Home  |  Contents 
Other Stuff
  Forum Index : Other Stuff         Section
Subject Topic: refrigerator insulation Post ReplyPost New Topic
Page of 3 Next >>
Author
Message << Prev Topic | Next Topic >>
Dinges
Senior Member
Senior Member


Joined: 04 January 2008
Location: Albania
Online Status: Offline
Posts: 510
Posted: 06 September 2008 at 5:13pm | IP Logged Quote Dinges

I've been toying with the idea of adding extra insulation to the refrigerator to reduce energy use. I know this project is by no means original, plenty of people have done this, but I've never seen anyone actually measure how much less energy the thus modified fridge uses.

For the past few months I had been eyeing the old refrigerator (Bauknecht) suspiciously, as it seemed to be running a lot of the time. Then, during the summer, I noticed it actually never turned off anymore: everytime I passed by it it was running. That couldn't be good, as it used 95W when on, so about 2.3 kWh/day... or about 185 Euro per year... Ouch.

So it was time to go shopping for another fridge. Here she is, the new Zanussi ZRG616WS, in factory condition:



Only 152 liter (5.5 cubic feet) but large enough for me. No freezer compartment as I don't need it; have a separate freezer for that. The manufacturer states that it uses 151 kWh/yr, i.e. .41 kWh/day. Compare that to the 2.3 kWh/day that the old fridge needed. The fridge cost 180 E (including 17 E removal tax, err, 'contribution') and as electricity over here costs .22 E/kWh, break-even point is at 14 months. This is assuming that we don't soon get another electricity rate increase of 27%, as we did last July...

Now, 410 Wh/day isn't too bad as-is, yet it can always be made better... But first I decided to make a few measurements using the kiloWatthour-meter before embarking on the insulation project. For a few weeks I measured electricity consumption at various thermostat settings. The results of the measurements are in the graph further below.

At 5 deg. C (setting '4' on the thermostat) the fridge uses 304 Wh/day, quite a bit less than the manufacturer's stated energy usage of 410 Wh/day. That's the first good news: the fridge uses 25% less energy than stated.

Ok, now that we have a baseline for comparison it's insulation time. First thing added was a radiant barrier between the fridge cabinet and condensor coil, to radiate the heat from the condensor away from the cabinet. Same with the compressor compartment, where more radiant heat barrier was added:





Then, as I took the top cover of the fridge off I noticed this was completely empty, apart from a small styrofoam spacer. This is 23 mm of space that the manufacturer could have easily filled with some insulation. Amazing. Even plain styrofoam (with a thermal conductivity of 0.038 W/m.K, which is mediocre as far as insulation goes) would have been better than absolutely nothing.



So I took a sheet of 30 mm styrofoam and cut it to a thickness of 23 mm using a hot-wire knife (being powered by an Oztules PC-PSU conversion... but don't tell him, he may want royalties), then cut it to size and fit it into the lid. Presto. Another 23 mm of insulation on the top. Admittedly, the top of the fridge is the warmest part so insulation will have the least effect here, but every little helps, I suppose...



Now that we have insulated both the rear (radiant barrier) and top, it's time to look at the rest. The door won't be insulated as I don't want the fridge to look as if cousin Bubba and I hacked it. The door will remain as is. To the sides I added sheets of 30 mm styrofoam, cut to size. As I didn't want to glue the insulation to the fridge (for easy cleaning and for warranty issues) I epoxied in a few 12x6 mm neodymium magnets. These hold the insulation to the fridge just fine:





The resulting energy saving of all the extra insulation:



After some measurements it turned out that at a thermostat setting of 4.5 the new energy use is 250 Wh/day, which used to be 340 Wh/day in the unmodified situation. So it turns out we're saving about 90 Wh/day, or 26%. Not too bad! That's another 33 kWh/yr extra shaved off, or about 7 E/yr at today's energy rates. Considering that it took about 2 E worth of styrofoam and a few leftover magnets... not too bad results, me thinks. It means break-even has been lowered to 13 months. Now, these modifications took me a few hours to make and not more than 3 E in materials. But if done by the manufacturer it would take only seconds to install and mere cents in material, but reduce energy usage by another 26%. Amazing that this isn't done at the factory.

Peter.
'a penny saved is a penny earned'

(more images can be found here: http://picasaweb.google.com/motorconversion/RefrigeratorInsu lation#)


Edited by Dinges on 06 September 2008 at 5:18pm



Back to Top View Dinges's Profile Search for other posts by Dinges
 
Bryan1
Guru
Guru
Avatar

Joined: 22 February 2006
Location: Australia
Online Status: Offline
Posts: 810
Posted: 06 September 2008 at 7:20pm | IP Logged Quote Bryan1

Hi Peter,
I'm not sure if you've see this before but I reckon its the cheapest way to cool for fridges.

