energy saving ideas for appliances

[gizmo]

In another thread about a twin tub washer, the discussion wandered off to cover low energy ideas for washing machines, fridges, etc. I thought rather than hijack the twinnie thread, we should drag it over here. so here it continues...

Refrigeration is my other hobby horse...

There is no excuse for current refrigerators using so much power. It is done simply because the mfrs want to put the biggest possible interior in the smallest possible exterior, and make it as cheap as possible. This means thin walls.

Refrigerators do not "make cold". They remove heat. The whole guts of the fridge works by collecting heat from inside the cabinet and transporting it to outside the cabinet. It all boils down to the old lesson in physics, "there is no such thing as cold. Cold is just the (relative) absence of heat."

The thinner the walls of a fridge, the faster the waste heat (which has just been dumped outside the box) travels through the walls back into the box, where the fridge will switch on again and dump it outside again. If fridge walls were about 120 to 150mm thick (5 to 6 inches) then the fridge would use only a tiny fraction of the power. Also "frost free" mechanisms which depend on a daily internal defrost cycle gobble energy unnecessarily.

The main thing we all could easily do to use less energy is to use a much smaller fridge. Half the stuff in most people's fridges doesn't need refrigeration. A lot of it is leftovers that will never get eaten, they will be refrigerated for a few weeks, then thrown out. A lot of it is redundant refrigerating, such as having six bottles of soda in the fridge instead of refrigerating just the one in use. Jams, pickles, peanut butter, many fruits and vegetables don't need refrigeration, they just need cool storage.
My current fridge is a gas fridge of about 150 litres. The freezer is tiny. We shop once a week and by end of the week the fridge is almost empty. When we move to the new house we will work on improving it, either by adding extra insulation to the cabinet (don't want to make it hideous though) or possibly by buying a low voltage DC equivalent. The new house has ducting built into the floor slab, to collect cool moist air from a ferny gully behind the house and blow it behind the fridge and into the pantry, using a couple of very low power DC fans. My current gas fridge also has a low power fan behind it, in hot weather I switch it on to dissipate the hot air from behind the fridge.

Anyway that's enough of me for now.

Chris.

 

[tolivac]

Another way to save energy for fridges is to NOT put the motor-compresser unit and condenser under the box-the heat from those rises back into the box so it has to be removed again!!The idea of the older GE "Monitor top" was to prevent that problem.
For storage of foods-here in the very humid South I have to keep my cerials in the fridge to keep them dry and crisp.If you store them in the pantry opened-they get stale quickly.And my homemade peanut butter has to be kept in the fridge.It will go stale if it is not.Another thing-those forced air cooled condensers have to go-not needed-Just mount the heat sink for the condenser on the back like as usual-it doesn't take much effort to vacuum those off-the forced air cooled ones under the box are a royal pain to clean-and that lint and dust collecting in them slows the dissapation of heat.Then the system has to run longer to compensate.

 

[Designgeek]

Good stuff, thanks for starting the new topic. Pardon the long posting; feedback definitely wanted on the last two paragraphs (the wild & crazy design ideas).

Gizmo, I like your design sensibilities; you're definitely what we'd call an "eco-industrial" where I come from. And yeah, I'm obsessing about refrigeration too.

Good point about biggest interior with smallest exterior. And about needless refrigeration. Though, here's a perverse paradox for you.

People in rural and suburban areas usually have to drive to the grocery store. So you buy your milk and so on, things that have to go in the fridge, and you try to save energy by driving less, so you buy a couple weeks' worth at one time. But now you need a larger fridge. Or if you have a smaller fridge, you have to drive to the store more often (unless you also drive to other destinations such as work every day and can go to the store on the way home). So there's a tradeoff between the fridge and the car.

Here's another perverse paradox. The larger the fridge, the more cubic volume is enclosed in a given external surface area, therefore the more efficient it will be (all other factors equal). A smaller fridge has a lower ratio of interior volume to exterior surface area, so it's inherently less efficient. Now of course it is also true that the smaller fridge uses less energy in an absolute sense, so in most cases the thing to do is have a smaller fridge.

Tolivac: right on target about putting the compressor/radiator on top. A couple of factors that come to mind re. why this hasn't been done for a long time:

Ability to store and transport fridges without a bunch of complex packaging to prevent an exposed device on top being damaged. The need to accommodate limits in the height of the appliance in typical installations. The possibility that above a certain height in the room, the normal presence of warmer air toward the ceiling might interfere with heat dissipation from a top-mounted radiator. Ergonomics: easier to put the compressor below since this provides more usable height above (within the height limits of the appliance), and people prefer to not have to stoop down to get stuff in the fridge.

