7/25/2019 Appropriate Technologies
1/23
APPROPRIATE TECHNOLOGIES
USED IN DEVELOPING COUNTRIESBy Trish Morrow
https://www.linkedin.com/in/trish-morrow-27959988
7/25/2019 Appropriate Technologies
2/23
What is a solar stove?
Any device which uses heat from the sun to cook food or boil drinking water.
Does not use electrical energy from photovoltaic modules, just uses heat.
http://www.solarcooking.org/gallery1.htmhttp://www.solarcooking.org/gallery1.htm
7/25/2019 Appropriate Technologies
3/23
Why use solar energy for cooking?In developing countries biomass is burnt as
the primary source of domestic energy for
cooking, heating and boiling contaminated
drinking water. (Kammen, 1991)
About half the population of China boil
their drinking water mostly over biomass
stoves 1% of Jakartas GDP is spent by the residents for
boiling their drinking water (Gadgil, 1998)
With an average cookstove efficiency of 12%,
fuelwood can only boil water three times its own
weighta typical family of five would use 12kg/day 1kg of firewood releases 440g CO2and ~650g C-
equivalent of non CO2greenhouse gases. (Gadgil,
1998)
50-100 acres of forest destroyed/minute(Lovejoy, 1991)
http://www.efn.org/~apro/atstove00.html
http://www.efn.org/~apro/atstove00.htmlhttp://www.efn.org/~apro/atstove00.html7/25/2019 Appropriate Technologies
4/23
Why use solar energy for cooking?http://www.webcom.com/bi/images/billboard.gif
Biomass burning in developing countries is firmly linked to acuterespiratory infection,a leading heath hazardto children in
developing nations, resulting in an estimated 4.3 million deaths per
year. (Kammen, 1991)
Other health effects - woodsmoke contributes to: pneumonia,
low birth weights, cataracts, and nervous or muscular fatigue.URL: htt ://www.solarcookin .or /cookin smoke.htm
Mara,D.D., Tropical Public Health Lecture Notes, University of Leeds, 2000.
http://www.webcom.com/bi/images/billboard.gifhttp://www.webcom.com/bi/images/billboard.gifhttp://www.webcom.com/bi/images/billboard.gifhttp://www.webcom.com/bi/images/billboard.gifhttp://www.webcom.com/bi/images/billboard.gif7/25/2019 Appropriate Technologies
5/23
How does woodsmoke compare with tobacco
smoke?CONSTITUENTS OF LEVELS FOUND IN LEVELS FOUND IN HEALTH
TOBACCO SMOKE WOOD SMOKE TOBACCO SMOKE EFFECTS
/ WOOD SMOKE (g/kg wood burnt) (ng/cigarette)
Aldehydes 0.6-5.4
Formaldehyde 0.1-0.7 70-100 Carcinogenic
Acetaldehyde 0.03-0.6 18-1400 Carcinogenic
Benzene 0.6-4.0 12-48 Carcinogenic
Benzo(a)anthracene 4x10-4 - 2x10-3 20-70 Carcinogenic
Chrysene 5x104- 1x10-2 40-60mg Carcinogenic
Benzofluoranthenes 6x10-4- 5x10-3 4-22 Carcinogenic
Benzo(a)pyrene 3x104- 5x10-3 20-40 Carcinogenic
Ideno(1,2,3-cd)pyrene 2xl0-4-1.3x10-2 4-20 Carcinogenic
Dibenzo(a,h)pyrene 3x104- lx10-3 1.7-3.2 Carcinogenic
Dibenz(a,h)anthracene 2x10-5 - 2xl0-3 4 Carcinogenic
Ca 9xl0-4-1.8x10-2 41-62 Carcinogenic
Cr 2x10-5 - 3x10-3 4-70 Carcinogenic
Ni lxl0-6 - lx10-3 0-600 Carcinogenic
References:URL: http://www.webcom.com/bi/table2.htmChemical constituents of Wood Smoke
URL: http://www.brown-and-williamson.com/Index_sub2.cfm?ID=18
Approximate Chemical Composition of Whole Mainstream Smoke
http://www.webcom.com/bi/table2.htmhttp://www.brown-and-williamson.com/Index_sub2.cfm?ID=18http://www.brown-and-williamson.com/Index_sub2.cfm?ID=18http://www.brown-and-williamson.com/Index_sub2.cfm?ID=18http://www.brown-and-williamson.com/Index_sub2.cfm?ID=18http://www.brown-and-williamson.com/Index_sub2.cfm?ID=18http://www.brown-and-williamson.com/Index_sub2.cfm?ID=18http://www.webcom.com/bi/table2.htm7/25/2019 Appropriate Technologies
6/23
How does a solar oven work?
http://www.solarcooking.org/sbcdes.htm#heat_gain
7/25/2019 Appropriate Technologies
7/23
How does a solar oven work?
