Re: A research team has managed to coordinate 100 domestic air conditioners to stabilise the power grid in real time, as if they were a flexible power plant.

On 6/14/2025 4:09 PM, KevinJ93 wrote:

On 6/14/25 3:29 PM, Don Y wrote:

On 6/14/2025 2:53 PM, Carlos E.R. wrote:

That's not what they are doing. They are changing the load in tiny parts of the cycle, 50 or 60 times per second. Changing the load waveform.

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No, they are deferring the start of the compressor and/or blower.
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As home thermostats are not precision devices -- AND ONLY MEASURE THE
TEMPERATURE AT ONE LOCATION IN THE HOUSE'S VOLUME -- an occupant
would likely never notice if the plant turned on at its "intended"
setpoint or some delta above.
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The question is whether or not the control algorithm allows the
local plant to be operated with greater *symmetric* hysteresis
or if it just lets the cooling cycle be delayed without regard
to the actual temperature.
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It's just silly to rely on antiquated control approaches when
it's so easy to have smarts "at the edge".  E.g., how smart is
it to allow the thermostat to call for cooling (or heat)
one minute before the setpoint temperature is SCHEDULED
(by the user's scheduling decisions!) to go up (or down) by
an amount that likely exceeds the hysteresis in the system?
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E.g., house maintaining 68F for heat and at 1 minute prior to bedtime,
the thermostat notices it is now 67.9F and calls for heat... when
the setpoint will be lowered to 62 a minute later?  (and, the
changing of the setpoint likely causing the heating cycle to be
prematurely aborted:  "Oh, the house is now at 67.93 degrees
and the setpoint is 62 so let's shutdown the plant instead of
waiting for it to attain the OLD setpoint of 68F...")
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Imagine the stresses on the equipment by all this ineffective
cycling (esp the compressor!)
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Ideally, you want to notice how the system behaves and tune
your controls to maximize *it's* ability to satisfy the
user's stated needs while reaping some rewards for the provider
(and, ultimately, for the user by way of reduced capital
investments)

 Many thermostats have had those features for at least the last decade.
 My ten year old Carrier thermostat addresses most of those items. It also has

Then, how many minutes BEFORE as setpoint change will it ignore the
scheduled change?  Does it look at the response of the interior to
such changes and adapt so the "back off" varies with temperature,
setpoint difference, outdoor temperature and wind speed?  Otherwise,
you're just shifting the point at which it makes an unfortunate
change in control.
[The thermostat that I designed for my parents, *40* years ago
does those things.  But, still for a single measurement point
in the house (e.g., my bedroom was always considerably warmer
than the rest of the house; the kitchen always considerably
cooler -- partly because of the house's orientation on the lot
and partly because of the way the heating was plumbed).  But,
the thermostat knew how to get the heat (no central air) *to*
the desired temperature *at* the specified time -- instead of
simply switching setpoints at those times]

an exterior outside temperature sensor and takes in weather predictions over the internet so that it ramps the temperature appropriately and maintains a comfortable temperature and humidity.

I do that here -- adding decision criteria as to when the swamp cooler
can be called on to provide cooling (cognizant of a "comfort factor").
If today's OUTDOOR temperature is likely to be more than ~30 degrees
above the desired indoor temperature, then the cooler is ill-advised
as refrigeration will be required once the indoor-outdoor differential
reaches that point.  As I (currently) have to rely on manual action
to vent the house adequately, you don't want to have to tell the
homeowner to close all the windows so the ACbrrr can come online.

The compressor protection is commonly built into the compressor control unit so that any command from the thermostat that compromises the compressor safety is ignored until safe.

The compressor won't usually turn ON until a suitable time has elapsed
to ensure the compressor's pressure has leaked off to a safe starting
point.  But, once commanded on, it will usually turn off as soon as
told to turn off.  Has it done any meaningful work in that short
time?  Or, just cycled out of blind devotion to the control signal?
This makes for some interesting design decisions.  E.g., if the
user specifies a setpoint of 68F at 7AM and 72F at 7:30AM, it is
possible that you might need to overshoot the 68F in order to
be able to attain the 72F.  Likewise, specifying 68F at 7A
and 65F at 7:30A... should it even bother trying to meet the
earlier specification given that the user has effectively
said he doesn't care about that temperature 30 minutes later?
Historically, the user is allowed to remain ignorant of the costs
of his decisions.  Largely because the control systems don't
have the knowledge -- nor ability -- to inform the user.
"If you raise your cooling temperature by 1 degree, I can save
you $X today."