Freezer to Fridge Conversion project in ReNew

Discussion in 'Hobby Electronics' started by David L. Jones, Sep 28, 2005.

  1. There is a "freezer to fridge" conversion project in this months ReNew
    magazine which claims to convert a freezer into a supper efficient
    0.1kWh/day fridge.
    It's basically a thermostat which switches the freezer mains power off
    and on to regulate its temperature.
    It's a follow up to an existing article which I haven't seen, so
    doesn't have much detail on how it works or how the measurements were
    taken.

    Although I don't know much about fridges or freezers, several things
    raised my "What the?" detector immediately:
    1) 0.1kWh/day is 36.5kWh/year, that's about 1/10th the power
    consumption of a regular fridge. Something ain't right there... what's
    the catch?
    2) The circuit is hardly "micro-power" as claimed, not that it really
    matters.
    3) The use of a battery to power the circuit when the freezer
    compressor is not on. WHY?. Presumably the author thinks it lowers the
    power consumption?. Looks like he's designed a Free Energy device!

    Here is the circuit:
    http://www.alternatezone.com/electronics/images/FreezerConversion.jpg

    Can a freezer be made into a more efficient fridge using this
    technique? My gut feeling is "maybe", but the amount claimed seems very
    unlikely. I suspect the author has goofed the measurements.

    Comments please...

    Dave :)
     
    David L. Jones, Sep 28, 2005
    #1
    1. Advertising

  2. David L. Jones wrote:
    > 3) The use of a battery to power the circuit when the freezer
    > compressor is not on. WHY?. Presumably the author thinks it lowers the
    > power consumption?. Looks like he's designed a Free Energy device!


    On second thought it is obvious that the author thinks that charging a
    battery and using that instead of having the mains transformer
    permanately powered is going to save some power. Possibly, have to go
    through the numbers I guess. The transformer has losses, but so does
    the battery and charging.
    The obvious thing is that if the battery fails your fridge dies. Then
    when it does die you have manually kick-start the thing again. Seems a
    silly way to go about it just to save some quiescent power.

    Dave :)
     
    David L. Jones, Sep 28, 2005
    #2
    1. Advertising

  3. "David L. Jones" <> wrote in message
    news:...
    > There is a "freezer to fridge" conversion project in this months ReNew
    > magazine which claims to convert a freezer into a supper efficient
    > 0.1kWh/day fridge.
    > It's basically a thermostat which switches the freezer mains power off
    > and on to regulate its temperature.
    > It's a follow up to an existing article which I haven't seen, so
    > doesn't have much detail on how it works or how the measurements were
    > taken.
    >
    > Although I don't know much about fridges or freezers, several things
    > raised my "What the?" detector immediately:
    > 1) 0.1kWh/day is 36.5kWh/year, that's about 1/10th the power
    > consumption of a regular fridge. Something ain't right there... what's
    > the catch?


    ## I would think the compressor would require just as much power to cool as
    a normal fridge. Perhaps it is the physical design of the freezer, where the
    bucket shape and better insulation holds the cool in better.

    > 2) The circuit is hardly "micro-power" as claimed, not that it really
    > matters.
    > 3) The use of a battery to power the circuit when the freezer
    > compressor is not on. WHY?. Presumably the author thinks it lowers the
    > power consumption?. Looks like he's designed a Free Energy device!


    ## Looks like SW1 has two settings - one to run the circuit off mains (to
    charge the battery) and the other to just run off the battery. Probably to
    reduce power consumption by limiting the use of the transformer.

    >
    > Here is the circuit:
    > http://www.alternatezone.com/electronics/images/FreezerConversion.jpg
    >
    > Can a freezer be made into a more efficient fridge using this
    > technique? My gut feeling is "maybe", but the amount claimed seems very
    > unlikely. I suspect the author has goofed the measurements.
    >
    > Comments please...
    >
    > Dave :)
    >


    How often does he use the fridge? I reckon that is the main factor in fridge
    power consumption. Or pehaps he is comparing a freezer with an efficient
    compressor to a dodgy old kelvinator.