Sunlight enters the oven through the glass lid. It strikes the black
absorber plate in the base and changes in wavelength.
The longer wavelength infrared radiation is trapped by the glass
which is only transparent to shorter wavelengths
Insulation in the walls reduces heat escaping through them.
http://www.solarcooking.org/sbcdes.htm#heat_gain
Consider:
Heat gain into a solar oven
Heat loss from the box
Heat transfer from the oven to the cookingvessel
Effect of materials used for the box
Materials used for reflector and glazing
Volume of the cooking space, compared
with volume of food to be cooked
7/25/2019 Appropriate Technologies
8/23
Thermodynamics of solar ovensHeat lossesare via
conductionthrough the oven walls andfloor,
convectionthrough any gaps in the lid or
around the glazing, air in the walls, or via
radiation.
http://www.solarcooking.org/fi/petrithe.htmRogers and Mayhew, 1981 Box Temperature as a functionof wall resistance
Thermal resistance due to conductionis defined by
the equation q = T1-T2R
where q is the heat flux (W/m2) and R is the thermal
resistance (m2W/C).
Heat flux due to radiationis given by the equationqr = 1 2K(T1
4-T24) A
1 - 1 2
whereis the emissivity of the wall surfaces and K is
the Stefan-Boltzman constant = 5.67 x 10-8(W/m2K4).
7/25/2019 Appropriate Technologies
9/23
Thermodynamics of solar ovens
Heat loss from radiation isapproximately three times the loss
from convection.
To be able to reach a cooking
temperature of at least 100C, aresistance of at least 1 unit is needed.
Doubling the wall thickness from
5cm thick to 10 cm thick gives only a
6% increase in resistance.
http://www.solarcooking.org/fi/petrithe.htm
Total wall resistance is given by considering
radiation and convection resistance in parallel,to give the following equation: R = Rrad Rc
Rrad + Rc
7/25/2019 Appropriate Technologies
10/23
Thermodynamics of solar ovens
Convection currents can be reduced by
providing a physical barrier to airflow eg. Abaffle or some insulating material.
Insulating materials used to prevent heat loss
include wood shavings, sawdust, rice husks,
peanut shells, newspaper, aluminium foil, andfor those who love wasting money, fibreglass.
Doubling the number of panes of glass (from
one to two) only decreases the heat loss
coefficient by 20%. Four panes instead of one
gives a 40% decrease only.
The most important mechanism of heat
transfer to the pot itself is by conduction from
the absorber plate. Optimum thickness 1mm.
http://www.solarcooking.org/fi/petrithe.htm
7/25/2019 Appropriate Technologies
11/23
Thermodynamics of solar ovens
Painting pots black is helpful but makes little
difference to the emissivity. Conduction is themost important form of heat transfer.
Elevating the absorber plate has no significant
effect overall.
Aluminium foil is the most effective reflector,given its low cost.
http://www.solarcooking.org/fi/petrithe.htm
Material Durability Cost Specular
Reflectance
Mirrors Breakable Very high 0.88Aluminium Foil Tears easily Moderate 0.86
Aluminium Sheet Good High 0.85
Aluminised polyester Tears Moderate 0.75-0.85
Metal from fuel tins Rusts Moderate N/A
7/25/2019 Appropriate Technologies
12/23
Other types of Solar Stoves
Parabolic solar stove
A hybrid type of
solar stove with a
sloping front and
multiple reflectors
Solar panel cooker uses reflectors like the
parabolic stove with an oven bag for glazing
http://xahlee.org/SpecialPlaneCurves_dir/Parabola_dir/parabola.html
Its all done with mirrors!
http://www.solarcooking.org/gallery1.htm
7/25/2019 Appropriate Technologies
13/23
Pasteurisation of drinking water
Women in Nepal testingwaterquality using a Colilert
test kit
A water pasteurisationindicator is used to
indicate whether water
has reached 65C for 6
minutes.
The Colilert Test Kit
http://www.solarcooking.org/gallery2.htm
http://www.idexx.com/Water/Products/prod.cfm?ID=2
http://www.solarcooking.org/solarwat.htm
7/25/2019 Appropriate Technologies
14/23
Where are solar stoves being used?
