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Old 06-13-2015, 06:13 PM   #121
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... look at the dollar chart, and one can see the shocking effect of the off-peak/on-peak difference in costs. It's the difference between 7.41c and 22.26c/kWh.

So, suppose I program the thermostat to cool the home down 1 deg in the hour preceding the rate change, then raise it back after the rate change. The precooling will delay the A/C running for a bit after the high rate kicks in.
As I made the above post, I just finished programming the thermostat to do what I thought of. And here's the result.

First, let me show you the dollar cost of the day before yesterday, 6/11/2015. The effect of the rate going from 7.41c to 22.26c at peak hours, a 3X increase, was quite dramatic.



Here's the consumption cost of yesterday, 6/12/2015, after I programmed the thermostat. See anything wrong?

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Old 06-13-2015, 06:41 PM   #122
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As I made the above post, I just finished programming the thermostat to do what I thought of. And here's the result.

First, let me show you the dollar cost of the day before yesterday, 6/11/2015. The effect of the rate going from 7.41c to 22.26c at peak hours, a 3X increase, was quite dramatic.

Here's the consumption cost of yesterday, 6/12/2015, after I programmed the thermostat. See anything wrong?

Hmmm, I assume weather and sunshine was roughly the same? And watch out for the shift in scales.

The increase before peak looks about as expected. The drop in peak is way more than expected. And what is the peak at ~ 9PM?

Was there some human intervention? Like, wow, it's cold in here, turn the thermostat up? Then later, wow, it's warm in here, turn the thermostat down?

At first I though maybe it was a weekday versus w/e thing, maybe different rates, but I see that is Thursday and Friday.

Do you have an answer, or do I need to update the "I don't know" thread?

-ERD50
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Old 06-13-2015, 06:52 PM   #123
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As I made the above post, I just finished programming the thermostat to do what I thought of. And here's the result.

First, let me show you the dollar cost of the day before yesterday, 6/11/2015. The effect of the rate going from 7.41c to 22.26c at peak hours, a 3X increase, was quite dramatic.



Here's the consumption cost of yesterday, 6/12/2015, after I programmed the thermostat. See anything wrong?

NW, just curious, but where are you getting the cost and usage data from?
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Old 06-13-2015, 07:03 PM   #124
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Heh heh heh... One just can't fool an engineer in technical matters...

The intention was as I described earlier: instead of 78F around the clock, decrease the temperature to 77F an hour before the rate increase to precool, then to go back to 78F at the rate increase. I would expect to save pennies a day, or a few dollars a year, something that just barely beats ERD50's $2.40/yr saving.

At about dinner time of 6 PM my wife complained that she felt hot. I thought it was warm, but assured her that it was just her. At 9 PM, she again complained of being hot. This time, I felt it too, so ran up to the thermostat upstairs to look. 85F. Holy cow! And the thermostat was in "override", meaning the normal program was interrupted and replaced with a fixed and manually entered 85.

How did that happen? I couldn't figure that out. To enter that mode required several button presses, and somehow I messed that up. Nobody else messed with that thermostat but me. Or did the thermostat hickup somehow?

Anyway, after I took it out of override mode, the AC ran non-stop for 1.5 hours to cool it back down to 78F. Hence, the peak at 9 to 10 PM.

Now, with this exercise, I learned that my AC consumes 5.8 kW, the 6.5 kW during that hour minus the "ambient" 0.7 kW due to the two fridges, fans, and lighting.

For a 5-ton AC, that's an EER of 10.3. I guess it's still OK for an AC that's 12-year old.
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Old 06-13-2015, 07:08 PM   #125
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AJA8888, the graphics were captured off the user's screen when I log on to my utility's Web account. They have smartmeters in my area that report hourly usage, and their Web site keeps that data going back 3 years.

This data is excellent, and I looked into it in detail just recently. The homeowner can study his usage pattern and learn a lot. For example, by comparing the 12-month costs before and after my pool pump change, I found out how much the variable-speed pump saves me a year ($260).
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Old 06-13-2015, 07:13 PM   #126
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AJA8888, the graphics were captured off the user's screen when I log on to my utility's Web account. They have smartmeters in my area that report hourly usage, and their Web site keeps that data going back 3 years.

This data is excellent, and I looked into it in detail just recently. The homeowner can study his usage pattern and learn a lot. For example, by comparing the 12-month costs before and after my pool pump change, I found out how much the variable-speed pump saves me a year ($260).
Thanks, I figured something like that. Entergy Texas has one bar graph per month of KW usage and that's it. I guess they don't want us knowing the good stuff.
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Old 06-13-2015, 07:16 PM   #127
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My utility company is SRP - Salt River Project. Their programmers beat Entergy's programmers. Perhaps you could send this info to them to shame them into doing better.

PS. I am waiting to see how much my expensive new windows are saving me a year, using this data.
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Old 06-13-2015, 07:41 PM   #128
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My utility company is SRP - Salt River Project. Their programmers beat Entergy's programmers. Perhaps you could send this info to them to shame them into doing better.

