The definition of the capacity factor, including that from Wikipedia: ".......
generator nameplate ratings multiplied by the total hours in a year ......."
points out to the obvious shortcoming of CF as an objective criterion for
comparisons. Any manufacturer that "underrates" its machine, that is punches a
lower number on the nameplate, will have a superior CF to the one that did not.
Short of anemometer measuring the wind energy input against the (net)
electricity output, the W/m² criterion is the best. Because serious wind farms
do measure the wind input, a Utilization Factor, or simply Efficiency, would be
a good number to have. Unfortunately, I see CF and UF treated as synonymous.
The same with evaluating direct solar installations - insolation input vs.
(net) electricity output is better that the somewhat arbitrary CF. Here,
measuring instantaneous insolation may not be necessary as maps of solar
insolation (area density) are available and thus the efficiency can be
determined easily. And also accurately if carried over a few years span. For
example, the GE plant I wrote about producing 6.8 W/m² used 3.4 % of the local
insolation of 200 W/m².
In my terminology, a plant could have a CF of 34 % and UF of 3.4 %
Stan Jakuba
----- Original Message -----
From: John M. Steele
To: U.S. Metric Association
Sent: 09 Sep 07, Monday 17:45
Subject: [USMA:45761] Re: Windfarms, was "Can journalists..."
The Wikipedia article has a nice table on national average capacity
factors (about halfway down the article)
http://en.wikipedia.org/wiki/Wind_power
--- On Mon, 9/7/09, James R. Frysinger <[email protected]> wrote:
From: James R. Frysinger <[email protected]>
Subject: [USMA:45760] Windfarms, was "Can journalists..."
To: "U.S. Metric Association" <[email protected]>
Date: Monday, September 7, 2009, 5:16 PM
I've done the math using the published Kentish Flats numbers and
found that 280 000 000 kWh over a year represents and average power level of
just under 32 MW for the 10 km2 site. That's 3.2 W/m2, a few times the
previously mentioned typical power generation site density. Of course, that's
quite a windy part of the world, the brochure claiming a mean wind speed of 8.7
m/s at 70 m above mean sea level.
I calculate the "90 MW" farm operates at 35.5 % capacity.
Dare it be said, those figures are at the site and do not account for
10 km of line losses just getting to shore but still needing to reach the grid,
which might deduct a few tenths of a percent of the power generated.
Jim
John M. Steele wrote:
> The only one that seems completed and operating is Kentish Flats.
It has capacity of 82.5 MW installed. Its booklet forecasts 280 million kWh
per year, which is an average power slightly less than 32 MW, which is a
capacity factor of about 39%.
> I can't find any actual data though. If it is actually delivering
280 million kWh per year, that is pretty good. Many come up quite short to
forecast. Are you able to find any ACTUAL production data locally.
>
> --- On *Mon, 9/7/09, Martin Vlietstra /<[email protected]>/*
wrote:
>
>
> From: Martin Vlietstra <[email protected]>
> Subject: [USMA:45755] Re: Can journalists be cured of their
affliction?
> To: "U.S. Metric Association" <[email protected]>
> Date: Monday, September 7, 2009, 3:06 PM
>
> I looked at the figures shown below. I then looked at a UK
website
> - http://www.pmsc.org.uk/windfarms.htm. The scale of things is
> quite different, and therefore so is the economics of the
situatiom.
>
>
>
------------------------------------------------------------------------
>
> *From:* [email protected]
[mailto:[email protected]]
> *On Behalf Of *Stan Jakuba
> *Sent:* 07 September 2009 02:11
> *To:* U.S. Metric Association
> *Cc:* USMA
> *Subject:* [USMA:45752] Re: Can journalists be cured of their
> affliction?
>
>
> Compare that Indiana "farmer's record" formulated by the usual
> "green" (or greed?) propaganda with the real homeowner's
record in
> sunny Austin TX. Again, from my paper:
>
> As for the usefulness of PV for small installations, below is a
cost
> analysis of a plant representing a typical system installed on
the
> roof of a family house in central Texas .
>
>
> Installed name-plate power . . .
. 3.24 kW
>
> Power actually measured over a year .
. . 0.44 kW
>
> Utilization (capacity) factor on 24/7 basis .
. 13.6 %
>
> Useful life of the structure . . .
. 20 years
>
> Electricity produced in that life span . .
