Second system extension extension.

User avatar
Joeboy
Posts: 8008
Joined: Mon May 31, 2021 4:22 pm
Location: Inverurie

Re: Second system extension extension.

#341

Post by Joeboy »

Stig wrote: Wed Jul 20, 2022 8:45 am I've been taking ice packs out of the freezer and sitting them on the bedside table overnight the last couple of nights*, then putting them back to re-freeze in the morning. Don't know how much it helps but anything's worth a try to get a better nights sleep at the moment!

*Don't put your phone next to them as there's quite a puddle of condensation in the morning.
Stig, I used huge tupperware boxes in Spring, not filled all the way to top and with lids on, probably about 3 ltrs per cube and did two of them. It was more for a power off icebox scenario here in Turkey. My point is that they took a LONG time to melt when I turfed them out onto the patio at the end of trip. I defo think the large ice cube and fan has potential in these overheating times.
19.7kW PV SE, VI, HM, EN & DW
Ripple 7kW WT & Gen to date 19MWh
42kWh LFPO4 storage
95kWh Heater storage
12kWh 210ltr HWT.
73kWh HI5
Deep insulation, air leak ct'd home
Zoned GCH & Hive 2
WBSx2
Low energy bulbs
Veg patches & fruit trees
openspaceman
Posts: 662
Joined: Mon Mar 21, 2022 7:37 pm

Re: Second system extension extension.

#342

Post by openspaceman »

Stinsy wrote: Wed Jul 20, 2022 7:14 am

I left the jug in the freezer from 11am-ish to 8pm, by that time it had partially frozen. I set the freezer to -14℃ overnight overnight and by morning the jug was completely frozen.

I wanted the jug to freeze in the daytime and defrost (at least partially) overnight. So that part is a “fail”. Maybe my freezer struggles to achieve super-low temperatures on a very hot day?
If the freezer temperature is accurate then if it all froze at -14C it was not a saturated solution.

The point is you are aiming for the solution to change state at very near the temperature you want to maintain in the freezer, it's the heat getting into the freezer from the outside that causes the temperature to go up and trigger the thermostat but if the heat getting in melts the brine without changing the temperature i.e. the heat of fusion of the ice is being absorbed but the temperature doesn't change.

Now it may just be that as water and ice are not very good conductors and as the difference in temperature is very low, from above and you need delta T for heat to flow from a high temperature (the freezer) to a lower temperature (the ice), then a solid block of ice may not have enough surface area to defrost overnight,
Morso S11
FIT
16 Sharp PV panels facing WSW 4kW
Solarmax 4200S inverter
Non FIT
3 Canadian solar DC coupled 1.75kW facing SSE
Storage
Growatt SPA3000TL BL inverter ac coupled
Growatt GBLI6532 6.5kWh lithium phosphate battery
User avatar
Stinsy
Posts: 2742
Joined: Wed Jun 02, 2021 1:09 pm

Re: Second system extension extension.

#343

Post by Stinsy »

openspaceman wrote: Wed Jul 20, 2022 1:47 pm
Stinsy wrote: Wed Jul 20, 2022 7:14 am

I left the jug in the freezer from 11am-ish to 8pm, by that time it had partially frozen. I set the freezer to -14℃ overnight overnight and by morning the jug was completely frozen.

I wanted the jug to freeze in the daytime and defrost (at least partially) overnight. So that part is a “fail”. Maybe my freezer struggles to achieve super-low temperatures on a very hot day?
If the freezer temperature is accurate then if it all froze at -14C it was not a saturated solution.

The point is you are aiming for the solution to change state at very near the temperature you want to maintain in the freezer, it's the heat getting into the freezer from the outside that causes the temperature to go up and trigger the thermostat but if the heat getting in melts the brine without changing the temperature i.e. the heat of fusion of the ice is being absorbed but the temperature doesn't change.

Now it may just be that as water and ice are not very good conductors and as the difference in temperature is very low, from above and you need delta T for heat to flow from a high temperature (the freezer) to a lower temperature (the ice), then a solid block of ice may not have enough surface area to defrost overnight,
Well I put it in the fridge (set to 6℃) last night and is is still only c. 30% defrosted!
12x 340W JA Solar panels (4.08kWp)
3x 380W JA Solar panels (1.14kWp)
5x 2.4kWh Pylontech batteries (12kWh)
LuxPower inverter/charger

(Artist formally known as ******, well it should be obvious enough to those for whom such things are important.)
openspaceman
Posts: 662
Joined: Mon Mar 21, 2022 7:37 pm

Re: Second system extension extension.

#344

Post by openspaceman »

Stinsy wrote: Wed Jul 20, 2022 2:10 pm
Well I put it in the fridge (set to 6℃) last night and is is still only c. 30% defrosted!
Then it will be that there is not enough heat exchange surface because a delta T of more than 6C should melt it. Perhaps a shallower metal tray?

I still cannot try this as our freezer is chocka.
Morso S11
FIT
16 Sharp PV panels facing WSW 4kW
Solarmax 4200S inverter
Non FIT
3 Canadian solar DC coupled 1.75kW facing SSE
Storage
Growatt SPA3000TL BL inverter ac coupled
Growatt GBLI6532 6.5kWh lithium phosphate battery
User avatar
Joeboy
Posts: 8008
Joined: Mon May 31, 2021 4:22 pm
Location: Inverurie

Re: Second system extension extension.

