
Fridge 0.1 - edward
http://joeyh.name/blog/entry/fridge_0.1/
======
daveguy
Hey Joey, fan of your projects. I'm not sure if the fridge you have pulls a
vacuum when it is closed, but pulling a vacuum can make a fridge much more
efficient. I worked with some of the engineers that designed this -80C freezer
for the International Space Station (where power is at a premium):

[https://en.wikipedia.org/wiki/GLACIER_(General_Laboratory_Ac...](https://en.wikipedia.org/wiki/GLACIER_\(General_Laboratory_Ac..).

One of the key efficiency factors was being able to pull and hold a vacuum.
And obviously the more efficient the engine that pulls the vacuum the better.

If it's a modern high efficiency unit, it probably already pulls a vacuum. If
not, it may be worth physically hacking.

~~~
simias
It probably goes without saying but if you're pulling a vacuum in the fridge
you have to consider how often you'll open it. If it's for long term storage
and you open it a couple of times every month at most it probably makes a lot
of sense but if it's your main fridge you open potentially dozens of times
every day it might not make sense to make a full vacuum every time.

That being said since the system doesn't use batteries to store energy it
might make sense to use any leftover energy to pump the air out of the fridge
even if you don't reach a full vacuum.

~~~
odonnellryan
Talking about high-efficiency systems like this it's a given that we're
testing for the best-case scenarios.

But you do make a really good point. In cruising, people who choose to have a
fridge have systems for this.

It is usually to get saltwater really really cold or frozen in some kind of
containers: it is popular to use PVC pipe, capped off of course, filled with
seawater (or a mix of fresh and sea).

You store your food in the freezer and charge up these pipes, cycling them on
to the top of your food in your cooler (not powered) once every 3-4 days.

This: "1 kilowatt of solar panels has managed to cool the fridge down close to
standard fridge temperatures."

Is kind of silly to me though... because that's an "incredible" amount of
power.

~~~
CiaranMcNulty
1kW is 'peak' rating, to get the real power a rule of thumb is that they'll
run at that peak for 3-5h each day (depending on climate)

Pessimistically that means 3kWh/day, which if you're storing it efficiently
(in a battery or as thermal mass like OP) gives you a nominal 125W supply

~~~
joeyh
Yep, and the actual kWH per day with the fridge has so far been in the range
of 1-2, and bear in mind that also runs everything else in my house including
a rather energy hungry satellite modem.

------
JonathonW
Temperatures seem more than a bit high to me-- FDA recommendations [1] are
that fridge temperatures should remain below 40°F (~4.5°C) for food safety (to
inhibit bacterial growth). This fridge is never making it below 5°C, and (from
the real-time data linked in the post) it's peaking uncomfortably close to
room temperature-- I see one spike all the way up to 16.5°C, and it doesn't
look like it recovers quickly at all.

[1]
[https://www.fda.gov/Food/ResourcesForYou/Consumers/ucm253954...](https://www.fda.gov/Food/ResourcesForYou/Consumers/ucm253954.htm)

~~~
shakna
It's generally sitting around 0.5-1C.

The relevant part from scuttlebutt:

@IBob on temp probe placement, I think I know why it was seeing such sharp
swings when outside the water. I had the wire coming down along the inner
fridge wall corner, touching it for a foot, and then the probe was pulled out
an inch from the corner. So, it was both very close to the walls, and wire's
contact would suck more heat away when the wall cooled down.

The spring thermometer I have mounted in there to measure the air temp now
avoids this problem, and has been staying just above freezing during long
compressor runs despite frost buildup on the walls

~~~
jjeaff
So make sure your food doesn't touch the walls of the fridge or it will spoil.
Got it.

~~~
StavrosK
Why will it spoil if it touches the walls? Wouldn't they be the same
temperature as the area inside?

------
slacka
Some serious over engineering going on here. The fridge should be set to the
coldest possible temperature without the food freezing, as close to 1 °C as
possible an run whenever there is solar power available. The only software
need I see would be a warning if the internal temperature got too warm.

Instead of smarter software, the focus should be on insulation and adding mass
to hold the heat. For example, I put a foam insulating board over my 22 cu.
Chest Freezer to improve it's efficiency.

