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I have said this for years

Posted by bus_driver (My Page) on
Thu, Feb 28, 13 at 17:19

When the wind slows down, a cloud passes over or darkness occurs, the output of wind and solar sources of electric power drop. Any conventional backup must be ready to instantly pickup the load. It takes days to get some conventional power plants started and stabilized from a cold start. It all is not simple at all

Here is a link that might be useful: Reliable?

Follow-Up Postings:

RE: I have said this for years

I've been seeing that hand-waving argument for years. This is just my SOTP response, but there are not many relevant numbers, and no equations in the linked article anyway, so I think it is fair.

1) How long does it take to spin-up a gas turbine?

2) When a "cloud passes over", it only passes over part of a solar large, commercial array, one of many large, commercial arrays or a small fraction of small residential or commercial arrays at a time. You might respond by pointing out that there are some days that have a lot of very large clouds. I might respond by pointing out that weather prediction is very good these days and see #1.

3) Why do you think that wind output drops with clouds?

4) Sure, in order to average the sources over the state or make up for low days, generating stations are going to have to be brought on line or a good grid needs to be maintained to transfer excess power. I think that the assumption has been that dino power is going to be expensive enough to warrant that cost.

RE: I have said this for years

bus driver, you can rest easy. That article seems to have been written by people who really don't understand the subject matter, the conclusions are uninformed.

For the regulators and those in the industry, insuring a consistent supply level is not complicated. The open challenges to enlarge the supply percentage from renewable sources are mostly defined and well understood. Sunshine and wind are very predictable - the passing cloud doesn't arrive unexpectedly. In California, for example, peak demand (in the summer for A/C) corresponds with the timing of peak production of solar and wind energy, so the stars are in alignment on that one.

One unsolved problem right now is "storage", how to save power when you have an excess to use when you have a shortfall. One approach with potential for more use is called "pumped storage" - water is pumped uphill at night, using power that would otherwise go unused, so that it can be released in the daytime.

Two of California's largest power plants work off of pumped storage. It's possible many more may be needed.

RE: I have said this for years

The biggest problem at the moment is the true believers don't have the stones to admit the whole thing is a stale dated pathetic rent seeking scam.

RE: I have said this for years

35 years ago, I remodeled an old house and added baseboard electric heaters to be used (eventually) as supplemental heat powered by solar. The published information at that time was that solar generated electricity would be very practical at any moment, extrudable plastic film that generates electricity will bring costs down dramatically, etc. I bought all the hype. I WAS a believer. I'm older now.
The plan for the heaters was to directly feed them with whatever power solar panels would produce and use batteries to store whatever was not used at the moment of generation. Baseboard heaters can utilize any electrical source, AC or DC, so long as the peak voltage does not exceed the design values.
Those heaters were never used.
How long to spool up a gas turbine? They DON'T TELL US! And why are they so stingy with technical facts? They should be proud to proclaim the truth everywhere.
Backup power sources must be able to pickup the load within a half cycle, 1/120 of a second, to avoid brownouts or blackouts. Turbine or Diesel cannot be started that quickly. And any such must not only be started, but must be stabilized and synchronized to the grid before being connected. This does not happen in a moment.

RE: I have said this for years

Here is some information.
It is clear that the investment in renewable wind and solar generation does not decrease at all the necessity for conventional plants. Thus the overall need for capital increases dramatically. And that also has a cost.

Here is a link that might be useful: Article

This post was edited by bus_driver on Fri, Mar 1, 13 at 8:39

RE: I have said this for years

You thought you were going to heat with lead-acid battery power reserves? Did you do the calculations?

"Backup power sources must be able to pickup the load within a half cycle, 1/120 of a second, to avoid brownouts or blackouts. Turbine or Diesel cannot be started that quickly"

This does not have to happen every time a cloud passes over one PV array or the wind slows down on one, or even a dozen large windmills.

RE: I have said this for years

As with all new technologies, there are growing pains and modifications needed over time and it is constantly improving and getting cheaper to produce. I don't think anybody would argue that wind and solar power is perfect, but it is definitely something that should be further explored and refined. The technology should not just be abandoned.

I wouldn't want to travel to Europe aboard the Wright brothers' plane.

RE: I have said this for years

"How long does it take to spin-up a gas turbine? "

Longer than you think I bet.

RE: I have said this for years

There are studies being conducted now for the 'storage' problem. Large railroad-car-sized batteries (not lead acid) are being studied to even out the flow from wind farms. There is also fly-wheel technology, but I haven't followed that for a while.

PV shingles for homes does now exist, but I'm not sure of the cost. I've see studies on PV paint (any color you want as long as it is white) for siding. There are also PV films that are now being used in office buildings covering large areas of glass and are transparent (like sun screens). Not hype, actual products.

