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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."
Solar panel, a bunch of lead-acid batteries and a George Foreman grill and they're good to go.
they would reject McDonald's hambugers, if they were sent.
I've got 101 mod points and you can't have them!
I wonder how they thought the original designs would be accepted in the first place - We've long incorporated larger tanks for solar water heating to provide hot water at night. Also, even rural types like their convenience, which means being able to cook inside. BTW, for the Americans - 200C ~ 400F. Considering 80% of my cooking is at 350F, that's sufficient. Reviewing the designs, I am a touch concerned that I don't see thermostats for keeping the temp steady. Not as necessary for meat, but if you're baking bread you need fairly fine control.
I don't read AC A human right
...and sell them at a loss. That way the villagers will attach some value to the things and actually use them.
If these villages can afford to be picky as to when they eat
Perhaps the problem is they can't afford to be picky when they eat. Ever consider they might need to be working during daylight hours.
The Sol^R solution (pdf) looks very promising, but this passage from the executive summary bothers me:
"In Rajasthan, [India,] the design will cost a total of $502. The cost of the unit is less important than if the unit is successful in replacing wood burning stoves. If implemented, the women of these rural villages will escape the health issues acquired from smoke inhalation while still working during the day."
Cost is extremely important. If they can't afford to build it they'll just stick to what they have. The goal of the project is to get it under $400 for a reason.
Solar powered cooker?
Grow trees using power of the sun. Sun dries out broken sticks and kindling. Rub stick on piece of wood with bow. When you get a glow- blow on it and light kindling. Cook food over resulting fire. Roast marshmallows- drink beer; get guitar (or sitar) out- everyone starts to sing Eagles songs.
Everyone is happy and goes to bed smelling like campfire smoke. Is there anything better?
"That's the way to do it" - Punch
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
You forgot to attribute that quote to who said it. Namely your parents.
This is just something simple, but some summers ago I made the "Fun-Panel" from the solarcooking.org plans. I was surprised how well it worked, was actually able to fully cook some small stuff. A fun and recommended geeky project.
Why does the stove need to be solar?
For the heat storage solutions, what happens when someone (a child) kicks the stove over by mistake? Burns, disfigurement, death. Great.
Why not just a propane stove with a "turn off if you tip over" design?
Too many people cutting down the trees day after day means....no more trees.
Kerosene is actually expensive as the price can fluctuate (even with subsidies the black market ensures price inflation). Kerosene is also responsible for many early deaths and chronic diseases due to inhaling the poisonous fumes, not to mention the fire hazards. A viable solar cooker would not only be more sustainable, but also safer for the users.
The Philips wood burning stove was way cooler than these looks good on paper solar contraptions. Not that this design would be suitable for these villages, but better wood stoves should have been first on the list.
http://www.research.philips.com/technologies/woodstove.html
I heat my cosy developed-world house using wood, and it's incredibly clean and efficient. And by clean I mean even "a little bit of dust" would be unacceptably dirty. The yearly chimney sweep shows that the combustion itself is very close to complete, and the fuel itself is free. Garden waste to most people.
They need a solar powered fridge to keep the food they cooked yesterday from going bad.
Coder's Stone: The programming language quick ref for iPad
The Japanese and the Amish use kerosene appliances quite heavily in their societies. A properly designed kerosene stove will burn just as clean as the LP/natural gas stoves that we seem to be entirely unafraid of, here in the US. Notice the incredibly clean, blue flame this stove burns with.
What it boils down to is, as you said, a problem of getting the subsidized fuel to the people who need it. It seems like that's the real issue here, not some engineering challenge to show off to some poor villagers how advanced our high tech is (again, never minding the fact many of us use electric stoves that get their power from dirty coal!).
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DRM is like antifreeze, to the MPAA/RIAA it's sweet, to the consumers it's poison.
I was very surprised when I saw a few--or a few dozen solar heaters in almost every Tibetan village when I went there in October. I have no idea if they get it all the way up took boiling. The main use seems to be to get the kettles hot and then finish on the stove.
