Less Baggage Less Stuff Less Procrastination

A different kind of travelogue. As an avid young traveller I often wondered what would it would be like when I got older, gathered commitments, created children and accrued debt. This is what it's like.

Solar Cooking on the Trail. OMG Labs #2

“Taking years of science training and using it for frivolous schemes.”

Well I stand before you the proud inventor of an umbrella that cooks. I didn’t invent it really but it worked but only up to a point.

IMG_8700

Previously I outlined a plan to cook using the sun on a trail using an umbrella in the OMG Labs #1 post. The lightest possible umbrella was the german made EuroSchirm LiteFlex. I contacted EuroSchirm and asked if it was possible to reverse the fabric and they sensible said No. They also said that they were keen to support the sort of nuttiness I was dreaming up and they sent me two (not one but two) freebie umbrellas. One was a second, for a reason I couldn’t find, and the other was perfect. Many thanks to Fay Ellis at the USA offices of EuroSchirm who was a joy to deal with and even pretended to get some of my jokes.

SWING

They did know that I intended to ruin their umbrellas. The one reconstructed was a variation on the LiteFlex called a “TeleScope”; heavier at 353 grams but telescopic with a closed lengths of 45 cms but a bigger canopy.

The larger canopy was what I needed. More canopy = more solar energy captured/reflected.

I proceeded to remove the canopy reverse it and sew it back on. The construction of the frame made this quite easy especially the threaded plastic tip arrangement. The pictures explain the process pretty well.

The next challenge was getting a pot to sit in the focal point of the suns reflected heat. The ideal point would be in the same place as the shaft which I didn’t want to damage as I do  want this to be multi-functional. There were two options I could see. One; Place two smaller narrow pots (something like a Vargo Bot) either side of the shaft thus achieving balance getting into the hottest part. Two; compromise. I went for option two and placed my old 900ml Evernew titanium pot just above the shaft. (An Evernew ECA417 if you really need to know that.) The handles didn’t fit into the structure of the erect umbrella but I figured out that by placing the filled pot with its handles towards the apex before locking the canopy open you could get the handles in the right place. Then you locked it in the erect position and not only was the pot secure but it needed no other support. I then did the same thing with a large clear plastic bag around the pot. This is to decrease the convective energy loss around the pot and simply required a rubber band to close it.

We were good to go. So far the only extra weight carried, if you trek with an umbrella, was the plastic bag and rubber band; 6 grams.

I placed it in the sun. It was a cool day (15 degrees Celsius )with a strong breeze and patchy cloud. The water started at 12 degrees celsius. After 15 minutes the water was at 60 degrees centigrade. Not enough and it didn’t get any hotter.

I took it on the trail and using a large orange Nite-Ize gear tie I could secure the umbrella to my pack for rain, sun and storage. The gear tie also secured it in position to cook.

The next day was colder with less cloud but still it only reached 60 degrees. You could maybe slow cook in that but really its not going to change the world or boil any water.

So was it a failure?

No. It was a proof of concept which proved much simpler than expected. There are several obvious impediments.

The pots are titanium with a slightly shiny exterior and not as effective at getting heated as a black pot due to reflection. Possible solution; stop cleaning the soot off my pot and let it go black.

The performance of titanium against steel may also impact the heat absorbed by my pot. Thermal conductivity of titanium [21.9 w/(m.K)]  is lower than steel but I don’t pretend to know all of the physical properties that would impact on the performance in this funny setting.

The “sweet spot” is made difficult to use due to the shaft. It may well be easy to remove a shaft in some Umbrella designs and that might make a big difference. The two Vargo Bot pot idea is attractive if only because I have always wanted a Vargo Bot but I shall have to wait for my Evernew to wear out and that looks like it might take most of my life time!

But the biggest and most important problem is the clever fabric on EuroSchirm reflective umbrellas. If you use a flat mirror you get a simple reflective performance; light comes in at a given angle and is reflected. With a true convex structure like the one below you can concentrate the energy.

We have that sort of shape BUT the fabric used by EuroSchirm is very finely woven but also deliberately textured. Thus I suspect that it is deliberately designed to reflect the sun in multiple directions. That is; it is designed to scatter the parts of the electromagnetic magnetic spectrum that it can reflect. This means that while the shape of the inverted umbrella is helping to concentrate energy the fabric is working against the concentration by reflecting the “suns rays” in multiple directions.

You can see how this would be the preferred performance in an umbrella with the silvered effect on the outside. A plain surface might give off an uncomfortable glare to those around it. It might be downright uncomfortable to look at.

So, is what I need a cheaper umbrella? No, the construction of this umbrella is excellent; strong and light. I may need a different fabric not intended for umbrella use. The shinier and smoother the better. That said a cheaper umbrella will be the start of the following experiments. 

I am still interested in starting to trek with an appropriate sun/rain umbrella as the hot sun here in Australia is pretty oppressive and I hate that sweating inside a rain coat experience . So I will also continue to look for the right fabric for the excellent light weight rame that I have now have from the EuroSchirm umbrella  and try to get better at sewing.

For now I have a slow cooker that has two other functions and I will continue the experiment. I enjoy cooking real food on the trail, that’s why I went for the Trail Designs Ti-Tri. I will be able to stretch my menu a little with this even as it is.

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A simpler cooker based on the Copenhagen Cooker, possibly using simple reflective silver bubble wrap, seems like the next one to try while I search. That can be a useful addition to my hammock insulation in the winter months.

copenhagen_solar_cooker_1

Keep an eye out for that one in the coming weeks. If that works it may replace the Exped MultiMat that I carry in my Gossamer Gear Gorilla as a pad insert which would actually represent a decrease in weight. As this continues I may well have half a dozen ways of cooking things for almost no extra grams.

It’s all good fun. A little bit of exercise for one busy little mind mixed with a big bit of exercise for two hairy little legs.

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4 comments on “Solar Cooking on the Trail. OMG Labs #2

  1. Fay Ellis
    06/05/2016

    We’re glad we could make a contribution to your experiment. Well worth sacrificing a couple of umbrellas in the name of science and the quest to pack lighter. Can’t wait to see what you come up with!

    • dougalynch
      07/05/2016

      Thanks for sending me the umbrellas! They’re very good. Even inside out and upside down!

  2. Fay Ellis
    09/05/2016

    You’re very welcome; let us know if you want to order one to use as an umbrella!

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