Putting it all together

Let me try to summarize the various cooking methods I hope to use regularly in future. Almost all involve a solar cooker at some point.

I’ll begin with what started this whole journey for me: the solar box oven. Pretty much any slow cooker recipe will work for a box oven. The main constraint is consistent sunlight for a long enough period of time. Intermittent clouds can sometimes reduce the oven temps below safe levels. Also, if you are not home to re-orient/aim the oven every hour or two, then longer cooking times will be necessary.

The parabolic cooker does not require as much sun time as the box oven, but you need to be ready to cook when the sun is out. This works fine if you have sunlight an hour or so before the planned meal. One way to extend the cooking time is to use a heat-retention method (hay-box or thermal cooker) to keep the food hot until mealtime. You can find other sources of insulation if hay is not handy.
Note: you can always click on an image to see a clearer (sometimes larger) version.

Thermal cookers (wide mouth thermoses work) and hay-boxes are especially good for cooking stews, curries & soups; dishes with high liquid content. The parabolic cooker would bring the food up to a boil and then the boiling hot food would be transferred to a pre-heated container to cook further in your choice of heat-retention apparatus. This way the food stays hot even if mealtime is hours away. When cooking for 4-5 people I use a 4 qt. Zojirushi thermal cooker. For 1-2 people I will be using this Thermos Nissan 48 oz. Wide Mouth Stainless-Steel Bottle.

Another tool to help with limited sun time is to use a pressure cooker. Recipes abound for this cooking method and you can often have a main dish ready with less than an hour of parabolic cooking time.

The final method is arguably not cooking per se, but dehydrated food can often help in speeding up cooking when sunlight is limited. It doesn’t take nearly as long to reconstitute dehydrated potatoes or meat as it does to cook them in from their raw state. Of course dehydrated fruit, veggies, jerky & fruit leather can be eaten as snacks.

To bring it full circle to solar cooking, the trays of my electric dehydrator can be placed into my solar box oven with a few modifications (subject for another blog post). I will have to pick the types of food to match the amount of sunlight anticipated on a given day, but if the weather doesn’t cooperate I can always complete the dehydration in the electric dehydrator.

To recap:
*box oven: slow cooking & dehydrating
*parabolic cooker: re-heating, fry/sauté & bringing to boil to put into hay-box or thermal cooker
*thermal cooker: slow cooking soups, stews, curries
*pressure cooker: too many to list
*dehydrator: almost anything you can think of including fruit leather, jerky, fruit chips, cooked corn/potatoes/beans…

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“Solar Burner” parabolic cooker: assembly and first impressions

I’ve been using the Solar Burner (SB) for a few days now and wow can this baby burn! I keep it covered anytime it’s not in use because it’s fairly easy to accidentally look at it and get seriously dazzled by the light. Even with sunglasses I find myself occasionally catching a flash.

But let’s rewind a bit and go back to the assembly. You can see details of the unassembled parts on this cantinawest page.

I’m a fairly slow & methodical assembler of things like this and it took me a bit over an hour to complete the assembly on my own. It would have gone faster if I had the appropriate cordless screwdriver attachments for the bolts. The included written instructions were not good. Fortunately Nathan at cantinawest provided some clearer photos and tips via the linked page above.

The product was fairly described as having sub-par fit & finish. There were some scuffs & scratches on the mylar surface, but they become practically invisible in the sunlight. Some edges of the metal parabola segments were a bit bent out of shape, but not in any critical spot. It’s what I expected from a $170 product and I think it’s great value at that price.

I cooked a curry in a pressure cooker on the SB yesterday. It took roughly the same amount of time as it would have on a gas stove. That was around 4:30 pm. At noon today I put some leftovers on to reheat and it got hot very fast, maybe even faster than the high setting on my stove. I was prepared to preheat the pot for warmups, but that’s not going to be necessary.

You can really see the difference in the vertical sun angle between noon and 4:30 pm. I don’t have to adjust that angle during a typical 30-60 min. cooking session, but I certainly will between noon and evening sessions. It also drove home the lesson already learned from SolarCooking forum members that adjusting that angle in a box cooker is also important, especially since my typical time frame for that cooker is noon to 5 pm.