#345

Post by Joeboy »

Well, with no salt to hand I filled a few lidded boxes to a total of 7 ltrs and stuck em in the freezer alongside the 3 types of gin, ice cubes and frozen glasses. Max we see out here is about 4 hours without power, at a push 6. I have a 200ltr water tank on ballcock in the highest part of house that kicks in, multiple usb battery packs and this added coolbox scenario. Keeps it all civilised in the GnT dept along with water for toilets and enough head pressure to run the lower level shower. Beyond that we go to scented candles and the fridge for ice cubes.... :D
I reckon we are good for about 2.5 days. :twisted:

Are you guys seeing the freezer box photo? Please confirm one way or t'other, thanks.

Image
19.7kW PV SE, VI, HM, EN & DW
Ripple 7kW WT & Gen to date 19MWh
42kWh LFPO4 storage
95kWh Heater storage
12kWh 210ltr HWT.
73kWh HI5
Deep insulation, air leak ct'd home
Zoned GCH & Hive 2
WBSx2
Low energy bulbs
Veg patches & fruit trees
Bugtownboy
Posts: 959
Joined: Tue Jun 01, 2021 12:35 pm

Re: Second system extension extension.

#346

Post by Bugtownboy »

All good, Joe - pic of the freezer portion of the fridge, various EtOH bottles.
User avatar
Joeboy
Posts: 8008
Joined: Mon May 31, 2021 4:22 pm
Location: Inverurie

Re: Second system extension extension.

#347

Post by Joeboy »

Bugtownboy wrote: Wed Jul 20, 2022 4:32 pm All good, Joe - pic of the freezer portion of the fridge, various EtOH bottles.
Epic! Cheers BTB! :D
19.7kW PV SE, VI, HM, EN & DW
Ripple 7kW WT & Gen to date 19MWh
42kWh LFPO4 storage
95kWh Heater storage
12kWh 210ltr HWT.
73kWh HI5
Deep insulation, air leak ct'd home
Zoned GCH & Hive 2
WBSx2
Low energy bulbs
Veg patches & fruit trees
AE-NMidlands
Posts: 2007
Joined: Wed Jun 02, 2021 6:10 pm

Re: Second system extension extension.

#348

Post by AE-NMidlands »

looks good... if a bit clean by our standards!
(Like others, our freezers are already full too, mostly summer fruit at this time of year.)

I can't get my head around the point of the brine yet, I see that it stays fluid at a much lower temperature, which might offset the lower SH, also that water-ice has a poor SH and thermal conductivity which count against it too.
I know that NaOH gives out a lot of heat when you dissolve it, also that CaCl gets cold, but I can't find any way that the salt in brine will mop up a lot of heat in a phase-change. https://en.wikipedia.org/wiki/Enthalpy_ ... f_solution shows that salt has a pretty trivial Enthalpy change on solution compared with big +ve and -ve numbers for other compounds. I don't think that latent heat of fusion is relevant here, although I was surprised to see that you can use latent heat of fusion to predict solubility.

I wondered whether it would be worth using water-ice but with heat conductors threaded through: like several upside-down top-hats of copper bar in the water tray so that the low conductivity of ice doesn't handicap it so much...
A
2.0 kW/4.62 MWh pa in Ripples, 4.5 kWp W-facing pv, 9.5 kWh batt
30 solar thermal tubes, 2MWh pa in Stockport, plus Congleton and Kinlochbervie Hydros,
Most travel by bike, walking or bus/train. Veg, fruit - and Bees!
User avatar
Stinsy
Posts: 2742
Joined: Wed Jun 02, 2021 1:09 pm

Re: Second system extension extension.

#349

Post by Stinsy »

Joeboy wrote: Wed Jul 20, 2022 4:17 pm Well, with no salt to hand I filled a few lidded boxes to a total of 7 ltrs and stuck em in the freezer alongside the 3 types of gin, ice cubes and frozen glasses. Max we see out here is about 4 hours without power, at a push 6. I have a 200ltr water tank on ballcock in the highest part of house that kicks in, multiple usb battery packs and this added coolbox scenario. Keeps it all civilised in the GnT dept along with water for toilets and enough head pressure to run the lower level shower. Beyond that we go to scented candles and the fridge for ice cubes.... :D
I reckon we are good for about 2.5 days. :twisted:

Are you guys seeing the freezer box photo? Please confirm one way or t'other, thanks.

Image
Not much food to perish in the every of an outage in there!
12x 340W JA Solar panels (4.08kWp)
3x 380W JA Solar panels (1.14kWp)
5x 2.4kWh Pylontech batteries (12kWh)
LuxPower inverter/charger

(Artist formally known as ******, well it should be obvious enough to those for whom such things are important.)
Bugtownboy
Posts: 959
Joined: Tue Jun 01, 2021 12:35 pm

Re: Second system extension extension.

#350

Post by Bugtownboy »

But a warm G&T :shock:

Disastrous !
Post Reply