energy saving ideas for appliances

[spinout]

On the point of HC refrigerents: They are at least 30% more efficient than any conventional CFC's (R12), HCFC's (R22), and, worst of all, HFC's (R134a). I have used HC's and they work great. As an example, R600a--which is isobutane, is an ideal refrigerant for ice boxes and apparently is being successfully used by some European manufacturers.

When the EPA banned the manufacture of chlorinated halogen refrigerents, it had to protect the chemical industry (i.e., big business) and give something back. The industry got patent protection on a difficult-to-make product as well as regulatory incentives and favoritism. R134a also receives a non-flammable rating (?) even though it is more combustible and toxic than HC's! Hmmm....

Worse yet, what we got out of the deal is R134a, an HFC which is a really poor and all-around lousy, inefficient refrigerant that costs too much.

It seems as if no one wants you to know that you can run a purified grade of Propane (in place of R22) in you home air conditioner, get better cooling capacity with the same equipment and save >30% on energy use.

Here's one HC manufacturers link with some interesting info.

http://www.hychill.com.au/tech/
As I have said, I have used HC's with very good results and can recommend them for most applications: including R12, and R134 retrofits.

---changing topics now---

Designgeek wrote: "...I'm told that those solid state diode thingies that work on DC (you find them in portable cooling chests and tiny micro-fridges designed to chill a single can of soda) are actually far less efficient than compressors & coils. Anyone have info/opinions on that point?..."

Yes, They are know as PELTIER coolers and they are only 20% to 30% efficient overall (i.e., very poor), depending on conditions. I have considerable experience with them and can tell you that they are not normally used for general refrigeration; rather, they are often specified for industrial and military apps where you have to cool an enclosure, equipment or cabinet and/or you have limited space, limited access and/or must eliminate moving parts to meet specialized reliability and MTBF requirements.

 

[tolivac]

Roaches---yes when I lived in apartments I had to store most foods in the fridge--otherwise I would be sharing the foods with my roach "roommates" I don't care how much they sprayed or exterminated-the little beasts would survive-after all roaches can survive radiation from nuclear blasts!But they don't like the cold from the fridge nor can they get in.This was when I lived in apartments in the Wash DC area.Roaches just love those apartment houses!!!lots of food and garbage!!and for them--so much to choose from.I also got lots of roaches in my small collection of vacuums back then-they loved to suck up the roaches.

 

[Designgeek]

Toggle, you don't need a gas flame for an absorption fridge; an electrical heat source will work as well and with high efficiency.

Nice article about the guy who converted the chest fridge. In fact that is absolutely brilliant and so simple I'm kicking myself for not having invented it. I was looking at chest freezers a while ago and got discouraged by the fact that they don't go above something like ten below freezing, but this idea never occurred to me.

What he's got there is an external thermostat that interrupts power to the chest freezer when the desired level of cold is reached. So you set the thermostat for, perhaps three to five degrees above freezing, or whatever you like, and that's all. Beautiful.

The chest freezer keeps its cold because when you open it, the cold air doesn't slosh out the door onto the floor. And if the article is correct, power consumption of 0.1 KWH/day = 36.5 KWH/year, which beats even Sun Frost.

Now the question is, what models of chest freezer could this be done to in the US? Or could the actual thermostats that come with these units be hacked like the water control on the Danby front-loader? So now we look up Danby chest freezers and discover:

Danby 3.6 cubic footer: 215 KWH/year.

Danby 5.5 cubic foot: 248 KWH/year

Danby 7 cubic foot: 276 KWH/year.

Something very cool about these (ha) is that they have oldschool ROTARY thermostat knobs on the front panel. Aha, says I! One of the product manuals says that the temp range is ordinarily -10 to -23 C (+14 to -10 F). So, I wonder about this: I'll bet that the thermostat is nothing more than a variable resistance. And I'll bet that adding or changing a resistor on the circuit board will change the effective temp range of the unit. If that doesn't do it, then the external thermostat control would do, as per the Australian article.

I found a Vestifrost 3.5 cubic footer that's rated at 248 KWH/year, so we can assume their ratings for their other units are similarly comparable. If the guy who hacked his freezer in Australia was using a 7 cubic footer, then we can assume Vestifrost would have been about 300 KWH/year un-hacked, down to 36 KWH/year hacked. Roughly speaking that's an 88% savings.

So now assume two Danby chest freezers (matched pair, one converted to a fridge, and one used as a freezer. Let's assume that for regular freezer duty, you want a temp of maybe -5 C or maybe somewhere in the 20s F. I'm going to make a wild guess that if the freezer normally has a max temp of 14 F, and you tweak it so it's running at maybe 25 F, you save conservatively 30% of the rated power.