. 280 GJ
>
> Sale (savings) of electricity in that life span will bring
$7,700
>
> Note: Supported by the net-metering law, the kWh rate is the
utility
> rate.
>
> Purchasing price, installed . . .
. $22,500
>
> Note: This cost was subsidized whereby the owner paid only 1/3
of
> that amount.
>
> Net gain (loss) at the end of the useful life:
. . $(14,800) or (66) %
>
> That percentage is based on the assumption that the repair and
> maintenance cost will be zero, insurance premiums zero,
net-metering
> will last, and taxes forgiven.
>
>
> Notice that if the owner had invested his purchase amount (that
one
> third) at a reasonable interest, say 5.5 %, he would have
$22,000 by
> that 20^th year. On the basis of all three thirds he would have
> $67,000. Instead, in addition to the monetary loss (mostly to
the
> taxpayers as of now), the owner will be facing the pain of
financing
> the dismantling and disposal of the plant or replacing the PV
panels
> and some electric/electronic components should he decide to
continue
> making his own electricity.
>
>
> The bottom line is: This “free” PV electricity would have to
sell at
> 240 $/GJ to break even instead of the 28 $/GJ (10 ¢/kWh) the
owner
> enjoys from the utility. In other words, a solar kWh costs
almost
> nine times more than the utility rate is, and the utility
operates
> at a profit while it buys fuel, cares for power lines, covers
> operating labor costs, pays dividends, 401(k), etc.
>
> Source: /Gusher of Lies/, by Robert Bryce, pg 217.
(PS:
> This is an excellent energy book, but not SI.)
>
>
> PV promoters claim that the cost of the PV collectors will come
down
> with time. Probably, but insufficiently, considering that, as
> examples, coal-fired plants are built for 2 $/W, nuclear plants
for
> 1.4 $/W, gas turbine plants for 0.7 $/W vs. the GE PV plant at
> 31 $/W. That gap is too wide to close significantly. Notice
that
> the above, roof-installed plant cost $51/W.
>
>
> On related subject, I am attaching a table that had been
> presented to this forum more than once before. It contains W/m²
in
> the middle column. The data have been collected over many years
from
> articles describing plants that were in operation for several
yearly
> cycles. These data are very hard to come by. Probably because
the
> owners do not want to admit how badly their investment turned
out.
> Calls for actual data are not returned from the people who
> know. Invariably, one is referred "our website" which is, of
course,
> if it at all refers to a period of measurement, compares it to
> "1/3rd of our operating cost) (what is it?) or powering 100
houses
> (dog houses?, wood burning cottages?) and are written in the
> style for school kids education.
>
>
> BTW, I heartily recommend Prof. Hayden's
> newsletter http://EnergyAdvocate.com
<http://energyadvocate.com/> A jewel among energy newsletters (although
somewhat reluctant to use
> W/m²) the articles are mostly metric, and, better yet, SI,
although
> not consistently.
>
> Stan Jakuba
>
>
> ----- Original Message -----
>
> *From:* John M. Steele
>
<http://us.mc824.mail.yahoo.com/mc/[email protected]>
>
>
> *To:* U.S. Metric Association
>
<http://us.mc824.mail.yahoo.com/mc/[email protected]>
>
> *Cc:* [email protected]
>
<http://us.mc824.mail.yahoo.com/mc/[email protected]>
>
>
> *Sent:* 09 Sep 06, Sunday 16:29
>
> *Subject:* [USMA:45749] Re: Can journalists be cured of
their
> affliction?
>
>
> Probably not. The journalist didn't measure anything
himself,
> and probably didn't compute anything himself. He simply
> reported pap, spoon-fed to him by the installer of the
system
> who has a very vested interest in making it sound good.
>
>
> The 13.4 kW rating is almost certainly "high noon" power.
The
> area of the roof is is about 171 m². At high angle and
> perpendicular incidence, sunlight is about 1 kW/m², and
> affordable solar cells are about 10% efficient. If the roof
> could be totally covered, perhaps 17 kW could be attained.
Given standard size panels, 13.4 kW peak is reasonable.
>
>
> I estimate for a flat, non-tracking array, at optimum
angle, he
> will get the equivalent of 4 h of peak power per day, or 54
> kWh/day. (This will be "smeared" over more hours, but
mostly
> lower power in bell shaped curve).