How many (if any) of those do you think are correct; or, what other factors do you think are relevant?

BTW, I think SunFrost still puts the radiators on top. SunFrost appears to be the gold standard for efficient fridges, however they are expensive, about $2,500 if I recall correctly. At present prices for electricity, payback can be @ 10 years. If your electricity comes from a natural gas or oil fired power plant, that payback time will be dropping steadily as gas & oil peak out and the price of that electricity soars. If you get your power from any combination of sun, wind, and nuclear, the price of electricity should remain steady so the payback period for a SunFrost won't decline over time.

The place where SunFrost pays for itself very quickly is in the tradeoff with additional photovoltaics & storage batteries.

---

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?

---

--- the stuff below is what I'd really like a critique about ---

What about designing a forced-air condenser system so that the warmer air is ducted into an adjacent room as a heat source where it'll do some good in the cold months? And while we're at it, put a decent filter on the intake side, to prevent dust getting into the coils.

Speaking of air filtration: what about a fridge with enclosed ductwork around the forced-air path and condensor coils, and then use washable cloth filters, something like a towel stretched over a frame with a removable secondary retaining frame? Every week you just change the towel and put the dusty one into the laundry. This would be intended to eliminate the need for disposable filters or the need to carefully hand-rinse the dust out of a plastic foam filter or other delicate material.

Last but not least, a wild and crazy idea, and BTW this is serious and I have a possible situation to actually use this if it's any good. Assume a fridge with forced-air condensor with radiator coils in an enclosed ductwork, where input air comes in via a reusable cloth filter that is similar to a towel. Assume a dry climate with an abundant water supply. OK, now what about evaporative pre-cooling of the air? Periodically soak the towel (or have an automatic system drip water onto it from above and collect overflow below) so that the air passing through it causes the water to evaporate and thereby the air is cooled. Now you have cool air passing over the radiator coils in the fridge. This would seem to make the heat transfer faster between the coils and the (cooled) air, right? Could this gain enough efficiency to make it worth while, or is it just becoming too much like a Rube Goldberg contraption?

Next wild & crazy idea, a whole lot simpler. Assume a purely conventional fridge with its coils mounted on the back. What about putting a highly polished aluminum or stainless steel sheet down the back between the coils and the box, to reflect the heat being radiated from the coils, away from the box? What difference if any would that make? The reflective sheet would be removable for periodic cleaning. Also what about mounting a fridge on rollers or casters like a portable washer, to make it possible to get it out into the kitchen easily for routine cleaning of the coils (and the reflective back panel)?

(Okay, too-long-posting limit reached six or eight paragraphs ago, more later

 

[Cybrvanr]

One of the other enormous energy users in refrigerator is the defrosting system. We seem to have taken a step back with this. Earlier frost-free fridges reversed the refrigerant cycle like a heat pump. Newer fridges though use a heating element that consumes 3 times more power than the compressor system would to make the same amount of defrosting heat. Still, the most efficient method is a manual defrost fridge.

Refrigerators also have all sorts of little things on them that can make them more inefficient. We don't think about the light bulb, but every time you open the door, you are turning on a 40 watt heating element. How about using LED's or compact flurorescents to illuminate the interior.

Another thing is all the darned fans. Each fan motor, in it's own right uses about 8-10 watts. Most refrigerators have two fans. One down below for the condensing coil, and one inside for the evaporator core. By moving the condensor to the rear of the fridge, it not only makes it more efficient because the heat doesn't radiate back inside, but becasue you eliminate a fan needed to pull the air over it. Exposing the coils to natrual airflow, versus ducting them saves energy in fans. It does however cost more, because more metal is needed in the coils, and in heat sink fins. Fans are probably cheaper than heat-conductive metals like copper and alumnium to manufacture Exposing the coils within goes by the same rules. Another fan is eliminated, but more heat-conductive metal is needed to expose the coils...and buyers don't think exposed coils are asthetically pleasing (they also tend to block the coils causing the fridge to perform poorly) Using filters isn't so much of a good idea as it sounds becasue they restrict airflow. This results in needing a bigger fan, and more noise.

Modern insuation technology thankfully has created materials perform better, but are thinner. One of the most notible is the use of foam insulation nowadays, where fiberglass used to be used. Foam gives a much higher R value for the same thickness as fiberglass. Still, even more performance can be achieved the thicker you go!