    Ross
     
    Ross Marchant, Sep 28, 2005
    #3
  4. David L. Jones

    KLR Guest

    On 27 Sep 2005 16:14:27 -0700, "David L. Jones" <>
    wrote:

    >There is a "freezer to fridge" conversion project in this months ReNew
    >magazine which claims to convert a freezer into a supper efficient
    >0.1kWh/day fridge.
    >It's basically a thermostat which switches the freezer mains power off
    >and on to regulate its temperature.
    >It's a follow up to an existing article which I haven't seen, so
    >doesn't have much detail on how it works or how the measurements were
    >taken.
    >
    >Although I don't know much about fridges or freezers, several things
    >raised my "What the?" detector immediately:
    >1) 0.1kWh/day is 36.5kWh/year, that's about 1/10th the power
    >consumption of a regular fridge. Something ain't right there... what's
    >the catch?
    >
    >

    it all depends on the size of the fridge (and this wasnt specified in
    your post), and how good the insulation is on it. The little "beer
    fridge" we have in our workplace (made circa 1987-88) draws 153w
    according to the specifications. I presume that this is the power the
    compressor draws when it is running, so if you assume that even if
    this compressor never turns off - its going to draw .153 Kwh.
    Depending on how often it gets opened, it probably would come close to
    the 0.1 kwh average power over a 12 month period.
    >
    >

    I think what these people are working on is the fact that a typical
    freezer is going to have a MUCH better insulation than a typical
    fridge, so if its run as a fridge (higher temperature than a freezer)
    the temperature will take longer to raise, due to the better
    insulation, and the much less time the compressor will have to run in
    the average day.
    >

    As an added bonus, if they are talking about "tucker box" freezers
    (with the top mounted lid), then when they are opened, very little
    cold will "spill" out, whereas with a standard fridge with the hinged
    front door, the cold air will "pour" out very quickly when opened -
    wasting a lot of energy !
    >
    >

    In a theoretical fridge that had a perfect seal with no heat leakage,
    and perfect insulation that the heat could NEVER pass through, and no
    metal parts going from the inside to the outside (to pass heat inside)
    the fridge would only have to be powered for long enough to bring it
    down to the desired temperature, and then it would stay at that
    temperature eternally, as long as it wasnt opened, and nothing in
    there gave off heat (food eventaully rotting etc)

    >2) The circuit is hardly "micro-power" as claimed, not that it really
    >matters.

    no. If they wanted to save power, and just had to have this
    "electronic control" they wouldn't be stepping down a 12vac secondary
    (more like 17vdc when rectified) to +5v via 2 series regulators, and
    they also wouldn't be using a relay (surely a triac would have less
    overall losses ?
    >
    >3) The use of a battery to power the circuit when the freezer
    >compressor is not on. WHY?. Presumably the author thinks it lowers the
    >power consumption?. Looks like he's designed a Free Energy device!
    >

    Save running the transformer all day, and all the other lossy crap in
    there. (mentioned above) Whether it saves any significant power is
    debatable though.


    ------------------
    If they are that worried about power wastage, then why not stick to
    the standard mechanical thermostat (used for decades without
    problems), and simply modify it (if needed) to achieve the desired
    temperature range ! it uses ZERO electrical power to operate !!

    There are millions of fridges out there at recycling centres, that you
    could take the thermostats from for this project, if the existing
    freezer one cant be set high enough.


    >Here is the circuit:
    >http://www.alternatezone.com/electronics/images/FreezerConversion.jpg
    >
    >Can a freezer be made into a more efficient fridge using this
    >technique? My gut feeling is "maybe", but the amount claimed seems very
    >unlikely. I suspect the author has goofed the measurements.
    >
    >Comments please...
    >

    I think it could be, but NOT because of the electronics used.