This is a big dish (5 ft. diameter) and some folks with short arm reaches may not feel comfortable having to reach out a couple of feet to hold and stir the pot. I’ve heard from more than one source that the Tinytech (or clone) is a more manageable size in that respect. With a 45″ x 45″ square reflector, the distance to the cooking platform is probably significantly shorter.

Two big thumbs up for the Solar Burner! Together with a pressure cooker and thermal pot, it’s going to get more use than my box oven. That will still see plenty of use as a slow cooker and dehydrator. I’ve got a small solar fan on its way from Hong Kong to help make the latter work.

Important note: Do not underestimate the burning power of the light reflected by such a large parabolic dish. As advised in many blogs & forums, I wore dark sunglasses to protect my eyes. Even then I avoided looking directly at the dish. Of course, NEVER put your hand near the focal area. Here’s the obligatory video shot.


The Long Road to a Parabolic Cooker


Yesterday I placed an order for the 1.5 m diameter (1.77 m² collection area) Solar Burner parabolic cooker from Cantina West. Although it’s only been a couple of weeks since I jumped into the solar cooking pond with a DIY box cooker, I’ve spent countless hours reading the archives of the Yahoo SolarCooking forum and other online sources. I decided to share some thoughts about the process of selecting a parabolic cooker.

The parabolic cooker (paracoo for short) is the one style of solar cooker that best simulates a traditional stove. If the collection area is large enough and there is sufficient sunlight, the level of heat concentrated at the focal point is just as capable of burning your hand as a gas or electric stove. For that reason, similar safety procedures need to be used when cooking with a paracoo.

I started my journey down the paracoo rabbit hole the same way I think many people will: let’s see if I can build it myself. So I searched satellite dish conversions and mylar reflective material. People were giving away unused satellite dishes, but they were usually in the 18-22″ range. These will work, but it’d take nearly an hour to boil a quart of water. Larger sizes were not available to me, but even if they were, I discovered the 4-5 ft. dishes were very heavy.

Then I stumbled on a discussion about the Solar Sizzler, a 3 ft. plastic parabolic dish covered with mylar.
I discovered the inventor and seller had recently died and the product was no longer available. I also discovered around this time that the mounting frame and aiming mechanism for these parabolic dishes were just as important as the dish itself. In the above photo, the dish is propped up on the ground and the cooking platform is hanging from a campfire tripod. That doesn’t make for very convenient or accurate aiming, which in turn makes the cooker less effective.

Unlike box, funnel, Parvati, etc. solar ovens, a paracoo requires more frequent re-orientation to the sun as it changes position in the sky. Not only that, you need to pay attention to both the vertical and horizontal changes in the angle of the sunlight. Now you should be doing that with the other solar ovens also, but the necessity for frequent daily vertical adjustments are just not as critical for the other ovens as it is for the paracoo.

Basically, even if I could find a used Sizzler or a similar standalone shiny dish, I’d still need to build the supporting frame for the dish, a frame for the cooking platform (to hold a pot or pan) and the aiming mechanisms. These cost money for raw materials (wood or tripods) and some construction skills. The result would be a finicky cooker with decent cooking power. Maybe you could boil a quart of water in half an hour on a clear, windless day if you moved the Sizzler frequently enough.

By this time I had belatedly given some thought to the type of cooking I was hoping to achieve with a paracoo. My box oven was great for the slow cook style, but it couldn’t do (easily) any of the stovetop stuff like fry, boil and pressure cook. So now my parcoo requirements had progressed to a 3-5 ft. diameter dish built on a frame that allowed simple adjustments and which had a stable cooking platform to hold my pots & pans.

Here’s where I started to go nuts chasing some of the high-end products. With the “help” of the good folks on the Yahoo forum (Mark, James, Steve, Luther et al…sorry if I missed anyone), I learned about the fabled SK-14 with its sleek, efficient, German-engineered polished aluminum reflectors. I also learned that these came with price tags in the hundreds. Although the shiny ones caught my eye first, I’m going to tell the rest of the story in reverse…starting with the least shiny of the lot.

