AfriGadget

Google Earth is one way to appreciate the crush in Kibera, Africa’s largest slum. Not surprisingly popular images of people living in desperate conditions aren’t far from the truth when it comes to this corner of Nairobi - but out of the madness comes a little hope.

I witnessed some amazing innovations in Kibera and conclude that people have adjusted to their situation and are making the most of it.  Because of the stress associated with limitations on land, energy, water, and food the people have found innovative ways of surviving. This post is mainly about farming.

Vertical farming

like this guy and his vertical garden which feeds his family and he even sells some produce. It’s a variation on what JKE wrote about in the post on Keyhole gardens in Botswana.

Finding land in rubbish

Now a local organic farming company Green Dreams has been documenting the progress of transforming a garbage dump to an organic farm on the Green Dreams blog. They are working with a local youth group comprising reformed criminals in converting garbage into organic manure, and garbage dumps into organic farms.

Irrigation taps the mains water and supplies nutrient rich feeds from organic fertilizer produced on the site from crops and worms, yes they harvested local earthworms to start vermiculture.

Check out the planting implements, a PVC Pipe adapted to deliver seeds into a perfectly dug hole!  This was invented to help with the back breaking work of planting.

After 3 months the community of 30 families were harvesting, eating and selling organic produce. Yum! Impossible to ignore how a dirty dump turned green, everyone wants a farm in Kibera now. This group is now selling their expertise to raise funds and help others.

Natural Bean Tenderizer

There was a smouldering fire where banana leaves were being reduced to ash, then the ash dissolved in water and the brown murky astringent solution sold for Ksh 50 ($.80) per 250 ml in vodka bottles! This is a bean tenderizer reducing the time to boil red kidney beans by 50%! Imagine the savings on charcoal/fuel.

Safe Dispensing of Fuel

Notice that there was no protection around the farm or it’s equipment. Apparently the reputation of these ‘reformed criminals’ is enough of a deterrent.

Life might be hard in Kibera but yet when you visit you can’t ignore the vibrancy, colorfulness, camaraderie amongst the inhabitants it was one time that I got the feeling that people here love life

Or How to get your camel milk to market in 40 degree C climate.

My brother Dominic Wanjihia invented this gadget which he calls Fine Lined Evaporative Cooler, for rural application in Somalia - the cooling of camels milk for transportation . He was working on a project for VETAID, Somali Pastoral Dairy Development Program - SPDDP,in Burao, Somalia June 2008. All this content belongs to Dominic who has allowed me to post it here- please seek his permission to use this content elsewhere dwanjihia@yahoo.com

Evaporative cooling technology

The evaporative cooling concept has been used for centuries in countless applications. Cooling occurs when a fluid changes state from liquid to vapor. Put simply, evaporation. In order to evaporate, the liquid requires energy or heat. It acquires this heat energy from its immediate surrounding. As the surrounding gives up this heat, it lowers in temperature or cools.

The rate at which evaporation occurs depends largely on two main factors, the amount of heat available and the humidity in the air.

The cooler must also be shaded from direct sunlight otherwise the surfaces absorb UV heat and warms up, becoming ineffective as a cooler.

In short

Evaporative cooling devices work most efficiently in windy, dry and shaded conditions

Charcoal cooler

Everyone knows how to make charcoal fridges. After carrying out extensive tests on evaporative coolers in hot arid Burao, Somaliland, with day temperatures as high as 36^OC in the shade, the charcoal would absorb ambient heat from the air and as opposed to cooling, would warm up the interior compartment.

Imagine wearing a wet thick winter jacket under the palms at a breezy beach. The jacket acts as a wetsuit and will insulate your body preventing heat from escaping.

Fine lined cooler

However, imagine wearing a wet skintight t-shirt in similar conditions. The water evaporates quite rapidly and cools your body.

I applied this concept to the cooler prototype pictured and achieved startling results. The cooler would drop as low as 15.5^OC at night when temperatures averaged 25^OC and maintain under 17^OC during the day at average temps of + 32^OC.

Construction

An elevated metal box is lined interior and exterior with a fabric. In this case I used locally available corrugated galvanized iron sheets for the container and sisal sacking fabric for lining. The upper ends of the fabric overhang in a water trough that rings the top of the cooler. Capillary action causes the water to slowly trickle over the inner and outer surfaces. A small vent keeps the interior air circulating and wind guides or tunnels direct air flow over the exterior surfaces. A low speed small solar powered fan can be incorporated in areas where there is not a constant breeze.

How it works

The circulating air in the interior causes evaporation on the wet surfaces. The necessary energy is acquired from the contents hence cooling them and is transfers to the iron sides.

Wind guides or tunnels direct an airflow over the external sides. The evaporation that occurs acquires energy from the sides causing further cooling of the interior.

Construction design

Cool-box with water-bath interior for rapid milk cooling application– Collection Point Cooler

Walk-in cold-room for vegetable storage

Vehicle mounted for long distance transporters

Features (Comparison to conventional charcoal coolers)

Very simple construction

Corrugated galvanized iron or GI sheets increase the surface area

Wind tunnels guide air flow efficiently over evaporation surfaces

Air flow coolers at tunnel entrances

Being galvanized, the sheets are long lasting

GI sheets are affordable and available in most rural areas

Secondhand sacking fabric is available in virtually every vegetable market

The simple capillary action dripping system replaces more complicated dripping apparatus

Convection current system to increase water-bath cooling efficiency

In hot arid regions, cooling the warm ambient air before it reaches the wet evaporation surfaces increase efficiency. Note. Setup for airflow from either direction

For further information and other rural development concepts and innovative designs, Dom can be reached on

mobile tel +254 722 700 530 dwanjihia@yahoo.com