    If you are going to do this, I would start with the most efficient
    freezer you can buy, not some old thing.
    >


    >
    >Dave :)
     
    KLR, Sep 28, 2005
    #4
  5. > ------------------
    > If they are that worried about power wastage, then why not stick to
    > the standard mechanical thermostat (used for decades without
    > problems), and simply modify it (if needed) to achieve the desired
    > temperature range ! it uses ZERO electrical power to operate !!
    >
    > There are millions of fridges out there at recycling centres, that you
    > could take the thermostats from for this project, if the existing
    > freezer one cant be set high enough.
    >
    >
    >>Here is the circuit:
    >>http://www.alternatezone.com/electronics/images/FreezerConversion.jpg

    >

    I agree, in fact why not have both 'stats installed with a changeover
    switch?
    Or I guess by using the 'off' setting on the freezer 'stat, the changeover
    switch would not be neccessary.

    --
    Regards ......... Rheilly Phoull
     
    Rheilly Phoull, Sep 28, 2005
    #5
  6. KLR wrote:
    > On 27 Sep 2005 16:14:27 -0700, "David L. Jones" <>
    > wrote:
    >
    > >There is a "freezer to fridge" conversion project in this months ReNew
    > >magazine which claims to convert a freezer into a supper efficient
    > >0.1kWh/day fridge.
    > >It's basically a thermostat which switches the freezer mains power off
    > >and on to regulate its temperature.
    > >It's a follow up to an existing article which I haven't seen, so
    > >doesn't have much detail on how it works or how the measurements were
    > >taken.
    > >
    > >Although I don't know much about fridges or freezers, several things
    > >raised my "What the?" detector immediately:
    > >1) 0.1kWh/day is 36.5kWh/year, that's about 1/10th the power
    > >consumption of a regular fridge. Something ain't right there... what's
    > >the catch?
    > >
    > >

    > it all depends on the size of the fridge (and this wasnt specified in
    > your post), and how good the insulation is on it. The little "beer
    > fridge" we have in our workplace (made circa 1987-88) draws 153w
    > according to the specifications. I presume that this is the power the
    > compressor draws when it is running, so if you assume that even if
    > this compressor never turns off - its going to draw .153 Kwh.
    > Depending on how often it gets opened, it probably would come close to
    > the 0.1 kwh average power over a 12 month period.


    Yeah, a small fridge might I guess.
    My fridge (500L or whatever) is rated at 500kWh/year, that's
    1.36kWh/day, and that is one of the lowest consumption ones on the
    market for that size.

    > I think what these people are working on is the fact that a typical
    > freezer is going to have a MUCH better insulation than a typical
    > fridge, so if its run as a fridge (higher temperature than a freezer)
    > the temperature will take longer to raise, due to the better
    > insulation, and the much less time the compressor will have to run in
    > the average day.
    > >

    > As an added bonus, if they are talking about "tucker box" freezers
    > (with the top mounted lid), then when they are opened, very little
    > cold will "spill" out, whereas with a standard fridge with the hinged
    > front door, the cold air will "pour" out very quickly when opened -
    > wasting a lot of energy !


    Very true.

    > In a theoretical fridge that had a perfect seal with no heat leakage,
    > and perfect insulation that the heat could NEVER pass through, and no
    > metal parts going from the inside to the outside (to pass heat inside)
    > the fridge would only have to be powered for long enough to bring it
    > down to the desired temperature, and then it would stay at that
    > temperature eternally, as long as it wasnt opened, and nothing in
    > there gave off heat (food eventaully rotting etc)
    >
    > >2) The circuit is hardly "micro-power" as claimed, not that it really
    > >matters.

    > no. If they wanted to save power, and just had to have this
    > "electronic control" they wouldn't be stepping down a 12vac secondary
    > (more like 17vdc when rectified) to +5v via 2 series regulators, and
    > they also wouldn't be using a relay (surely a triac would have less
    > overall losses ?
    > >
    > >3) The use of a battery to power the circuit when the freezer
    > >compressor is not on. WHY?. Presumably the author thinks it lowers the
    > >power consumption?. Looks like he's designed a Free Energy device!
    > >

    > Save running the transformer all day, and all the other lossy crap in
    > there. (mentioned above) Whether it saves any significant power is
    > debatable though.


    Even if it does, it's a naff way to do it. Dead battery = lost food.

    > ------------------
    > If they are that worried about power wastage, then why not stick to
    > the standard mechanical thermostat (used for decades without
    > problems), and simply modify it (if needed) to achieve the desired
    > temperature range ! it uses ZERO electrical power to operate !!
    >
    > There are millions of fridges out there at recycling centres, that you
    > could take the thermostats from for this project, if the existing
    > freezer one cant be set high enough.


