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Posted by Paul M. Eldridge on February 12, 2007, 10:39 am
Hi Bill,
There are electronic thermostats for electric heating applications
that modulate output (I have some from Aube that control with my
in-floor radiant heat), but they're fairly expensive. I suspect their
high cost and perhaps concerns related to long-term reliability would
limit their use elsewhere. Variable wattage control would be a nice
feature from the utility's point of view (i.e., by smoothing out
demand), but I suspect most consumers wouldn't care one way or the
other.
Cheers,
Paul
wrote:
>Does anyone manufacture a "variable heat" electric range, where when you
>select the heat setting, it would have a constant heat at a certain
>temperature? (Like you can do with a gas range...)
>
>This would be sort of like a dimmer switch for a light where you can adjust
>how much light is output from the bulb.
>
>The way electric ranges work now is they go on and off, on and off.
>
>Less heat means the "burner" goes on for a little while, then off for quite
>awhile. Then with more heat, the "burner" is on for a long time, then off
>for a little amount of time.
>
>With a gas range, you can adjust the heat so it is constant - no off and on.
>Seems they could do this with an electric range as well....
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Posted by on February 12, 2007, 10:49 am
wrote:
> Hi Bill,
>
> There are electronic thermostats for electric heating applications
> that modulate output (I have some from Aube that control with my
> in-floor radiant heat), but they're fairly expensive. I suspect their
> high cost and perhaps concerns related to long-term reliability would
> limit their use elsewhere. Variable wattage control would be a nice
> feature from the utility's point of view (i.e., by smoothing out
> demand), but I suspect most consumers wouldn't care one way or the
> other.
>
> Cheers,
> Paul
This makes no difference to the utility, because they have thousands
of stoves and similar loads, which are all randomly cycling on and
off, effectively averaging it all together, so smoothing out demand
from one stove doesn't do anything. They would never see it.
The reason its done the way it is on electric ranges is it's a cheap
mechanical switch, that cycles it on and off for varying periods.
To make the heating more even would require turning it on and off
rapidly, which is what is done in wall switch dimmers, which do it on
each AC cycle. That requires electronics. And to do that for a
dimmer, which is 600W max, takes a smaller, less expensive
semiconductor than it would require for a range. It's possible
someone offers it, but I haven't seen one.
>
> wrote:
>
>
>
> >Does anyone manufacture a "variable heat" electric range, where when you
> >select the heat setting, it would have a constant heat at a certain
> >temperature? (Like you can do with a gas range...)
>
> >This would be sort of like a dimmer switch for a light where you can adjust
> >how much light is output from the bulb.
>
> >The way electric ranges work now is they go on and off, on and off.
>
> >Less heat means the "burner" goes on for a little while, then off for quite
> >awhile. Then with more heat, the "burner" is on for a long time, then off
> >for a little amount of time.
>
> >With a gas range, you can adjust the heat so it is constant - no off and on.
> >Seems they could do this with an electric range as well....- Hide quoted text
-
>
> - Show quoted text -
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Posted by Paul M. Eldridge on February 12, 2007, 1:31 pm
I'm not so sure about that. My utility, Nova Scotia Power, like
virtually ever utility here in Canada, is winter peaking and these
peaks typically occur around 17h30 when street lights start coming on
and electric ranges are being used to prepare evening meals.
**Anything** that helps minimize concurrent demand, no matter how
small, would be helpful from the utility's perspective, especially in
light of the high percentage of homes that are electrically heated in
this country.
Let's say the average electric oven draws 3.0 kW (my convection oven
happens to be 5.5 kW). We might expect the typical household oven to
operate at full power for the first ten minutes or so, then cycle on
perhaps one third of the time thereafter (i.e., an average of one
minute on for every two minutes off). Let's also assume there are
100,000 electric ovens in use province-wide during the suppertime peak
(and here in Nova Scotia, virtually all ovens are electric since only
500 or so homes are currently served by natural gas).
