As a tool for saving money and trees, I get the feeling that solar rice cookers do not really catch on. I don’t want to debate their merits, but wonder if electric rice cookers can be powered by self contained batteries which are powered by dedicated solar panels. Even if the electric cooker could only be run every other day, it would be sufficient for many small poor households.
So, how much power does an efficient cooker require? Are solar panels for medium appliances able to handle this job without being so expensive that small subsidies put it out of reach?
What would be the advantage over the direct ones? The parts of the world where they would be used tend to be pretty sunny, and you don’t need to use it at night, so that shouldn’t be an issue. And the direct solar rice cookers are incredibly cheap: They’re basically just a folding sheet-metal box. You could probably make a thousand of them for the same price as one electric one. If the cheap ones haven’t caught on, why would the expensive ones?
My small 3-cup rice cooker draws 600 watts. That much juice is very expensive to obtain via photovoltaic panels. (Home Depot sells a DIY solar kit designed to be installed on a house that puts out about 1,200 watts for about $8500)
It’d be far more cost-efficient to just put a pot on a fire.
To the people that insist that solar cookers alone work…they have never caught on even after decades of people promoting them. I’m pretty convinced that they are just not consistent enough for people to adopt them (and they aren’t that cheap) not matter how cool others think they are.
A friend of mine made a solar cooker out of a cardboard box lined with aluminum foil, and a piece of glass. I probably cost all of $3, and worked fine - anything that can be cooked in a crock pot could be cooked in his fancy solar oven.
Photovoltaics are rather pricey and very inefficient. They turn about 10%-20% of the sun’s heat into usable electricity which you then turn into heat to cook rice.
If you can get a large enough parabolic mirror (or an array of them), it could cook faster than those smaller boxy ones… though you’d want to ensure your pot/cookware distributes heat evenly enough so you don’t end up burning one portion of the rice while the rest is cool.
Here’s a home-made parabolic solar cooker made from a papasan chair. (That was a shameless plug for Appropedia, the Wikipedia of appropriate technologies, meaning tech that’s not only geared towards sustainability but which is also culture/location/cost/etc. aware). PV panels, for example, while generally considered “sustainable”, would be utterly inappropriate in poorer areas simply because of their high cost.
I’ll speak now from my experience with people trying to promote improved cook stoves- a sort of clay ring that could take the place of the traditional three rock hearth- in Cameroon.
$3.00 is three days wages for the most of the people who would benefit from solar cookers. In my experience, people are very unlikely to invest in what is to them a very unproven technology. Economically, even a small outlay of capital is going to be unattractive to people who already have a system that works for them.
Culturally, the hearth in every culture is a bit of a sacred place. In many areas, this is actually more formal with the hearth having serious religious and cultural significance. Furthermore, the hearth is overseen by women, who are less likely to be educated and understand the long-term costs of cooking over wood or charcoal. Chances are this is going to be one of the most traditional areas of a household, and so you’ll have a much harder time changing people’s habits.
Finally, people are just used to what they are used to. They don’t want to learn a new way to cook, or do they want to learn to adapt their traditional dishes. The women who keep the hearth have spent a lifetime learning and perfecting their cooking. They are not going to be interested in changing all of that for some shiny foreign thing.
Cameroonians swore up and down that food cooked over wood was infinitely tastier than food cooked over expensive, dangerous and hard-to-buy gas. You just aren’t going to be able to swoop in with some crazy contraption and change everyone’s mind. It’s like how everyone thought the microwave was going to change cooking forever. Well, it turned out it’s very good at a couple of things, very bad at most things, and is more of an accessory than a primary cooking tool.
The only place I’ve seen solar cookers widely used was in Tibet, where they use it to heat tea water. Since tradition calls for always having a supply of boiled water and the sunlight is strong a direct, it works for them. In places like sub-Saharan Africa where water is generally not boiled and weather patterns are different (Hammatan haze would make solar cookers useless in cold season and afternoon monsoons would make it useless in rainy season in north Cameroon) they are going to be harder to promote.
Even Sven is right. I would add to this that the solar cookers are not consistent in their output and the good ones are expensive. Foil on cardboard? People in developing nations are very efficient with what little they have (you can see kids make very complex toy cars out of garbarge); if foil on cardboard was all they needed, they would have done it long ago.