    Sounds like the go.

    > >Here is the circuit:
    > >http://www.alternatezone.com/electronics/images/FreezerConversion.jpg
    > >
    > >Can a freezer be made into a more efficient fridge using this
    > >technique? My gut feeling is "maybe", but the amount claimed seems very
    > >unlikely. I suspect the author has goofed the measurements.
    > >
    > >Comments please...
    > >

    > I think it could be, but NOT because of the electronics used.


    Gotta agree!

    > If you are going to do this, I would start with the most efficient
    > freezer you can buy, not some old thing.


    No plans to do it myself.

    I figure it's all probably a load of bollocks in a practical sense. To
    get any sort of direct comparison figure you'd have to have a fridge
    and freezer of the same size and construction, being opened the same
    amount of time every day.
    If freezer mechanisms were somehow more efficient then every
    manufacturer would be using then in fridges.
    The electronics in the article is doing nothing a normal fridge
    thermostat doesn't do (except waste some extra power).

    The idea of converting a chest freezer might have some merit if you
    were going to store long term stuff in there for instance. Bit useless
    for practical day to day use though.

    A job for Mythbusters!

    Dave :)
     
    David L. Jones, Sep 28, 2005
    #6
  7. David L. Jones

    Mark Harriss Guest

    One possible efficiency boost a chest freezer would have over
    a fridge is you retain most of the cold air inside when you
    open the lid, opening a fridge door would lose nearly all of
    the cold air inside.

    It remains to be seen just how much BTU's can be removed from
    room temp air with a given humidity.
     
    Mark Harriss, Sep 28, 2005
    #7
  8. David L. Jones

    Mark Harriss Guest

    Mark Harriss wrote:
    >
    > One possible efficiency boost a chest freezer would have over
    > a fridge is you retain most of the cold air inside when you
    > open the lid, opening a fridge door would lose nearly all of
    > the cold air inside.
    >
    > It remains to be seen just how much BTU's can be removed from
    > room temp air with a given humidity.



    Assuming a 500L air volume at room temp I get a figure of 600
    Joules per degree. So assuming that's correct 600 x 25= 15 Kj
    (30 deg ambient) lost each time you open the door.
     
    Mark Harriss, Sep 28, 2005
    #8
  9. David L. Jones

    Rick Measham Guest

    David L. Jones wrote:
    > 3) The use of a battery to power the circuit when the freezer
    > compressor is not on. WHY?. Presumably the author thinks it lowers the
    > power consumption?. Looks like he's designed a Free Energy device!


    I haven't seen either of these issues of ReNew, but my guess is that the
    battery is there because the owneer uses solar panels for most of his
    power, but is on the grid if he needs it (and isn't using one of those
    two-way meters that means he's always on the grid). That way, he can use
    the solar panels, via the battery, for most of the time. But his lettuce
    doesn't go mushy if the solar panels/battery fail as he can switch the
    fridge back to the grid.

    Cheers!
    Rick Meaham
     
    Rick Measham, Sep 28, 2005
    #9
  10. David L. Jones

    quietguy Guest

    Just thought I'd mention that Silicon Chip Mag desribed a similar project -
    turning a fridge or freezer into a wine 'celler' I think - but same
    principal, different temps - might be worth a look

    David

    KLR wrote:

    > On 27 Sep 2005 16:14:27 -0700, "David L. Jones" <>
    > wrote:
    >
    > >There is a "freezer to fridge" conversion project in this months ReNew
    > >magazine which claims to convert a freezer into a supper efficient
    > >0.1kWh/day fridge.
    > >It's basically a thermostat which switches the freezer mains power off
    > >and on to regulate its temperature.
    > >It's a follow up to an existing article which I haven't seen, so
    > >doesn't have much detail on how it works or how the measurements were
    > >taken.
    > >
    > >Although I don't know much about fridges or freezers, several things
    > >raised my "What the?" detector immediately:
    > >1) 0.1kWh/day is 36.5kWh/year, that's about 1/10th the power
    > >consumption of a regular fridge. Something ain't right there... what's
    > >the catch?
    > >
    > >

