and will continue to be so for many decades. In the end, most US states are more concerned about economic growth than CO2 emissions.

And finally, no offense intended, but most of what is printed in the NY Times is a bunch of left wing drivel for the feeble-minded.

Warmest regards,
Terry
 
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I couldn't agree more about your assessment of the NY Times. I was quite suprised when I found an article there that I was able to read all the way through. While the bucket usually holds tripe, the article that I linked to seemed to be well done.

David
 
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Actually, biomass is probably the most readily available and easy to use renewable resource we have right now, and it's the best fit for our current coal infrastructure. In the US biomass recently outpaced hydro-power as the #1 renewable for power generation. The best bet is to offset coal by burning the biomass mixed with coal in the existing boilers. Most power producers could do this today with minimal expense as long as the percentage of biomass doesn't go over 10%. Of course it depends upon the type of boiler in use. None of this ramping up and down of power plants, no huge environmental footprint or cost like wind, and no cycling or storage problems like solar...simple, elegant and carbon-neutral.

Dan

Dan's Blog
 
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The conventional plants don't have to be set on idle, unless we are talking about some microgrid or somthing. If we are talking about a reasonably large grid, or a national grid, the conventional units could all be run at a slightly reduced output of Peak_load - wind - solar quite easily and all units still be well within their efficient operating ranges. Conventional power plants with multiple units can be ramped to a close load matching tolerance and in most cases (although not all) wind and solar are not going to make up much more than 20% of the total load at any given time anyway. That range is well within the efficient operation ranges of base load supplying units made up of "clean" coal fired plants plus nuclear plus gas turbines plus hydro, plus others that will all be supplying close to their characteristic percentage of the grid demand.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus
 
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Yes, but the assumption is that it's recycled by replacement bio mass in a relatively short time frame.

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I don't think that that is it KNEAT. The assumption is that the biomass would decompose, releasing CO2 or it could be burned, releasing the same amount of CO2. No net gain. Theoretically.

David
 
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That's another way to look at it, back at school though I'm pretty sure the required response was the one I gave - but my memory fades;-).

Posting guidelines faq731-376 (probably not aimed specifically at you)
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Oh, and I just remembered my other point that I was starting to post but got distracted.

What I say holds for plants deliberately grown for fuel.

What you say holds for byproduct that would other wise be treated as waste.

Posting guidelines faq731-376 (probably not aimed specifically at you)
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When we burn fossil fuels we are releasing carbon dioxide into the atmosphere that was sequestered 300 million years ago. So the combustion of coal, oil and natural gas effectively brings "new" carbon into the equation that has not existed in the atmosphere since we became a species. When we burn biomass we are only releasing the CO2 that the plants have sequestered recently and would eventually release anyway when they are eaten (by animals, fungi or bacteria). This is what people mean when they say biomass is "carbon neutral"...basically the CO2 liberated by burning wood (for example) will be captured by regrowth. Obviously, if we were to mow everything down and burn it in one year without replanting anything then this argument falls on its arse.

Dan

Dan's Blog
 
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tbuelna beat me to the pumped storage hydro thing.

I saw one in the hills near the delaware water gap and it looked like a good idea to me.
 
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Teh GReenies hate dams so how is hydro going to get up? They also hate nuclear. So one has to look deeper at the agenda here. Its about population control and international expansion of socialism. It is not an engineering issue!


"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

 
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Come on. Of course it is an engineering issue. We can design the perfect widget, but if it does not fill a need or generate profit then we have not engineered the product very well. We must first design for profitability, always. It would be foolish to say that you've designed the perfect kitchen gadget if nobody has one in their kitchen. We engineer products to fill a need, and many times those needs are driven by public opinion...for better or worse. If we, as engineers, had 100% control over what devices, processes and technologies were worthy of being pursued who would be Big Bother then?

Dan

Dan's Blog
 
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Eltron,

If we design for "profit" how did wind power and solar energy get uP? Government hand outs for ideological reasons is how they happened.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

 
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The Tennessee Vally Authority has been using pump storage for years at several dams.

Along the lines of pumped storage, we need to harness some of the potential power from the Morganza and Bonnet Carre Spillways to pump the water somewhere.
The often proposed water turbines for the Mississippi River would be humming now.
 
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