Hybrid Car – More Fun with Less Gas

What abt Mt Best fridge?

register ::  Login Password  :: Lost Password?
Posted by me on August 8, 2007, 11:03 pm
Something to this?

Really work?

I'm serious.... live in Missouri and wanting to slowly
go off grid even while living in an apartment

Seems to me the fridge is first and best place to start

see link


Id be wiling to get the module if someone has real
experience with it

Posted by Eeyore on August 8, 2007, 11:54 pm

me@privacy.net wrote:

Why on earth would you want to do that ? You won't save the planet. In fact
you'll probably damage it a little bit through the required waste of resources.


Posted by wmbjkREMOVE on August 9, 2007, 12:19 am
 On Wed, 08 Aug 2007 18:03:03 -0500, me@privacy.net wrote:

Some previous threads on the topic. http://tinyurl.com/224fxf

IMO the Mt Best claims are wildly exaggerated, and most of the gain
comes from having the unit in a cool location. Compare with Sunfrost
units with really thick insulation http://www.sunfrost.com/
http://www.aceee.org/consumerguide/refrigeration.htm  and ask yourself
how the Mt Best conversion could do so much better.


Posted by Windsun on August 9, 2007, 7:25 am
 And see this about SunFrost. http://www.windsun.com/Misc_AE/Sunfrost.htm

Probably better off just buying a good EnergyStar unit.


Posted by Neon John on August 9, 2007, 1:17 am
 That's a funny site.  This guy is a real True Believer in the Church of the
Environment.  There are some elements of truth in that article but on balance,
one that I'd recommend trying to duplicate.

It is true that a freezer converted refrigerator is very energy efficient
compared to
an upright.  Based on past experience I don't particularly believe his figures.
converted a freezer in my house but I've yet to measure it long enough to say.  I
expect it to be significantly below a half a KWh per day but I'm not yet ready to

That kludge of a thermostat is inappropriate.  Poor, overly complicated design
and a
failure point waiting to happen.  The temperature control is quite poor.  He
between 4 and 7 deg C.  In more familiar terms, 39 and 47.  That is both high and
wide.  47 deg exceeds the USDA's recommended maximum temperature and the
maximum for commercial establishments.  More importantly, food spoils much more
quickly even at 39 deg relative to near freezing.

A simple mechanical thermostat can hold the dead band to better than 2 degrees,
better with a little tuning.  Based on a lot of both research and
experimentation, I
keep my fridge in the range of 31 to 33 degrees in the middle of the chest.  A
colder lower and a little warmer higher.  See my other post in this thread.  All
with the thermostat that came with the device.

A major point.  The built-in thermostat in many, perhaps most, freezers can
simply be
turned up to this range.  Probably even as high as 40 if you really like hot
refrigerated food.  No need to glom together some sort of external controller.
common mechanical thermostat is a highly refined device that lasts for decades
without attention and is impervious to all the things that destroy electronics.

Now step back a little and take a systems view.  As is typical for these eco-nut
types, he didn't.  He's sweated microwatts at the freezer level while ignoring
comparatively huge losses associated with powering the freezer from a
running 230 volt inverter.  He's stomping on embers while the forest fire blazes

Philosophically, one should avoid energy conversions whenever possible for
overall efficiency.  That means running everything you can from the base power
available from the storage system (batteries).  If the battery system is 12 or 24
volts then choose as many loads as possible that run on those voltages.  12 or 24
volt CF lights, for example.

In this example, if I were off-grid and had limited power resources I'd convert
'fridge to a Danfoss or similar 12 or 24vdc power compressor.  This entirely
eliminates losses when the compressor isn't running and eliminates the inverter
conversion loss when it is.

I use Engel refrigerators and freezers in my RV, an off-grid application with
limited electrical resources.  This device uses a "swing" or directly
compressor.  The piston is directly driven back and forth by coils operating
a permanent magnet on the piston.  The piston is mechanically resonant so very
energy is required once it is set in motion. No crankshaft or rotary motion is
involved.  Incredibly efficient.

I measured the freezer's efficiency last year while using it in a truck.  Hot cab
much of the time and a -20 deg F setpoint.  322 Wh per day.  I haven't measured
refrigerator yet but just judging from the difference in duty cycle, I'm going to
guestimate something around 75 Wh per day.

What is interesting is to listen to this thing start and stop.  The solid state
driver is designed to gently push the piston along, inputting just enough energy
keep it going.  There is no starting inrush.  When the controller decides that
time to run the compressor, it starts vibrating and gently builds to full
over several seconds.  Like gently pushing a pendulum.  When it turns off it
continues to vibrate with the decay taking a couple seconds.

This unit is smaller than a domestic chest freezer but to remain man-portable,
it has
thinner walls.  I'd not be surprised to learn that a freezer/fridge of the size
guy was messing with would demonstrate sub-100 Wh per day performance with
either a
Swing or Danfoss compressor.

One other thing to keep in mind is that use patterns will swamp all these minor
considerations.  If you have kids in and out of the 'fridge all day and
load it with warm groceries and hot food from the kitchen then it's going to
have to
run a LOT more just to handle the heat load.  OTOH, if you're like me, only in
fridge 5-10 times a day then these little details can mean a lot.


On Wed, 08 Aug 2007 18:03:03 -0500, me@privacy.net wrote:

John De Armond
See my website for my current email address
http://www.johndearmond.com  <-- best little blog on the net!
Tellico Plains, Occupied TN
You have a magnetic personality... That must be why all your mental floppies are

This Thread
Bookmark this thread:
  • Subject
  • Author
  • Date
please rate this thread