One of the other issues I've always been annoyed about fridges is the fact that one must open the entire compartment to get out one article. A fridge that has slide out drawers...sort of like the professional models, would probably save enormous energy because there would be less air space opened up to go inside.

One of the last things that I have read about too that would probably save energy is the use of hydrocarbon refrigerants. They carry more heat than any of the CFC or HFC refrigerants, and carry little environmental risk. The chemical industries have successfully lobbied the EPA into making them illegal however due to unsubstansiated claims that they are flammable and explosive. yes, they are explosive and flammible when they leak, combined with oxygen, and are then exposed to an ignition source. The issue is though is how often do refrigerators leak? Not too often, and even when they do it's a slow leak that produces too low of a concentration to be flammable. The stuff obviously isn't going to ignite within the refrigeration loop because one of the necessary things to do when charging refrigerant is to vacuum out all the air! Many Chinese and other asian companies are building hydrocarbon refrigeration systems in their fridges and AC units, but they cannot sell them in the USA. Their efficiency ratios however are staggeringly high!

You are right however...running a big fridge is cheaper than running a bunch of small fridges. Another thing is that adding thermal mass to an otherwise empty fridge saves energy too. Fill your fridge with water bottles if you aren't using the space! Refrigerating food that doesn't need to be refrigerated is a good because it adds thermal mass, but your best bet like you said Gizmo is just to get a smaller refrigerator!

Many of you all have plenty of good ideas. Many of which would not add significantly to the cost of the refrigerator at all.

 

[Cybrvanr]

assemble it yourself refrigerators!

Shipping refrigerators is particularly expensive, they are big, heavy, and easy to damage. What about if one were to make a refrigerator that comes disassembled?

My thought is to ship the cooling unit as a compete part, and the food compartments as a buildable box, sort of like Ikea sells their furniture! When you unpack your fridge, you get a box with the cooling system in it, and all the panels to make the sides, back, and the doors for the front. You attach the panels to the cooling unit and bolt them together into a unit.

This would greatly shrink the size of the transported package, and would minimize the risk of damage that could occur.

 

[sudsmaster]

Refrigerators, at least in the USA, have made major strides towards energy conservation in the past 10 years or so.

15 years ago, the average fridge used well over 1500 kWH/year.

Now, the same capacity fridge uses close to 500 kWH/year. The stimulus came from a government agency award to the company that could show the biggest improvement in efficiency. Whirlpool won that award (I think it was $30 million) and their fridges have consistently been the most efficient since then.

There are some new technologies that may make their way into products for even greater efficiency... such as using sound waves to compress coolant. Or so says Popular Science a while ago.

 

[panthera]

back to absorbers?

I don't have any current figures with which to compare the efficiency, but it is obvious that absorbers are much easier to integrate into a solar/battery/other "weak" but constant energy supply system.
Pity they haven't really come back more into fashion. My last one was a very large "Linde" and worked great.
As to the defrost systems...I recall there being nothing but trouble with the reversing mechanisms. This also did in a lot of heat pump/air conditioner combos. My folk's refrigerator uses the warmth removed from the unit to evaporate the defrosted water, by the way. A bit of savings.
The knock down idea is great. Of course, with modern compresors it would be easier to put one back on top, too. They can be much smaller than the older ones were.
Some great ideas here...

 

[gizmo]

When we still lived in civilization, we had a two door cyclic defrost fridge/freezer of 200 litres. It belonged to my partner when we met.
When I got interested in energy stuff, I borrowed a kwh meter and plugged in the fridge. It was averaging 4 kwh per day! This was in a mild climate and a house with almost no heating - just a gas room heater in the lounge. I thought something must be wrong. I did notice that the top of the fridge was always very cold on the outside, like the insulation was failing.
I removed the top laminex cover and found the polyurethane insulation was full of ice. Spoke to a refrig mechanic who explained the insulation needs to be sealed tight from outside air or atmospheric moisture works its way in and freezes. There was a small puncture in the back panel which was just silver paper over the foam, only the sides and base were steel. (A cheap fridge) thus the moisture getting in.
I pulled out the icy foam, replaced it with new polyurethane sheet, put rigid plastic over and sealed up the edges with silicone.
With the insulation repaired the power was down to 2.8 kwh per day.
When pulling it apart I found some other horrid things. The cold plate (evaporator) inside the fridge compartment had a small heating element. It was wired across the thermostat so that whenever the motor was NOT running, the heater was running to defrost the evap. So as soon as it stopped cooling, it started heating inside the fridge. Also around the doors there is a small heating element to stop frost forming around the door edges. (called a mullion heater), this is mainly a concern in humid areas where moisture in the air condenses on the cabinet and it looks like the fridge is sweating.

