S
Sylvia Else
Guest
mm wrote:
Sylvia
And I'm arguing that they do not achieve that goal.
Sylvia
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D
D Yuniskis
Guest
[bits elided to trim this to manageable size]
Sylvia Else wrote:
heat much faster than heat infiltrates the home. E.g., in the
hottest portions of the summer, our ACbrrr rarely hits a 30%(?)
duty cycle.
Coonsider that the amount of hysteresis on many (most?) thermostats
is only a few degrees, at most, so we are essentially calling on
the HVAC system to maintain a comfort region of 2 or 3 degrees.
(some thermostats allow this to be adjusted but I suspect
you will find most users don't know this nor do they even know
why they might *want* to adjust it!). Deferring the onset of
the ACbrrr just increases the hysteresis temporarily. The
overall duty cycle remains largely unaffected.
increasing the hysteresis that is acceptable to you (assuming you
don't, at the same time, alter the setpoint lower). You save
*more* by increasing the setpoint. What the utilities want is
for you to shift *when* you use that electricity.
I.e., if you shift your usage by 10 minutes, the utility still gets
the same amount of money from you -- because you are still
purchasing the same amount of electricity (essentially). *But*,
they have saved money by not having to overload their distribution
or production system in that 10 minute window!
A "thought experiment" <grin> :
Imagine all ACbrrrs require a 30% duty cycle to maintain their
respective residences at the "right temperature" (whatever
*that* is -- it may be different from one residence to the
next). Now, imagine that all of these were synchronized such
that they ALL turned on their compressors at the exact
same instant EACH TIME. The ACbrrr is the largest single
load in most homes -- it can account for up to 30% (?) of the
peak power capabilities of most homes. Most homes typically
don't use anywhere near their *capacity* ON AVERAGE.
Yet, this pathological behavior would have the utility seeing
a *huge* demand... followed by negligible demand (the load that
the rest of your house represents)... followed by that same
huge demand, etc.
And, this would happen while businesses were (elsewhere)
placing *their* huge demands on the system.
As I said:
But, letting each *huge* load (ACbrrr) operate independantly
of each other (as they do currently) means that there is a high
probability (certainty?) that several of them will engage
concurrently. If all of them coincide, then you get a big peak!
Even if that load is only present for a *minute*, the system
has to handle it -- or, "shed it" (by blowing fuses).
distortion brought about by economics.
See if EPRI (Electric Power Research Institute) has any
publications on the subject (I know they have, I am just
not sure if they are available to the public -- I'm not
sufficiently motivated to go dig through my files... :> )
(sort of like matching source impedance to load). You don't want
excess capacity (if it will never be needed) so you want to get
your capacity to exactly fit your load and then you want that load to
*behave* (i.e., if it is likely to increase, then you will need
excess capacity -- which you don't *want*).
Note that the utilities aren't doing this for *your* benefit
(at least not directly). If they were, they could elect to
automatically set your thermostat higher when you are away
at work, etc. They want to sell you power. They just want
to sell it when it costs them the least!
Sylvia Else wrote:
Yes. But, the ACbrr is typically sized such that it can removeD Yuniskis wrote:
Sylvia Else wrote:
There's not much point in having a comfort feature if it's likely
to get turned off at the time of greatest need.
It's not "turned off", per se. Rather, it is *deferred*.
I.e., maybe 10 minutes later your ACbrrr will kick in
instead of at the (slightly) earlier time when the
thermostat called for cooling.
But, as I've commented elsewhere, as soon as the AC is powered up it
will stay on for longer to bring the temperature down again.
Yes, but not *much* longer.
The AC has to run long enough to pump out the heat that's flowed in
during the time it was turned off. Heat is ariving in the building at a
rate that's largely a linear function of the difference between inside
and outside temperature, and the energy required to pump it back out is
a slimilarly linear function. So to calculate the average energy
heat much faster than heat infiltrates the home. E.g., in the
hottest portions of the summer, our ACbrrr rarely hits a 30%(?)
duty cycle.
