[Greenbuilding] Triac Thermostats

[Corwyn]

On 12/24/2011 10:55 AM, Richard Garbary wrote:
> Corwyn:
>
> Argument:
> "First, outside temperature changes slowly."
>
> Response:
> 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.

> Argument:
> "Second, temperature changes happen at different times in different areas."
>
> Response:
> 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.

> Argument:
> "Third, different houses react differently to outside temperature changes."
>
> Response:
> 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.

> Argument:
> "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."
>
> Response:
> 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,

Corwyn

-- 
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
http://www.greenfret.com/
topher at greenfret.com
(207) 882-7652