PS. I am waiting to see how much my expensive new windows are saving me a year, using this data.
We are supposed to get smart meters 'sometime soon', though probably in the next year or two. I'm pretty sure they allow hour-by-hour readings, I sure hope so. Heck, I'd like to be able to drill down to 1 minute intervals, to see things like the well pump and sump pumps kicking in. I mentioned we had a leak at the well, and even an hourly breakdown might have led me to wonder about the energy increase overnight (somewhat expected every third day when the water softner runs and the pump needs to feed it).

Yep, those humans keep messing up our well conceived experiments!

I hope you continue with the 1 or 2 degree delta though, it would be interesting to see the effect, and if you can go any further with it. I might need to cut my little experiment back - while it still seems pretty light at sunset, a full hour after is kind of long to wait, it is getting pretty dark. Change it to half an hour for a $1/year savings? If I can only find a few hundred more things like that, we are talking some real money!

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Old 06-15-2015, 11:32 AM   #129
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Looking at that TOD peak rate chart, I wonder if it would make sense for refrigerators to come with a set-back thermostat? Run it a few degrees below average for a few hours before peak rates to get a good thermal 'soak', then raise it a few degrees during peak. A well insulated fridge won't lose much in a few hours.

And the defrost cycle could be programmed around those times (I think they normally go every 8 hours to quickly remove a small amount of frost at a time?)


If you were really gung-ho, put the dinner food in a cooler ahead of time to avoid open/close the fridge during the peak.


Probably a very small savings, but it would cost near zero - the fridges already have controllers in them. Ahhh, but an added plus would be the fridge would not be dumping out heat at this time, which also has to be removed by the A/C!

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Old 06-15-2015, 12:47 PM   #130
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Looking at that TOD peak rate chart, I wonder if it would make sense for refrigerators to come with a set-back thermostat? Run it a few degrees below average for a few hours before peak rates to get a good thermal 'soak', then raise it a few degrees during peak. A well insulated fridge won't lose much in a few hours.
How much of the country has peak use pricing for electricity?
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Old 06-15-2015, 01:01 PM   #131
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How much of the country has peak use pricing for electricity?
I don't know, probably not much %-wise. But this would cost near nothing in any fridge that already has a chip controller and some sort of display ( or a bluetooth link).

Mostly just theorizing, probably not much gain at all.

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Old 06-15-2015, 04:20 PM   #132
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... I wonder if it would make sense for refrigerators to come with a set-back thermostat? Run it a few degrees below average for a few hours before peak rates to get a good thermal 'soak', then raise it a few degrees during peak. A well insulated fridge won't lose much in a few hours.

And the defrost cycle could be programmed around those times (I think they normally go every 8 hours to quickly remove a small amount of frost at a time?)

...

Probably a very small savings, but it would cost near zero - the fridges already have controllers in them. Ahhh, but an added plus would be the fridge would not be dumping out heat at this time, which also has to be removed by the A/C!
Or delay making ice during peak hours. The software implementation to have a "smart" fridge is piece of cake as the fridges all have microcontrollers, but the saving is also small, compared to CFLs and LEDs, and consciously turning lights off when not in use, taking shorter showers, etc...
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Old 06-15-2015, 07:17 PM   #133
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but the saving is also small, compared to CFLs and LEDs, and consciously turning lights off when not in use, taking shorter showers, etc...
Doesn't matter, right? It's all about the marketing and 4 color sticker you can put on the door of the floor demo fridge. "World's first Smart Fridge! Saves you money every day by automatically detecting your patterns of use and shifting high-energy use to periods of cheapest electricty in your area."

Or, a green approach: "Saves energy every day. High energy tasks automatically get moved to times of greatest Carbon-Free energy production."
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Old 06-15-2015, 08:52 PM   #134
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Souns like a good business marketing plan to me. When do we go into business?

Darn, how did we reveal all this to the public before applying for a patent?

No, on 2nd thought, I am willing to bet someone has patented this long ago.

Well, perhaps so long ago that the patent has gone expired, so anybody can do this now.
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Old 06-19-2015, 09:51 PM   #135
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... I hope you continue with the 1 or 2 degree delta though, it would be interesting to see the effect, and if you can go any further with it...
We just descended back from the high country down into the oven, and I just looked up the power usage of yesterday. It was a hot day, with a high of 114F.

Here's the hourly energy usage. It peaked up a bit in the hour before the peak rate, and was 0.6 kWh higher than the preceding hour (5.1 vs 4.5). And as the thermostat was raised back 1 degF, the power was 0.9 kWh lower than the hour afterwards (4 vs 4.9 kWh).



In terms of dollar costs, here's the chart. I saved about $0.14 a day with this precooling. Note that I only lowered the temperature 1F, then returned it back to the normal setting. I would save more by raising it 1F in the hour after the peak rate (to keep the daily average temperature the same). But if I can be comfortable with 79F, then I can raise the average setting up and save even more. So, we have to make it a goal to not going over a certain desired temperature.

By lowering, but never raising it above a desired setting, I can save money while being cooler at the same time. How about that?

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Old 06-20-2015, 10:49 AM   #136
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Pretty neat, NW-Bound.