I disconnected both heaters. As a last energy saving effort I removed the screws holding the black pipes (condenser) to the back of the fridge, added a sheet of 3/4 inch polystyrene sheet to the back of the cabinet, covered that with foil, and re-attached the condenser with longer screws and spacers to maintain the clearance.
The power consumption fell to 1 kwh per day.

Current low voltage DC fridges made in AU especially for solar, similar size and also cyclic defrost, use about 0.4 kwh per day.

With careful design a cyclic defrost fridge can be sesigned to defrost itself between cycles without a heating element, its all to do with careful thermostat selection and placement of the thermostat probe on the evaporator plate.

Chris.

 

[sudsmaster]

Gizmo,

Some newer TOL fridges here (again, usually Whirlpool) are designed to sense when there is frost buildup on the evaporator coils, and to only turn on the defrost heater when that occurs. As you've discovered, this can save a lot of energy.

Older designs have the defrost heater activating once every 24 hours, whether it needs it or not.

Anyway, you're prompting me to think that my '40's something GE fridge may be in the sub-1kWH/day range. Which would be very good. I won't enjoy the regular defrosting it will require, but it will look much better next to my '58 KA top load dishwasher than the current modern KA stainless top freezer. Which works great, I just have tired of the stainless look. Plus the door panels have a defect that has caused them to suck in and look severely dented over time.

Speaking of which, modern fridge don't have porous foam or fiberglass insulation any more. It's more like the urethane insulation you used to replace your soaked stuff. Higher density, better insulating, and I don't think it will absorb water and freeze like older stuff. It also allows for thinner cabinet walls. However, it also transmits sound better than older insulation, which means that some consumers find their new fridges are noisier than their old ones. Better and quieter compressor designs are used to counter this louder operating sound level.

 

[Designgeek]

What are the yearly power consumption figures in KWH, for those hydrocarbon based units? That would be interesting to know.

---

Yes, I have one of those obnoxious fridges that uses 4 KWH/day. It's an old Montgomery Ward unit that came with the place, and if I wasn't planning to get out of here ASAP (regional earthquake hazard), I'd ask property management to remove it and I'd replace it with another unit.

Here's some quick research I did last year, using a KWH meter on my fridge and using published figures for other brands:

My fridge, default mode, per day: 4.83 KWH, warm weather. After defrosting, and cleaning the coils at the back of it (not easy, the screaming idiot who installed it before I moved in wedged it into the space, it can't be pulled out w/o serious tools), 4.54 KWH/day. After adding a PC-type cooling fan & dryer duct to get air circulation back there (it is in a location that has minimal airflow normally, and very close clearances to cabinets), 4.41 KWH including the fan. Per day. Per year that's 1,609.65 KWH. Which still stinks bigtime.

For the rest of these, the figures are per year.

Large Whirlpool, per year: 675.

Best of smaller units (10 cubic foot), per year: Sanyo SR-1030: 331. However, Sanyo's website lists this at 350, so something is odd here.
First-cost for this unit: $225.00

Best of all: SunFrost RF-12: 105.9.
First cost for this unit: $2,200.00

At 14-cents per KWH, the Sanyo is still more economical than the SunFrost, even over a 20-year period (assuming the SunFrost is put on the mortgage when a house is bought). However, the SunFrost could be more economical in off-grid installations where the cost of additional photovoltaic or wind capacity, plus battery storage, has to be figured into the picture. And the SunFrost is a viable choice where generating capacity is strictly limited and one must necessarily reduce all usages to the bare minimum.

The crossover point (where the SunFrost becomes more economical than the Sanyo) for 20-year total cost, is at 45 cents / KWH.

The crossover point for 10-year total cost, is at about 95 cents per KWH.

Tonight, going to various manufacturers' websites, we find:

The smallest Whirlpool (model ET0WSRXM) is just under 10 cubic feet, and listed at 386 KWH/year. Most-efficient unit in its size class, among all manufacturers, is listed by the Canada EnerGuide at 331 KWH/year, which is probably the Sanyo.

Now we go to Sanyo's web page and discover that there is a non frost-free version of this, which is rated at 321 KWH/year, however this does not have a separate door to the freezer compartment, and the freezer compartment appears somewhat smaller, so that may not be useful. The energy guide ratings here show that the most efficient model is 273 KWH/year in the class 8.5 to 10.4 cubic feet, which is a considerable savings. However I can't find a 273 KWH/year unit on Sanyo's web page.

