New refrigeration or wishful thinking?

[begreen]

What say ye? How does this differ from TEGs or the little thermal coolers in portable electric coolers? Has there been a breakthrough in efficiency that makes the practical for the average home refrig? What about the freezer?

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Phononics is claiming their commercial refrigerator has 30% greater capacity and 30% lower operating costs, while providing almost silent, refrigerant-free refrigeration. They also talk about a small heatpump based on this technology.

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[Socratic Monologue]

It says they got a grant to increase the efficiency of thermoelectric coolers (Peltier coolers, I know them as). Not clever, exactly, but sounds like a good idea.

I never knew that modern refrigerants had such an effect on global warming.

 

[begreen]

It says they got a grant to increase the efficiency of thermoelectric coolers (Peltier coolers, I know them as). Not clever, exactly, but sounds like a good idea.

I never knew that modern refrigerants had such an effect on global warming.

Yes, peltiers. It's not just home refrigerators, but all refrigeration which is much larger when one looks at the harvesting, storage, processing, transportation and grocery store components. And then there is air conditioning, which is the elephant in the room. That includes AC in cars which is huge. Add this all up and it is listed as the number most addressable problem that we can correct to reduce climate change according to Drawdown.

Interesting info: Space cooling required nearly 2,000 terrawatt-hours of electricity in 2016, according to the IEA

 

[begreen]

It would be great if this tech helped EVs to use less battery power, though I wonder how fast they are at heating and cooling.

 

[Corey]

Well, lets see... I can go out today and buy a compressor AC system with a reported Seasonal Energy Efficiency Ratio (SEER) of 42:

Carrier Launches the Most Efficient Air Conditioner You Can Buy in America

www.carrier.com

We can approximate nominal Energy Efficiency Ratio (EER) by: EER = SEER * 0.875, or EER = ~37

One more step gets that to a more familiar Coefficient Of Performance (COP) by: COP = EER / 3.4121, or COP = ~10.7

So for every btu I put into the Carrier minisplit, I move 10.7 btu out of the house. If my early morning math holds, we can incorrectly but for roughly consider that as an "efficiency" of 1070%

Phononic seems to make several vague claims: [brackets are my questions]

Phononic’s ENERGY STAR® certified refrigerators deliver up to 40% energy savings versus compressor-based refrigerators. [any specific compressor based systems?]

We have made significant improvements in the ability of our devices to deliver heat pumping with high efficiency—using up to 30% less power—high heat flux, and improved cooling. Standard thermoelectric coolers (TECs) can’t compare. [So 30% less power compared to standard TECs?]

Going by the last quote, one of the first standard TECs on the search shows a COP of 0.85

Efficient Thermoelectric Cooler 2780 BTU/HR (815 watts) For 240 Input

Efficient Thermoelectric Cooler the AHP-4252 is an advanced Peltier-driven air conditioner. The thermoelectric enclosure cooler Model AHP-4252 will maintain both efficient cooling and the NEMA rating of your weatherproof enclosure. Its ECO-Mode temperature control feature helps save on power use.

www.thermoelectric.com

So if we give Phononic the benefit of doubt and assume they've reduced power consumption of a system like that by 30%, that would put their COP around 1.0 or just slightly higher. So still seems like they need massive improvements to get close to the more efficient compressor systems with COP close to 10?

[edit: online calculator seems to have goofed the EER/COP calcs... longhand and conservative SEER > EER calculation is above]

 

[begreen]

I am skeptical and need to see some actual numbers from them. The primary difference is not just efficiency, it is that the system is freon free.

 

[peakbagger]

My understanding is the refrigerant issue is on its way out as an issue of concern. Large users are starting to transition to CO2 as a refrigerant. https://refrigeranthq.com/r-744-carbon-dioxide-refrigerant-fact-info-sheet/
The problem is CO2 and a lot of the replacements require higher pressures to do work and that means thicker tubing and more expensive compressors. This costs more so the temptation is for the third world and emerging economies to use the older refrigerants as the equipment is easier and cheaper to make. There was a fairly widely reported bump up in phased out refrigerants detected in the atmosphere a few years ago after years of tapering down, the actual source was never reported but there was strong hints that it was coming from manufacturers in China.

There has been a lot of work on thermoelectric modules for a long time. To date any improvements have been incremental but seem to be stalled. In order for them to be a substitute for a compressor based system they would need a radical improvement.

 

[ABMax24]

The other option is to use traditional hydrocarbons as a refrigerant.