Cheers Bryan


2008-09-06_191910_chest_fridge.rar
Back to Top View Bryan1's Profile Search for other posts by Bryan1
 
Gill
Senior Member
Senior Member
Avatar

Joined: 11 November 2006
Location: Australia
Online Status: Offline
Posts: 669
Posted: 06 September 2008 at 7:48pm | IP Logged Quote Gill

Peter,
A very interesting read.
I've just had my old gas fridge fail, so it's over to the backup 12 Volt chest fridge freezer. Basically it's a small fridge lain on it's back with legs and castors added. A 12 Volt Danfos compressor is fitted to the engine bay with fancy tailored evaporator pipework in the box. In spite the 'Solar' name and 12 Volt compressor it is still a fridge as far as insulation goes and not very thick either considering it could run as a freezer too.

I had thought of adding extra insulation but then thought the manufacturer didn't so it can't help much. But with your results that job is now back on the job list. Just when I thought I could put the feet up.


__________________
was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
Back to Top View Gill's Profile Search for other posts by Gill
 
GWatPE
Senior Member
Senior Member
Avatar

Joined: 01 September 2006
Location: Australia
Online Status: Offline
Posts: 2127
Posted: 06 September 2008 at 9:29pm | IP Logged Quote GWatPE

I added an inch of polystyrene to all accessable sides on my Engel camping fridge, back in the 70's. This reduced the power consumption to 50%.

The reason the manufacturers don't bother is they don't pay for the power a unit consumes.

If we all only brought the highest efficiency devices, then we could exert a demand for them. As long as the purchase price steers what we buy, then we get what we pay for.

Gordon.


__________________
become more energy aware
Back to Top View GWatPE's Profile Search for other posts by GWatPE
 
Dinges
Senior Member
Senior Member


Joined: 04 January 2008
Location: Albania
Online Status: Offline
Posts: 510
Posted: 07 September 2008 at 1:29am | IP Logged Quote Dinges

Bryan, thanks for the file but was already familiar with the Mt. Best freezer-to-fridge conversion. In fact, before scrapping it I took out the electro-mechanical thermostat of the old Bauknecht fridge exactly for possible future duty in such an application.

Gill wrote:

I had thought of adding extra insulation but then thought the manufacturer didn't so it can't help much. But with your results that job is now back on the job list. Just when I thought I could put the feet up.

Sorry mate, wasn't my intention to put more work on your platter... Manufacturers basically produce what sells, i.e. what most consumers desire: a fridge/freezer that is as small as possible (outside dimensions) yet has as much volume as possible (maximum inside dimensions). Guess insulation suffers as a result. BTW, shopping for that fridge was an eye-opener. If I hadn't seen with my own eyes I wouldn't have believed they sold fridges with inbuilt TVs....

Gordon, I fully agree. The consumers get the products they desire, as the manufacturers will only produce products that sell. At the moment most consumers just don't care about energy use; and the energy-class ratings (B, A, A+, A++) helps only to muddy the waters (why do they feel the need to introduce vague, ambiguous 'classes', where a simple kWh/yr rating says it all ? One figure expressed in kWh/yr is all it takes. If people are getting confused by this 'technical jargon', maybe they should translate it simply into 'this fridge uses 123 Euro per year worth of electricity'...?) But it's my strong conviction that with rising electricity cost energy efficiency will become more of an issue in the decision making process.

Trivia: this new fridge uses 1/9th (11%) of what the old fridge used. The saving is 750 kWh/yr, or 21% of the electricity bill.

Now, I did seriously consider buying an A+ class refrigerator, one that is more energy efficient than mine originally was. However, that'd have cost 65E more. I figured I could save the money for a new freezer (highest item on the priority list right now) and simply add a little extra insulation to the fridge to upgrade it to A+ class. Even turns out it now nearly attains A++ class at 90 kWh/yr.

This fridge will pay for itself in slightly over a year, the freezer will take about 3 years to break even (at current electricity rates). But with a new freezer the total reduction of the electricity usage would be 48%.... Saved just by replacing the fridge, freezer and PC (from full-tower to notebook).

Now, if I can get rid of that electric water heater too... IPSWH?... then electricity consumption might be low enough to start considering going off-grid. I figure that I could reduce electricity useage down to 1 kWh/day with some effort. Fridge, freezer, PC, some lights, radio, washing machine, HAM gear, occasionally using the microwave. Yes, I think 1 kWh/day should be attainable without quality of life suffering...

Edited by Dinges on 07 September 2008 at 2:31am
Back to Top View Dinges's Profile Search for other posts by Dinges
 
GWatPE
Senior Member
Senior Member
Avatar

Joined: 01 September 2006
Location: Australia
Online Status: Offline
Posts: 2127
Posted: 07 September 2008 at 10:34am | IP Logged Quote GWatPE

Hi dinges,

you would be doing exceptionally well to maintain lifestyle on 1kWhr/day. I monitor most appliance usage and my home uses an average approx of 1kWhr per person per day. The water heating is a seasonal problem as we have a solar electric system. We have off peak electric rates for solar shortfalls.

The biggest daily culprit for us now is the TV. The electric oven uses a lot, but it is cheaper than eating out. We don't use electricity for heating and we don't need air con. BTW our 25 year old fridge uses 1kWhr per day. We don't run a freezer as the running cost was more than the money we saved by buying food in bulk. The 4star rated freezer still consumed 610kWhr/year. We only use it when we defrost the fridge now.