Coonsider that the amount of hysteresis on many (most?) thermostats
is only a few degrees, at most, so we are essentially calling on
the HVAC system to maintain a comfort region of 2 or 3 degrees.
(some thermostats allow this to be adjusted but I suspect
you will find most users don't know this nor do they even know
why they might *want* to adjust it!). Deferring the onset of
the ACbrrr just increases the hysteresis temporarily. The
overall duty cycle remains largely unaffected.
Again, you're not trying to *save* anything. You *do* save byconsumption - ie power - you just look at the rate at which heat is
flowing in. That rate is minimally altered by deferring the turn on of
the AC. As I've observed, the rate is slightly lower because the average
difference between the inside and outside temperatures is slight lower.
On a very hot day, which is when this load shedding mechanism is likely
to be most used, the saving will be modest, because the change in
average temperature will be a small fraction of the total temperature
difference.
increasing the hysteresis that is acceptable to you (assuming you
don't, at the same time, alter the setpoint lower). You save
*more* by increasing the setpoint. What the utilities want is
for you to shift *when* you use that electricity.
I.e., if you shift your usage by 10 minutes, the utility still gets
the same amount of money from you -- because you are still
purchasing the same amount of electricity (essentially). *But*,
they have saved money by not having to overload their distribution
or production system in that 10 minute window!
A "thought experiment" <grin> :
Imagine all ACbrrrs require a 30% duty cycle to maintain their
respective residences at the "right temperature" (whatever
*that* is -- it may be different from one residence to the
next). Now, imagine that all of these were synchronized such
that they ALL turned on their compressors at the exact
same instant EACH TIME. The ACbrrr is the largest single
load in most homes -- it can account for up to 30% (?) of the
peak power capabilities of most homes. Most homes typically
don't use anywhere near their *capacity* ON AVERAGE.
Yet, this pathological behavior would have the utility seeing
a *huge* demand... followed by negligible demand (the load that
the rest of your house represents)... followed by that same
huge demand, etc.
And, this would happen while businesses were (elsewhere)
placing *their* huge demands on the system.
As I said:
Sure it can! Yes, the overall demand is higher on hot days.The goal isn't to save energy (though I think the laws of thermo
say you *do* save in this case). Rather, the goal is to
get you to *shift* your energy consumption (in time).
The infrastructure is sized for some percentage above nominal.
Of course, going too far *beyond* that causes things to *break*
(hence the blackouts that become newsworthy).
But, things like diesel/coal/gas fired plants that are there
*deliberately* to respond to these short term fluctuations in
demand could, theoretically, be eliminiated if the demand could
be "leveled".
But the demand cannot be levelled by short term adjustments to things
like airconditioner demand. The overall demand is higher on hot days.
But, letting each *huge* load (ACbrrr) operate independantly
of each other (as they do currently) means that there is a high
probability (certainty?) that several of them will engage
concurrently. If all of them coincide, then you get a big peak!
Even if that load is only present for a *minute*, the system
has to handle it -- or, "shed it" (by blowing fuses).
As I said, that is how some businesses operate, in a perverseDeferring an airconditioner load by ten minutes won't alter that.
Getting people to defer their airconditioner loads until night time
would be better, but of course that's not going to happen, at least not
distortion brought about by economics.
It isn't. Hence the motivation for these tariffs.until and unless airconditioners based on a large cold sink become the
norm. That might be a bit of an own goal anyway, environmentally,
because the cold sink would have to be kept cool against the possibility
that the day following would be hot. There would always be some leakage,
so the overall energy consumption of such systems would be higher, even
if they were running on cheaper power.
I suppose it could be argued that some transient peaks arise from a
disproportionate number of AC thermostats switching to on at the same
time, but given the number of ACs around, I'd be surprised if that were
really an issue - the probability of a significant deviation from the
short term average due to such an effect would have to be very low.