    > it all depends on the size of the fridge (and this wasnt specified in
    > your post), and how good the insulation is on it. The little "beer
    > fridge" we have in our workplace (made circa 1987-88) draws 153w
    > according to the specifications. I presume that this is the power the
    > compressor draws when it is running, so if you assume that even if
    > this compressor never turns off - its going to draw .153 Kwh.
    > Depending on how often it gets opened, it probably would come close to
    > the 0.1 kwh average power over a 12 month period.
    > >
    > >

    > I think what these people are working on is the fact that a typical
    > freezer is going to have a MUCH better insulation than a typical
    > fridge, so if its run as a fridge (higher temperature than a freezer)
    > the temperature will take longer to raise, due to the better
    > insulation, and the much less time the compressor will have to run in
    > the average day.
    > >

    > As an added bonus, if they are talking about "tucker box" freezers
    > (with the top mounted lid), then when they are opened, very little
    > cold will "spill" out, whereas with a standard fridge with the hinged
    > front door, the cold air will "pour" out very quickly when opened -
    > wasting a lot of energy !
    > >
    > >

    > In a theoretical fridge that had a perfect seal with no heat leakage,
    > and perfect insulation that the heat could NEVER pass through, and no
    > metal parts going from the inside to the outside (to pass heat inside)
    > the fridge would only have to be powered for long enough to bring it
    > down to the desired temperature, and then it would stay at that
    > temperature eternally, as long as it wasnt opened, and nothing in
    > there gave off heat (food eventaully rotting etc)
    >
    > >2) The circuit is hardly "micro-power" as claimed, not that it really
    > >matters.

    > no. If they wanted to save power, and just had to have this
    > "electronic control" they wouldn't be stepping down a 12vac secondary
    > (more like 17vdc when rectified) to +5v via 2 series regulators, and
    > they also wouldn't be using a relay (surely a triac would have less
    > overall losses ?
    > >
    > >3) The use of a battery to power the circuit when the freezer
    > >compressor is not on. WHY?. Presumably the author thinks it lowers the
    > >power consumption?. Looks like he's designed a Free Energy device!
    > >

    > Save running the transformer all day, and all the other lossy crap in
    > there. (mentioned above) Whether it saves any significant power is
    > debatable though.
    >
    > ------------------
    > If they are that worried about power wastage, then why not stick to
    > the standard mechanical thermostat (used for decades without
    > problems), and simply modify it (if needed) to achieve the desired
    > temperature range ! it uses ZERO electrical power to operate !!
    >
    > There are millions of fridges out there at recycling centres, that you
    > could take the thermostats from for this project, if the existing
    > freezer one cant be set high enough.
    >
    > >Here is the circuit:
    > >http://www.alternatezone.com/electronics/images/FreezerConversion.jpg
    > >
    > >Can a freezer be made into a more efficient fridge using this
    > >technique? My gut feeling is "maybe", but the amount claimed seems very
    > >unlikely. I suspect the author has goofed the measurements.
    > >
    > >Comments please...
    > >

    > I think it could be, but NOT because of the electronics used.
    >
    > If you are going to do this, I would start with the most efficient
    > freezer you can buy, not some old thing.
    > >

    >
    > >
    > >Dave :)
     
    quietguy, Sep 29, 2005
    #10
  11. David L. Jones

    John Dunkley Guest

    This kit is available from JAYCAR. Kit number is KC-5413 and actually looks
    pretty good!

    Is a revamp of the ReNew project.

