[Greenbuilding] Triac Thermostats

Richard Garbary richard6 at gmail.com
Fri Dec 23 12:05:36 PST 2011


"The grid cares about the total size of the electric load (resistive or
inductive) and the peakiness of it."

Yes, I agree. Especially when a cold front comes in and temperatures and
thermostats drop drastically. Simultaneous switching on of baseboards puts
a heavy load on the grid. Let's call this "The EastEnders Effect"
When outside temperatures are static, you'll have random switching on and
off with no peakiness and no need for the grid to "cope". Billions of
dollars in "coping" infrastructure sit idle most of the time just to deal
with these swings in demand. Pumped storage and peaker plants should not be
looked at as the first line of defence. Demand-side management will go a
long way to help right-size the grid. For example: "Pumped storage projects
are net consumers of energy in that for every one kWh of energy generated
during peak periods, more than one kWh of off-peak energy is required for
pumping. Due to evaporation losses from the exposed water surface and
mechanical efficiency losses during conversion, only between 70% and 85% of
the electrical energy used to pump the water into the elevated reservoir
can be regained in this process."
http://uspowerpartners.org/Topics/SECTION2Topic-PumpedStorage.htm. So, we
end up inflating our base load infrastructure to deal with the peaks!
 That's why I don't worry too much about the minimal thermal loses on my
well insulated 375 watt water heater and think triacs have a place in
helping an overburdened grid.



On Mon, Dec 19, 2011 at 8:01 PM, John Straube <jfstraube at gmail.com> wrote:

>  Modulating electric heaters WONT save money if you discount the unproven
> (and unlikely in my opinion) comfort savings.  Exact same energy will be
> delivered.
> All that changes with any strategy is temperature stability.
> It is quite easy to buy a new electronic thermostat for baseboards that
> control +/-0.5.  The built-in thermostat that often come with baseboards
> often are +/-1.5F.
> I sure would not recommend these for most space heating applications.  For
> special applications,  they are neat.
> Dr John Straube, P.Eng.
> www.BuildingScience.com
> On 11-12-19 6:13 PM, Corwyn wrote:
> > On 12/19/2011 5:32 PM, John Straube wrote:
> >> You cant use a normal on-off thermostat with a modulating control.
> >> The simplest thermostat for use with an SCR or TRIAC would have
> >> what is called proportional control. For example, if the
> >> temperature fell below 68F by 0.1 F, 100W would be delivered to the
> >> heater, of the temperature dropped to 67.8F, 200W would be provided
> >> and if it dropped to 67F, 1000W would be delivered. Because a
> >> smaller amount of heat is added with small temperature drops, the
> >> temperature does not oscilate as much as an on-off control with a
> >> 3F deadband as described in the example.
> >
> > But, it isn't, in fact, delivering 100W to the heater. It is
> > delivering 1000W to the heater for 1 second out of 10. Or perhaps
> > 0.1 seconds out of 1 second. I guess that is the point I am trying
> > to make.
> >
> > Since I have trouble believing that anyone *needs* within 0.1F
> > stability in their house temperature; a thermostat upgrade will get
> > most of the accuracy improvement anyway; and since no one has shown
> > energy savings, I would recommend these only if the lifecycle
> > benefits make them cheaper.
> >
> >
> > Thank You Kindly,
> >
> > Corwyn
> >
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