And, as I mentioned above, the model SR-1030 is listed at 350 KWH/year. There is a 3.6 cubic foot fridge (no freezer) listed at 319 KWH/year, which doesn't help since after all we're only looking at units with freezers.

For comparison, a GE 11.9 cubic foot unit shows a rating of 409 KWH/year. GE's website is sufficiently slow to load pages, that I don't feel like doing any more digging there at the moment, but in any case these numbers are within the reasonable range.

I'm thinking that any fridge's efficiency could be improved easily by a) putting a reflective surface behind the coils, i.e. removable polished aluminum sheet that can be sponge-cleaned when needed, and b) putting the fridge on casters (or on a low platform with casters) so it can be rolled out for easier access to the coils in order to vacuum them regularly. (This would also make it easier to vaccum behind and under the place where the fridge normally resides.) In an earthquake zone, you'd include some means of locking it down when it's not being moved around.

 

[toggleswitch]

oooho that Toggle has a big mouth.

Older designs have the defrost heater activating once every 24 hours, whether it needs it or not.

Hopefully the thermostatic control on these heaters limits energy usage once the frost has been melted. I guess the trick is to get the unit out of *defrost* cycle quicker (unlike today's traditional timed systems)and back to its regular job of cooling.

As for absorption (gas/heat) fueled refrigeration. Unless vented to the out-of-doors, I regretfully report that I am still dead-set against the polution of indoor air and generaly degradation of air-quality unvented indoor gas-burning of any type brings.

(Yes, everyone is entitled to my opinion. *LOL*)

 

[toggleswitch]

For storage of foods-here in the very humid South I have to

Here in New York City, EVERYTHING possible gets stored in the ref. to avoid cockroaches.

When you dont have space or money to buy perfectly air-tight containers for everything- cookies, cakes, cereal boxes etc MUST go in the fridge as-is so the little critters don't feast at your casa.

P.S Roaches love to stimulate their bodies by rubbing against surfaces...so get rid of those bags stuffed between the refigerator and the cabinets! Wide open spaces are your friend.

http://wywy.essortment.com/howdoigetrid_rgus.htm

 

[toggleswitch]

Look you can see the stars.............

Energy Star program and refrigerators

http://www.energystar.gov/index.cfm?c=refrig.pr_refrigerators

 

[toggleswitch]

hi-tech savings.

I am still looking to find an article I once saw where there was an energy-saving controller to send modified AC to the compressor or something.

IIRC it plugged into the wall and the ref. plugged into it....

http://www.buyusa.gov/india/en/fuse.html?exp_cat=5099&exp_pid=73

 

[toggleswitch]

Ask Mr. Electricity

How much energy does a refrigerator use? - by Mr. Electricity

 

[toggleswitch]

ooohhh nice chest.

It's long, it's PANK and it saves energy

Chest fridge

Chest fridge Using vertical doors in refrigeration devices is an act against the Nature of Cold Air. Understanding and cooperating with Nature rather than acting against it leads to much better efficiency. My chest fridge (Vestfrost freezer turned into a fridge) consumes about 0.1 kWh a day. It...

mtbest.net

 

[toggleswitch]

I have had WAY too much coffee; sorry about the logorhhea

The Power Planner from EnergySmart: NOT RECOMMENDED
I guess I no longer have to recommend against this $30 device, which purports to reduce the electical usage by refrigerators and other appliances by "up to 23%", since the company making it went out of business.

THERE IT IS AT THE END OF THE PRIOR LINK!

 

[sudsmaster]

Toggle,

I bought one of those "energy savers" a while back and found it didn't do much for my electric fan energy consumption (I run a big fan in the patio in the summer to blow cool night air into the house during hot weather spells). So I think I returned it to Costco for a full refund. I didn't use it on my new KA top freezer because I was worried it might harm the compressor. Plus, that 22 cu ft fridge is already quite energy efficient - about 550 kWh/yr.

As I understand it, devices such as the energy saver work by improving the power factor for electric motors.

Designgeek,

If I'm not mistaken, the most energy efficient Whirlpool/KA 25 cu ft side by side refrigerators use less than 600 kWH/yr these days. I'm assuming that smart defrosting is part of the savings picture.

 

[petek]

Ah those magic microscopic words "up to" mean shite. That's why they're always written 1/100 the size of the the big number with a percentage sign.
When was the last time you ever found something for 70% off at a store blitzing their "up to 70% OFF SALE". If you're lucky you'll find something 5% off and most of it zero.