If all 100,000 ovens were energized at the same time, we would expect
this load to be 300 MW. We're assuming, of course, that as each of
these ovens come up to temperature, the actual load at a 33% duty
cycle, would be closer to 100 MW, and since these ovens are not all
turned on at the same time, a coincidental peak of 100 MW is probably
within spitting distance of the mark. If, however, each of these
ovens were equipped with variable wattage controls and, again,
assuming a 33% duty cycle, our coincidental peak should drop to just
33 MW.
On a typical winter's day, Nova Scotia Power's peak falls between
1,500 to 2,000 MW, so a 67 MW reduction in provincial demand would
represent a peak savings of perhaps as much as 3 to 5 per cent. In
theory, it would exceed the province's total installed wind capacity
of some 60 MW (which, assuming a 40 per cent annual capacity factor, I
take it might be closer to just 25 MW). Even if we were to cut the
number of ovens in operation by half, the impact on a utility such as
Nova Scotia Power is not exactly insignificant.
Cheers,
Paul
On 12 Feb 2007 07:49:37 -0800, trader4@optonline.net wrote:
>This makes no difference to the utility, because they have thousands
>of stoves and similar loads, which are all randomly cycling on and
>off, effectively averaging it all together, so smoothing out demand
>from one stove doesn't do anything. They would never see it.
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Posted by on February 12, 2007, 2:12 pm
wrote:
> I'm not so sure about that. My utility, Nova Scotia Power, like
> virtually ever utility here in Canada, is winter peaking and these
> peaks typically occur around 17h30 when street lights start coming on
> and electric ranges are being used to prepare evening meals.
> **Anything** that helps minimize concurrent demand, no matter how
> small, would be helpful from the utility's perspective, especially in
> light of the high percentage of homes that are electrically heated in
> this country.
>
> Let's say the average electric oven draws 3.0 kW (my convection oven
> happens to be 5.5 kW). We might expect the typical household oven to
> operate at full power for the first ten minutes or so, then cycle on
> perhaps one third of the time thereafter (i.e., an average of one
> minute on for every two minutes off). Let's also assume there are
> 100,000 electric ovens in use province-wide during the suppertime peak
> (and here in Nova Scotia, virtually all ovens are electric since only
> 500 or so homes are currently served by natural gas).
>
> If all 100,000 ovens were energized at the same time, we would expect
> this load to be 300 MW. We're assuming, of course, that as each of
> these ovens come up to temperature, the actual load at a 33% duty
> cycle, would be closer to 100 MW, and since these ovens are not all
> turned on at the same time, a coincidental peak of 100 MW is probably
> within spitting distance of the mark. If, however, each of these
> ovens were equipped with variable wattage controls and, again,
> assuming a 33% duty cycle, our coincidental peak should drop to just
> 33 MW.
This also means that you have eliminated the normal full on heating
mode of the oven and reduced it to 1/3 of that. Which means now
everyone has to wait 3X as long for the oven or burner to warm up,
which few people are going to put up with. After that, the oven or
burner will be cycling randomly anyway and the sum of them all cycling
randomly is the same And presumably, this cooking load comes late in
the day, like 6PM+, which is after industrial/commerical use is
decreasing. With all the other loads I fail to see how this is going
to make any difference in the generating capacity needed to meet peak
demand or save the utiltiy even 5cents. It will mean a lot of pissed
off users though, who can't get their oven hot in a reasonable time.
>
> On a typical winter's day, Nova Scotia Power's peak falls between
> 1,500 to 2,000 MW, so a 67 MW reduction in provincial demand would
> represent a peak savings of perhaps as much as 3 to 5 per cent. In
> theory, it would exceed the province's total installed wind capacity
> of some 60 MW (which, assuming a 40 per cent annual capacity factor, I
> take it might be closer to just 25 MW). Even if we were to cut the
> number of ovens in operation by half, the impact on a utility such as
> Nova Scotia Power is not exactly insignificant.
