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Cooking in rural Africa
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kenneal - lagger
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PostPosted: Tue May 14, 2013 2:40 am    Post subject: Reply with quote

Reflective solar cooking or a rocket stove both combined with hay box methods would be far cheaper and more energy and resource efficient than any sort of PV.

Not so much eco bling though.
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Little John



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PostPosted: Tue May 14, 2013 8:18 am    Post subject: Reply with quote

clv101 wrote:
The population growth problem is virtually solved. Most of the increase for the next couple of decades isn't due to high, unsustainable birth rates. Instead it's due to the high survival rate of girls born a couple of decades earlier now having their own children. The world fertility rate has fallen from 2.8 in 2000 to 2.5 today. The global replacement rate (where growth tends to zero) is 2.33. We're going to get there soon!

The main thing driving future growth is that the age distribution hasn't yet reached equilibrium. It's a population lag effect, not high birth rates today.
If/when it gets to 2 then presumably that would mean that the population has peaked, yes? In which case it is still growing, albeit more slowly than previously yes?
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clv101
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PostPosted: Tue May 14, 2013 8:28 am    Post subject: Reply with quote

It is still growing now - but mostly due to population lag, not high birth rates. That's my point.

Also, it doesn't need to get to 2. In the UK, replacement fertility rate is 2.1, globally, replacement fertility rate is 2.33.
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Tarrel



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PostPosted: Tue May 14, 2013 7:54 pm    Post subject: Reply with quote

RenewableCandy wrote:
I remember being astonished to find that Africa is a lot less densely populated than Europe (including E. Europe). There really is enough land there, to grow enough stuff. The trick is to stop cutting the trees down. Cooking with anything that isn't wood is going to be a huge help.

As for what the fellas can do, here's a chap who built his own wind turbine! (this is an olde article and I'm sure he's gone on to greater wind turbines since).


I have the book; "The Boy Who Harnessed The Wind". Excellent!
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Tarrel



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PostPosted: Tue May 14, 2013 8:02 pm    Post subject: Reply with quote

Electric slow cookers over here tend to be used in two ways:

The "all in one" method, where you chuck the raw ingredients in and let the heat from the cooker raise the temperature, or..

The "economy" method, where you bring the ingredients up to cooking temperature in a pan on the stove, then put them in the slow cooker. The energy from the slow cooker substitutes for the lack of insulation compared to, say, a haybox.

In Africa, if using a haybox, one would still need to put the energy in to bring the food to cooking temperature. As said, this could be done with a solar cooker, but important to understand that all a haybox does is conserve heat, not create it.

Agree it is important to reduce wood usage where possible. As well as reducing desertification due to deforestation, it can reduce the incidence of respiratory disease and CO poisoning. Another (often unsung) way to achieve this is through UV water purification, reducing the need for boiling.
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kenneal - lagger
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PostPosted: Wed May 15, 2013 12:56 am    Post subject: Reply with quote

Tarrel wrote:
Another (often unsung) way to achieve this is through UV water purification, reducing the need for boiling.


A clear plastic bottle of roughly filtered water left on a roof in full sun for a day is rendered safe to drink, biologically. Chemically is another matter.
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adam2
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PostPosted: Wed May 15, 2013 9:31 am    Post subject: Reply with quote

The usual practice in Africa seems to be to bring the ingredients for a stew to boiling point on a gas ring and then to transfer to an electric slow cooker for prolonged simmering.
LPG is readily available and affordable for a few minutes quick boiling, but becomes expensive for any prolonged cooking.

12 volt slow cookers are now cheap but tend to be small.
The larger 240 volt slow cookers are easily powered from a cheap square wave inverter, though for reliable operation this needs to be generously sized.
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PostPosted: Wed May 15, 2013 10:36 am    Post subject: Reply with quote

RenewableCandy wrote:
I remember being astonished to find that Africa is a lot less densely populated than Europe (including E. Europe). There really is enough land there, to grow enough stuff. The trick is to stop cutting the trees down.


The other trick is finding enough water.
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adam2
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PostPosted: Wed May 15, 2013 11:55 am    Post subject: Reply with quote

In many parts of Africa there is a rainy season with regular flooding and road washouts. The problem is storing enough water for the months with little or no rain.
On a household scale this may be done with tanks of a few thousand liters capacity that are filled from the roof of a house in the rainy season.

For a farm or community, then building a reservoir can be worth it, though grid power, diesel fuel, or a substantial RE installation are needed for pumps to fill or empty.

On a regional scale, large dams for both water storage and power production have been tried, with mixed success.

