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solar cooking under clouds - Page 5

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Posted by dow on October 4, 2010, 8:05 pm

I agree. But therre are already solar cookers that work well in places
where there's plenty of sunshine. If we want people in other parts of
the world to be able to cook by the sun, we should try to design
cookers that will work in cloudy conditions.

Cooking temperatures below 60C are regarded as potentially dangerous,
since they allow the proliferation of bacteria. As a round number, I'd
suggest 80C (176F) as the minimum temperature that a cooker should be
able to reach and maintain under normal operating conditions. For some
purposes, of course, it is necessary to boil water, requiring 100C, or
to "brown" food, requiring even higher temperatures.

Yes. Quantitative data would have been useful.


Besides the PV idea, I know of one other that definitely works, and
has been used in practice for thousands of years. Use plants to absorb
light, even dim light under clouds, and use it to make organic
material by photosynthesis. Later, cut and dry the plant material, and
use it as fuel in cooking fires.

This isn't what we normally mean by "solar cooking", but it is cooking
with energy that has come from the sun. As traditionally practiced, it
has many well known disadvantages. But maybe we could work on it to
clean it up. Instead of cutting down forests, maybe the plants could
be grown in dedicated plantations. Perhaps we could find species that
would grow fast, photosynthesizing relatively efficiently. And maybe
we could burn the material in stoves that would produce little
atmospheric pollution, and from which the mineral-rich ash could be
retrieved and recycled to the ground.

Or maybe we could use algae, growing in ponds, or some other kind of
plant life.

Just because an idea is old doesn't necessarily mean that it is bad.


Posted by Morris Dovey on October 4, 2010, 8:55 pm
On 10/4/2010 3:05 PM, dow wrote:

Ok, but I'm not very optimistic about practical solar cookers for polar

Excellent! The good news is that 100C shouldn't be too difficult with a
flat panel using an efficient absorber/exchanger and materials that
provide good insulation to prevent systemic losses. The bad news is that
a good "browning" is likely to be extremely difficult without a
(probably unacceptable) boost in complexity and cost.

I've put a Q&D concept sketch (cross section) of a simple flat panel oven at


Let's do the 100C version first, then use what we learn along the way
to do a 150C second generation, and then go for the 200C finale.

Yuppers, but it worked a lot better when there weren't 6 billion of us
wanting hot suppers. :)

This is a non-starter for me. I think this creates/worsens more problems
than it solves, and I think we can do much better with non-combustion
solutions. I do like the notion of growing more trees, though... :)

Morris Dovey

Posted by dow on October 4, 2010, 10:10 pm
No? The way things are going, the poles may be the most comfortable
places to live before long.

There are plenty of places that are usually cloudy, basically along
the windward coasts of the continents. In northern North America and
Europe, that's the west coast. In lower latitudes, it's the east
coast. My girlfriend has been on the east coast of Australia for the
last couple of weeks. We usually think of Australia as hot and sunny,
but it has been cloudy and rainy all the time she has been there.
They're worried about a plague of locusts, which thrive in damp

Looking out of my window right now, I see it's overcast and a bit
drizzly. There's no wind, and the ambient temperature is about 10C.
Would your oven reach 100C, or even 60C, in these conditions?

Quite so. So what are we going to do about that? Nature gave us a
solution called AIDS a few years ago, but we seem to have wrecked

Would you be as opposed to it if the whole thing were enclosed in a
box? Put the plants into a big greenhouse, and do the combustion in
there too. In principle, nothing needs to escape into the environment.

Posted by Morris Dovey on October 4, 2010, 11:16 pm
 On 10/4/2010 5:10 PM, dow wrote:

If it isn't one thing, it's another. At least there's hope they'll
escape a season of forest fires. Did you let her know that locusts are
an excellent source of protein? (and they don't require cooking!) ;-)

Maybe/depends - can you post a link to a local webcam? (It might be iffy
this late in the day.)

However effective, that's not a solution strategy I'd choose.

Opposed? Probably not. It would appear to hold some promise as a means
of disposing of excess tax revenue - but that doesn't seem to be a
current problem here. Waxing cynical: infrastructure exists to fail

Morris Dovey

Posted by dow on October 5, 2010, 2:23 am
It's a bit late for that. She's flying home tomorrow - unless the
plane's engines get clogged with locusts.

Go to cp24.ca . That's a local Toronto news channel. On the right side
of the screen it shows pictures from traffic cameras. I'm not sure how
much use they'd be to you, but they are there. When I'm travelling, I
sometimes use this to see what the weather is like at home.

I think we're past the point of being free to make choices.


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