Freezer Insulation of R-40 per inch or better

[SV THIRD DAY]

Originally Posted by Waterrat10

I see what you are referring to about cutting energy in half. Let me asked this which may clarify this for you. Do you save the same amount of amp hours going from R2- R12 as you would save going from R12 to R22?

Sticking with our 80AH R10 example that I gave in my first response to seeing your graph for simplicity:
R10 80AH
R20 40AH = Saves 40AH
R40 20AH = Saves 20AH

You save half as much daily power with each successive doubling of the R-value. That's why there is a diminishing return of the power savings...cutting in half of a smaller number each time you double the R-value keeps giving you a smaller number. It's why most people settle on a R20 or R30 Box but rarely do they go up above the R40 range, it just isn't worth it from a Cost/Energy savings standpoint.

[Waterrat10]

ENERGY BOOMER: Why Doubling Attic Insulation Does Not Cut Your Energy Use in Half

This might explain it a little better. I do agree that you are cutting the energy need each time in half but each additional half is a small piece of the whole. If I have a pizza with 8 slices and we cut that in half we get 4 slices. If I cut the 4 slices in half again we get 2 slices not an additional 4 slices. Each reduction in half is a smaller percentage of the whole.

If I have 100 amp hours on a R2 fridge and insulate it to R10 I will save 80 amp hours. If I go to R20 I will save a total of 89.5 amp hours. If I then go to R40 I will save a total of 94 amp hours. So yes I am cutting it in half each time I double insulation but the percentage of the total is less and less of a gain.

[SV THIRD DAY]

Originally Posted by Waterrat10

So yes I am cutting it [Energy use] in half each time I double insulation but the percentage of the total is less and less of a gain.

Cruisers don't care about the % of the total being less with each doubling, they care about total daily power usage. Real world vs Chat Room.

But I'm glad you came around to exactly what I have been saying from the start...whew...that was like pulling teeth...

[Terra Nova]

Originally Posted by Waterrat10

ENERGY BOOMER: Why Doubling Attic Insulation Does Not Cut Your Energy Use in Half

This might explain it a little better. I do agree that you are cutting the energy need each time in half but each additional half is a small piece of the whole. If I have a pizza with 8 slices and we cut that in half we get 4 slices. If I cut the 4 slices in half again we get 2 slices not an additional 4 slices. Each reduction in half is a smaller percentage of the whole.

If I have 100 amp hours on a R2 fridge and insulate it to R10 I will save 80 amp hours. If I go to R20 I will save a total of 89.5 amp hours. If I then go to R40 I will save a total of 94 amp hours. So yes I am cutting it in half each time I double insulation but the percentage of the total is less and less of a gain.

No need to over-complicate it. SV stated it clearly.

[Waterrat10]

Originally Posted by SV THIRD DAY

Sticking with our 80AH R10 example that I gave in my first response to seeing your graph for simplicity:
R10 80AH
R20 40AH = Saves 40AH
R40 20AH = Saves 20AH

You save half as much daily power with each successive doubling of the R-value. That's why there is a diminishing return of the power savings...cutting in half of a smaller number each time you double the R-value keeps giving you a smaller number. It's why most people settle on a R20 or R30 Box but rarely do they go up above the R40 range, it just isn't worth it from a Cost/Energy savings standpoint.

I did not see this post when I posted my last post. It sounds like we are in agreement. Diminishing returns on effort. What I have been saying all along. It is exponential decay. Therefore you gain less and less the more you insulate. Going from R20 to R40 is less then a 5% reduction in energy where going from R2 to R20 is a 90% reduction in energy use. I believe we are debating around the same point.

[CaptnBry]

Looks like the Cost per R value (SV THIRD DAY) is a good Guide! Thanks!

I built a Prototype refrigeration system and am now looking at Aerogel or VIPs to get the thickness down, while keeping the system efficient.
Pic attached: Partially built, a box in a box with an extra "Bread Box" on top to keep the sun off everything.

The current prototype is of R-5x1"panels "wall insulation", not Polyiso.
Thickness is 4" to 8". The thinner being in "front" where people need to reach over and past the insulation for access. This and the lid/hatch are of best ROI for Aerogel.

The BD35 is SP water cooled Isotherm 2351. Yes, boat movement helps efficiency noticeably)
Total solar power is 250W. (LEDs lighting)
Battery is 12v x 225AH (plus a starter 12v batt)

The whole yacht's usage recharges on a typical day by 2pm latest, allowing for desalination work thereafter (Spectra 200C 7amps makes 8gallons per hr)

The prototype runs about 14Ahr overnight (tough to isolate like a Lab, with the sun rising) Ambient is about 75F day, 62F nights.
It has FOUR sections:
1) Freezer where the evaporator is. 15-25F Thermostat is above the evaporator, in contact)
2) Below that is 1/2Cft freezer storage. Blue-Ice filled-in; 20-30F
3) After 1" of R-5, there is the refrigeration area. 38-55F (usually lined with beer cans)
4) Above all this, 4" of R-5 away is a "Bread Box" to keep the window's heat off the fridge. always below 65F.


a 4-ch temp monitor (by Perfect Prime, AMAZON) shows the temps as stated above.
I've Cruized this setup for several weeks throughout the Channel Islands, CA this summer full time and it works well. Yes the fridge area is a bit warm when 55F. One goal was to fast freeze fish in the evaporator, then store that below in the 'freezer storage'; which works well. The Bread Box was almost a joke when built since the boat shape just kinda dictated it. But this too has been great, since handmade bread keeps longer, 4 days+ and is good for soft butter too (yum)

The final version will be built inside-out; tech first, wood finish last.
The HighTEch isulation ($$) will be at LEAST for the front, top, and hatch.
I'll fibreglass the whole thing, no drain, inside for a water-tight tub.
The hatch I'll cast in-place with FRP, 404 filler, and an 1/8" freezer seal with hardware latch.