~~~
niftich
The classic, low-tech (and sustainable!) way of adding thermal mass is to
embed it in the ground and leverage the thermal mass of the earth around you;
seemingly pointed out by comments [1][2] that haven't gotten as much traction
as ones discussing high-tech. Then you don't have to cool nearly as much. Talk
about over-engineering.

[1]
[https://news.ycombinator.com/item?id=17107254](https://news.ycombinator.com/item?id=17107254)
[2]
[https://news.ycombinator.com/item?id=17107439](https://news.ycombinator.com/item?id=17107439)

~~~
icebraining
That's a pretty good option if you already have a basement, but if not, seems
way more over-engineered to me. Excavating, building walls, dealing with water
leaks...

------
Keloo
My parents live in a village, they have basement, few meters underground
(under the house) the average temperature is 0-5C (even in the summer when
outdoor temp is 30C). All the food is saved there for years!

Engineering sometimes is so wrong, people before tech had a lot of simple an
nice hacks!

------
dsr_
My new freezer says that in the event of a power outage, if we don't open the
door food will remain frozen for 48 hours. All the walls are unusually thick,
which I presume indicates a lot of insulation.

Mr. Hess might want to consider adding additional insulation to the outside of
his unit, especially as temperatures rise in summertime.

~~~
emmelaich
Yes, I'm pretty sure standard refrigerators have far less insulation than they
could have. Probably mostly for weight and cost reasons.

A good quality camping coldbox (e.g. made of fibreglass or thick polyethylene
plastic) can keep ice solid for days even in an Australian summer.

~~~
kickscondor
On long river and fishing trips, a standard cooler can work with the help of a
good shady spot and a towel that has been dipped in the river and draped over
it.

~~~
emmelaich
Evaporative coolers were popular in Australia before the widespread
availability of electricity:

[https://en.wikipedia.org/wiki/Coolgardie_safe](https://en.wikipedia.org/wiki/Coolgardie_safe)

~~~
tonyedgecombe
A smaller version is useful for storing insulin on the go:

[https://shop.diabetes.org.uk/collections/frio-
wallets](https://shop.diabetes.org.uk/collections/frio-wallets)

~~~
emmelaich
I don't think they're evaporative. Plus you need to recharge?

Also, "patented crystal technology" what?!

~~~
tonyedgecombe
They are, you soak them before use to 'recharge'.

------
dkuebric
Cool project. He's loaded the fridge with some ballast (17 gallons of water),
so while there isn't an electric battery, there is a reserve of another kind.

~~~
eric-hu
In cooking, I like to think of large thermal masses as a thermal battery.
Thus, a cast iron pan is good for searing steaks than typical pans because
it's a beefier battery.

~~~
dTal
A capacitor is an even better analogy - "charge" is asymptotic, and the
function of the cast iron (and the water in the fridge) is to smooth out local
fluctuations in heat (rather than to store it long term).

~~~
eric-hu
Interesting observation. Is the line between capacitor and battery a matter of
intended storage duration?

------
n1000
Nice project. Dependig on the location a ground fridge could be an
alternative. Soil temperature is close to the annual mean in a few meters
depth.
[https://www.builditsolar.com/Projects/Cooling/EarthTemperatu...](https://www.builditsolar.com/Projects/Cooling/EarthTemperatures.htm)

------
Gravityloss
There is a massive amount of inefficiencies in our power usage.

Resistor based water heaters and space heaters, heat pump / compressor based
air conditioners and water and space heaters, fridge and freezer cooling
compressors, work air compressors etc all could be used to increase grid
stability instead of now decreasing it. Or, if you have your own generation or
are off grid, to reduce the electricity trading or storage needs

------
seltzered_
“the fridge itself becomes the battery -- a cold battery.”

Wildly my first thought from from this is that you theoretically could use a
peltier in reverse to generate energy. It wouldn’t be efficient but possible.

At a different level, you can also think about your interactions with the
fridge. You could segment the fridge such that it had different insulated
sections that you use.