We export a lot of power now, so this offsets the peaks.

Good luck, but don't go without too much.

Gordon.


__________________
become more energy aware
Back to Top View GWatPE's Profile Search for other posts by GWatPE
 
oztules
Guru
Guru
Avatar

Joined: 26 July 2007
Location: Australia
Online Status: Offline
Posts: 1391
Posted: 07 September 2008 at 11:15am | IP Logged Quote oztules

Dinges...................when I get back to the island, I will be looking for the royalty checks....... yippeee

Good homework there Dinges, like Gill, it looks like some modifications are in order.... curses.


........oztules

__________________
Village idiot...or... just another hack out of his depth
Back to Top View oztules's Profile Search for other posts by oztules
 
Dinges
Senior Member
Senior Member


Joined: 04 January 2008
Location: Albania
Online Status: Offline
Posts: 510
Posted: 08 September 2008 at 4:48am | IP Logged Quote Dinges

oztules wrote:
I will be looking for the royalty checks.......


If you don't find it it means you haven't looked enough...

Had another brainwave today as I was cleaning up the mess I call 'workbench'. Harddrive magnets. Should have used those worthless, no good magnets to epoxy into the styrofoam sheets instead of those left over, but nice, 12x6mm round neos. HDD magnets are useless for much else but perfect for this application, even if you damage the plating when removing them: they will be covered in epoxy anyway.
Back to Top View Dinges's Profile Search for other posts by Dinges
 
Bryan1
Guru
Guru
Avatar

Joined: 22 February 2006
Location: Australia
Online Status: Offline
Posts: 810
Posted: 08 September 2008 at 8:32am | IP Logged Quote Bryan1

Ok Oz time to spill da beans on this PC power supply conversion. I did have a look on feildlines without any luck and with me finally going the right way with my shed wiring a pc power supply conversion is right up my alley for a project or 3

Cheers Bryan
Back to Top View Bryan1's Profile Search for other posts by Bryan1
 
oztules
Guru
Guru
Avatar

Joined: 26 July 2007
Location: Australia
Online Status: Offline
Posts: 1391
Posted: 08 September 2008 at 8:57am | IP Logged Quote oztules

Hi Bryan,
Dinges did an excellent how-to on fieldlines here:Dinges showing his stuff
It should give you some idea of the conversion process... (and another whole lot of waffle besides).

He has also used them for his beautiful looking spot welder here :Dinges spot welder

If you start a thread of your attempts as well, we can guide you through it if you have any trouble, and perhaps others looking at it, may find better ways to do it too.

Go for it Bryan, you won't look at psu's at the tip the same way ever again.... ask Dinges.


.......oztules

__________________
Village idiot...or... just another hack out of his depth
Back to Top View oztules's Profile Search for other posts by oztules
 
Dinges
Senior Member
Senior Member


Joined: 04 January 2008
Location: Albania
Online Status: Offline
Posts: 510
Posted: 08 September 2008 at 10:46am | IP Logged Quote Dinges

Bryan,

Must definitely have a look at this thread (esp. response 31 and further), where Oztules originally explained the modifications a few years ago:

http://www.fieldlines.com/story/2006/4/24/92132/1267

One thing I'd certainly add though is a 22/47/100n capacitor over the wiper of the voltage-control potmeter. This helped one PSU from tripping to a halt, and I strongly suspect it's the reason why another PC PSU I was building for Ron blew up (actually, it was all finished up and encased; as I quickly needed a power supply for some experiment I grabbed that PSU, only to have it blow up as I adjusted the voltage potmeter)

As I said somewhere in the thread, Oztules deserves an innovation award for turning worthless, useless PC junk into valuable laboratory supplies. One of them even kept a friend's Jung grinding machine working for 3-4 months as we were waiting for a new transformer to arrive from Switzerland (darn; forgot to send Oztules a royalty check for that one). Once you have such a power supply you will wonder how you ever managed to live without it... .

This is *incomparable* to the web-nonsense where you see people adding power posts to an otherwise unmodified PC PSU and claiming that it's now a laboratory supply... But Oztules' mods *will* turn it into one.

Edited by Dinges on 08 September 2008 at 10:49am
Back to Top View Dinges's Profile Search for other posts by Dinges
 
domwild
Guru
Guru


Joined: 16 December 2005
Location: Australia
Online Status: Offline
Posts: 802
Posted: 11 September 2008 at 10:05pm | IP Logged Quote domwild

Peter,

Interesting article and thanks for it. As you know some members simply buy a freezer and add a different thermostat setup. But this is certainly a dearer option.

The gap on top must be used to fool customers into believing they are getting a larger fridge.



__________________
Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.

Winston Churchill
Back to Top View domwild's Profile Search for other posts by domwild
 


Page of 3 Next >>
In the news...
 
Post ReplyPost New Topic
Printable version Printable version
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Powered by Web Wiz Forums version 7.8
Copyright ©2001-2004 Web Wiz Guide

This page was generated in 0.0781 seconds.
Privacy Policy     Process times : 0, 0, 0, 0.08