We bought a freezer 1.5 years ago that uses Pentane as a refrigerant, works just like any other freezer just no ozone damaging refrigerants. The only issue could be it is flammable should it ever leak, but it is only a small amount of Pentane in the system.

We also have an LG Fridge with the Linear Compressor, it uses less than 100 Watts when running, but it does have to run longer. The only thing is it has a traditional refrigerant.

I don't see Peltier cell cooling being that efficient. They have been around for a while as portable 12 volt automotive coolers, but they take a fair bit of power to run.

I see for more potential for an efficient Peltier cell to be used in reverse as a TEG to generate electricity from waste heat. Could you imagine how much energy could be recovery from a vehicles cooling system or exhaust.

 

[begreen]

Just a guess, but maybe they have figured out a way to drop costs and size in order to create large matrices of cells? The cell looks about 1.5cm sq. Getting back to smoke and mirrors, do peltier coolers also use lattice waves (phonons) to transfer energy?

 

[Corey]

Some 'light' reading on TEC/TEGs, phonons, etc https://arxiv.org/ftp/arxiv/papers/1401/1401.0749.pdf

On the TEC side, looks like they give a COP equation (2.27) on p13. Guess anyone with time to kill could punch in some real numbers and see what pops out. Then go wild with some exotic ZT material on the 'wishful thinking' side.

On the TEG side, the real kicker comes on p46 where they discuss 'real world' system efficiencies of 5-7%, possibly pushing up near 15% for an 'ideal' system and ~25% for a theoretical maximum.

 

[jetsam]

Real world peltiers aren't in use for any application requiring efficiency because they have to have very specific operating conditions to rival the efficiency of a heat pump. If you hop on Amazon and buy "a peltier" to cool your CPU or whatever, expect abysmal efficiency.

They are used in applications where silence or zero air exchange are more important than efficiency, though.

As you might guess if you are familiar with the Peltier's cousin the TEG, peltiers get more efficient as the temperature difference between the cold side and the hot side gets smaller. For efficient use, you size it to run at a fraction of it's rated power... but not too low or efficiency falls off the cliff again, and you can wind up with a heater. To run efficiently, you have to vary the current through the module based on the difference in temperature on the hot side and the cold side, which means that you are measuring both temperatures, computing the difference, and using that result to control power to the cooler. This is more complexity than electric lunchbox makers are really up for, both in terms of designing a properly sized system, and in terms of needing a computer to run the cooler.

Moar reading

 

[woodgeek]

Huh. My research area is adjacent to phononics, which IS seeking high efficiency new Peltier Materials. I was not aware of a breakthrough, but think that huge improvements are theoretically possible with nanomanufacturing.

I think it will eventually come to pass.

And I think they are trying to phase out the greenhouse refrigerants. That will happen before phononics scale, and should.

 

[EatenByLimestone]

We could always use anhydrous ammonia as a refrigerant again. They're typically propane refrigerators, but any heating element would work. It would be simple to make the heater electric and then it would work with solar. Couple that with foam insulation and it could use very little energy.

 

[ABMax24]

We could always use anhydrous ammonia as a refrigerant again. They're typically propane refrigerators, but any heating element would work. It would be simple to make the heater electric and then it would work with solar. Couple that with foam insulation and it could use very little energy.

Absorption refrigerators are not very efficient. They typically have a COP of around 1, where a standard refrigerator should be greater than 3.

I have one in my fifth wheel, when plugged into the electric of my house I double my daily energy consumption. It pulls 400 watts to run the heater in the fridge and has to run about 75% of the time.

 

[EatenByLimestone]

My first question is if your 5th wheel manufacturer was worried more about insulation or size when choosing a refrigerator to install. Up the insulation and energy consumption goes down. On top of that, you dont have moving parts. No more compressor failures. Keep it upright and it'll last a heck of a long time. Longevity should calculate into efficiency too.

 

[ABMax24]

My first question is if your 5th wheel manufacturer was worried more about insulation or size when choosing a refrigerator to install. Up the insulation and energy consumption goes down. On top of that, you dont have moving parts. No more compressor failures. Keep it upright and it'll last a heck of a long time. Longevity should calculate into efficiency too.

I don't care how much insulation they put in, when you are using a process that requires at least 3 times more energy to remove the same amount of heat you will never be more efficient.

This is the reason that 99% of household refrigerators use a reciprocating compressor.

 

[EatenByLimestone]

I don't buy that. If the means used to cool the fridge is 3x more efficient, and they don't put insulation in, how can it be more efficient?