Other parts of Africa have very little rainfall and are really not habitable without a lot of relatively high technology such as bulk long distance water transport or large scale desalination.
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featherstick



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PostPosted: Wed May 15, 2013 12:26 pm    Post subject: Reply with quote

adam2 wrote:
The usual practice in Africa seems to be to bring the ingredients for a stew to boiling point on a gas ring and then to transfer to an electric slow cooker for prolonged simmering.


This is what we do, but with a haybox (polystyrene bead box) rather than a slow cooker. It's a great way of having lunch or dinner on the table within a few minutes of getting back from a walk or a day out.
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RenewableCandy



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PostPosted: Wed May 15, 2013 1:25 pm    Post subject: Reply with quote

Hayboxes also have the advantage that if there's a power cut during the day and you're out, you still get a hot meal!
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kenneal - lagger
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PostPosted: Wed May 15, 2013 2:41 pm    Post subject: Reply with quote

adam2 wrote:
In many parts of Africa there is a rainy season with regular flooding and road washouts. The problem is storing enough water for the months with little or no rain...........


Part of that is caused by the clay soils which bake hard in the dry season and then shed water when the rains come. Part of the problem here is over grazing which bares the soil to the sun and part is under grazing. I'm not sure what the problem is with under grazing but it is a problem according to this Ted Talk. Mob grazing (watch the talk for an explanation) would seem to answer this.

Permaculture also has an answer in the form of "on contour berms and ditches" which slow the flow on water off the land and allow it to soften the clay and then soak in. This retains more water in the landscape so that it doesn't dry out so quickly in the dry season.

A problem with Africans is their desire to have all the modern technology of the west. This can be seen in their penchant for concrete block houses and tin roofs. It might be modern but it is almost entirely unsuitable for most African climates: the tin roof acting like a huge radiator and heating the house and the concrete block exacerbating this.

Africans need to be more choosey in their adoption of Western technology. A traditional thatched roof would give a more comfortable living environment and would protect concrete block walls from the sun, for instance. The adoption of hay box cooking together with solar heating and a backup form of heating food for the rainy season would save them a lot of energy and therefore money.

They have skipped a technology by going straight for mobile phone instead of land lines; perhaps they should do the same with cooking. Perhaps that should be the way that we suggest it to them then they can save the PV and batteries for important things like lighting and refrigeration.

Edit - URL corrected
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adam2
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PostPosted: Mon Mar 05, 2018 6:15 pm    Post subject: Reply with quote

Update time.
A much improved electric slow cooker has been made by the people that I know in Ghana.
A wooden box containing a standard 240 volt electric cooking ring on which is placed a large thick walled aluminium pot, fixed in place.
The apace between the inside of the box and the outside of the fixed pot is filled with vermiculite or fibre glass matting as fire proof thermal insulation.

The food to be cooked is placed in an inner pot that is readily removable.

A lightweight removable insulated lid covers the inner and outer pots so as to retain heat.

Something broadly similar has been considered and tried for years with mixed results.
The main problem being that on 240 volts the whole thing would get dangerously hot, but with 12 or even 24 volts it would only be lukewarm.
A recent advance is affordable DC/DC converters to produce most any voltage from 12 volts.
36, 48, or 60 volts work well, it depends on the original rating of the cooking ring, the size of the pots and the ambient temperature.
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kenneal - lagger
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PostPosted: Mon Mar 05, 2018 8:28 pm    Post subject: Reply with quote

Africa is doomed if they're so stupid as to want to mimic the mistakes that the west has made instead of using directly what they have i.e. the sun. A pv cell is only maybe 20 to 25% efficient whereas using the heat of the sun directly to heat food would be much more efficient.

Adam, you wouldn't advise someone to install PV and a 12V immersion to heat water or even PV an inverter and a 240V immersion when a hot water solar panel is available to heat the water directly, would you? Why do the same with heating food?
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clv101
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PostPosted: Mon Mar 05, 2018 8:40 pm    Post subject: Reply with quote

kenneal - lagger wrote:
A pv cell is only maybe 20 to 25% efficient whereas using the heat of the sun directly to heat food would be much more efficient.

Adam, you wouldn't advise someone to install PV and a 12V immersion to heat water or even PV an inverter and a 240V immersion when a hot water solar panel is available to heat the water directly, would you? Why do the same with heating food?


This is an often made, and flawed argument. Yes direct solar heating is more 'efficient' than PV heating, both for cooking and water heating, BUT, what if you already have the PV set up? When grid feed in (for a reasonable payback) is not available and as electricity storage is so expensive it makes perfect sense to use the PV for heating and water heating.
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