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By lowering, but never raising it above a desired setting, I can save money while being cooler at the same time. How about that?
80 deg F still seems darn hot to me. If you can save money while pre-cooling to 79 deg, I'd sure looking in to going to 78 or 77 to save even more and be a bit more comfortable for longer. And I wonder if the reductions in the peak energy use would be greater if the setback began an hour earlier (giving time for dense materials like drywall on the interior walls, etc) to achieve a lower temp during a longer "cold soak" period.

Despite your 14 cent savings, you're actually using more power (because the heat loss through the walls is higher for a higher temp difference). The power company's variable rate structure is encouraging higher energy consumption overall (though at a time they can better handle it, I guess). I'm not sure if that was the intent. . .
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Old 06-20-2015, 12:18 PM   #137
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No, as I said the normal setting is 78F around the clock. The precool temperature is 77F. It's quite comfortable here where it is dry.

Yes, the total power usage may be a bit higher despite the $0.14 savings due to the rate structure. Yes, that's not the utility's intent. However, individuals always operate to their economics advantage, oui? That's how we take advantage of tax breaks, deductions, etc...
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Old 06-20-2015, 12:39 PM   #138
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Pretty neat, NW-Bound.


80 deg F still seems darn hot to me. If you can save money while pre-cooling to 79 deg, I'd sure looking in to going to 78 or 77 to save even more and be a bit more comfortable for longer. And I wonder if the reductions in the peak energy use would be greater if the setback began an hour earlier (giving time for dense materials like drywall on the interior walls, etc) to achieve a lower temp during a longer "cold soak" period.

Despite your 14 cent savings, you're actually using more power (because the heat loss through the walls is higher for a higher temp difference). The power company's variable rate structure is encouraging higher energy consumption overall (though at a time they can better handle it, I guess). I'm not sure if that was the intent. . .
I think he is using 78 as 'normal', and dropping to 77 before peak to pre-cool. Going to 79 would be the warmer setting, that he feels if he could handle part of the day why not all day?

Even not wanting to go above 78F, I'd try pre-cooling a bit more/longer to get more 'soak'. Like maybe 1 hours at 77, one hour at 76, then hit peak? Maybe even a couple hours of peak at 77 before going back to 78 so the change is slower? Still looks like we talking small $s, until he gets that thermal mass installed. "Dear, why are you stacking 1,000 jugs of water in front of the A/C vents?"

Quote:
Despite your 14 cent savings, you're actually using more power (because the heat loss through the walls is higher for a higher temp difference). The power company's variable rate structure is encouraging higher energy consumption overall (though at a time they can better handle it, I guess). I'm not sure if that was the intent. .
Utilities pay a premium for peak power, so while conservation would be 'better' than shifting, even an increase in total power might be desirable. The entire infrastructure needs to handle the peaks - marginal costs skyrocket if it means more capacity.


Hmmm, but this didn't change the peak capacity required, it only lowered it for an hour or two. I guess if those prices reflect the utilities costs, they don't care? But the real good thing for the grid would be lower peak usage throughout the peak, every day.

Our utility offers an option to have your AC compressor shut off for 15 minutes out of an hour ( limited number of times a day I think). No thanks, my AC is not over-sized, and we have occasionally had a large number of guests on the hottest day of the year, and our AC really doesn't keep up with people going in/out. I don't want it shut off just when I need it most! But I guess that little bit of flexibility can help the utility manage their peak (but if the average AC is not running more than 75% duty cycle, it wouldn't seem to do much - unless they really had a 15 minute peak?). A dual stage AC probably negates this effect anyhow - the larger stage will just kick in to make up the difference?

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Old 06-20-2015, 01:32 PM   #139
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The reason I could save a bit of money while enjoying a cooler temperature briefly was a side effect of the binary rate structure. It has a cliff, not unlike the income cliff in the ACA subsidy schedule.

The rate change for peak hours should be more gradual, but that makes it too complicated for the home owners to deal with. Ideally, it should be in real-time, and fluctuates with the "market rate". OK, so you will have a real-time display of the costs, so that you can look at it before dinner time and say to yourself "Well, the rate is 50c right now, so today maybe I should be microwaving a frozen dinner instead of making that beef stew".

Anyway, anytime you have some non-linearities in the system like these cliffs, you tend to have all kinds of contradictory results. Control system engineers know that non-linearities are terrible to deal with, if one tries to optimize the system.
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Old 06-20-2015, 01:38 PM   #140
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No, as I said the normal setting is 78F around the clock. The precool temperature is 77F. It's quite comfortable here where it is dry.

Yes, the total power usage may be a bit higher despite the $0.14 savings due to the rate structure. Yes, that's not the utility's intent. However, individuals always operate to their economics advantage, oui? That's how we take advantage of tax breaks, deductions, etc...

Not only is 80 to warm for me, so is 78! I will economize at night by hanging the meat only in my bedroom at night and shut the house unit off. But that is as far as I go. I need 74 degrees for perfect boxers and tshirt room temp. But my peak August bill will be $130 tops on a heat wave and that equates to less than $5 a day to be comfortable. If my bill was considerably higher I imagine I would convince myself I am very comfortable at 78 though.


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