------
JasonFruit
For my diabetic mother in a disaster, I would pay a few grand for something
like this that is reliable — it could even be tiny!

~~~
tonyedgecombe
[https://shop.diabetes.org.uk/collections/frio-
wallets](https://shop.diabetes.org.uk/collections/frio-wallets)

~~~
JasonFruit
That's pretty fascinating, and might be something I can work with. Thanks!

------
dingdingdang
What is potentially most interesting with this project is that the thermal
mass allows a 14 hr down-cycle - could a regular-on-grid fridge be run like
this, or close to it, with economic benefit in terms of electricity use?

Or would this simply just cause spikes in electricity usage to compensate for
the down-cycle along with increased mechanical wear?!

~~~
wongarsu
Any economic benefits would likely come from using cheaper off-peak
electricity. Once smart meters and flexible power prices become more common I
would expect fridges (and other appliances) with such features to become more
common.

------
quickthrower2
Another hack is to not store things in the fridge that don't need to be.

Bread, eggs, etc.

Maybe curdle the milk!

That looks like a big fridge, maybe then it can be smaller.

Although smaller doesn't necessarily mean more efficient you may want to check
the star energy rating.

~~~
joeframbach
He has made the fridge "smaller" by putting 17 gallons of water in it (per the
scuttlebot link). This is even better than a smaller fridge, because the cold
water itself keeps the fridge cool when it is off.

~~~
quickthrower2
Thanks, that's interesting. I like to read the article before commenting, but
I don't usually go a level deeper!

------
gumby
Instead of an electrical fridge, use the solar heat directly to boil the
refrigerant, as with a gas-powered fridge (once common, now rare due to
widespread electrification). The power loss of solar->PV->motor compressor is
quite large while a gas refrigerator has no moving parts:
[https://home.howstuffworks.com/refrigerator5.htm](https://home.howstuffworks.com/refrigerator5.htm)

------
kpil
I have three old solar panels in my boat for a total of 105 W, and 2 cheap
85Ah marine deep cycle 12 V batteries.

It copes with keeping a number of phones, radios, tablets and a small laptop
charged, some moderate use of lights, an occasional run of a webasto diesel
air heater, and continously powering a compressor driven fridge box.

I think the batteries are one of the cheapest thing in my system.

~~~
joeyh
Batteries are one of the most expensive parts of an offgrid PV system once you
start looking at prices over decades.

My 1.5kw solar panels and electronics cost $2k (self-installed) and will last
20+ years.

To run the fridge on demand from batteries during the night and rainy days,
I'd need something approaching the capacity of a powerwall, $6.6k every 10
years.

------
jabl
On a larger scale something like this has been proposed (or maybe even already
implemented somewhere?) as an economical way to deal with variable renewable
energy (wind, solar); when VRE is plentiful and cheap, giant industrial
refrigerated warehouses cool down a few degrees, and conversely when VRE is
scarce and expensive, let it heat up a few degrees.

~~~
floatrock
[http://www.axiomexergy.com](http://www.axiomexergy.com) \-- they build "ice-
batteries" where they create ice at night when it's cool and electricity is
off-peak, then use that ice to cool industrial refrigerators (supermarkets,
cold storage facilities, etc) during the day.

------
e12e
From the scuttlebutt thread (on mixing water and glycerol in order to target a
freezing point close to 5C or so):

> Glycerol sadly has the tendency to supercool,so once all of your solution
> melts you will lose all of your seed crystals and then you have to drop down
> to a really low temperature before it will get back to a solid.

Add sand to the water tanks?

------
gregimba
12 volt fridges used for car camping might be much more efficient than a
regular fridge if you rely on solar power.

------
memco
How are the graphs being done? I'd like to look at using them for a project.

~~~
PascalW
[http://javascriptrrd.sourceforge.net/](http://javascriptrrd.sourceforge.net/)

------
tzahola
Why don’t you use a supercapacitor bank instead of the powerwall?

------
MisterOctober
this has much merit

------
BrentOzar
Somewhere, a team of coders at a top government agency is furiously designing
Stuxnet 2.0 to break his fridge, bring him back to the grid life, and raise
the nation's GDP again.