So, you have just as many ovens running longer. Unless you have
proof that ovens are causing a peak demand that results in either
higher capital cost for generators to meet peak capacity or are
causing the need to kick in some higher cost energy source during
dinner time, this is just a pipe dream.
>
> Cheers,
> Paul
>
> On 12 Feb 2007 07:49:37 -0800, trad...@optonline.net wrote:
>
>
>
> >This makes no difference to the utility, because they have thousands
> >of stoves and similar loads, which are all randomly cycling on and
> >off, effectively averaging it all together, so smoothing out demand
> >from one stove doesn't do anything. They would never see it.- Hide quoted
text -
>
> - Show quoted text -
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Posted by Paul M. Eldridge on February 12, 2007, 4:13 pm
On 12 Feb 2007 11:12:27 -0800, trader4@optonline.net wrote:
>This also means that you have eliminated the normal full on heating
>mode of the oven and reduced it to 1/3 of that. Which means now
>everyone has to wait 3X as long for the oven or burner to warm up,
>which few people are going to put up with. After that, the oven or
>burner will be cycling randomly anyway and the sum of them all cycling
>randomly is the same And presumably, this cooking load comes late in
>the day, like 6PM+, which is after industrial/commerical use is
>decreasing. With all the other loads I fail to see how this is going
>to make any difference in the generating capacity needed to meet peak
>demand or save the utiltiy even 5cents. It will mean a lot of pissed
>off users though, who can't get their oven hot in a reasonable time.
No, please go back and re-read what I said; to whit:
"We might expect the typical household oven to operate at full power
for the first ten minutes or so, then cycle on perhaps one third of
the time thereafter..."
Followed by:
"If all 100,000 ovens were energized at the same time, we would expect
this load to be 300 MW. We're assuming, of course, that AS EACH OF
THESE OVENS COME UP TO TEMPERATURE, the actual load at a 33% duty
cycle, would be closer to 100 MW, and since these ovens are NOT all
turned on at the same time, a coincidental peak of 100 MW is probably
within spitting distance of the mark...."
So there are two key points here:
a) the load on our utility during the suppertime peak is minimized
due to the cycling of these elements at what I had estimated
to be 33% and, secondly,
b) due to the fact these ovens are not all turned on at precisely
the same time, the impact of that first ten-minute start-up
is thereby diminished.
Nowhere did I say these ovens would operate at reduced power upon
start-up. Each could continue to operate at full power for as long it
takes to come up to temperature, then drop to the lowest wattage
required to maintain a constant set temperaturer; if the oven element
is rated at 3,000 watts and it normally cycles on one-third of the
time, then it's fair to say a constant 1,000 watts is all that's
needed to maintain a steady temperature from this point forward.
There would be absolutely no inconvenience to the consumer whatsoever
and the utility would still benefit from reduced aggregate load.
>So, you have just as many ovens running longer. Unless you have
>proof that ovens are causing a peak demand that results in either
>higher capital cost for generators to meet peak capacity or are
>causing the need to kick in some higher cost energy source during
>dinner time, this is just a pipe dream.
You claim these ovens would run longer but as I indicated above, they
won't. In any event, according to U.S DOE EIA, the generating
technology with the lowest capital cost would be a 230 MW advanced
combustion turbine at a cost of $US367.00 per kW (O&M and T&D extra).
Source
http://www.eia.doe.gov/oiaf/aeo/assumption/pdf/0554(2006).pdf#page=77
Thus, if we can effectively reduce peak demand from by just ***ONE***
MW, the capital savings to the utility is a minimum of $367,000.00 US
($436,730.00 CDN); at 67 MW, the savings amount to $CDN 29.3 million.
To this you would add the additional operational and maintenance costs
(and this *is* the single most expensive way to generate electricity
by conventional means), plus the added transmission and distribution
expenses. Also, bear in mind, the utility continues to sell the same
amount of energy as before, so there's no resulting loss in revenue,
BUT it does get to pocket all these other savings.
Cheers,
Paul
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