It's a system. Look at what it costs to run the machine. Or I'll buy the lifetime figures taking into account energy used to manufacture the product.

Telling me a car is more efficient because it has LED headlights seems to be ignoring an awful lot in a complex machine.

 

[woodgeek]

The problem with your analogy Randy is that you are arguing to switch out the engine for one with 1/3 the mpg, and saying you can make it up with better tires and weight reduction.

 

[semipro]

I am skeptical and need to see some actual numbers from them. The primary difference is not just efficiency, it is that the system is freon free.

...and free of moving parts with less noise.
Agreed though that that the lack of refrigerant is the big bonus.

 

[semipro]

We could always use anhydrous ammonia as a refrigerant again. They're typically propane refrigerators, but any heating element would work. It would be simple to make the heater electric and then it would work with solar. Couple that with foam insulation and it could use very little energy.

I had an RV once that used ammonia refrigerant, it about killed me when it all leaked out while I was inside.

 

[peakbagger]

Build it solar has a deadlink to a novel refrigeration system. Someone set up a motor free icebox in his basement. The tricky part was he located a freon coil outdoors connected to freon coil in a large insulated tank of water in basement that had a icebox inside it. The tank surrounded the icebox on 5 sides with a heavily insulated door on the front When the weather was below freezing the colder temps of the freon outdoors would cause it to condense and natural sink to the basement where it would freeze the water in the tank. The warmest freon in the basement would rise back up to the outdoor coil and then cool down again. This would go on all winter until there was a huge block of ice in the tank around the ice box. They did not need to turn the freon on and off as if the inside was colder than the outside the freon would not circulate to the outdoors. They could run all summer and use the ice block to cool the icebox. By the end of the warm season it would just start ciculating. I dont remember the details but the water tank was quite large.

Not very practical especially since it could not sustain sub freezing temps unless they went with a salt solution to get the ice to freeze at a lower temp so no frozen foods but ingenious.

At one point I think there was an entrepreneur that equipped walk in coolers with free cooling coils in VT. When the temps outside was below the temperate inside the cooler they would circulate glycol from a coil outside to the inside the cooler. It would reduce the year round refrigeration cost to a business. Not sure if he is still doing it.

 

[EatenByLimestone]

I like that idea!

 

[begreen]

Build it solar has a deadlink to a novel refrigeration system. Someone set up a motor free icebox in his basement. The tricky part was he located a freon coil outdoors connected to freon coil in a large insulated tank of water in basement that had a icebox inside it. The tank surrounded the icebox on 5 sides with a heavily insulated door on the front When the weather was below freezing the colder temps of the freon outdoors would cause it to condense and natural sink to the basement where it would freeze the water in the tank. The warmest freon in the basement would rise back up to the outdoor coil and then cool down again. This would go on all winter until there was a huge block of ice in the tank around the ice box. They did not need to turn the freon on and off as if the inside was colder than the outside the freon would not circulate to the outdoors. They could run all summer and use the ice block to cool the icebox. By the end of the warm season it would just start ciculating. I dont remember the details but the water tank was quite large.

Not very practical especially since it could not sustain sub freezing temps unless they went with a salt solution to get the ice to freeze at a lower temp so no frozen foods but ingenious.

At one point I think there was an entrepreneur that equipped walk in coolers with free cooling coils in VT. When the temps outside was below the temperate inside the cooler they would circulate glycol from a coil outside to the inside the cooler. It would reduce the year round refrigeration cost to a business. Not sure if he is still doing it.

Reminds me of the old ice houses we had back in CT. They had very thick wall cavities that were filled with sawdust. The ice house would get filled up with blocks of ice from the nearby pond and stored there. In a good year there would still be ice throughout the summer.

 

[peakbagger]

There are still a few places that keep up the ice sawing tradition in NH and Maine. They wait until the ponds ice up and then store the ice in an icehouse to use all summer, I think there is summer camp that does it to keep their ice house stocked for the summer. Sawdust is the traditional installation. I remember as a kid (1960s) there was still a milkman in the neighborhood and in addition to milk he also carried ice blocks for sale.

I think I read that one of the biggest exports from Maine in the 1800s was ice.

 

[sloeffle]

Reminds me of the old ice houses we had back in CT. They had very thick wall cavities that were filled with sawdust. The ice house would get filled up with blocks of ice from the nearby pond and stored there. In a good year there would still be ice throughout the summer.

The Amish in our area still use ice houses. In the middle of winter they will have a work party and get out on one of the local lakes and cut ice. My Amish buddy told that they then use the ice throughout the summer.