Insulated Solar-Electric Cooking: Technology and Uganda, Pete Schwartz, Cal Poly Physics

Insulated Solar-Electric Cooking: Technology and Uganda, Pete Schwartz, Cal Poly Physics


>>Half the world’s people
cook their food everyday by burning biomass in
thee three-stone fires. Total disaster. The World Health
Organization estimates that four million
people die annually from breathing this
indoor air pollution. It results in widespread
deforestation and the soot and carbon dioxide emissions from these fires is a
significant contributor to climate change. And yes, that’s a bed
for sleeping by the fire with a burning coal on it. So after spending about five
years building these high-power solar concentrators as
a cooking alternative, we noticed how cheap solar
panels were becoming. In fact, every five years, the cost of a solar
panel is cut in half. So we thought, how about just
having an electric burner connected directly
to a solar panel? However, the thousand-watt
panel to power a burner capable of boiling a liter of water
in six minutes is still going to be way too expensive. So we proposed how
about a 100-watt panel? That would be much cheaper. But that’s never going to boil
water because you lose heat. But if you insulate the chamber
where you’re heating food, you won’t lose any of this heat. And so you can boil your
liter in one hour or in a day, you could cook about
six kilograms of food, enough for a family. So this is what our
first prototype looked like made for barbecuing food. But a boil and simmer cook pot
may be much more compelling because one, a good portion of the world’s people
cook with boil and simmer. And two, by placing the burner
in direct contact with your pot of food, you can
keep it cool enough so that it doesn’t start
the insulation on fire. And this allows us to
use natural insulation. We experimented with several
different kinds of heaters. We made them with nichrome
wiring and concrete but the one we liked best was
this immersion heater made with stainless steel
tubing, nichrome wire and magnesium oxide
insulation inside the tube. Because if the immersion heater
is placed directly in the food, then there’s no need
for an insulating wall between the pot and insulation. The pot that you would have used
anyway can be placed directly in the insulation. And so the only expense
besides the solar panel is that immersion heater,
assuming that you don’t pay for the natural insulation. In our publication, we show
our heating and cooling data that we compared to our model. And yes, the technology
works very well but the big question is are
people going to use this? So we partner with
Aid Africa in Uganda and four students spend one
month studying village life, how people cook and introducing
two solar electric cook stoves. The broad technology consisting
of just the solar panel, a heater and insulation
allows for a lot of variations and so people can
collaboratively design a method that works best for them. The very rough initial prototype that the students introduced
was found to be very ugly and also unacceptable
because it was on the ground. So the women who are
going to use it redesigned with a reed perimeter so that it
stood higher and looked better. We published our results inDevelopment Engineering
in January 2017. I’m Pete Schwartz from Cal Poly and Peter Keller runs
Aid Africa in Uganda. We had 10 student co-authors. Three of them designed and built
the original barbecue prototype. Six of them designed and built
the boil and simmer prototype and four of them went to
Uganda to study village life and implement two prototypes. So it turns out that the
family did use the two stoves but mostly to heat bath water. And although we recognize that heating bath water
provides a service to the people that they wouldn’t have
otherwise, we don’t need $100 to heat bath water
with sunlight. Also, better technology is not
displacing the biomass cooking associated with the respiratory
diseases, the deforestation and the global climate
change emissions. And because this use would
not displace greenhouse gases, the technology wouldn’t
be eligible for carbon market funding. So our plan for the coming year
is to implement 50 to 100 stoves in a single community so the people there can
share cooking ideas and also to provide solar water
heaters with each stove. The recipients would
be more likely to use those stoves
for cooking needs. Also the two families with
the new stoves expressed that they would like
more available power. And so at Cal Poly, we’re developing thermal
storage capability so that one block can
get hot during the day and cook very quickly
when people want to use it in the evening. Additionally, we hope to see a
hybridization strategy, that is, people could heat their
food first on a fire and then insert it into
the insulated chamber. Low intensity fires for just
keeping food hot are very inefficient and have
more emissions than high intensity fires. So keeping food hot inside of
an insulated chamber rather than having low intensity
fires would go a long way at reducing deforestation
and the emissions associated with both climate change as
well as respiratory disease. Want to know more? Please read the paper. So we’re interested
to collaborate with anyone who wants to. Please contact if
you’re interested. Thank you.

2 thoughts on “Insulated Solar-Electric Cooking: Technology and Uganda, Pete Schwartz, Cal Poly Physics”

  1. hi,
    our team is trying to develop solar cooking fuel cells. So that we can develop cheap and eco friendly system for every one.
    i hope that we can develop solar cooking system using lithium ion battery.

  2. Excellent video.
    I am interested in trying this for myself.
    Can I ask where you purchased that immersion heater or did you make it ?
    I have seen many of the common cup immersion heaters, but they are a tight spiral shape and 500-800W.

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