However, the solutions and implementations are not simple. I think T. Pickens learned this himself after investing heavily in wind in Texas. IIRC, he has divested from this venture.

This post was edited by weedmeister on Fri, Mar 1, 13 at 13:55

RE: I have said this for years

"Longer than you think..."

If you give me SI or some other relatively standard unit, real discussion can happen. Otherwise, we are still hand-waving.

RE: I have said this for years

I saw some discussion about PV shingles some time ago. Compared to conventional panels, cost and reliability are a problem. Thin films can be applied to flat metal roofing panels (standing-seam, not R-panels) or other flat material. You can buy standing-seam with the PV already on them. Output is about half of conventional panels on an area basis (fine if you have a lot of space) and the reliability track record has not yet been established.

Any storage mechanism has associated losses. Conventional ead-acid batteries are only about 80% efficient, IIRC. Compressed air as a storage mechanism has a problem that most people don't think about. You have to recover and store the heat associated the compression process.

Click on the "full rundown" button for the 1 March show or search on "compressed air".

Commercial-scale pump-back hydro has been in place for a very long time. I don't know how efficient that is:

RE: I have said this for years

Ionized, your posts almost always are well thought out and helpful. I do appreciate that and respect you for that.
In this case the emotion of the moment seems to have taken over.
I posted "supplemental heat". I think that implies something which is not the primary source. Thus reliability is quite a secondary priority. Your reading was apparently quite hasty.
My knowledge in SOME aspects of this subject is rather good with significant gaps that I am working to fill.
Another recent article on the subject apparently will not be available online for about another month. I hope to post the link later.

RE: I have said this for years

"If you give me SI or some other relatively standard unit, real discussion can happen. Otherwise, we are still hand-waving."

I have installed gas turbines as part of backup power system for many large buildings that HAD to have reliable power.

And the battery systems that bridged over during start-up.
It takes many minutes, up to even half an hour, to spin up large gas turbines.

At one pint units with mated air turbine ad large compressor system with big storage tanks saw some use.

It still took at least a good five minutes to get those on line, and that was only by allowing slightly wider than normal variation in the voltage and frequency output.

A decent size turbine has a lot of mass to get up and spinning, and the power for that has to come from something.

The faster starting units need better field control to make SURE the voltage stays within limits.

Most of the larger units are pretty far from a 'standard' thing, though some manufacturers will advertise 'data' from units they have previously produced (often with some of the details missing).

It is after all advertising, and puffery still occurs.

POCOs will keep turbines spinning (often with grid power) to shorten the start-up lag.

It is almost like keeping diesel 'peaking power' generators at idle on hot summer days when they are reasonably sure they will be needed as afternoon temperatures peak.

The fractionating of the POCO industry in many places into power generator and distribution companies has NOT helped.
It takes a much more robust distribution network to smooth out a system with multiple smaller sources & irregular power delivery.
Large coal fired plats often have the boilers running all the time at a low level since start-up of the boiler is anything butt instant.

This post was edited by brickeyee on Sat, Mar 2, 13 at 14:15

RE: I have said this for years

1/2 hour seems like a very short time if we are talking about the weather. I was thinking that a couple of hours would be enough.

RE: I have said this for years

Weather-dependent renewables must have at least two facets depending on size. A typical residential net-metered system must be between 1 and 10 kW. I bet that most of them are 5kW and below, to have them winking on and off is really no different from a large residential load coming on and off.

Large wind and PV "farms" are different. They, and the aggregate of the smaller, residential, systems will be managed by weather forecasts. Yes, there will be some cost in maintaining back-up generation capability and it needs to be available with hours notice.

RE: I have said this for years

" will be managed by weather forecasts."

Ahh, the ever reliable weather forecasts.

keep dreeaming, since that is what it is, a dream.

Or maybe we can declare a few western states as photo voltaic generators for the whole country and borrow another trillion dollars from the Chinese to install their solar panels over most of a couple states.
Redundancy and local weather you know.

Bring on the multi-million volt DC long distance lines since 60 Hz has1/4 wavelength problems past about 777 miles.

RE: I have said this for years

I don't know what rock you've been hiding under if you have not noticed how good the weather forecasts have become. They are usually spot-on several days ahead. Even in my part of the country (South Coast USA) they are good even though a few degrees of difference in wind direction makes a huge difference between humid air coming from the Gulf and dry air from the continent.

RE: I have said this for years

How predictable.

RE: I have said this for years

Here's a little something about solar shingles. I have not read through this, but it is here.

Here is a link that might be useful: How solar works- shingles

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