See if EPRI (Electric Power Research Institute) has any
publications on the subject (I know they have, I am just
not sure if they are available to the public -- I'm not
sufficiently motivated to go dig through my files... :> )
Exactly! You want to size your load to (ideally) fit your capacity.Nuclear power plants, for example, like to put out a steady amount
of power (can we *please* not let this discussion digress into
the pros and cons of nuclear power? :< ) which doesn't lend
itself to rapid response. If you had <fill-in-the-blank> power
source that was ecnomical to operate and had this characteristic,
then you would have a big incentive to coerce users into
adapting their usage patterns to match.
Also, it is important to define what crteria you actually want to
optimize. E.g. "efficiency" can be defined in a lot of different
ways -- many of which are inconsistent with each other :-/
While nuclear, and indeed coal, plants cannot respond rapidly to changes
in demand, that is not the reason they are not used to handle peak
loads. It's purely a question of economics. It is not cost-effective to
have such plants lying idle - if that's going to happen, you don't build
them, because they're too expensive to be used that way. You build less
capital intensive plant for that purpose - typically gas or oil powered
(though what we do when the gas/oil runs out isn't clear).
(sort of like matching source impedance to load). You don't want
excess capacity (if it will never be needed) so you want to get
your capacity to exactly fit your load and then you want that load to
*behave* (i.e., if it is likely to increase, then you will need
excess capacity -- which you don't *want*).
Note that the utilities aren't doing this for *your* benefit
(at least not directly). If they were, they could elect to
automatically set your thermostat higher when you are away
at work, etc. They want to sell you power. They just want
to sell it when it costs them the least!
D
D Yuniskis
Guest
Sylvia Else wrote:
you would have to investigate in each particular locality
where such tariffs exist. Note that the extent to which the
tariff is adopted (by customers) will directly impact how
effective this technology can be (i.e., if very few folks
"subscribe", then the utility doesn't have much of a tool
at its disposal).
Air conditioners are very reactive loads. As the power system
is stressed, you get voltage sag. For a resistive load, this
is fine -- the decrease in voltage creates a propportional decrease
in *load*.
But, AC compressor motors are essentially "constant power"
devices -- as the voltage decreases, the amount of current
that they require goes up. And, the relationship (phase)
of that current requirement is not coincident with the
supplied *voltage* (i.e. reactive).
Motors *starting* are even worse. (e.g., preventing
ACbrrs from *starting* is more effective than turning *off*
existing ACbrrs, all else being equal).
Note that, to avoid a "catastrophic event", it may only be
necessary to shift a load by a small time interval --just
long enough for alternate supplies to come on-line. E.g.,
imagine a high tension line tripping and effectively
resulting in a reduction of supply -- sag -- so existing
load has to be carried by other -- redundant -- lines.
Until additional lines can be brought into service, the
system is stressed. If you can shed loads at the consumer
you can avoid shedding *all* the consumers (i.e., a major
outage).
The system can *always* break. You are just trying to reduce
the number of scenarios/criteria under which it is brittle.
I think much of this is the basis for the move (in the US) to
upgrade the power distribution infrastructure (aka "Smart
Grid"). No idea how things are done elsewherein the world
but, here, the infrastructure is really pretty outdated.
[N.B. I don't know enough about the "Smart Grid" issue
to comment one way or the other -- I'm just hypothesizing
as to its intent]
How effective they are at doing this currently is something thatmm wrote:
On Thu, 29 Oct 2009 23:35:06 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:
OTOH, if they were to raise their thermostat's setpoint
that degree (or two?) all the time, they would probably not
notice the difference.
But, as I've commented elsewhere, as soon as the AC is powered up it
will stay on for longer to bring the temperature down again.
There is an energy saving,
Radio-controlled AC turn-offs are not meant to be energy saving.
They're meant to be peak-load lessening. It's meant to prevent
brown-outs because of too much load at one time.
And I'm arguing that they do not achieve that goal.
you would have to investigate in each particular locality
where such tariffs exist. Note that the extent to which the
tariff is adopted (by customers) will directly impact how
effective this technology can be (i.e., if very few folks
"subscribe", then the utility doesn't have much of a tool
at its disposal).
