The 4WD Solar Fridge Project (2001 posting from old site – Page 1)
The following article from 2001 shows the system I developed in the early 1990s, and mounted on a 1989 Isuzu Trooper. This was the earliest prototype of the Solar Fridge system.
Freedom to live where you want - up a desert wash, far from civilization, for days, for two weeks - with fresh cold food and drink, without having to go to town for ice or deal with sloshy ice and water.
Your own independent power source for laptop computer, video camera, lights, etc.
Here's the vehicle in-situ in the Anza Borrego desert (January 1996). The panels are obviously in the up position. I actually found that they did not need to be raised to get adequate power. I just parked and left them where they were in a horizontal position. The solar radiation in the desert is more intense because their is less moisture in the air, and of course there is usually very little cloud cover.
You can just see the refrigerator inside the vehicle, to the left of the deep cycle battery on the right. The raised sleeping bed above it is in the tilted-up position to allow access to storage and the fridge underneath. You can just make out the wire going from the vehicle towards the tent. (More detailed photos of these features are on the next 3 pages).
They Said it Couldn't Be Done
Everyone I talked to was quite negative - thought I would need $1000 worth of panels, or that it just wasn't practical to run a fridge off solar in a vehicle. I had a gut feeling it was doable though, and they were just basing their estimates on what had been done in the past, or on average conditions and typical scenarios. But I was doing something relatively unique, with a particular set of hand-picked parts. It's called "thinking outside the box". Or how to make cold inside a box in the middle of nowhere in this case!
The selection of the refrigerator was a critical part of the picture. After some research, I came up with this small, low-duty cycle, 12V RV refrigerator made by NORCOLD (see photo below).
The NORCOLD Tek II (with Rowan my Queensland Heeler posing for scale) uses only about 2.5 to 4 amps (when running), with less than a 50% duty cycle (how much the cooling pump is actually running). They are made for motorhomes and the like - and this is the smallest unit they make. They run on both 12V DC and 110VAC, and are relatively efficient in terms of cold storage. The estimates of the duty cycle the manufacturer gave I found to be very conservative. These things are not cheap though - it was over $600.00. But this is a real refrigerator, not a wimpy thermoelectric unit.
We've also used this as an overflow refrigerator in the house at Thanksgiving time (can run off 110V AC too). The efficiency of this fridge together with the intensity of the desert light in the dry air made it all a possibility. I could come back to my locked truck after a hike on a hot day, and the truck would be like an oven inside. This little fridge would be purring away, nice and cool inside, no problem. And since the sun that was heating the vehicle was also hitting the panels at full force, there was enough current, and no over-drain on the battery.
On (Cheap) Thermoelectric Coolers
I looked into the little electric coolers that you can pick up for around $50. They are basically styrofoam ice chests with a Peltier element (a solid state heat pump) with a large heatsink and fan. The problem with them is that they are: One – horribly inefficient, and Two: noisy. If you wanted to cool down some beer and sandwiches for example, you'd have to either cool them down in your real fridge and then put them in the cooler that has been running for a while, or if you put the stuff in warm, run the cooler for something like 6 or 8 hours.
This NORCOLD unit however, could make ice in the middle of the Mojave in short order. Just park in the sun, crank the dial to "5", and come back from your hike to frozen beer (well, OK, it's just an example). It's also very quiet. I'm very sensitive to noise, and often slept in the Trooper in the desert silence, and was not bothered by the noise it made when it switched on.
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