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Old 08-31-2010, 09:54 PM   #1 (permalink)
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Ecomodding my fridge

Ever since I read this article:

DIY, Super-Efficient Fridge Uses .1 kWh a Day |

I've realised my 1KWh/day fridge is much less efficient than it should be. Unfortunately, the above super-efficient setup wouldn't work for me. I would need to find room for a second chest freezer for frozen foods.

The converted chest fridge is set to ~5C, while I set mine to 1C to keep wasted food to a minimum. His fridge in my house in the summer would use 0.2KWh/day due to the difference between our ambient and set temperatures. Add in a standalone freezer, and I'd be looking at around 0.6KWh/day. So my fridge/freezer isn't as hopeless as it appears. I need to find a 40% reduction in energy consumption to match his performance, not the 90% reduction that it looks like at first glance.

Door opening losses supposedly account for 7% of heat loss from a typical fridge, so switching from an upright to a chest fridge seems like a poor compromise between efficiency and convenience. I tried some window shrink wrap as a curtain to keep cold air in on the lowest shelf, but it's far too lightweight, crinkly, and annoying. It blows around every time you open the door. I bought a clear vinyl shower curtain at the dollar store, and I've hung it up to outgas and unwrinkle itself. Hopefully, it'll be ready to install next week.

The greatest room for improvement is insulation. Some folks say you can't insulate a fridge. But you can insulate the sides and top of any upright fridge, which accounts for half of its surface area. I currently have a sheet of 2" thick polystyrene insulation on top of my freezer. A thermal probe between the insulation and freezer confirms that it's holding heat in better now.

The back of my fridge has no vents or coils, and is cool to the touch. It sounds like insulating that is fair game, too.

I can't have bare insulation in the kitchen. Fiberglass presents a health concern, exposed polystyrene is a fire hazard in a room with so many ignition sources, and cotton would get filthy. I'd have to build a cabinet to mostly enclose the fridge, probably out of thin plywood. It would have to be built very precisely to keep air from infiltrating between the insulation and the fridge.

I suspected that since the compressor and condenser are on the bottom, heat enters through the bottom of the fridge compartment. A probe below the vegetables drawer under a kitchen towel reads 17C (versus 10C elsewhere in the fridge), and confirms that I need more insulation there.

I'd like to replace the fruit and vegetables drawers with fiberglass batting, but I'm not sure if it's okay to keep fiberglass in the fridge. Cotton batting (or corrugated kitchen towels) would be ideal, if only it was locally available and affordable. I've got an old wool blanket in there for now (the same one as my A/C seat cover is made from), but what if I spill some milk or beef juice in the fridge?

I'm open to suggestions. How can I keep insulation in the fridge clean? Does the insulation cabinet sound easy enough to build? Any thoughts on what to do with the door of the fridge?

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