OK, so now our modded 3.5 CF unit used as a freezer would use 129 KWH/year, and our modded 5.5 CF unit, as a fridge, would use maybe 30. Total for both is about 160 KWH/year. Recall that our hypothetical SunFrost was 105 for $2,300.

And, you can always use the space atop the units as part of your kitchen counter space, though not for heavy work that involves a lot of weight or pressure. This also lends itself to a whole set of different ideas in terms of how kitchens are designed & laid out. Hmm....

 

[Cybrvanr]

Most mechanical thermostats are nothing but a bi-metal coil with a reed switch on one end. As the bi-metal coil heats up, it bends, and trips the switch. When it gets cooler, the metal straightens out, and cuts the switch.

Some thermostats have a calibration set screw that will bend the bi-metal strip for you, and allow you to set the range. i don't know if you will be able to adjust it high enough to operate in the refrigeration range, versus the freezing range or not. I imagine if you wanted to increase the temperature range, you could just cut away some of the metal out of the coil, so that it starts bending at a higher temp.

An easier method however would be just to buy a $20 refrigerator themostat from FHP, or another appliance part supplier, and replace the freezer thermostat with one that operates at a higher temperature range.

Those KWH amounts sound really promising! They should be even lower when operated as a fridge, versus a freezer!

 

[Designgeek]

SCORE!

Woo-hoo!, score!

Go here:

http://www.solarray.com/TechGuides/Refrigerators_T.php
What you will find is a graph showing total cost for setting up fridges for offgrid use. Guess what comes in lowest of all? "Modified Danby Freezer." Way better than SunFrost.

Since they don't sell it on that website, next step for me is to find out what/where exactly they came up with that. If someone hasn't started selling those commercially, I see a biz opportunity for some of my eco-industrial geek friends & I.

Not only that, but...

If you do a search for "refrigerator thermostat" and similar terms, you quickly run across a bunch of webpages from companies that make equipment for folks who home-brew beer. What they have there is a little gray box made by Johnson Controls (don't bother with the Johnson Controls website, it's a tangled maze of bad website design), cost is about $60.

Apparently the home-brewing community has been putting external thermostats on freezer & fridges for some time now, the better to control the various processes it takes to get a tasty brew.

Cybrvanr, re. refrigerator thermostats: Question is how to mount the replacement part without having to modify the cabinet significantly. My sense of these things is that they are designed for specific mounting situations, in specific models of fridges, and may not be readily interchangeable with the units in chest freezers. OTOH, I've never hacked a fridge or freezer (yet!), so I may be wrong here. Re. bimetallic strip units w/ set screws: that's interesting, though my inclination is to avoid messing around with those or attempting to bend the bimetallic strips; that would require a lot of empirical calibration for an individual unit and couldn't easily be done commercially. So are there thermostats that use a variable resistance in a circuit, or something else? I know I'm missing some really basic info here; sorry if this sounds like a dumb-dumb query

It would appear that we are well on our way to a convergent solution to the biggest energy issue in the home after heating & cooling, which is the next item to tackle.

Grand Irony Department: First the door to the washing machine migrated from the top to the front. Now the door to the fridge is migrating from the front to the top. If you build an eco-industrial geek kitchen, be careful when your friends come over. "Help yourself to soda or beer, they're in the fridge..." "Hey wait a minute, that's the washing machine!" And if they come over with a load of laundry to do, watch out that they don't put it in the fridge!

 

[gizmo]

Designgeek

Absorption fridges can be used with an electric heating element but the efficiency is VERY poor. even the least efficient compressor fridges would use way less energy than a similarly sized absorption fridge.
For example: Electrolux 150 litre single door fridge, absorption gas/electric: on electric uses a 180 watt element which operates CONSTANTLY (never cycles off) = 4.3 kwh /day.
A similar compressor fridge would use 1 to 2 kwh/day, an efficient low voltage fridge would use 0.3 kwh/day.

The article on the modified "chest fridge" was in Renew magazine, which published by an organization of which I am a member, the Alternative Technology Association. I used to be on the committee of the association but that is several years ago now.
Here is a link to the assocations's website:
Chris.

http://www.ata.org.au

 

[Designgeek]

Gizmo, thanks for the info on the inefficiency of using electricity for absorption fridges. This is convergent with what we're finding, that modified chest freezers are the best solution. Though, absorption fridges still have a place in the big picture, especially if they can be modded to work with any available heat source, in which case they could be "multi-fuel" designs. For example, imagine some way of connecting up the heat input to the fridge, with the waste heat output of a combined home heating & water heating setup.