As you can see in this picture, they also make a great dog bed.
a modern high efficiency wood stove might sufficiently solve the problem to the point that it renders the solar stove unnecessary.
Also, a wood stove is a stored solar powered stove. You don't have to burn only wood in it, just woody material. Which comes from growing stuff in sunlight. One of the best converters of Sunlight to burnable biomass is hemp. You can use the fiber to make ropes/clothes/paper, then use the rest as fuel.
All ideas^H^H^H^H^Hprocesses in this post are Patent Pending. (as well as the process of patenting all postings)
What's wrong with a regular-old wood burning stove?
No, his parents said "What a waste of fucking time."
The truth is that all men having power ought to be mistrusted. James Madison
I wrote the article for Engineering for Change and I'm so glad to see this discussion on Slashdot. I've been a fan reading the daily email for a while now. It's interesting to see that, in a just a few comment strings, some of you came to the same conclusions about the best ways to introduce new technologies that it has taken maybe decades for people who are educated in development issues to reach. Also, your discussion of better solutions other than solar (efficient wood stoves) and better materials (why olive oil?) is the same kind of thing that the community at Engineering for Change struggles with. Our members find different answers that sometimes conflict, and often a solution depends a lot on the place where you use it. So, a universally perfect cook stove might not exist. Just a few thoughts. Thanks again! Rob
Why havent dung fired stoves and indoor pollution been addressed in these comments?
200C =473 K /-175F?
So your CPU was running at 158K/-115C
Temperatures are only proportional if measured from 0K.
In my experience (around three years with Engineers Without Borders), there are two main reasons a solar cooker would be desirable over a wood oven:
1) Indoor air pollution. A lot of houses in developing countries don't have proper venting for their fires/wood stoves, so the smoke just stays inside and creates a load of health problems. This can be solved either with wood stoves with proper venting or solar cookers that don't give of smoke at all.
2) In some countries (Haiti and parts of Central America, for example), wood is rare and/or moderately expensive. Using solar cookers can free up a significant amount of money that a family can use for other expenses to help them slightly raise their standard of living.
That being said, if wood is plentiful and cheap and stoves are available with sufficient venting, it's better than a poorly vented stove or an open fire. The point of organizations like Engineering 4 Change is to raise standard of living by creating solutions that are simple to use and sustainable in the sense that if something breaks, the community can fix it for a cost that is not prohibitive. Environmentally friendly solutions are certainly preferred, and are often the side effect of having to work with very minimal or costly energy sources, but being green is typically not the biggest concern of the target communities - it's usually something more along the lines of getting enough water or building a bridge above a ravine so the hospital is 10 minutes away instead of an hour away.
Dammit, for some reason the computer logged me out when I was posting this so now it's anonymous.
Sorry. Couldn't resist after seeing the following comment here https://www.engineeringforchange.org/news/2012/02/04/ten_solar_cookers_that_work_at_night.html
Re: Ten solar cookers that work at night
Hi I has been worked for a better new solar cooker, These schemes seems applicable,i am interested to see their details, Please send them to my email : mashhoodim2@asme.org thanks
It should be a device that is solar assisted as it should work conventionally when the sun don't shine.
Also wood is not so plentiful as you see many bodies float down the river Ganges as they stop the cremating fires when the families depart to save the wood and dump the bodies.
We direct solar power at a large body of water, and collect the precipitation runoff in a basin (natural or otherwise). When needed, we allow the collected water to flow down through turbines to generate electricity, which we distribute and run through a resistor below the cooking surface.
You really don't know what an aluminum pie pan is?
Your chains must be very thick and heavy.
There are some real idiots on Slashdot who can't think outside the box that is their mothers basement.
Wood burning has some nasty side effects. First off, wood isn't all that efficient for burning, meaning you need a lot of it. Neither can you turn it on/off as you want, meaning you waste a lot of energy. Consider a gas grill to a coal one. The coals needs to first burn up, then glow and finally cool down. The gas grill is hot in an instant and the moment you stop using it, you can turn of the supply of fuel.