Solar radiation in Europe
Tens of thousands in China, hundreds of thousands in India
Projects in Chile, Nicaragua, Tanzania, Sierra Leone, Nepal,
Kenya, and Guatemala, to name but a few
Some used in developed countries, eg. United States
Solar radiation in Australia
We are
here!
URL http://www.bom.gov.au/sat/solrad.shtml: http://www.satellight.net/core.htm
http://www.satellight.net/core.htmhttp://www.satellight.net/core.htm7/25/2019 Appropriate Technologies
15/23
How does a composting toilet compare with
any other type of toilet?
They turn excreta into a valuable fertiliser, without contamination with
heavy metals.
They are usually built above ground (no pit to excavate)
They usually dont use any water for flushing (or very very little) .
http://www.compostingtoilet.org
7/25/2019 Appropriate Technologies
16/23
How does a composting toilet compare with
any other type of toilet?Feachem et al, 1983
RANKING OF EXCRETA DISPOSAL TECHNOLOGIES BY EASE OF
OPERATION & MAINTENANCE, WATER NEEDS & HEALTH BENEFITS
Technology Lack of Effort Requireda WaterNeeds Health Benefitsb
User Municipality Ideal Actual
Flush Toilet/sewers/ 10 4 H 10 9
oxidation pond
Vault/Vacuum truck 8 0 L 8 6
Pit Latrine 8 5 L 8 6
Septic Tank 6 5 H 8 7
Aqua Privy 5 5 M 9 6
Bucket Latrine 3 1 L 5 1Batch Composter 1 10 L 8 5
Continuous Composter 0 10 L 7 3
L = low M = medium H = high
a 0 = maximum effort 10 = minimum effortb 0 = no benefits 10 = maximum benefits
7/25/2019 Appropriate Technologies
17/23
Why use Composting Toilets?
Reduced use of expensive chemical
fertilisers Suitable for areas with high water table
No need for back-breaking work
digging latrine pits when the ground is too
stony
Water saving (40% of potable treatedwater is used for toilet flushing)
Energy saving (like all forms of on-site
sanitation)
Sale of compost may finance
composting latrine
Save money on water rates and septic
tank pumping
Avoid water and groundwater pollution
7/25/2019 Appropriate Technologies
18/23
How does a composting toilet work?
True composting toilets provide a controlled environment to enable aerobic
decomposition.
Some toilets which separate urine primarily work by dehydrading the
faeces so that the pathogens die by dessication
May use baffles, mixers or fans to improve airflow, and may use heatingunits
Two types:
Batch(includes Carousel composting)
Continuous
http://www.compostingtoilet.org/3makers/aussie.htm
Wh i il b i
7/25/2019 Appropriate Technologies
19/23
Where are composting toilets being
used?Mexico, Guatemala and
VietnamSome used in developed
countries, eg. Australia,
United States, United
Kingdom
Composting Toilets sold in the UK
BRAND NAMES COMPANY PRICE
Sun Mar Ecolet, Excel, Centrex Eastwood 1000
Clivus Kingsley Clivus
Dowmus Elemental solutions 2000
Aquatron Elemental solutions
http://www.elementalsolutions.co.uk
http://216.32.240.250/cgi-bin/linkrd?_lang=EN&lah=ccce88da2f4221c4bb581fa9b1b29426&lat=981312927&hm___action=http%3a%2f%2fwww%2eelementalsolutions%2eco%2eukhttp://216.32.240.250/cgi-bin/linkrd?_lang=EN&lah=ccce88da2f4221c4bb581fa9b1b29426&lat=981312927&hm___action=http%3a%2f%2fwww%2eelementalsolutions%2eco%2euk7/25/2019 Appropriate Technologies
20/23
Solar photovoltaic energyEnvironmentally sound (42 gCO
2/kWh vs 450g CO
2/kWh
for gas, Greijer et al, 2000)
Solar energy is more labour intensive, creating employment
(Solar thermal power employs 2.14 times more workers than
coal fired power stations, Truax, 1992)
Cost of system for one 30W panel, a battery and 4 x 10wfluorescent light tubes ~$600USD = 400
Appropriate Technologies Used in Developing Countries
7/25/2019 Appropriate Technologies
21/23
Low Cost
Water Supply
Appropriate Technologies used in Developing Countries
7/25/2019 Appropriate Technologies
22/23
Biogas for cooking
7/25/2019 Appropriate Technologies
23/23
Indigenous peoples technical knowledge & skills