>
>
> My estimate is strongly at odds with the claim of saving
$230000
> over 25 years at current electric rate of $0.116/kWh. The
> implication of this statement is 217.3 kWh/day, roughly 4X
my
> estimate. Time will tell. Note that this estimate
requires 16
> h of full power operation per day (average for the year. On
> average, how long is a day. It's not all full power
either). :)
>
>
> As to the CO2 savings, the federal government uses a
decade-old
> figure of 1.34 lb/kWh. I note that 48240 lb is EXACTLY the
CO2
> emission of 36000 kWh. However, the 36000 kWh number
doesn't
> seem to relate to either power estimate above. As an annual
> estimate, it would apply to generating capability of 98.6
> kWh/day (call it 100) more or less the geometric mean of
the two
> estimate.
>
>
> The article is a pile of environmental voo-doo (or doo-doo)
> unlikely to translate to real results over the course of the
> year. However, the real problem is not the reporter's math
> ability but that all the "facts" came from the seller and
there
> was no fact-checking or critical view of (very dubious)
data.
>
>
> As to units, until we get AP to change the AP Style Guide,
there
> is not a snowball's chance in hell of the units being all
SI.
>
>
>
> --- On *Sun, 9/6/09, James R. Frysinger /<
> [email protected] >/* wrote:
>
>
> From: James R. Frysinger < [email protected] >
> Subject: [USMA:45748] Can journalists be cured of their
> affliction?
> To: "U.S. Metric Association" <[email protected]>
> Cc: [email protected]
> Date: Sunday, September 6, 2009, 2:23 PM
>
>
> Journalists, as a rule, are terrible at dealing with
> measurements. Case in point,
> " Indiana Farmer Turns to Sun to Run Operation"
> Saturday, September 05, 2009
> Associated Press
> http://www.foxnews.com/story/0,2933,547042,00.html
>
> The story describes a solar photovoltaic installation
on a
> farm in Indiana .
>
> Comments:
> "The 66- by 28-foot roof supports 60 photovoltaic solar
> panels, each producing 224 watts of electricity. The
panels
> are aligned in four rows, or two sub-arrays, with each
> sub-array producing 6.7 kilowatts, making the entire
system
> produce 13.4 kilowatts of electricity..."
> The journalist should have said whether that claimed
> power output was the ideal, peak value (the most likely
> case) or the average over the length of a typical day.
There
> is a huge difference, especially since power output
must be
> zero at night!
>
> "The farm in southern Vigo County has at least 200
acres of
> electric fencing to contain a herd of beefalo..."
> Fencing is sold by length, not by area. Let's call
200
> acres 80 ha (close enough), or 800 000 m2. If the field
is 1
> m by 800 000 m, then the fence around it would be 1600
km
> long. If the field is square, then 3.6 km of fencing
would
> suffice.
>
> "The fencing itself uses 600 volts of power...
> Power is measured in watts, not in volts.
>
> "The Lovealls' system will avoid the release of 48,240
> pounds of carbon dioxide into the atmosphere..."
> Is that per day, per week, per year, over the life
of
> the system? There is a huge difference between 24 t of
CO2
> per day and 24 t of CO2 per score of years!
> Also, climatologists measure CO2 outputs in metric
tons
> (symbol t), not in pounds. And it's not terribly leading
> edge to still be using feet, square feet, and acres.
Since
> the electrical units which were misused in this article
are
> SI units they should have stuck to the SI -- and should
have
> used it properly.
>
> Not as a matter of measurement ignorance, but a lack of
> common sense:
> "The solar panels are part of a "phase one" project,
Roberts
> said. A second phase for the Loveall farm will add more
> solar panels, plus move an existing 66-foot wind turbine
> next to the barn to produce wind power to allow the
farm to
> be 100 percent energy independent. The farm would remain
> connected to Win Energy's power grid as a backup."
> You betcha they need that backup! What happens at
night
> when the wind is not blowing hard enough to generate all
> their needs? The fallacy ignored by the green crowd is
that
> systems such as this use the grid and its mainline
nuclear
> and fossil fuel plants to serve as their energy surge
> reservoirs!
>
> Can journalists be cured of this affliction they have
that
> prevents them from understanding how to measure things?
And
> the news media wonders why we don't trust their reports!
>
> Jim
>
> -- James R. Frysinger
> 632 Stony Point Mountain Road
> Doyle , TN 38559-3030
>
> (C) 931.212.0267
> (H) 931.657.3107
> (F) 931.657.3108
>
>
-- James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