The second problem is that wood is not a renawable resource if you use it up to fast. Trees only grow so fast and it is VERY easy to use them up faster then they can regrow. Land is also expensive and often owned by someone. You can't just go around collecting wood from anywhere and the more people there are, the more this is true. Removing trees even if you intend to replace them also causes climate change. Don't believe this? The rain forest causes most of its own rain, trees evaporate a hell of a lot of water but also capture a lot of it again, it is a complex system that can easily turn forest to desert if upset. See the expanding Sahara as an example.
Then there is another issue, collecting wood is a labor intensive task, often falling down to the women. Gathering it means they can't go to school, can't do anything else. It also forces them to go outside their village, in Africa especially this opens them to attack. Not every area in the world is safe to go outside. One of the reasons for putting wells inside villages is pricesly this, to protect the women and stop them to having to spent every waking hour collecting basic resources.
The solar stove is a good idea. There is just one snag. Those making the decisions ain't the ones who would benefit from it. The mentioned problems of cooking outside sunlight hours are trivial to solve by adjusting how you eat. But the ones in charge don't want to do that, the old ways suit them just fine. They can afford to send their women out to collect wood, and if they get attacked, they are just killed to spare the family shame. Never underestimate the evilness of a village elder.
Change will come but it will come slowly, just as it did in our own history. It isn't so long ago we cooked on wood and coal and suffered from it. Research the clean air act of Britain. You would be suprised how recent it is.
Take it slow with this solar cooker, don't get the adults or old people involved at all, show the kids at school. Those girls will one day have to buy their own stove and if they have learned they can cook at least some percentage of their food without having to spend a fortune on fuel, some might just do it when they got the chance.
Similar things happened in our own history, the bicycle was a huge liberator. While the proper women thought they were indecent, lots of young women took them as it allowed them to take jobs far further from home and thus increase the earning capacity of their family. If you get payed by the hour, any hour not spend travelling means more money and the further your range, the more options you have.
These things go faster then you might think but slower then you might wish. The solution for the solar cooker is already known and used. Hot stones. Heat a stone, it retains the heat for long enough to continue cooking after the fire has gone out (sun has gone down). And people adjusted to this. Just takes time for the old to be replaced by the young.
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A couple of years ago, the IEEE magazine of the Society for the Social Implications of Science and Technology had a fascinating article about this very topic. (Although it did not involve solar stoves; instead it was about combination stoves/small generators to supply low levels of lighting and communication access to a rural village, in addition to a stove.) I can't remember how the electricity was generated; it was something non-mechanical... As an added bonus the stoves vastly improved the air quality of the dwelling; at least, they would have if they were used.
What they determined was that the style of cookstove used varies by region, and that a design put together by some appliance designer many thousands of miles away is invariably not going to design a stove that is going to get used in some isolated rural village in the boondocks.
It'd asking somebody that's used an oven all their life to start doing all their cooking over an open fire... given the choice, I'm just going to keep doing what I've been doing.
The project also failed to account for distribution and transportation difficulties. A bulky stove weighing a couple of hundred pounds is really hard to transport into a mountain village accessibly only via a one-week journey by donkey.
i have to question the "wisdom" of interfering with traditional ways
of living, like this. i remember seeing a report somewhere that
said it was disgraceful that people in poor countries didn't have
lights, to which the answer is, "so you want to have people not only become dependent on electricity, but you also want them to stop living in tune with nature, make them deprive themselves of sleep, and place them in front of flickering light sources?"
in other words, they wanted to inflict the exact same kind of pain and suffering that the first world subjects itself to, onto the third world.
in this case, they seek to inflict non-traditional cooking routines and methods onto these people who have lived generations of lives eating at times which make sense in their environment.
_why_??
My Solution:
Use solar power aka sunlight to grow wood. Use it as firewood, cook whenever you want. Proven technology.
Also, a wood stove is a stored solar powered stove.
