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I had to look up this thread when I saw the article on the Magnetic Refrigerator...
So to start off, I'd like to post about the fridge that uses only 0.1kWh of electricity per day - that's the same as a 100W light bulb running for an hour. This guy's taken a chest freezer (makes more sense coz the cold air doesn't escape a chest freezer when you open it) and attached an external thermostat that keeps the contents at fridge (rather than freezer) temperature. The result is a fridge that only runs for 90 seconds out of every hour...
Cool idea - pun intendedMagnetic Refrigerator Needs No Electricity
Sep 20, 2007 | Posted by Susan Suarez
Scientists at the Technical University of Denmark created a refrigerator that uses magnets to cool instead of electricity.
Although these refrigerators first prototype won’t be available till 2010, these refrigerators could easily replace existing refrigerators using a fully environmentally friendly power source and would provide an expected 60 percent higher efficiency than most standard refrigerators.
The method used involves opposing magnetic fields to increase the temperature of materials. The heat energy is transported through a non-volatile fluid (like water) and then thermodynamically reversed to a cold temperature. Scientists have already been able to cool a room from 20 degrees Celsius to 11 degrees Celsius.
The Brown government is set to unveil an ambitious proposal to build 7,000 new wind turbines off Britain's coast by 2020, effectively producing enough electricity - 33 gigawatts - to power all of the country's homes.
Anyone know where to buy solar panels in SA? As well as an invertor and deep cell batteries. I figure the deep cells should be easy enough to get at a marine store, invertor should be obtainable around the electric shops too I suppose.
Just where does one buy a few panels?
Well I cooked my first ever meal in a solar oven yesterday.
My boss knows I'm into eco stuff so she gave me a solar oven last week. It's basically just a box with a reflective interior and a perspex lid. This one's quite a cheapie, so the inside reflective material's actually quite matt - looks like brushed aluminium.
Anyhoo. Yesterday I put together a kind of potjie thing (I've never made a potjie before), and popped the pot with the lid on inside the solar oven at 09h00. I left it in there until about 16h30, turning the oven every 2 hours or so to keep it facing directly into the sun. By the time I took it off, the potjie was perfectly cooked and very delicious I might add.
Having done it once, I think I'm going to do one every Sunday (it's the day with the best possible name for solar cooking), weather permitting.
Some thoughts on improving it by possibly reducing cooking times or being able to cook things that require hotter temps:
1) I need to buy a black cast iron pot which will reflect much less heat than the shiny stainless steel pot I used.
2) I want to try and polish up the reflectors for better reflecting.
My dad has one. He puts it out the back door and makes some cakes and stuff in it. He also switched his kitchen stove to gas (in a container) so as not to depend on the power utility. His gas container can last him over a year of cooking.
But yeah, solar cookers are cool. There is a way to make ice with them as well. If interested I will dig up the instructions for you.
How to Use the Solar Funnel as a Refrigerator/Cooler
A university student (Jamie Winterton) and I were the first to demonstrate that the BYU Solar Funnel Cooker can be used - at night - as a refrigerator. Here is how this is done.
The Solar Funnel Cooker is set-up just as you would during sun-light hours, with two exceptions:
1. The funnel is directed at the dark night sky. It should not "see" any buildings or even trees. (The thermal radiation from walls, trees, or even clouds will diminish the cooling effect.).
2. It helps to place 2 (two) bags around the jar instead of just one, with air spaces between the bags and between the inner bag and the jar. HDPE and ordinary polyethylene bags work well, since polyethylene is nearly transparent to infrared radiation, allowing it to escape into the "heat sink" of the dark sky.
During the day, the sun's rays are reflected onto the cooking vessel which becomes hot quickly. At night, heat from the vessel is radiated outward, towards empty space, which is very cold indeed (a "heat sink").
As a result, the cooking vessel now becomes a small refrigerator. We routinely achieve cooling of about 20º F (10º C) below ambient air temperature using this remarkably simple scheme.
In September 1999, we placed two funnels out in the evening, with double-bagged jars inside. One jar was on a block of wood and the other was suspended in the funnel using fishing line. The temperature that evening (in Provo, Utah) was 78º F. Using a Radio Shack indoor/outdoor thermometer, a BYU student (Colter Paulson) measured the temperature inside the funnel and outside in the open air. He found that the temperature of the air inside the funnel dropped quickly by about 15 degrees, as its heat was radiated upwards in the clear sky. That night, the minimum outdoor air temperature measured was 47.5 degrees - but the water in both jars had ICE. I invite others to try this, and please let me know if you get ice at 55 or even 60 degrees outside air temperature (minimum at night). A black PVC container may work even better than a black-painted jar, since PVC is a good infrared radiator - these matters are still being studied.
I would like to see the "Funnel Refrigerator" tried in desert climates, especially where freezing temperatures are rarely reached. It should be possible in this way to cheaply make ice for Hutus in Rwanda and for aborigines in Australia, without using any electricity or other modern "tricks." We are in effect bringing some of the cold of space to a little corner on earth. Please let me know how this works for you.