    JD

    "quietguy" <> wrote in
    message
    news:...
    > Just thought I'd mention that Silicon Chip Mag desribed a similar
    > project -
    > turning a fridge or freezer into a wine 'celler' I think - but same
    > principal, different temps - might be worth a look
    >
    > David
    >
    > KLR wrote:
    >
    >> On 27 Sep 2005 16:14:27 -0700, "David L. Jones" <>
    >> wrote:
    >>
    >> >There is a "freezer to fridge" conversion project in this months ReNew
    >> >magazine which claims to convert a freezer into a supper efficient
    >> >0.1kWh/day fridge.
    >> >It's basically a thermostat which switches the freezer mains power off
    >> >and on to regulate its temperature.
    >> >It's a follow up to an existing article which I haven't seen, so
    >> >doesn't have much detail on how it works or how the measurements were
    >> >taken.
    >> >
    >> >Although I don't know much about fridges or freezers, several things
    >> >raised my "What the?" detector immediately:
    >> >1) 0.1kWh/day is 36.5kWh/year, that's about 1/10th the power
    >> >consumption of a regular fridge. Something ain't right there... what's
    >> >the catch?
    >> >
    >> >

    >> it all depends on the size of the fridge (and this wasnt specified in
    >> your post), and how good the insulation is on it. The little "beer
    >> fridge" we have in our workplace (made circa 1987-88) draws 153w
    >> according to the specifications. I presume that this is the power the
    >> compressor draws when it is running, so if you assume that even if
    >> this compressor never turns off - its going to draw .153 Kwh.
    >> Depending on how often it gets opened, it probably would come close to
    >> the 0.1 kwh average power over a 12 month period.
    >> >
    >> >

    >> I think what these people are working on is the fact that a typical
    >> freezer is going to have a MUCH better insulation than a typical
    >> fridge, so if its run as a fridge (higher temperature than a freezer)
    >> the temperature will take longer to raise, due to the better
    >> insulation, and the much less time the compressor will have to run in
    >> the average day.
    >> >

    >> As an added bonus, if they are talking about "tucker box" freezers
    >> (with the top mounted lid), then when they are opened, very little
    >> cold will "spill" out, whereas with a standard fridge with the hinged
    >> front door, the cold air will "pour" out very quickly when opened -
    >> wasting a lot of energy !
    >> >
    >> >

    >> In a theoretical fridge that had a perfect seal with no heat leakage,
    >> and perfect insulation that the heat could NEVER pass through, and no
    >> metal parts going from the inside to the outside (to pass heat inside)
    >> the fridge would only have to be powered for long enough to bring it
    >> down to the desired temperature, and then it would stay at that
    >> temperature eternally, as long as it wasnt opened, and nothing in
    >> there gave off heat (food eventaully rotting etc)
    >>
    >> >2) The circuit is hardly "micro-power" as claimed, not that it really
    >> >matters.

    >> no. If they wanted to save power, and just had to have this
    >> "electronic control" they wouldn't be stepping down a 12vac secondary
    >> (more like 17vdc when rectified) to +5v via 2 series regulators, and
    >> they also wouldn't be using a relay (surely a triac would have less
    >> overall losses ?
    >> >
    >> >3) The use of a battery to power the circuit when the freezer
    >> >compressor is not on. WHY?. Presumably the author thinks it lowers the
    >> >power consumption?. Looks like he's designed a Free Energy device!
    >> >

    >> Save running the transformer all day, and all the other lossy crap in
    >> there. (mentioned above) Whether it saves any significant power is
    >> debatable though.
    >>
    >> ------------------
    >> If they are that worried about power wastage, then why not stick to
    >> the standard mechanical thermostat (used for decades without
    >> problems), and simply modify it (if needed) to achieve the desired
    >> temperature range ! it uses ZERO electrical power to operate !!
    >>
    >> There are millions of fridges out there at recycling centres, that you
    >> could take the thermostats from for this project, if the existing
    >> freezer one cant be set high enough.
    >>
    >> >Here is the circuit:
    >> >http://www.alternatezone.com/electronics/images/FreezerConversion.jpg
    >> >
    >> >Can a freezer be made into a more efficient fridge using this
    >> >technique? My gut feeling is "maybe", but the amount claimed seems very
    >> >unlikely. I suspect the author has goofed the measurements.
    >> >
    >> >Comments please...
    >> >

    >> I think it could be, but NOT because of the electronics used.
    >>
    >> If you are going to do this, I would start with the most efficient
    >> freezer you can buy, not some old thing.
    >> >

    >>
    >> >
    >> >Dave :)

    >
     
    John Dunkley, Sep 29, 2005
    #11
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