Refrigerador eficiente

A fridge that takes only 0.1 kWh a day?
By Tom Chalko, Mt Best, Australia, mtbest.net There is no mistake in the title. This article describes an inexpensive fridge that is 10 to 20 times more energy efficient than an average fridge on the market. It also demonstrates that the biggest limitations are our habits and mediocre attitudes, not technology or cost. My dream is to live a near-zeroemission life. Step by step I come closer to bring this dream to reality. After all, the rainforest here at Mt Best is so beautiful and so unique that I hesitate to disturb it with any kind of pollution. Insulating and double-glazing my RAL home reduced my winter energy requirement to about 20 Watt per square meter of floor area. I do not like “star ratings”. I think they are misleading and promoteignorance rather than understanding of energy efficiency. Reflective solar heating (described in issue 88 of Renew) nearly halved my heating energy (and the firewood) needs in winter. However, to achieve a near-zero emissions I needed to find a clean renewable source of energy to replace the firewood altogether. The system of choice became a geothermic storage heat pump system that will be describedin my next article. However, since I generate my own electricity from wind and sun, I needed to save some energy to run the heat pump. For almost 2 years I tolerated the fridge that I did not like a little tiny bit. The list of things I did not like about it is too long to mention here. If I could eliminate this fridge, I would have enough energy to run the heat pump…

Chest fridge
Comparingthe energy consumption of various refrigeration devices available on the market I noticed that well-designed chest freezers actually consume less electricity than fridges of comparable volume, even though freezers maintain much colder temperatures inside. While chest freezers typically have better thermal insulation than fridges, there is another reason for their efficiency. Vertical doors inrefrigeration devices are inherently inefficient. As soon as you open a vertical fridge door – the cold air escapes, simply because it is heavier than the warmer air in the room. When you open a chest freezer – the cool air stays inside, just because it’s heavy. Any leak or wear in a vertical door seal (no seal is perfect) causes significant loss of efficiency. On the other hand, even if you leave thechest freezer door wide open, the heavy cool air will still remain inside. Have you ever wondered why chest freezers in supermarkets have their doors either wide open or not thermally insulated? Designing refrigeration devices with vertical doors is clearly an act against the Nature of Cold Air. Shouldn’t we cooperate with Nature rather than work against it?

I become really curious just howefficient a chest fridge can be. After contacting some leading fridge manufacturers and discovering that no one has ever made and tested a chest fridge, I decided to make my own test. I bought a good chest freezer and turned it into a fridge.

Turning a chest freezer into a chest fridge
The main difference between a freezer and a fridge is the temperature maintained inside. Freezers maintainsub-zero (freezing) temperatures down to –25o C, while fridges operate somewhere between +4o and +10o C. Hence, turning a freezer into a fridge meant changing the temperature control. Rather than interfering with mediocre thermostat of the freezer, I decided to install an external thermostat to cut the power off when the temperature of my choice has been reached. For my research I bought a VestfrostSE255 chest freezer with 600a refrigerant and a $40 battery-powered thermostat equipped with digital temperature display and an internal 5A/240V latching relay. The main feature of the latching relay is that it consumes battery power only during actual switching so that the thermostat equipped with it is a true micro-power device and its 2 AAA batteries last for many months. Connection diagram...