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Making a Better Solar Cooker
New submitter jank1887 writes "Back in 2010, the aid organization Climate Healers gave a number of solar-powered cookstoves to rural Indian villages. The stoves were rejected by the communities, mainly because they were useless when they were wanted most: for the evening meal sometimes after the sun goes down, and for breakfast before the sun has risen. Following this, the group issued a challenge to EngineeringForChange. Details of the challenge include the need to provide 1kW of heat at about 200C for two hours in both early morning and late evening, and the users should be able to cook indoors, while sitting. A number of groups, mainly at U.S. and Indian engineering institutions, accepted the challenge, and developed potential solutions. Now, almost a year later, the ten finalist designs have been selected. The actual papers have been posted to the E4C challenge workspace. The goals of most of the designs are to keep the technology simple, although there are a few exceptions, and many include sand-, oil-, and salt-based concentrated thermal storage. Many reports include some level of discussion on the social and economic considerations, barriers to acceptance and sustainability, and how to overcome initial resistance to adoption."
Try to build it within their cost requirements, present your prototype and compare it with the other designs. If you think you can do better, then help out - you could really make a difference to the lives of many people. I suspect you'll find that your initial idea won't be quite as good as what the other guys came up with, but generally there is always a better solution around somewhere. One more person looking for that can't hurt.
There are actually government subsidies on kerosene in place in India specifically to prevent deforestation. The kerosene stoves are actually quite safe, efficient, clean burning and relatively inexpensive (by developed nation standards). Now before you start with the "OMG fossil fuels BAD!!!", remember that the grid-connected electric ranges that are so popular here in the USA are running on varying percentages of power derived from nasty, dirty coal - with the added bonus of generation and transmission losses. Since we're talking about a point-of-use fuel, these "third world" kerosene stoves are actually a pretty green solution. Perhaps instead of providing these people with pie-in-the-sky solar stoves that we wouldn't even use ourselves, we should offer good old kerosene stoves and maybe take a closer look at our own wastefulness.
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DRM is like antifreeze, to the MPAA/RIAA it's sweet, to the consumers it's poison.
Reading the article, the first contender came with a proposal to give them efficient wood stoves first, to displace the open fires they're currently using. Doesn't imply that they have gas.
Of course, it makes me want to point out that a modern high efficiency wood stove might sufficiently solve the problem to the point that it renders the solar stove unnecessary. Wood is a renewable resource, they apparently have sufficient quantities of it, and from what I remember, ye old wood stoves were ~10x as efficient as open pit fires at heating and cooking, and modern high efficiency ones are ~50% more efficient than the ye old varieties.
So you're lookng at using 1/15th the wood. At which point you have to convince people that using the solar stove is more convienient/valuable than dealing with the much smaller amount of wood the solid fueled stove needs. Well, don't forget cleaning requirements.
Let's see, stove rating areas:
The more you get, the better the product.
I don't read AC A human right
Doh... Of course you're correct, and I'm mostly thinking of my micro-production at home. Of course, back in the day you had the village baker, the average family didn't bake their own bread. What I get for trying to be among the first to post. ;)
I should have stated a concern more for how easy it is to control the temperature of the stove - keeping it reliable is more important than the exact temperature, and many older ovens were large enough that if you wanted hot you used the back of the fire/oven, if you wanted lower temperature you kept it nearer the front.
As for the outdoor brick/mud oven - if it's solar powered you need something to control the damper, and if you're using stored heat you need a way to moderate the heat from extremely sunny/hot days, while still keeping it hot enough on rainy days.
Supplimental heat from a fire, or like in the one case it's 'add water here, get steam there', so if you have some sort of steam limiter, you have temperature control.
I don't read AC A human right
I would think you think you're being clever or well informed, but I regularly cook things in my Sous Vide machine at the FINAL temperature I want them to be. With this method you cannot overcook your food, it will hold at temperature and in most cases not degrade the texture of the dish if something comes up and you wait 30 minutes to pull it out of the water bath. Some high end restaurants use this method to keep popular foods just shy of done, when an order comes in they give them a quick sear in a pan and put them on a plate.
A lot of the 300-400 degree cooking methods are too-efficient transmission directly from the pan through the meat so when the center is 170 and safe to eat, the outside is 240+ and either beef jerky or charcoal. Likewise air is a poor heat conductor so it takes hours in an oven for the center of the meat to reach 160, see every Thankgiving turkey ever.
With Sous Vide you never overcook and the moisture in the food isn't driven out by the cooking process.
So I'll see your Newton's Law and raise you Fourier's Law
"Writing about sous vide led Myhrvold to think more deeply about how heat moves through different media (which is why Modernist Cuisine may well be the only cookbook ever published with a long disquisition on Fourierâ(TM)s law, the equation for calculating heat transfer)."
http://www.wired.com/magazine/2011/02/ff_myhrvold/all/1