Finish Carpentry is my weak spot, and awful expensive....thats another Thread, LoL!
Thanks for your expert advice SV Third Day and All!!

[CaptnBry]

pic of Prototype

[SV THIRD DAY]

Originally Posted by Waterrat10

Going from R20 to R40 is less then a 5% reduction in energy.

Amigo, check your math because cutting the power usage from 40AH to 20AH by doubling the R-Value is a 50% reduction in energy usage, not a 5%.

[Terra Nova]

Originally Posted by CaptnBry

...
The hatch I'll cast in-place with FRP, 404 filler, and an 1/8" freezer seal with hardware latch.

Finish Carpentry is my weak spot...

Unless you want "Engineering" to be a close second (weak spot) rethink your hatch plan and 1/8" gasket.

[Waterrat10]

If anyones statements are misleading sir it would be yours. It is not linear. It is classic exponential decay. The more I add the less I get for each addition. So real world wise going from R20 to R40 will only make a minuscule difference in your amp hour if you open your fridge a couple of times a day to drink said beer. Your 5% savings will really only be .5% savings if you are lucky. If I shell meet you someday we can open our fridges and share some beers and argue circles some more. Cheers

[Waterrat10]

Originally Posted by SV THIRD DAY

Amigo, check your math because cutting the power usage from 40AH to 20AH by doubling the R-Value is a 50% reduction in energy usage, not a 5%.

Sir you forgot about the R2-R10 and R10 - R20 part of the equation which is by far the biggest gain. There are plenty of old boats in real world that have R2-5 with air leaks, poor missing insulation etc etc. You are cherry picking.

[Waterrat10]

Overall energy use.
Going from R-2 to R-10 save me about 80 amp hours
R-2 = 100 amp hours needed
R-20 = 10 amp hours needed
R-40 = 5 amp hours needed

That is a very small gain. If I open this fridge 5 times a day that 5 amp hours mean squat.

[SV THIRD DAY]

Originally Posted by Waterrat10

So real world wise going from R20 to R40 will only make a minuscule difference in your amp hour if you open your fridge a couple of times a day to drink said beer.

Ha ha ha...first he agrees with me...then he falls back off the cliff and forgets everything we managed to teach him in this thread. So lets do one final review before flunking him from the class:

Going from a R20 to a R40 Box cuts your power usage in half (something you previously admitted but have now forgotten)
So if you were using 60AH you would be down at the 30AH range.
Our friend Waterrat10 can call a 50% reduction in power usage "minuscule" but to real cruisers out in the real world that's a big deal.

Originally Posted by Waterrat10

Sir you forgot about the R2-R10 and R10 - R20 part of the equation which is by far the biggest gain. There are plenty of old boats in real world that have R2-5 with air leaks, poor missing insulation etc etc. You are cherry picking.

Who's forgetting about anything?
Going from R2-R10 and then from R10 to R20 does not have ANY bearing on the simple math and fact that going from a R20 to a R40 will cut your power usage by 50% and not 5%. Going from R10 to R20 also cuts it in half...again...simple Math. Each time you double the R-Value of a Box you cut the energy usage in half. And each time you are cutting a number in half, the real number gets smaller, it's simple math Sir.

Originally Posted by Waterrat10

Overall energy use.
Going from R-2 to R-10 save me about 80 amp hours
R-2 = 100 amp hours needed
R-20 = 10 amp hours needed
R-40 = 5 amp hours needed
.

In your OWN EXAMPLE you show that the power usage in going from R20 to R40 is a 50% power savings (10AH down to 5AH is 50% but above you said it was 5%)...for the love of Pete, try and work with me here will ya...

Listen, it's not my problem that you can't get it and I know I can be a smart ass at times, but I've went above and beyond here in trying to help you and it's just time to give up. So class is closed for today, at least for you because I'm sending you to the principal's office and I have to work on my teak deck replacement project. Epoxy Day!

[Terra Nova]

Originally Posted by SV THIRD DAY

...it's not my problem that you can't get it, I've went above and beyond here in trying to help you..

Indeed you have. And he doesn't.

[newhaul]

Originally Posted by Waterrat10

Overall energy use.
Going from R-2 to R-10 save me about 80 amp hours
R-2 = 100 amp hours needed
R-20 = 10 amp hours needed
R-40 = 5 amp hours needed

That is a very small gain. If I open this fridge 5 times a day that 5 amp hours mean squat.

5 ah means more than you give it credit it means that I can run a couple extra fans at night to keep cool or run a forced Air heater to keep warm as the case may be.