That's getting a bit pedantic, isn't it? I know a dude who calls wind mills and farms 'solar power' because the energy in the wind ultimately came from the sun. However, the means by which you utilize the power is very different. As are some of the concerns - you typically get more pollution with the wood furnace, for example.
So a solar furance is 'directly' powered by the sun, a wood furnace is powered by wood. If you have some practically microscopic wood farm inside the device, and said wood is then fed into a furnacce, then I'd consider it to be be a 'solar furnace'.
As for using hemp as a fuel - from a cost perspective you're probably better off burning it directly, though I could see a hemp rope/cloth facility using the leavings to power itself. For something this small, I'd be concerned that the materials would burn too hot/fast without extensive and therefore expensive processing. BTW.that's true of most grasses and other non-woody plants. Ultimately there are many potential fuel choices.
I don't read AC A human right
I think for this parts of the world a small gasifier or woodgas stove would work better. I have one that I use when I go camping and I pretty much just burn trash in it and it cooks at the same time. I break branches into small pieces or dry grass works.
Look for the web site for practical action to see what well designed stoves or micro turbo sites can do
http://practicalaction.org/
You can use the fiber to make ropes/clothes/paper, then use the rest as fuel.
Surely you don't mean all of the rest...
I can't remember where I saw it, but somewhere online is a story about a village that just used a solar concentrator to heat up a huge iron block all day, and then everyone would share cooking duties on it in the evening. Apparently you could fry stuff on it for hours.
I agree that being able to cook morning/evening meals would be handy, but strongly disagree that this is sufficient reason to reject them.
I have a small home-made panel cooker that I use to boil drinking water (here in Kenya, tap water is not safe to drink). It takes about 5 hours to boil 5 litres of water. I just leave it out in the morning and by the time I get back from work it's done. For me this represents a pretty substantial energy saving. In fact I'm pretty sure that on most days I use more energy to prepare drinking water than to cook meals.
That is going to save a lot of natural assets, if people will actually use the solar cookers.
It would be great, if they invent a cheap heat storage and just use some safe lenses to focus the sun into it during the day. No need for big mirrors then.
Plastic lenses could heat up the stove more space-efficiently, if the heat could be kept inside for longer time.
hmm
using the solar furnace and converting the heat to electric , use the electric to convert water into h2 and o2 , storing the h2 and you have a store of h2 that can be used to cook with on demand at any time of day or night while not having the need for batteries that use large amounts of expensive and toxic chemicals
choice and availability of suitable materials for the power and gas storage are the main issues
crisp packet sealer to make storage bags / balloons ? , using standard pipe fittings for as much as possible of the parts needed to make a stirling engine ? a car alternator for the power generator ?
ok so some custom machined parts are going to be needed
although I am unsure of the size needed to produce enough h2 to meet the requirements
and I have not looked at the designs there considering in the main article
Dammit, for some reason the computer logged me out when I was posting this so now it's anonymous.
That happens when you switch to Private Browsing :-)
Thanks for letting us know, though.
8 of 13 people found this answer helpful. Did you?
Interesting. Is there a way to store that safely in my campervan?
I want to put some of these ideas into practice. so far I have:
-preheat water in black bag on the roof ....just not sure which fuel is best yet...
-paint pressure cooker black and leave in the sun
-put water into pressure cooker
-use a stove with a fan to get a good clean burn on fuel...
Everythings easier in the sun of course. I wonder if the expanding effect of ice freezing could be utilised?
In all of this I'd like to stress that water tends to be just as finite a resource too.
Regards the pressure cooker,
I already use a very small pressure cooker and it still takes about 15mins to soften vegetables. Then you got the washing up afterwards which needs water. All in all I often don't bother and go with cold food instead.
All these findings are useful for people trying to be offgrid in places with a bit more cash too; boaties, log cabins.
A blog I run for the wealth
And why is it NEVER Africans who are 'helping' them?
Hilarious.
Wouldn't breeding a better fuel source like a woody weed just right for fueling a rocket stove be a smarter idea and much easier to disseminate?