Also I found a page on someone's website that's pretty critical of SunFrost. The page says that SunFrost's effciency claims are exaggerated, and that the units suffer from QC and workmanship problems. I don't know if this is the truth or just someone with an axe to grind but I'll be looking into it.

The next bit of fun I'm going to have with this, is to see how these things will fit into existing kitchen designs, and into hypothetical new kitchen designs.

 

[Cybrvanr]

I was right suprised about how "interchangable" the parts are for the physical aspects these days. You may be able to interchange a mechanical thermo without too much difficulty. I replaced the thermostat in my old Coleman air conditioner in my RV (wasnt't the actual source of the malfunction). About a year later, my fridge thermo went out. The two parts looked practically identical physically, but of course they responded to different temperatures.

Thermister thermostats have just recently come into use on some of the fancier refrigerators. What these do is have two resistors in them. One resistor is the user adjustment. The second resistor is the thermister that senses the compartment temperature. They are set up in a little logic comparator circuit so that if the power across the thermister is higher (indicating a higher temp) than the user's set temp resistor, it forward-biases a transitor, which in turn turns on a compressor relay. When the voltage across the thermister eventually drops below that of the user's temp, the bias to the transistor is dropped, and the compressor shuts down.

Now, this setup has also been enhanced lately with even more electronic controls. Some of the newest fridges have digital temperature readouts and full digital control. While they may use an electronic thermostat like above, they use a digital microprocessor to read and adjust temp. Some of these fridges also have humidistats in them to, and warning indicators and sensors that will let you know if there's a malfunction, or if someone's left the door open!

To "hack" one of these would simply be to put a different value thermister in there that responds to a different temperature/resistance curve. Your temperature display will end up reading a different temperature than what the compartment is actually at. It will take some calculations and manufacturer information to find out what the acutal temp curve of the manufacturer's thermister is, and then you can calculate the size larger or smaller the you would need to get it into the thermal range you want.

 

[48bencix]

whirlpool award

I bought the Whirlpool 25 cu. ft. side by side that was made after the award (mentioned by sudsmaster) for best efficiency. It is labled at $56.00 per year at $.08/kwh. There are a few side by side units made today that are a little more efficient. I think it's about 8 years old. So that's about 2 kwh per day. It has ice and water through the door and is a great food storage system.

I thought about energy saving years ago and wondered if the built-in fan should force air up from the front bottom edge when the door is opened, sort of an air curtain. This would prevent the cool air from falling out. Sort of makes the upright into a chest. When we were kids, we always opened the door to see what was in there, wasting a few cubic feet of cool air each time.

 

[Designgeek]

Interesting point you have there about an air curtain. Anyone have a sense of whether that would work?

 

[toggleswitch]

Sounds good to me

and how about a buzzer/chime that gently reminds one to SHUT THE DOOR after a timed period (adjustable of course).

 

[brisnat81]

Our F&P fridge already does it

After 3 minutes it will start beeping, twice at first, and then the frequency continues to increase until its a solid beep.

 

[DADoES]

My GE Artica has door-open alarms, but it isn't adjustable for the trigger-time.

 

[gizmo]

the air curtain won't work, in fact it would make it worse.

Moving air will INCREASE the loss of cold air in the fridge, not decrease it. That's why there are fans fitted to heaters, to increase the transfer of heat.

One possibility would be to divide the fridge compartment into sections with transparent inner doors covering access to each section. The idea would be to trap the cold air in each compartment. This would however probably be pretty fiddly and annoying. I used to be quite keen on the idea of a top opening fridge, I started to build one some years ago. It had a freezer chest and a fridge chest in one unit, the freezer was about a 300mm cube (one foot cube), the fridge was about 150 litres. It was to have six inches of polyurethane insulation all round, the freezer was the main refrigerated section with the fridge being cooled mainly by a lack of insulation between it and the freezer, and a very small evaporator carrying vapor back from the freezer evap to the compressor. I had some help designing it from a local fridge mechanic and I was going to get him to do the connections and gas it up, use a Danfoss BD low voltage DC compressor. I never got the project off the ground, as I had to build a house to put it in first, and I guess I am getting soft in my old age (middle age) I just want a front opening fridge and Idon't mind buying a couple of extra solar panels or using a whisker more gas to run it. I still have some of the bits but I don't think I will ever build it.

Chris.