The Solar Burner (SB) at $170 (all prices in USD, include shipping to U.S.) is the least expensive of the commercially available paracoos currently offered. It is made of painted steel and the reflective surface is mylar. It is solidly built with so-so fit & finish. At 1.5 m it is also the largest of the paracoos I considered, so even though the mylar is not as reflective as polished aluminum, it packs considerable power. The horizontal adjustment is easy, but the vertical adjustment requires hand loosening a water valve-like bolt and tilting the dish before re-tightening.

For twice the price at $350, there’s the Solar Parabolic Boiler (SPB), previously known as the Tinytech.

Made in India, it comes with a 45″ x 45″ square parabola (1.30 m²) of polished aluminum sheets made in Germany. That’s a significant step up in quality for the reflectors, so the smaller collection area compared to the SB doesn’t really result in much reduction of real-life power output. The smaller parabola means a shorter reach to the cooking platform. That would be an important consideration for folks with shorter arms than mine. The other critical difference is that the parabola rotates up & down, which makes the vertical adjustment very simple. But in order to adjust horizontally, it seems like (maybe SPB owners can confirm) you have to lift one side of the cooker and pivot to turn. The framing is also painted steel, probably of equal fit and finish to the SB.

Next step up in price is the $400 Pika Hunt.
Made in Japan, it not only matches the polished aluminum sheets from Germany, it also sports a tripod stand and frame made of aluminum. The dish rotates freely around both vertical and horizontal axes, so making aiming adjustments is as easy as can be. At 80 cm in diameter (0.50 m²), it qualifies as a portable paracoo and is sold with a convenient carrying bag. Unfortunately, the price for that portability is anemic power. The Google Translate version of their website states “When sunny, 38 minutes makes a lot of excitement in 1L of water.” If the price was a bit lower, I would have asked an uncle who speaks Japanese to call and confirm that it was powerful enough to get a pressure cooker up to 15 psi in a reasonable timeframe.

Finally we get to the legendary SK series from Germany.
Now re-named Premium 14 (1.4 m, 1.54 m²) and Premium 11 (1.1 m, 0.95 m²), these polished aluminum reflectors are mounted on galvanized steel frames. Like the Pika, these parabolas rotate freely around both axes. With the high quality of reflector, even the smaller Premium 11 is well capable of providing convenient cooking power. The kicker is the premium prices of $460 and $550. But considering that these are likely to last decades (if properly maintained), those are really not unreasonable prices.
UPDATE: A company in Barcelona apparently still manufactures the older SK-10 design. You’d want to verify that the website is accurate, but 170 € for the unit + shipping could be ~$350. Aside from the lower price, I prefer the seemingly more stable stand. Although it is not as convenient as the freely rotating stand of the current model, the ^-shaped legs make for a very simple aiming device; just line up the shadows of the legs. Select K10 in the left column:
http://translate.google.es/translate?hl=es&sl=es&tl=en&u=http%3A%2F%2Falsol.es%2F

If you’ve read this far, you can understand that it was a long and winding route before I finally decided to go with the $170 Solar Burner. Portability would have been fantastic, but for at least the next year or so I was unlikely to use the paracoo away from home. If money was no object, I would probably order a matching set of SKs. As with all buying decisions, personal budgetary constraints and intended use will influence the final choice. Hopefully some of the information shared here will help you in your solar cooking journey.

Parabolic cooker designs

UPDATE 2: The German maker of the SK series is now selling on eBay as “cooksolar”. The Premium 11 costs $448 shipped to the U.S. as of Aug. 2011.
eBay listing for Premium 11

UPDATE 3: The 1.1 meter diameter “Premium Solar Cooker” is $378 as of Sep. 2012. The “Solar Burner” is now $150. If I were making a purchase decision today (9/25/12), I would spend the extra money for the German made unit. The Solar Burner still functions well enough, but rust and mylar degradation after a year does not bode well for longevity. The cooking surface is also not very stable when rotating the parabolic dish, so I’ve lost a couple of meals when heavy pots took a tumble. My guess is the more expensive unit is more stable and easier to use on a daily basis.