[Greenbuilding] Triac Thermostats
corwyn at midcoast.com
Sat Dec 24 09:18:21 PST 2011
On 12/24/2011 10:55 AM, Richard Garbary wrote:
> "First, outside temperature changes slowly."
> The slower the acceleration and smaller Delta T = fewer baseboards
> coming on simultaneously = less demand on the grid.
> The greater the acceleration and bigger Delta T = more baseboards
> coming on simultaneously = more demand on the grid.
Only if the change is faster than the cycle time of the heater. Let's
say that a baseboard heater in a hypothetical house comes on for 10
minutes every thirty minutes to maintain the house for a given outside
temperature. If the outside temperature changes slower than than the
inaccuracy of the thermostat, in thirty minutes, then the turn on time
of the heater will be essentially random. Thus causing no peak load
when averaged with all the others on the grid.
> "Second, temperature changes happen at different times in different areas."
> True, there's no question lots of weather phenomenon is localized, but
> cold fronts usually affect broader geographic regions
My point isn't that weather doesn't affect larger regions, but rather
that it doesn't do so all at once. If a front takes longer than 30
minutes to pass through an entire grid region, then a front will have no
peak effect on the grid. Yes, the cold will increase the electrical
usage of the grid but there will be no east-ender effect. Imagine a
front traveling such that it crosses the grid area in thirty minutes.
Each 1/3 of the region turns it heat on when the front hits, for an
extra 10 minutes boost. The rolling across the area would mean that
each 1/3 would turn on their heat just as the preceding section turned
theirs off. Perfectly flat demand curve. Anything slower than that, is
essentially random. Only if fronts travel faster than the heat cycle
time would there be a *possibility* of a peak event.
> "Third, different houses react differently to outside temperature changes."
> All else being equal, is there a house that will require less energy for
> heating when the temperature drops?
Depends on what you mean by 'all else being equal'. Two identical
houses, in identical locations, with identical occupants will require
identical heating energy. However, the Canadians did that experiment
and discovered that occupants could vary energy requirements by 40%
(IIRC). So, no, all things are NEVER equal. The difference in actual
cases I have seen is over 700% for single family dwellings in my area.
> "All of those changes happen much slower than the cycle time for
> baseboard heaters. Changing that cycle time from a few minutes to a few
> seconds is going to have a near zero affect on the peak load of
> thousands of customers."
> The quicker the response and at lower wattage per heating element
> guarantees less overlap of large demand not only within the house but
> over many thousands of households.
If every house reacted instantly, the overlap would increase not
decrease. Randomness and averaging are our friends, uniformity is the
enemy. Of course, if you could instantaneously adjust to exactly the
needed energy requirements of your heat loss, your house would have the
lowest peaks, but on the level of an entire grid, no one would notice.
If one really wanted to reduce the peaks in the grid, there is a much
easier way. Just adjust the cost of electricity to the instantaneous
cost, and transmit that cost to all the smart meters in the grid. The
rest would take care of itself.
Thank You Kindly,
Green Fret Consulting
Kermit didn't know the half of it...
topher at greenfret.com
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