Air conditioners are very reactive loads. As the power system
is stressed, you get voltage sag. For a resistive load, this
is fine -- the decrease in voltage creates a propportional decrease
in *load*.
But, AC compressor motors are essentially "constant power"
devices -- as the voltage decreases, the amount of current
that they require goes up. And, the relationship (phase)
of that current requirement is not coincident with the
supplied *voltage* (i.e. reactive).
Motors *starting* are even worse. (e.g., preventing
ACbrrs from *starting* is more effective than turning *off*
existing ACbrrs, all else being equal).
Note that, to avoid a "catastrophic event", it may only be
necessary to shift a load by a small time interval --just
long enough for alternate supplies to come on-line. E.g.,
imagine a high tension line tripping and effectively
resulting in a reduction of supply -- sag -- so existing
load has to be carried by other -- redundant -- lines.
Until additional lines can be brought into service, the
system is stressed. If you can shed loads at the consumer
you can avoid shedding *all* the consumers (i.e., a major
outage).
The system can *always* break. You are just trying to reduce
the number of scenarios/criteria under which it is brittle.
I think much of this is the basis for the move (in the US) to
upgrade the power distribution infrastructure (aka "Smart
Grid"). No idea how things are done elsewherein the world
but, here, the infrastructure is really pretty outdated.
[N.B. I don't know enough about the "Smart Grid" issue
to comment one way or the other -- I'm just hypothesizing
as to its intent]
V
Van Chocstraw
Guest
mm wrote:
Peel it off and find out.Will sunlight damage the electronics of a circuit board?
The power company installed a radio-controlled switch on my air
conditioner, and mounted it on the side of my house. It has an ugly
label which clashes with the natural look of my little yard.
I was peeling it off when I noticed that it covered a fairly darkly
tinted plastic window, and inside the window was the circuit board
that included the receiver and the control that turns the AC off when
the Power Company Central Command wants it to.
There is a much window below the label through which one can see a
green LED. In the late afternoon shaedI only knew I could see the
circuit board because I could see the glowing LED. (Does anyone know
if that means there is power to the AC, or only that there is power to
the controller device itself?)
I stopped unpeeling at that point. I don't want to cause their
product to wear out sooner than normal. I Would the sunlight harm
anything inside?
BTW, after I signed up up for this, a man showed up at my door, handed
me a brochure and then went about mounting the thing to my brick wall.
I watched. He drilled two holes and then two holes for a cable clamp,
all in the mortar, but when it's gone, I'll have to replace the mortar
and the replacement won't match in color. After he was gone I read the
brochure and it said he could mount it to the air-conditioning
condensor if I wanted. I much would have preferred that, so I
wouldn't have to look at the ugly thing at all, label or no label.
But the guy, affable and pleasant as he was, didn't say a thing about
that. The previous device had been mounted to the AC, and didn't have
a label either, but it was a little narrower, and didn't come with
such a long cable.
Thanks.
A
Allodoxaphobia
Guest
On Wed, 28 Oct 2009 17:49:50 -0400, mm wrote:
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm
Just paint the $#%^$ thing to match the side of the house.Will sunlight damage the electronics of a circuit board?
The power company installed a radio-controlled switch on my air
conditioner, and mounted it on the side of my house. It has an ugly
label which clashes with the natural look of my little yard.
I was peeling it off when I noticed that it covered a fairly darkly
tinted plastic window, and inside the window was the circuit board
that included the receiver and the control that turns the AC off when
the Power Company Central Command wants it to.
There is a much window below the label through which one can see a
green LED. In the late afternoon shaedI only knew I could see the
circuit board because I could see the glowing LED. (Does anyone know
if that means there is power to the AC, or only that there is power to
the controller device itself?)
I stopped unpeeling at that point. I don't want to cause their
product to wear out sooner than normal. I Would the sunlight harm
anything inside?
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm