UNDERSTANDING   STOVES  For Environment and Humanity    Sai Bhaskar N. Reddy
U n der sta n din g St ovesFor Environment and Humanity1st Edition, released 2012(OK) This is an ‘Open Knowledge’ book as ...
For ‘The Earth’
Foreword    This book presents the results of a decade of dedicatedpromotion and experimentation with fuel efficient stove...
much required as developing new methods of energy production –be it from algae, solar, the earth’s heat, water currents or...
Table of Contents  INTRODUCTION .................................................................................1     UND...
AIR FOR COMBUSTION .................................................................... 54   PRIMARY AIR ....................
STOVERS ........................................................................................ 108DESIGNING STOVES ........
Picture 1 A school Girl cooking food for the family
Understanding Stoves                                                             1Introduction      This book draws from m...
2                                                  Understanding Stoveswood, animal dung and crop waste) and coal. Nearly ...
Understanding Stoves                                                                     3Understanding stoves      Improv...
4                                                              Understanding Stoves    Over time, my work on stovesexpande...
Understanding Stoves                                                  5Other    advantages of      improved      stoves in...
6                                                                Understanding StovesMy journey into stoves               ...
Understanding Stoves                                               7    I have visited about 50 household kitchens. I noti...
8                                                      Understanding Stovesstoves with grates about 15 years back. Those s...
Understanding Stoves                                                           9Biomass stoves for sanctity    Many      p...
10                                                         Understanding Stovescommon good such as rains, good harvest, pe...
Understanding Stoves                                                 11    Exposure to smoke also increases the longevity ...
12                                                  Understanding StovesFacilitating good stoves     Human beings have ste...
Understanding Stoves                                                13in the schools, I would often ask the children one q...
14                                                    Understanding Stoves     Picture 9 Participation of women in choosin...
Understanding Stoves                                                             15Biomass fuel for stoves     A variety o...
16                                                          Understanding Stoves     Crop residue is another important sou...
Understanding Stoves                                                            17                                        ...
18                                                                Understanding Stovessolutions. Being lighter, drier and ...
Understanding Stoves                                                19cutting them into small and thin sticks. These are o...
20                                                           Understanding StovesCooking conditions        In semi-arid re...
Understanding Stoves                                               21adults return). During these two periods, cooking bec...
22                                                           Understanding StovesFuel feeding     Cooking on stoves that n...
Understanding Stoves                                                 23    Batch-loading fuel stoves are not convenient fo...
24                                              Understanding Stoves     Picture 17 A woman cooking on traditional stove
Understanding Stoves                                                             25Physical aspects of stoveSize of stove ...
26                                                 Understanding Stovesaround 6-7 inches in diameter are ideal, given the ...
Understanding Stoves                                                                         27Stove material and efficien...
28                                                     Understanding Stoves     Insulation and refractory quality are two ...
Understanding Stoves                                                  29they lose a greater amount of heat through radiati...
30                                                             Understanding Stoves     For transport and spread overwider...
Understanding Stoves                                                             31     There are stoves with scopeonly fo...
32                                                      Understanding StovesCapacity of domestic stoves      A domestic st...
Understanding Stoves                                                     33Flame    Observing the flame is veryimportant, ...
34                                                   Understanding StovesCombustion process      In the combustion process...
Understanding Stoves                                                       35          Picture 25 Behaviour of flame - und...
36                                                              Understanding Stovesexplain to the stakeholders the import...
Understanding Stoves                                                              37     Greater the part of the flame’s p...
38                                                        Understanding StovesColour of flame     The   colour    of     t...
Understanding Stoves                                               39Behaviour of flame    There are different types of fl...
40                                     Understanding Stoves     Picture 29 Dancing flame   Picture 30 Climbing flame     P...
Understanding Stoves                                                    41           Picture 33 Rocket flame            Pi...
42                                                     Understanding Stoves      Picture 37 Silent flame – briquette     P...
Understanding Stoves                                                 43    Rushing flames are common where there is a chim...
44                                                     Understanding StovesThermal aspects     In a stove, there are three...
Understanding Stoves                                                 45most of it into ash. Ash is white in colour; it doe...
46                                                    Understanding StovesConvection     Convection currents within a stov...
Understanding Stoves                                              47stoves, the convection currents are stronger. It is du...
48                                                   Understanding StovesRadiation     Radiation is another mode of heat t...
Understanding Stoves                                                          49No Smoking    “Smoke is smoke” and too muc...
50                                                         Understanding Stoves      Of late, many youth haveinquired abou...
Understanding Stoves                                                               51Soot and smoke     Pieces of carbon l...
52                                                             Understanding StovesPicture 46 Circular frames made of clay...
Understanding Stoves                                                                       53Emissions    The pyrolysis an...
54                                                              Understanding StovesAir for combustion      Depending upon...
Understanding Stoves                                                55Side air    In a majority of the traditional stoves,...
56                                                              Understanding StovesSecondary air     Use of secondary air...
Understanding Stoves                                                    57Tertiary air    Tertiary air helps in complete c...
58                                                  Understanding StovesBurners     Burners are the components in stoves t...
Understanding Stoves                                                                    59The primary air holes from the s...
60                                                                Understanding StovesThe air from the central pipe also a...
Understanding Stoves                                                                 61Option of fins in the burner for pr...
62                                                              Understanding Stoves  Primary air, secondary air and side ...
Understanding Stoves                                                                  63 The pyrogas from a gasifier is fo...
64                                                                Understanding StovesSimple TLUD batch load gasifier – lo...
Understanding Stoves                                                       65Concentrators    Concentrators      are   sim...
66                                                       Understanding Stoves     Picture 52 Top view of concentrators - r...
Understanding Stoves                                                                 67Air controls    With      scope    ...
68                                                  Understanding Stovesanother at the exit point in the chimney — are pre...
Understanding Stoves                                                69Grate and stove bottom    In domestic stoves, the ga...
70                                                    Understanding StovesPots and efficiency     The efficiency of a stov...
Understanding Stoves                                                              71   Picture 55 Stoves designed by Dr N ...
72                                                         Understanding StovesHeat transfer     Pots made of material suc...
Understanding Stoves                                             73cooked. The temperature range 300 – 600 degrees centigr...
74                                                  Understanding StovesFoils for pot     To certain utensils, which are f...
Understanding Stoves                                                     75Pot sizes    Utensils used for       cookingcom...
76                                                  Understanding Stoves     One observes that hemispherical / curved / al...
Understanding Stoves                                                            77Pot rest    Pot-rest is one of the mosti...
78                                                               Understanding Stovesiron, wrought iron or iron are also u...
Understanding Stoves                                                        79                                    Pot Rest...
80                                                  Understanding Stoves       Pot rest with gaps      The radial pot rest...
Understanding Stoves                                                 81Air gap    In all non-chimney stoves, an air gap is...
82                                                    Understanding StovesSkirts for pots     Although skirts improve the ...
Understanding Stoves                                                                 83Chimney stoves    Chimney stoves ha...
84                                                   Understanding Stovesexpensive. In the case of domestic stoves, the ch...
Understanding Stoves                                                          85Special features in stoves      There have...
86                                                    Understanding Stovesamount of hydrogen gas generated from the steam ...
Understanding Stoves                                               87Charcoal from stoves    Many stoves achieve higher ef...
88                                                   Understanding Stoves     Picture 65 A girl cooking on an efficient st...
Understanding Stoves                                                            89Facilitation of domestic stoves    Facil...
90                                                            Understanding Stoveswritings, posters, skits, plays, worksho...
Understanding Stoves                                                  91    Monitoring: Monitoring the performance of the ...
92                                                           Understanding StovesInstitutional Stoves     Institutional   ...
Understanding Stoves                                                                      93    Even though efficient stov...
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Understanding Stoves

  1. 1. UNDERSTANDING STOVES For Environment and Humanity Sai Bhaskar N. Reddy
  2. 2. U n der sta n din g St ovesFor Environment and Humanity1st Edition, released 2012(OK) This is an ‘Open Knowledge’ book as declared by the author.Dr. N. Sai Bhaskar Reddy, 2012saibhaskarnakka@gmail.comhttp://goodstove.comFront cover photo: A tribal woman cooking on a three-stone stove.Back cover photo: Author creating awareness on good stoves in a village.Note: The author drew sketches and mostly took the photos presented in this book.Published in 2012 byMetaMetaPaardskerkhofweg 145223 AJ s-HertogenboschThe Netherlandswww.metameta.nl
  3. 3. For ‘The Earth’
  4. 4. Foreword This book presents the results of a decade of dedicatedpromotion and experimentation with fuel efficient stoves in India bymy friend Sai Bhaskar Reddy Nakka. Sai Bhaskar’s approach hasbeen original in many ways. He has investigated the different mixesof biomass used in different areas of India – not just fuel wood butalso leaves, dung, pellets, briquettes, seeds and other materials. Hethen designed the different stoves accordingly. Sai Bhaskar alsolooked at different products from the stoves – obviously the directheating but also the possibility of producing charcoal (Biochar) as aby-product from the stoves. This work is not lab-based butundertaken in the promotion campaigns he has been involved withinAndhra Pradesh and parts of other states in India. The relevance of this work is large. Many people are and willremain dependent on local biomass for their daily needs. This issueof biomass has often associated with the degradation of thesurrounding environment: the depletion of natural tree stands or theloss of nutrients to the growing cycle. It has also been associatedwith hardship: collecting biomass – typically by women – over largeareas, and health issues because of excessive smoke from in-housefires. Because of such reasons the constant improvement ofhousehold stoves and stoves used in institutions and others is as
  5. 5. much required as developing new methods of energy production –be it from algae, solar, the earth’s heat, water currents or winds – orsafe methods to extract fossil fuel. Moreover, there are important developments to make biomassconsumption more and more renewable. In several areas I have seenfarmers starting to grow fuel wood on a commercial base, either onfield boundaries or as special plantations. We recently came acrossthis in Yemen where farmers had set up acacia plantations with themain aim to produce charcoal. For all these reasons I am very happy that this book of ‘TheStove Man’ could be prepared, to share the praxis-based knowledgedeveloped by a unique innovator and to serve as a source ofinspiration and new ideas for those working in energy anddevelopment. We hope that this book gives an impulse to theconstant effort to make lives better and richer.Frank van Steenbergen
  6. 6. Table of Contents INTRODUCTION .................................................................................1 UNDERSTANDING STOVES ........................................................................ 3 MY JOURNEY INTO STOVES ....................................................................... 6 BIOMASS STOVES FOR SANCTITY ................................................................ 9 FACILITATING GOOD STOVES ................................................................... 12 BIOMASS FUEL FOR STOVES ............................................................ 15 COOKING CONDITIONS .......................................................................... 20 FUEL FEEDING ...................................................................................... 22 PHYSICAL ASPECTS OF STOVE .......................................................... 24 SIZE OF STOVE ..................................................................................... 25 STOVE MATERIAL AND EFFICIENCY ............................................................ 27 CAPACITY OF DOMESTIC STOVES .............................................................. 32 FLAME ............................................................................................. 33 COMBUSTION PROCESS.......................................................................... 34 COLOUR OF FLAME ............................................................................... 38 BEHAVIOUR OF FLAME ........................................................................... 39 THERMAL ASPECTS .......................................................................... 44 CONDUCTION ...................................................................................... 44 CONVECTION ....................................................................................... 46 RADIATION ......................................................................................... 48 NO SMOKING .................................................................................. 49 SOOT AND SMOKE ................................................................................ 51 EMISSIONS .......................................................................................... 53
  7. 7. AIR FOR COMBUSTION .................................................................... 54 PRIMARY AIR ....................................................................................... 54 SIDE AIR ............................................................................................. 55 SECONDARY AIR ................................................................................... 56 TERTIARY AIR ....................................................................................... 57 BURNERS ............................................................................................ 58 CONCENTRATORS ................................................................................. 65 AIR CONTROLS ..................................................................................... 67 GRATE AND STOVE BOTTOM ................................................................... 69POTS AND EFFICIENCY ..................................................................... 70 HEAT TRANSFER ................................................................................... 72 FOILS FOR POT ..................................................................................... 74 POT SIZES ........................................................................................... 75 POT REST ............................................................................................ 77 AIR GAP.............................................................................................. 81 SKIRTS FOR POTS .................................................................................. 82CHIMNEY STOVES ............................................................................ 83SPECIAL FEATURES IN STOVES ......................................................... 85CHARCOAL FROM STOVES ............................................................... 87FACILITATION OF DOMESTIC STOVES .............................................. 89INSTITUTIONAL STOVES................................................................... 92 PREPARATIONS FOR INSTALLATION ........................................................... 94 INSTALLATION OF STOVES ....................................................................... 96 STOVE EFFICIENCY ................................................................................ 98 ADOPTION FACTORS............................................................................ 100HONOUR OF STOVE ....................................................................... 106
  8. 8. STOVERS ........................................................................................ 108DESIGNING STOVES ....................................................................... 109 COMPARING STOVES WITH A HOME ....................................................... 112TESTING STOVES ............................................................................ 113 WHO CAN TEST STOVES? ..................................................................... 117PROMOTING STOVES..................................................................... 119 RIGHT PRICE ...................................................................................... 123 MARKETING STRATEGIES ...................................................................... 126 ENTERPRISES ..................................................................................... 127 STOVES FOR CHICKEN! ......................................................................... 130STOVES AS PART OF EDUCATION ................................................... 131MEDIA ........................................................................................... 133ONE BILLION GOOD STOVES .......................................................... 137NOTES ........................................................................................... 143ACKNOWLEDGEMENTS .................................................................. 145REFERENCES .................................................................................. 148
  9. 9. Picture 1 A school Girl cooking food for the family
  10. 10. Understanding Stoves 1Introduction This book draws from myseven-year journey towardsunderstanding stoves and thepeople using them. It gathers myexperiences, observations andinsights into stoves. This work hasgiven me immense happiness, forI believe it can help the cause ofenvironment and humanity. I was iinvolved in designing stoves ,improving existing stoves, testingstoves and conducting studies.During the course, I interactedwith communities and workedwith them: creating awareness, Picture 2 Smoke from stoves is asensitivity and on capacity hazard for womendevelopment. According to World Health ii  On UnderstandingOrganisation (WHO, 2011) , stoves; Authors journey intoaround 3 billion people cook and designing stoves; the valueheat their homes using open fires of stoves and the importanceand leaky stoves that burn of facilitation of stoves.biomass (about 2.7 billion use
  11. 11. 2 Understanding Stoveswood, animal dung and crop waste) and coal. Nearly 2 millionpeople die prematurely from illnesses related to indoor air pollutionfrom household solid fuel use. Nearly 50 % of pneumonia deathsamong children under five are due to particulate matter inhaled fromindoor air pollution. More than 1 million people a year die fromchronic obstructive respiratory disease (COPD) that develops due toexposure to such indoor air pollution. Both women and menexposed to heavy indoor smoke are 2 - 3 times more likely todevelop COPD. Given this, it is estimated that there is a need forabout 1 billion good stoves across the globe. In India alone, about 570,000 premature deaths among poorwomen and children every year, and over 4 % of Indias estimated iiigreenhouse emissions are attributed to the impacts of cook stoves .
  12. 12. Understanding Stoves 3Understanding stoves Improving stoves is aneffective way of improving theenvironment and servingcommunities. My work in thisarea provided me a greatopportunity to meet a diversity ofpeople and visit many places.Some of the primary stakeholdersI could meet were the poorest of Picture 3 People living on pavements, cook food on the road.the poor: tribal communities Location: Mumbai City, Indialiving in remote areas, ruralcommunities, people living in urban slums, sex workers, artisans etc.Besides, I also met representatives of various government / non-governmental organizations, policy makers and scientists. I had never imagined that I would be exposed to such a mosaicof human beings and understand so much about the environmentthrough stoves. My work got the press’ attention. They called me-‘Poyla Sir’ (Stoves Sir), ‘Gramala Nestham’ (Friend of villages) and‘Manchi Manishi’ (‘Good Man’). I consider these no less than honorsbestowed upon me.
  13. 13. 4 Understanding Stoves Over time, my work on stovesexpanded into other research area –biochar / biocharculture, sustainableagriculture, safe water, habitats,sanitation, etc. Through the process, Icame to realize the importance of 1‘Open Knowledge’ to achieving thecommon good. Therefore, I havedeclared all my work so far as open and freely available to all whomay need it or find it interesting. Adoption of good stoves by communities is an effective meansto mitigate harmful environmental impacts. It also addresses climatechange-related issues, since it is linked to the reduction ofgreenhouse gases (especially Carbon Dioxide) and the reduction ofblack carbon, an important factor accelerating global warming. BlackCarbon accelerates global warming through excessive heatabsorption, browning of skies (especially as observed in the southAsian region) and reduced albedo from the sky. Improved stoves can help carbon sequestration, such as when ivthe biochar from them is applied to the soil to improve its fertility. 1 Open Knowledge: The belief and commitment that knowledge andtechnologies relevant to common people should be open and not be patented for thecommon good. http://okgeo.org
  14. 14. Understanding Stoves 5Other advantages of improved stoves include conservation,sustainable use of biomass, and reduced indoor air pollution. In most countries, biomass is still the main source of fuel formany people. Energy is always a concern, as a resource that is scarce,diminishing, costly, time-consuming, uncertain in supply and ofteninaccessible. Poor people spend a considerable amount of time on sourcingthe biomass for fuel. The urban poor visit backyards of industries /railway lines to look for fuel. Sometimes security personnel bartersexual favours with women, in exchange for letting them accessthese areas. There are instances of women being raped when theygo wandering around common lands or forest areas looking for fuelwood. When there is no free access, people are forced to buybiomass, sometimes at very high prices. There is a need for large-scale awareness and educationregarding the extent to which access to fuel can affect the quality oflife, especially that of the less-privileged. There is no value to an innovation or technology relevant to common people if it is held up in patents
  15. 15. 6 Understanding StovesMy journey into stoves 2 One day I was in a villagetrying to understand the ruralenergy situation in India. Adistinct observation was that inthe courtyards of many houses,there was heaps of fuel wood.This fuel wood was collected, foruse in cooking for severalmonths. It was harvested from the Picture 4 Fuel wood stored in the courtyard of housesvillage commons and / or thenearby-degraded scrubland. Onan average, people spend up to 4 days a month collecting fuel wood.Considering the rural wage rates being currently offered undergovernment programs, it amounts to no less than $ 10. A majority ofthe rural poor earn around $1 per day. Their spending on fuel woodsometimes works out costlier than the Liquid Petroleum Gas (LPG) 3promoted by the government through a range of subsidies . 2 Srirangapur Village, Kondurg Mandal, Mahabubnagar District, AndhraPradesh, India. 3 Fuel is highly subsidized in India; Government of India is bearing a cost ofRs. 30.10 per liter on kerosene and Rs. 439.50 per 14.2-kg domestic LPG. (March2012).
  16. 16. Understanding Stoves 7 I have visited about 50 household kitchens. I noticed that abouthalf the stoves were ‘three-stone’ stoves and the rest made fromclay. Such stoves are highly inefficient, rudimentary and primitive. Iwill never forget those visits, for they made me realize what a largenumber of people are stuck with them and exposed to their harmfuleffects. The stoves and the kitchens do not reflect the changes in thelives of the families over the years. Many people are now living inconcrete houses, eating higher-value food, can afford mobilephones, can send their children to English-medium schools, havesatellite television connections, motorbikes, tractors to ploughfields… and so on.. Despite all the winds of change anddevelopment, the kitchen remains a smoky place with dark-sootywalls and roof. Even traditionally, kitchens have occupied relativelysmall spaces inside or outside the house. I decided that my first step would be creating awareness aboutindoor air pollution and its harmful effects. I went to communitiesand showed them pictures of their stoves through a projector.Although people in general were interested in watching the slideshow, women objected when it came to seeing their own stove. Thisis because the kitchen was not a place of pride for them, eventhough they respect the stove very much. I then explained to thecommunities the impact of indoor air pollution and its multipliereffects on them. They were quite interested in adopting efficientstoves, but were helpless, as they did not have access to them. Inone of the villages, the state government had promoted chimney
  17. 17. 8 Understanding Stovesstoves with grates about 15 years back. Those stoves were nowhereto be found. Within a few years, the stoves had disintegrated, thechimneys had been choked with soot, the grates burnt down and thestoves disappeared. The design of the stoves did not take intoaccount how adaptable they were to local conditions and practices.The stoves had been distributed under a government scheme andwere subsidized. Nevertheless, they could not find acceptance orsustainable demand from the local community. This exposure made me sensitive towards the issue of stoves in vrural areas and I was motivated to help improve their stoves’ design.I realized that there could not be a single globally good stove, andthat the challenge was adapting designs to fit local needs. As I started off, I could not easily access specialists in the field ofgood stoves. However, through the internet, I found numerous,diverse stove designs that had evolved around the globe - inresponse to a variety of food habits, cooking methods, culturaltraditions, types of available biomass fuel, family sizes etc. Studyingthem formed the basis of my initial understanding of stoves, andsubsequent research and design efforts.
  18. 18. Understanding Stoves 9Biomass stoves for sanctity Many people say thatbiomass cook stoves should bebanned altogether. However, allthe elements of sanctity andsanitation can be found in them:Fire, Smoke, Charcoal and Ash.Cooking on biomass stoves isalso a way of engaging with andrespecting the elements ofnature. Fire is highly respectedeven by the most primitive ofcommunities. Fire is consideredauspicious by many spiritualbeliefs / systems / religions /societies. Some of them evenworship it as a deity. In manyreligions, praying rooms areattached with kitchens.Considering smoke to be harmful Picture 5 Fire, Smoke, Charcoal and Ash - sanctify a placedoes not fit with the culture ofusing incense sticks for worship, common to many religions. The stove also signifies the cultural connection of the communitywith fire. As mentioned above, fire is widely regarded as a deity andbiomass stoves adorn kitchens also used as prayer rooms. It is themedium through which offerings are made to the Gods as a plea for
  19. 19. 10 Understanding Stovescommon good such as rains, good harvest, peace and harmony. InIndia, this is evident in ceremonies like Yagnas, Homas andAgnihotras (or Holy Altar). Cooking on biomass stoves, thus,represents this cultural respect for fire. In rural areas, where poorpeople use fuel wood to cook,there is always some smoke.Smoke from biomass stovesprotects them from a variety ofpests. In many countries, termitesare a major cause of economiclosses. In many rural communities,seeds collected for sowing in the Picture 6 Seed is stored in kitchennext season are commonly stored as the smoke protects and preserves it.in the kitchen. Smoke protectsthatched huts from pests such astermites and woodborers. It isvery common in such places forpeople to use smoke as a meansto repel mosquitoes and preventdiseases like malaria. On theother hand, cockroaches andinsects are common in kitchens Picture 7 Unattended thatchedusing Liquefied Petroleum Gas. house roof, attacked by Termites
  20. 20. Understanding Stoves 11 Exposure to smoke also increases the longevity of thatchedstructures. It has been observed in tribal habitats that, if unattended,the roof of a hut could be destroyed by termites within 3 to 6months. On their part, thatched roofs are porous enough to allowsmoke and soot to exit the hut. Charcoal and ash are two other important by-products of thebiomass stove. Many poor communities use charcoal for cleaningteeth, and the ash for cleaning utensils. Ash from holy altars is usedas a vermillion to apply on the forehead and other body parts. Attimes in small quantities, it is also recommended as medicine byfaith healers. In agriculture, the charcoal is used as biochar forimproving soil-health and fertility. Ash is an important additive foracidic soils and an important source of potash and phosphate. Some smoke is good and too much smoke is bad
  21. 21. 12 Understanding StovesFacilitating good stoves Human beings have steppedon the moon, and explored thesolar system and planets manylight years away. However, we stillhave not been able to provideefficient cooking systems formillions of people living on thisEarth. Providing one billionefficient stoves is a mission asimportant as any other mission is. Picture 8 Creating awareness toYet, this mission is yet to be children on good stovesachieved. There are not many professionals trained in the ‘GoodStoves’ technology. We require many of them: researchers,designers and trainers. Universities and Institutes should conductprofessional courses to meet this challenge. As a policy, only a few countries have taken up the causeseriously. Crucially, the lack of awareness means that the issue hasnot caught the imagination of the youth. And as for the media, thesilent death of millions due to indoor air pollution does not seem tohave enough news value. Given the sheer number of people who areaffected, it should be their responsibility to understand the issue andspread awareness about it. It is very rare to find professionals with relevant education andtraining working on stoves. During awareness programs conducted
  22. 22. Understanding Stoves 13in the schools, I would often ask the children one question: “There isan important task on earth yet to be accomplished i.e., facilitatingone billion good stoves. How many of you will be willing to work onthis in the future?” Rarely did anyone put his or her hand up. Acommon refrain was that ‘our parents will not approve of it’. Besides,it was all too noticeable that even the word ‘stove’ was notmentioned anywhere in the school curricula. This reflects the generallack of emphasis on the subject, which also explains the lack ofinitiatives on the part of the government. Thanks to the global reach of e-groups and networks related tostoves, there is now scope for interested stakeholders to cometogether, share, understand, design and facilitate good stoves. Someof the most important international networks include ‘Improved viBiomass Cook Stoves’ (website and e-group) , ‘Partnership for Clean vii viiiIndoor Air’ (PCIA) , ‘Household Energy Network’ (HEDON) , ‘Global ix xAlliance for Clean Cookstoves’ , ‘Winrock’ , ‘Deutsche Gesellschaft xi xiifür Internationale Zusammenarbeit’ (GIZ) , ARECOP , Aprovecho xiiiResearch Centre , et cetera. Whatever progress the human beings are doing on this earth, we can take is no pride in them if people are still using three-stone stoves
  23. 23. 14 Understanding Stoves Picture 9 Participation of women in choosing Good Stoves
  24. 24. Understanding Stoves 15Biomass fuel for stoves A variety of biomass is usedas fuel for cooking-stoves.Biomass can be sourced fromvarious types of plants, and inmany forms - trunks, branches,sticks, twigs, bark etc. Regionally,some types of biomass arepreferable to others, because of Picture 10 Head load of fuel wood being carried, an arduous taskcost, access, calorific value,density of wood, ease of fuelwood preparation, whether theyare fast growing species, easy to  On biomass as fueldry, etc. Exotic, invasive species for cooking; conditions ofsuch as Prosopis Juliflora and cooking and the use of fuel.Acacia plants are highly preferred as fuel wood in many tropicalcountries. Some of the indigenous forest species come underfederal / provincial forest legislations, which means that it is illegal touse them for this purpose (among others). Picture 11 Types of biomass used as fuel
  25. 25. 16 Understanding Stoves Crop residue is another important source of fuel, availableseasonally. Sometimes the loose biomass is converted intobriquettes or pellets for use in stoves. In some stoves, loose biomassis used in various forms such as sawdust, wood shavings, rice husk,leaves, grasses, seeds, corncobs, shells (groundnut, coffee, etc.), etc.In places where biomass is not available, animal dung is also used asfuel. Dung / clay is used with charcoal dust for making briquettes /balls for use in stoves. Preferably, naturally occurring biomass orbiomass available as by- product of various grades should be used. Itis easier to come up with a good design for a stove if one knowswhat fuel would be used in it. Picture 12 Briquettes and wood shavings used for cooking Wood moisture is another factor important to efficientcombustion. Wood moisture varies seasonally, based on thesunshine, precipitation (rain, snow, fog, etc.). In many tropical andsemi-arid environments, wood moisture varies between 12 to 18 %on a dry day.
  26. 26. Understanding Stoves 17 Thin wood dries easily and has greater surface area as compared to large-sized wood. Very thin wood (less than one cm in diameter) is used for kindling. Sometimes, kerosene is used (about 5 to 10 ml) to start the fire. Papers, cardboard, wax, camphor, Picture 13 Wood shavings and saw vegetable oil, pinewood,dust used as fuel pinecones, seeds etc., are alsoused for starting the fire. Communities for cooking (except forkindling) do not prefer thin wood. Thin wood burns convenientlywith very less smoke, but sometimes emits excess soot. The stoveusers do not like soot deposit on their utensils and their kitchenwalls. Similarly, bark of plants, although good for fire, sometimesleads to excess soot and smoke. The kerosene added for starting thefire can also emit quite some soot. Torrefaction (French for roasting) of biomass (e.g. wood) can bedescribed as a mild form of pyrolysis at temperatures typicallyranging between 200 to 320 degree centigrade. During torrefaction,the biomass’ properties are changed in a way that, as a fuel, it leadsto much better combustion and gasification. It turns the biomassinto a dry product, leaving no scope for undesirable biologicalactivities like rotting. Torrefaction of biomass in combination withdensification (pelleting / briquetting), is a promising step towardsachieving logistical economy in large-scale sustainable energy
  27. 27. 18 Understanding Stovessolutions. Being lighter, drier and stable in storage, such pellets /briquettes are easier to transport, store and use. Often, thin and neatly cut sticks are used for testing the stovesfor efficiency and performance. However, the wood used in domesticcooking stoves is about 5 to 7 centimeters in diameter. The wood isnever split perfectly into square cross sections, say 2 x 2 centimeters,like the wood pieces used for testing stoves. Splitting the wood inthat manner is very difficult and demands lots of energy and timetoo. Picture 14 Fuel longs of more than 6 feet length used in stoves Typically, the length of the pieces of prepared / collected fuelwood is about 40 to 100 centimeters. Carrying, bundling andtransporting them is not convenient if they are much shorter. AcrossIndia, it is common for people to carry fuel wood by balancing it ontheir heads or on bicycles. In tribal areas, people can be foundcarrying whole trunks and branches of trees on their heads, without
  28. 28. Understanding Stoves 19cutting them into small and thin sticks. These are often 150centimeters to 350 centimeters in length and nearly 10 centimetersto 30 centimeters in diameter. It is also common to use whole trunksin stoves, especially among communities living in/around forests. Facilitating Good Stoves is simple to achieve.... but we are far away from doing that
  29. 29. 20 Understanding StovesCooking conditions In semi-arid regions, cookingis often done in semi-ventilatedconditions, as rainy days are few.Cooking pots are covered withlids while cooking. Sometimes,while stirring / simmering of riceetc., the lid is removedcompletely or covers the pot onlypartially. While making Rotis (flat Picture 15 Food being cooked with half covered lidIndian bread), the pan iscompletely uncovered. Poor families often do not have separate kitchen areas at all.Even in well-off households, kitchens are often dark and dingy.Ventilation is poor, windows/ ventilators are rare. Even in well-ventilated kitchens, traditional stoves cause a lot ofindoor pollution. No one enjoys cooking because, for many, cookingamounts to smoking. Sometimes, such stoves emit as much smokeas 50 to 100 cigarettes, over 2 to 3 hours. Cooking during the rainydays often leads to highest release of smoke, due to higher levels ofmoisture in the wood and the stoves. Cooking is mostly done early in the mornings (or the domesticrush hour – when children are leaving for their schools and adultsare leaving for work) and in the evenings (when the children and the
  30. 30. Understanding Stoves 21adults return). During these two periods, cooking becomes all themore difficult. Exposure to smoke from inefficient stoves makescooking even more difficult. Those who cook, therefore (and it ismostly women), do so with little willingness. Picture 16 Cutting trees for wood is one of the decentralized form of depleting biomass
  31. 31. 22 Understanding StovesFuel feeding Cooking on stoves that need to be fed fuel wood continuously,is like feeding a baby. It requires immense patience. One has to startthe fire with the thinner sticks and then move to the ones with largerdiameters. It is important that the ignition be done at the tips.Sometimes, users push the sticks too deep into the stoves. The stovethen bellows out smoke the way a baby throws up when overfed.Therefore, using a given type of stove efficiently requires a certainamount of experience with it. ‘Novice’ users should be careful not tojudge a stove’s efficiency too quickly. Good stoves are designed in away that allows for proper air circulation and mixing inside them.This makes them easy-to-use even for the less-experienced users. Certain types of stoves, such as most of Top Lit Up Draft (TLUD)stoves, allow for ‘batch-loading’ of fuel. This means that the biomassfuel (chips of wood, wood shavings, small bunch of sticks, pellets,etc.) can be loaded just once, and then ignited at the top. As the 4pyrolysis moves down the heap, wood gas is released which mixeswith the secondary air just underneath the pot and combusts. After a xivbatch of fuel is exhausted completely, charcoal / biochar getsaccumulated at the bottom of the combustion chamber. It can thenbe emptied and reloaded. 4 Pyrolysis is a thermochemical decomposition of organic material at elevatedtemperatures with very little participation of oxygen. It involves the simultaneouschange of chemical composition and physical phase, and is irreversible.
  32. 32. Understanding Stoves 23 Batch-loading fuel stoves are not convenient for communities toadopt, as one needs considerable experience to handle them. Forexample, there is always a chance that one could add too much ortoo little fuel. Despite controls to regulate natural draft and forcedair, controlling the power of the stove could get very difficult indeed.
  33. 33. 24 Understanding Stoves Picture 17 A woman cooking on traditional stove
  34. 34. Understanding Stoves 25Physical aspects of stoveSize of stove A stove of 8 inches height isideal. Any stove too high (about12 inches or more) isinconvenient. Women prefersitting comfortably on the floorwhile cooking. In rural areas,many women carry out manydaily activities while sitting.Especially when making rotis (flat Picture 18Women prefer to sit whilebread), they prefer a low stove. cooking Scientifically, the ‘chimney effect’ in tall stoves would manage thesmoke and aid combustion more efficiently. However, as per theergonomics and local practices, they are not convenient to the user. Often the pan for makingrotis is about 10 to 12 inches in  On Physical aspectsdiameter. A 4 - 5-inch diameter of the stove – size of thestove, the stove needs to be stove; types of material usedoperated at high power for the for production of stoves andflames to spread underneath the the efficiency of the stoves;pan sufficiently, for the roti to be and capacities of thecompletely cooked. Stoves domestic stoves.
  35. 35. 26 Understanding Stovesaround 6-7 inches in diameter are ideal, given the various types ofthe utensils used by an average-size family. Two of my stove designswere failures, for having a small diameter and for being too tall. Thedesigner needs to strike a balance between the scientific principlesand the user’s requirements.Sensitivity leads to awareness, knowledge and action. It is more important to be sensible than to be knowledgeable
  36. 36. Understanding Stoves 27Stove material and efficiency Thermal efficiency is alsodependent on the mass of thestove. In Water Boiling tests,relatively lightweight metalstoves prove to be thermallymore efficient, especially during 5the cold start high power phase. 6During the hot start high powerphase they show slightimprovements in thermalefficiency. Heavy stoves, on theother hand, are thermally less Picture 19 Proud owners of anefficient during the cold start efficient stovephase, but due to retained heatand during the hot start phase they exhibit higher efficiency. In real-life conditions, high-power cooking is not preferable as the taste andthe value of the food cooked is not as good compared to normalcooking. In addition, a compact stove is more adaptable than onewith many movable or removable parts. Stoves made of two or morematerials are costlier and sometimes less durable. 5 Cold Start: Tester begins with the stove at room temperature 6 Hot start: Tester conducts the test after the first test while stove is still hot.
  37. 37. 28 Understanding Stoves Insulation and refractory quality are two important factors instove-design. A material, which has both the properties, is of greatvalue. The refractory material options currently available in themarket are of high density and are bad insulators. Moreover, the costis very high: each refractory brick costs about $1. Firebricks or refractory bricks usually contain 30-40 % Aluminumoxide or Alumina, and 50 % silicon dioxide or silica. A stove made ofthem is guaranteed to last up to 10 years. However, its thermalefficiency is compromised. By combining lightweight insulatingfirebricks along with regular firebricks, thermal efficiency can beimproved. There is much difference between lightweight, insulatingfirebricks and heavy, dense firebricks. Insulating bricks are refractoryand withstand very high temperatures, but their thermal conductivityis lower than required. They do not absorb the heat well at all. Thesebricks are mainly used for heat insulation. They are used on the outerside of the stove (around the heavy firebrick walls or under the floorbricks and the slab used as a foundation for the stove) to keep heatfrom the combustion chamber from escaping, and to thus achievehigher thermal efficiencies. Insulating Fire bricks are made up ofAlumina: 37 %, Silica: 61 % and Ferric Oxide: 1.6 %. The cost of the stove goes up when constructed using refractorybricks and insulating firebricks. Overall, the weight of the stove alsoincreases, making it inconvenient to transport. While such stoves aremore durable, their volume and surface area are relatively high and
  38. 38. Understanding Stoves 29they lose a greater amount of heat through radiation (where onlyrefractory bricks are used). The cylindrical and hemispherical shapedstoves have less surface area and radiate much less heat, ascompared to box-shaped stoves. Air is the best insulation media. Even by using the thin metalsheets for combustion chamber (with side air and secondary airholes), the life of the combustion chamber can be increasedsignificantly. Even as air is sucked into the combustion zone, thecombustion chamber is being continuously cooled. This increasesthe durability of the combustion chamber. As a measure of safety from excessive heat emitted from thebody of the stove, an external wall can be made out of a thin sheetor wire mesh. The surface area of contact between the hot parts andother parts of the stove should be minimum possible. This can beachieved by using pointed / thin screws, ceramic watchers, etc., thusminimizing the heat transfer between the grate / combustionchamber and the outer body. Many traditional stoves do not havesuch safety walls around them. The space between the inner andouter walls is often left vacant or filled with insulation material, suchas broken pieces of glass, coarse sand, ash, pumice rock pieces, rockwool, etc., which are refractory and insulatory.
  39. 39. 30 Understanding Stoves For transport and spread overwider areas, the weight of thestove should ideally be around 2to 5 kilograms. Stoves weighingmore than 10 kilograms are moredifficult to market as a sustainableenterprise. They are also moredifficult for a team of people todemonstrate and promote over a Picture 20 An efficient good stove –large area. Often, stoves Avan series, for cooking mid-day meals to the childrenpromoted through subsidies /government programs are too heavy. Therefore, those in charge ofpromoting them do so unwillingly and ineffectively. The fact is thata majority of the stoves available in the market and sold on a largescale (although many are inefficient) are always lightweight. Beinglight, they cost less and are less durable. The lightweight stoves are 7much less likely to pass the simmering test than the heavier stoves,if the stove user is novice. Ideally, the holes in the stove grate should be small, but not sobig as to affect its durability. Too much or too little primary airentering the stove from below, and through the grate into thecombustion chamber, hampers the stove’s performance. 7 Simmering test: This portion of the test is designed to test the ability of thestove to shift into a low power phase following a high-power phase in order tosimmer water for 45 minutes using a minimal amount of fuel.
  40. 40. Understanding Stoves 31 There are stoves with scopeonly for primary air; they are alsocalled blower stoves, becausethey are often found withblowers. It is common to seecharcoal stoves often fitted withblowers underneath the grate.Grates made up of forged iron Picture 21 Air blower fitted to a stove, supplies additional air and createsare cheap and durable. Many draft for efficient combustionimproved stoves fail because thegrates fail. Grates need to be most durable of all the parts in a stove.In the ‘Good Stove’ Avan Series design, the grate is avoided. Over araised platform, fuel wood sticks are fed horizontally. The sticks donot fall into the combustion pit due to gravity, and the fuel wood iscombusted only at the tips. Through the side hole at the bottom, theprimary air reaches the fuel wood from below.Picture 22 Primary air comes from the wood, supports pyrolysis and combustion (GoodStove – Avan Series).
  41. 41. 32 Understanding StovesCapacity of domestic stoves A domestic stove often serves, on an average, a five-memberfamily. When guests visit, the same has to support, say, 10 members.It is very difficult for many families if their stove cannot provide thisflexibility. On an average, cooking pots are 1 to 6 liters in capacity.Similarly, the number of people to be served through institutionalstoves (used in big establishments such as restaurants / hostels /schools / religious places, etc.) is highly variable. Life is being curious, knowing, acting and experiencing
  42. 42. Understanding Stoves 33Flame Observing the flame is veryimportant, and photographs aremore useful than videos for thepurpose. In a dark room,observing the flames gives abetter indication of the stove’sperformance. One of the reasonsis that a blue flame is more visiblein the dark. Picture 23 Flame from a wick lamp emits very good light.  On types of flames; combustion process; colour of flame and behaviour of flame.
  43. 43. 34 Understanding StovesCombustion process In the combustion process, the flame is the simplest thing tounderstand. Take a matchstick, light it and you will observe thefollowing things: while striking a matchstick, due to friction and thechemical reaction, the flame starts at the tip. The matchstick headcontains either Phosphorus / Phosphorus Sesquisulfide as the activeingredient, and gelatin as the binder. The process of combustion ofwood (as in a matchstick) is like a controlled chain reaction. Theinitial heat (about 200 plus degrees) generated by the chemicals willpyrolyse the matchstick and release combustible gases. Usually,matchsticks are thin and made of lightwood, and so get pyrolysedeasily at low temperatures. If the head of the matchstick is raised,only a limited amount of heat from the flame would reach the stick.This would prevent pyrolysis andthe matchstick might beextinguished. If the tip of thematchstick is lowered, thematchstick will pyrolyse rapidlyand combustible gases would bereleased more. The flame will belarge. Therefore, keeping thematchstick horizontal, or its headtilted slightly towards the ground,would help combustion. Picture 24 A burning matchstick
  44. 44. Understanding Stoves 35 Picture 25 Behaviour of flame - understand through observation The core of the flame, dark in colour, is where the pyrolysishappens. One can see the pyrolysis gases when the flame is blownout. This is most clearly visible in incense sticks. As long as there isflame at the tip of the stick, there is very little smoke. Once the flameis extinguished, smoke is observed. This experiment is important to
  45. 45. 36 Understanding Stovesexplain to the stakeholders the importance of smoke as acombustible gas, otherwise wasted. As the flame moves towards the hand holding the incense /match stick, the tip gradually turns to ash. After the stick burns outand the flame is extinguished, one can clearly see the ash at thecombusted end. The amount of carbon (visible as the black colourformed from wood) reduces gradually from the tip of the match tip(where the flame started) towards the other, un-burnt end. Ash Fire Charcoal Wood Picture 26 Ash – fire – charcoal – wood: As seen in a matchstick burning The byproducts of combustion are smoke, moisture, soot, tar,Polycyclic Aromatic Hydrocarbons and Volatile Organic Compounds.
  46. 46. Understanding Stoves 37 Greater the part of the flame’s path that lies in the combustionchamber, more is the chance for the smoke and air to mix andcombust completely. Also important in the process is the ‘flash 8point ’ temperature of the smoke.There could be as many stove designs as the shoes to suite everyone’s need 8 - The flash point: Materials at certain temperature will burst into flames. Thistemperature is called a materials flash point. Woods flash point is 572 degreesFahrenheit (300 C).
  47. 47. 38 Understanding StovesColour of flame The colour of the flameindicates much about the kind ofcombustion and whether it isoptimal. Reddish flames yield themost soot. The yellowish-redflame is the most common. Thebluish-yellowish-reddish flame isoptimal. Observing the flames is anexperience by itself. One could Picture 27 The sooty reddish flamespend hours just watching them, from pinewood burningbecause the colours are energeticand the flames are dynamic,changing their form continuously. The warmth from the flames isalso enjoyable especially during cold weather.
  48. 48. Understanding Stoves 39Behaviour of flame There are different types of flames: rushing flames (as in rocketstoves and chimney stoves), raging flames, forced flames, dancingflames (say as in Magh 3G stove), climbing flames, still or silentflames (wick flames), etc. Picture 28 Magh 3G stove with options for using all types of biomass and charcoal as fuel
  49. 49. 40 Understanding Stoves Picture 29 Dancing flame Picture 30 Climbing flame Picture 31 Raging flame Picture 32 Rushing flame
  50. 50. Understanding Stoves 41 Picture 33 Rocket flame Picture 34 Radial flame Picture 35 Radiation and flame from Picture 36 Gasifier flame briquette
  51. 51. 42 Understanding Stoves Picture 37 Silent flame – briquette Picture 38 Twister flameburning with less and constant air supply Picture 39 Forced rocket flame Picture 40 Secondary and Tertiary air
  52. 52. Understanding Stoves 43 Rushing flames are common where there is a chimney effect, ora chimney. In a rushing flame stove, although the flames appeardynamic and impressive, the conduction of the heat to the pot islow. In a dancing flame stove, air mixes thoroughly with thecombustible gases, and the flame takes its time to combust gaseswithout rushing below the pot. Therefore, the heat conducted to thepot is high. In forced air stoves, the flames are forceful; one can evenlisten to the sound of the flames quite clearly. Forced air flames hitthe pot and are deflected immediately. The rate of absorption of theheat from these flames is lower than dancing or still flames.Sometimes, due to excess air in the forced air stoves, there could bea cooling effect on the pot. Silent or still flames are observed in wickstoves or lamps. Under calm conditions, the flames in a biomassstove could be still or silent. The silent flame is a result of acontinuous release of combustible gases and constant mixing of air.On the other hand, a raging flame is the most uncontrolled. It isformed when too much fuel is added and the air mixesuncontrollably.
  53. 53. 44 Understanding StovesThermal aspects In a stove, there are threeways in which heat is transferred  On thermal aspectsto the pot and its contents. of flame – Conduction, Convection and Radiation.Conduction When the flames touch thepot directly, the mode of heattransfer is called conduction. Therate of transfer of heat throughconduction is the highest. Peoplecommonly believe that food canbe easily cooked only throughconduction. In many traditionalstove designs, the height of the Picture 41 Traditional three stonestove is kept very low to enable stoves are of low heightefficient conduction. People are not easily convinced that, in good stoves withefficient designs, heat transfer can happen through convection andradiation as well. During conduction, the flames embrace the potsideways at times, and could reach even higher than the pot (asoften seen in low-height three-stone stoves). When that happens,very little black soot is left on the pot, as the excessive heat burns
  54. 54. Understanding Stoves 45most of it into ash. Ash is white in colour; it does not stick to theutensils and therefore the pot surfaces appear relatively cleaner. In the traditional low-height stoves, black soot appears mostlyon the kitchen walls and less on the pots. In the taller, efficientstoves, little soot is formed on the walls, but some soot is found onthe pots on the outside. On stoves with chimneys, the flames do notrise and embrace the pot as high as they do on traditional stoves.The soot particles, along with the wood vinegar / tar, tend to stick tothe pot. However, overall, the amount of black soot formed onkitchen walls due to efficient stoves is very less. On ‘cool pots’, thechilling effect also contributes to the deposition of soot. If the potsare smooth, less soot is deposited on them. Fire wants to keep away from coming in contact with surfaces,and move forward. Therefore, it is important to keep the walls of thecombustion chamber straight and smooth to minimize heat loss dueto conduction. Many people focus more on what the stove looks likefrom the outside, rather than the inside. When constructing a stove,especially using materials like bricks and clay, one should make surethat the walls in the combustion area are smooth on the inside.
  55. 55. 46 Understanding StovesConvection Convection currents within a stove always move from bottom totop. They are formed due to pressure-difference: high pressure atthe bottom of the stove and very low pressure at the top. Thisdifference in pressure is, in turn, due to the difference intemperatures: high temperature right below the top creates an areaof low pressure and colder, heavier air at the bottom of the stovecreates high pressure. The convection currents support the mixing ofthe air with combustible gases inside the stove and sustain the fire. Sometimes, the cold air in the stove has a dampening effect onthe fire. Part of the energy is also consumed for preheating the airbefore it can join the combustion / pyrolysis zone. Preheated air iseasily combustible. All the air streams (Primary air, Side air,Secondary air and Tertiary air) support the formation of convectioncurrents. The intensity of the currents is reduced by the drop inpressure due to air flowing in from the side and secondary sources.In Magh 3G stoves with primary air, side air and secondary airsources, the flame is dancing rather than rushing. If the convection currents are stronger after the initial burning ofthe fuel, and when the stove is hot, the size of the air holes is not amajor concern. In that case, more air is easily sucked into the flame.When running a stove on high power, the excess intake of air formsinto a strong convection current. This reduces the efficiency of thestove. In windy conditions (that add to the draft), and in forced draft
  56. 56. Understanding Stoves 47stoves, the convection currents are stronger. It is due to convectioncurrents that a stove continues to burn when started. Many traditional stoves have to be warmed up. This is doneusually by operating the stove at high power for some time. Once astove is extinguished, it has to be blown into to rekindle the flame.The blowing is also meant to initiate the convection current. Theprimary air, preheated by the charcoal embers at the bottom of thegrate, is crucial for continuous combustion in the stove.
  57. 57. 48 Understanding StovesRadiation Radiation is another mode of heat transfer that many stove usersdo not understand easily. One of the best examples to explain it ishow, without any media, heat is transferred between the sun and theearth. By placing hands around the stove, one can feel the heat fromthe stove; that is radiation. In less insulated and metal stoves, theradiation is more easily perceived. Heat-loss due to radiation occurs in all directions. Radiation alsotransfers heat to the bodies of those cooking on the stove. In placeswith colder climates, it is radiation through which interiors of homesare heated. Cooking food is a culture and the recent adoption ofmodern cooking methods is not a substitute for traditional biomass stoves
  58. 58. Understanding Stoves 49No Smoking “Smoke is smoke” and too muchexposure to smoke is always bad. In manycountries, governments have bannedsmoking in public places. When millionsof people are being killed due to indoorair pollution globally, why is smoke notbanned inside every house? Sometimes,exposure to smoke released by cookingstoves every day is more harmful thansmoking 100 cigarettes. There is, ofcourse, a difference: cooking is acompulsion and exposure to smoke from Picture 42 Similarly theinefficient stoves is a hazard, whereas campaign for good stoves issmoking cigarettes is a habit and neededvoluntary. Overall, kitchens are not thehighest priority for most people.  On Smoke, SootKitchens are smaller than other and the emissions fromrooms in a house. The money cook stoves.spent on constructing a kitchen bypoor people is always minimal, and usually less than the amountthey spend on toilets. Even in government housing schemes,kitchens are not given priority.
  59. 59. 50 Understanding Stoves Of late, many youth haveinquired about biomass stoves.They have wanted to give one totheir mothers / grandmothers, whoare still cooking on smoky,inefficient ones. Many olderwomen in rural areas are afraid ofLiquefied Petroleum Gas (LPG) Picture 43 Children usually close tostoves, which they think are their mother while cooking are exposed todangerous to operate. smoke Cooking is a compulsion and exposure to smoke fromstoves is an inevitable hazard, whereas smoking tobacco is a voluntary habit and for pleasure
  60. 60. Understanding Stoves 51Soot and smoke Pieces of carbon left in thestove after cooking is calledcharcoal. Soot is made up of verysmall pieces of carbon flying outfrom a fire. Smoke includes soot,moisture, combustible gasesPolycyclic Aromatic Hydrocarbons(PAHs) and Volatile OrganicCompounds (VOCs). Soot is seenon the stove, the utensils used forcooking and on the kitchen walls.It is a highly undesirable Picture 44 Soot accumulated on thesubstance: black soot in the air walls of kitchencontributes towards globalwarming. Black soot that reachesand is deposited on ice capsreduces their ‘albedo’, orreflective power. With a loweredalbedo, ice absorbs the heat thatit could have otherwise reflected,and melts faster. Picture 45 Soot accumulated on the roof of a kitchen
  61. 61. 52 Understanding StovesPicture 46 Circular frames made of clay / metal used for prevention of soot on cookingutensilsPeople do not take pride in their kitchen. It is the last place in the house shown to a visiting guest
  62. 62. Understanding Stoves 53Emissions The pyrolysis and combustion ofwood in biomass stoves produceatmospheric emissions of particulatematter: carbon monoxide, nitrogen oxides,organic compounds, mineral residues and,to a lesser extent, sulphur oxides. Thequantity and type of emission is highlyvariable, depending on a number offactors including the stage of thecombustion cycle. During the initialstages, after a new wood charge isintroduced, emissions (primarily VOCs)increase dramatically following the initial Picture 47 Shooting sootperiod of rapid burning. There is also a particles from a stovecharcoal stage in the cycle, characterizedby slower burning and lowered emissions, but invisible andundetectable carbon monoxide emissions are then high. Emissionrates during this stage are cyclical, characterized by relatively long xvperiods of low emissions and shorter episodes of emission spikes .
  63. 63. 54 Understanding StovesAir for combustion Depending upon the point of  On sources of air forentry, air entering a stove can be efficient combustion –classified as Primary Air, Side Air, Primary air; Side air;Secondary Air and Tertiary air, Secondary air; Tertiary air. Types of burners, concentrators and air controls. Grate and itsPrimary air functions. This is the air entering thestove mainly from the bottom ofthe grate / underneath thebiomass fuel. The excess flow ofprimary air will lead touncontrolled combustion. Primaryair is always required in lowamounts. If it is preheated beforereaching the fuel, the combustionis efficient and the stove performsbetter. After the preliminarycombustion, the embers at the Picture 48 Primary air enters underneath a gratebottom of the grate serve topreheat the primary air. In TLUD stoves limited amount of primary airentry leads to the release of woodgas.
  64. 64. Understanding Stoves 55Side air In a majority of the traditional stoves, this is the only source ofair. Side air gushes in through the fuel feed opening. In ‘three-stone’stoves, air gushes into the combustion zone from all three sides. Toomuch air streaming into the stove (for example when it is situatedoutdoors, in the open) has a dampening effect on the flames.Controlling the gushing side air is very important. In Magh 3Gstoves, a shutter controls the entry of side air. If the mouth of thefuel feed is completely closed due to overfeeding of fuel wood (ascould happen in traditional stoves), the flame could be extinguishedand release excess smoke. Small holes on the sides, as provided inMagh 3G, also keep the stove from extinguishing. In good stoves,the fuel feed opening should be made smaller, as there is alreadyscope for primary air to enter through the grate. It is easy to design a stove for a specific fuel
  65. 65. 56 Understanding StovesSecondary air Use of secondary air is an important feature of TLUD stoves. Thisfeature can also be incorporated in any stove (with fewer holes thanTLUDs); it will help the complete combustion of smoke. In stoveswithout chimneys, this is an especially useful feature. Preheatedsecondary air helps in clean combustion of the gases. The secondaryair can be preheated by passing the air through the hot parts of thestove before it enters the combustion zone. Picture 49 Source of secondary air, side air and primary air in Magh 3G stove
  66. 66. Understanding Stoves 57Tertiary air Tertiary air helps in complete combustion of the gases anddrastically reduces emissions. Preheated tertiary air is morebeneficial than cold tertiary air. This is a rare feature, not found in amajority of stoves. Picture 50 Tertiary air enters after secondary air entry into combustion zone
  67. 67. 58 Understanding StovesBurners Burners are the components in stoves that ensure completecombustion of fuel. In stoves with burners, there are four types of airentering the pyrolysis / combustion zones:T - Tertiary air - > FS - Secondary air -> I R <-Si - Side air EP - Primary air - > Burners, pot rests, grates, ash containers, handles and safetyscreens etc., are important components of stove design. The burners shown below can work with forced air or naturaldraft air.
  68. 68. Understanding Stoves 59The primary air holes from the sides are The primary air holes at the bottom are suitable for small size TLUDs. suitable for large size TLUDs.Side air is a feature for largesize and tall The central conical primary air facility isTLUD stoves, in which the biomass is fed suitable for large size TLUDs. from the side.
  69. 69. 60 Understanding StovesThe air from the central pipe also a source The pattern of holes incorporating flow of of primary and secondary air. three types of air - Primary, Secondary and Tertiary air for complete combustion. Gradient secondary air holes are suitable Double secondary air holes are suitable forfor Tall TLUDs, which provide the primary big-size TLUDs. air initially until the biomass collapses after combustion.
  70. 70. Understanding Stoves 61Option of fins in the burner for preheating Steel wool around metal combustion air - through surface contact, increased chambers for preheating the air. surface area and increasing the speed of air entry. Fins for preheating secondary air. The very small holes used for the central pipe for primary and secondary air.
  71. 71. 62 Understanding Stoves Primary air, secondary air and side air flow into combustion zone of the stove. Thiscomponent also acts as a slide – loose biomass fuel such as wood shavings, groundnut shells, etc., can be fed in.
  72. 72. Understanding Stoves 63 The pyrogas from a gasifier is forced out The secondary air is forced. It sucks the and secondary air enters naturally mixes pyrogas from the gasifier and mixes well and combusts. before burning. The burner need not be upwards. By rotating the burner, one 9has options to incorporate different types of gasifiers . 9 Gasifier is the technology for Gasification (for example Top Lit Updraft Gasifierstove / woodgas stove). Gasification is a process that converts organic or fossil-basedcarbonaceous materials into carbon monoxide, hydrogen and carbon dioxide. This isachieved by reacting the material at high temperatures (>700° C), withoutcombustion, with a controlled amount of oxygen and / or steam. The resulting gasmixture is called syngas (from synthesis gas or synthetic gas) or producer gas and isitself a fuel.
  73. 73. 64 Understanding StovesSimple TLUD batch load gasifier – loaded Side load gasifier. from top. Top load gasifier Top load gasifier A – Fire, B- Secondary Air, C-fuel feed, and D- Primary Air and grate for ash removal (Note: Arrow directions indicate air draft also) .
  74. 74. Understanding Stoves 65Concentrators Concentrators are simpleobstructors that help mixing of airand gases and ensure completecombustion. They are of varioustypes. Simple concentratorsconstrict the flow of gases into asmall hole. Some concentratorsachieve this by using of a numberof small holes. Picture 51 A simple tin stove with a concentrator
  75. 75. 66 Understanding Stoves Picture 52 Top view of concentrators - red colour is the fire Picture 53 Conical concentrators – Side view
  76. 76. Understanding Stoves 67Air controls With scope for regulatedentry of all the kinds of airs -primary, side, secondary andtertiary, a stove can be usedeasily even outdoors. Bycontrolling the entry of air intothe combustion zone, any stovecan be used to its maximumefficiency. With enoughexperience and understanding,one can cook even on a three-stone stove with great efficiency. Picture 54 Butterfly valve for For efficient combustion, the controlling airflowuse of primary air should beminimal as compared to side and secondary air. When a stove runsat high power, excess draft is created and flames are intensified. Thisreduces its efficiency. In stoves with chimneys, the excess draftcreated due to the chimneys reduces their efficiency. By having aircontrols within the chimney, the efficiency of the stove can beimproved. Butterfly valves can be inserted in the chimneys for thispurpose. Institutional stoves should have thermometers installed in them,because it is otherwise difficult to observe the temperatures withinthe stove. Two thermometers – one at the bottom of the pot and
  77. 77. 68 Understanding Stovesanother at the exit point in the chimney — are preferable. Adampener (for example Butterfly valve) can be inserted into thechimney for controlling the heat lost through it.By careful observation and monitoring measurements, one can tame the flames as desired
  78. 78. Understanding Stoves 69Grate and stove bottom In domestic stoves, the gap between grate and bottom of astove could be around 1.5 to 2 inches. Seldom do people removeash while cooking. Ash being a good insulator protects the bottomof the stoves from overheating. The embers falling beneath the gratehelp to preheat the primary air entering the stove. However, the ashhas to be removed from time to time to make sure that themovement of the primary air is not blocked. In institutional stoves, this gap can be sized as per the specificneeds of the establishment. In a stove used for cooking for 200people, the gap should be around 6 inches. In all cases, a mechanismto control the primary airflow helps efficient combustion. The aircontrol could be in the form of a sliding shutter, a door with holes, asliding door, a butterfly valve, etc.
  79. 79. 70 Understanding StovesPots and efficiency The efficiency of a stove is theamount of heat (energy) that  On pots and theirneeds to be transferred through it efficiencies – heat transfer,for the ultimate purpose, which is special features to pots forcooking the contents in a utensil. heat transfer, size of theIt should be noted that heating pots, pot rest, air gap andthe utensil is not the ultimate skirts for pots.purpose. The same stove couldexhibit different efficiencies under different conditions. Therefore,one needs to consider the average efficiency as its defining feature.One of the main factors affecting the efficiency of a stove is its mass. There are more toilets displayed in museums than stoves
  80. 80. Understanding Stoves 71 Picture 55 Stoves designed by Dr N Sai Bhaskar Reddy at “Stoves Museum”, GEO Research Center, Peddamaduru Village, Devaruppala Mandal, Warangal District, Andhra Pradesh, India
  81. 81. 72 Understanding StovesHeat transfer Pots made of material such asaluminum or shining steel reflectpart of the heat transferred tothem. Some metals – such assteel, aluminum and copper -have a higher capacity for heatabsorption and transfer ascompared to earthen potstraditionally used by the poor.Sometimes, people apply soil tothe pots in order to increase theirheat absorption capacity. Anotherimportant advantage of thispractice is that it minimizes theamount of soot accumulating onthe utensil, making it easier toclean. Applying soil to utensils isa common practice in many partsof India. Metal pots that transfer alarge proportion of the heat Picture 56 Soot released fromreceived to their contents, do not burning of pine sticksdo so uniformly. When stoves runat high power, the food is not cooked well. The flavour, taste andaroma of the food also depends on the temperature at which it is
  82. 82. Understanding Stoves 73cooked. The temperature range 300 – 600 degrees centigrade isideal. Cooking is also a means for releasing the nutrients of the food,in order to maximize its value to the consumer. At highertemperatures, the aromatic ingredients of the food are also lost asvolatiles. Cooking food is a culture and tradition developed through theuse of biomass stoves over centuries. Modern means of cooking donot achieve the same taste, flavour and nutrient value as cooking onbiomass stoves. Some of the common ways of high temperaturecooking used today are: LPG stoves, microwave ovens, electricstoves, induction stoves, etc. High pressure and temperature cookingis done by using pressure cookers. During high power cooking, metal pots made of aluminum andsteel transfer excessive heat to the food, and not uniformly so. Thefood cooked in earthen pots is more tasty and nutritious, due to theslow and low transfer of heat to the food that they facilitate.However, this is not the preferred mode of cooking now-a-days.New cooking methods have to adapt to modern sources of fire /heat.
  83. 83. 74 Understanding StovesFoils for pot To certain utensils, which are fixed to the stoves, thin metallicfoils can be fixed to increase their efficiency. Many sugarcanefarmers produce jaggery as a household-level business. Thesugarcane juice is boiled in large shallow pans fixed to large-sizedbiomass stoves. The heat transfer to the pans increases due to thinmetal foils fixed to them. Of the cost of a house, a good stove costs one to two per cent and a toilet five to ten percent
  84. 84. Understanding Stoves 75Pot sizes Utensils used for cookingcome in different shapes andsizes: cylindrical, tapering fromthe middle of the pot, semi-spherical, bowl-shaped, etc. Potsof the same volume but differentsizes (height versus diameter) and Picture 57 While cooking rice on ashapes have different efficiencies. large scale, embers are placed over theA tall pot is less efficient than a lid at the endwide-bottom pot of the same volume. Similarly, pots with sphericalbottoms are embraced by the flames more easily. More air, then, canbe drawn into the flames as they climb up along the sides of the pot.Thus, heat is transferred not only from the bottom, but also from thesides. As the pot-rests are fixed, when round bottom pots are used,there is an excess air gap and the efficiency of the stove comesdown. For making curries, pots with hemispherical bottoms andtapering tops are most suitable. Cooking curries require frequentstirring. Therefore, due to the tapering tops, the loss of heat fromsuch pots is low. For cooking rice, flat-bottom cylindrical pots areused. In cooking rice, water is the main medium. Therefore,cylindrical, flat-bottom, low-height pots are able to distribute heatuniformly. For large scale cooking, flat or slightly convex bottompots with tapering mouths are preferred. In a big utensil, the rice atthe top often stays uncooked, so people often place charcoal emberson the lid after cooking.
  85. 85. 76 Understanding Stoves One observes that hemispherical / curved / almost flat pans areused for frying, roasting, baking etc. They are open and not veryefficient. For boiling milk, tall utensils are preferred. They are lessefficient and lose some heat due to radiation, but their shape keepsthe milk from boiling over. Promoting less efficient cooking stoves knowingly is a crime
  86. 86. Understanding Stoves 77Pot rest Pot-rest is one of the mostimportant components in a stove.The durability of the pot rest isvery critical, because the pot hasto bear all the weight of theutensil with food. Parts of the pot-rest are subject to the highesttemperatures in a stove duringcooking. Where large size pots areused, they are inevitably dragged Picture 58 Metal Pot restover the pot-rest. To withstand all that, it has to be one of thestrongest and most durable parts in the stove. In a three-stone stove, theportions of the three stonestouching the pot act as the pot-rest. Domestic three-stone stovesare relatively small in size, andmostly made of stones (orsometimes bricks). In clay andmud stoves, small pebbles /stones are used as the pot-rest. Picture 59 Pot covered outside withOften, women maintain and mend a layer of clay, for easily cleaning the soot after use and to increase efficientstoves using plaster made out of heat transferclay and cow-dung. They do notforget to plaster over the pot-rests as well. Pot-rests made of forged
  87. 87. 78 Understanding Stovesiron, wrought iron or iron are also used widely; they are moredurable. In some stoves, a dummy circular frame rests above the pot-rests. This frame prevents soot from forming on the sides of theutensil, besides acting as a pot rest by itself. Picture 60 In large scale cooking the pots are sometimes dragged – often leading to damage of pot rests
  88. 88. Understanding Stoves 79 Pot Rest Designs Simple pot rest Simple pot rest Pot rest with circular holes Pot rest with gaps
  89. 89. 80 Understanding Stoves Pot rest with gaps The radial pot rest sitting on three stones, increases stability of the pot Pot rest with a chimney Radial movement of heat and fire, to increases the surface contact with the pot and also reduces emissions
  90. 90. Understanding Stoves 81Air gap In all non-chimney stoves, an air gap is required between thestove and the utensil. This allows a draft, without which the flame willnot move upward and make contact with the pot. Too much or toolittle air gap reduces the efficiency of the stove. In domestic stoves,the air gap is about one inch. In a charcoal stove, the gap betweenthe fuel and utensil should be even less, since there are noaggressive flames and cooking happens mainly through radiationand convection. Flames need to accelerate before hitting the pot for efficienttransfer of heat to the pot. Too much cold air entering thecombustion zone sometimes dampens the flame and leads tosmoke. The ideal air gap also varies with the shape and size of thepots. In general, almost all the pots used for cooking are cylindricalwith circular bases. In keeping with this shape, the combustionchambers are usually cylindrical as well.
  91. 91. 82 Understanding StovesSkirts for pots Although skirts improve the efficiency of stoves, they are rarelyused in households. With well-designed skirts, the air gap can bemaintained perfectly, and the heat can be forced onto the sides ofthe utensil. When the cooking is simple-- say with few utensils-- it isconvenient to have a skirt for each pot. When pot shapes and sizesare diverse, flexible pot skirts can be used. In practice, pot skirts are used mostly in institutional kitchens atbig establishments: such as schools, restaurants, etc. In suchkitchens, the pots are sometimes fixed to the stoves and the perfectair gap is maintained. A pot is more stable on three stones rather than on fourstones, therefore there are “three-stone stoves” being used widely
  92. 92. Understanding Stoves 83Chimney stoves Chimney stoves have greatlyreduced exposure to indoor airpollution. Any stove with achimney reduces emissionsconsiderably. The cooks’exposure to heat is also greatlyreduced, because in chimneystoves there is no air gapbetween the pot and stove.Sometimes, chimneys withoutdampeners create excess draft,leading to excessive combustionof fuel. The placement of a Picture 61 Smoke including moisturechimney does not make the from an institutional stovesmoke disappear completely.Sometimes, the smoke comingout of the other end of thechimney is an area of concern. Chimney stoves are notnecessarily more efficient. In fact,most often, they are less efficient.Their rushing flame does notconduct heat to the pot very well.Moreover, chimney stoves are Picture 62 Butterfly valve used in a chimney
  93. 93. 84 Understanding Stovesexpensive. In the case of domestic stoves, the chimney sometimescosts as much as the stove. Besides, their upkeep is difficult. It takesa brush with a very long handle to clean a chimney. In villages,people use leafy branches from trees. If not cleaned frequently, thechimney is blocked with soot, which reduces the stove’s draft. Manya times, villagers fail to maintain their chimneys, which are thenremoved and used for other purposes (as drainage pipes, forexample). At times, the heat lost in chimney stoves is as much as theamount of heat required for cooking! Concrete chimneys are less durable. They have to withstand veryhigh temperatures. Any stove design with a chimney can be sold as agood stove with low indoor air pollution, but need not be efficient orpollution free. In cold countries, the excessive heat channeledthrough the chimney is used for heating rooms / water and warmingthe beds, etc.
  94. 94. Understanding Stoves 85Special features in stoves There have been efforts todesign stoves in which steam oratomized water is introduced intothe burning fuel, to splithydrogen from water to helpcombustion. Very few stoves havethis feature and the increase inefficiency is very low. The amountof energy required for splittingwater (H2O) into hydrogen andoxygen is very high. It is only at2200 °C that about three percent Picture 63 A metal tube coil for steam generation used in a stoveof all H2O molecules aredissociated into various combinations of hydrogen and oxygenatoms - mostly H, H2, O, O2, and OH. Nevertheless, the idea ofincorporating multi-fuel mixes is in its infancy and we will mostprobably see more such designs in the future. Water will be an important source of fuel in times to come.When steam is added in a blue flame, orange / pinkish flames arevisible. Some people have observed increased efficiency in a stoveupon introduction of steam. The increase in efficiency could be mostlikely due to the decrease in the rate at which combustible gases arebeing formed in the stove. Most biomass stoves generate heatbetween 300 - 700 degrees centigrade under the pot, and the
  95. 95. 86 Understanding Stovesamount of hydrogen gas generated from the steam would be verylittle. Thermoelectric generators (also called thermogenerators) aredevices that convert heat (temperature differences) directly intoelectrical energy. This phenomenon is called the "Seebeck effect" (orthe "thermoelectric effect"). Their efficiency is typically around 5 – 10%. The University of Nottingham has designed a biomass stovewith thermoelectric power generation capability, calledSCORE (Stove for Cooking, Refrigeration and Electricity).
  96. 96. Understanding Stoves 87Charcoal from stoves Many stoves achieve higher efficiencies when the charcoalcontinues to remain in the stoves (including TLUD stoves). People arereluctant to remove charcoal left behind after previous cooking, andcontinue to cook. In such cases, the stove functions as charcoalstove. The charcoal yield varies across types of stoves. For example,in Magh 3G stoves it is about 15 % by weight, in TLUD stoves theyield is about 25 %. Picture 64 Charcoal yield from Magh-1 gasifier stove Sometimes a scientist is successful in the lab, but fails when he goes out to the community
  97. 97. 88 Understanding Stoves Picture 65 A girl cooking on an efficient stove in the open
  98. 98. Understanding Stoves 89Facilitation of domestic stoves Facilitating good stoves requires a number of steps: Reconnaissance: This involves a study of existing stoves, biomassand other fuels being used in a geographical area. Withoutreconnaissance and a preliminary understanding, stoves should notbe recommended directly. Picture 66 Demonstration and Picture 67 Seeing is believing –comparison of traditional and efficient comparing the wood saved usingstoves traditional and efficient stove Awareness and sensitization: Intensive awareness andsensitization should be created at the community level regardingbiomass conservation, and about the need to adopt efficient stoves.The sensitization creates a sustainable motivation among thecommunity. Awareness can be created through various means: Wall
  99. 99. 90 Understanding Stoveswritings, posters, skits, plays, workshops, demonstrations, meetings,presentations, films, videos, press, etc. Design: The stove designshould be simple, preferablymade using locally available rawmaterial. Testing stoves andsubsequently improving theirdesign is an integral part of thedesign process. Picture 68 Women with least skills can be easily trained on certain stove Demonstration: Explaining designsthe stove’s design andperformance with the community through village-leveldemonstrations / workshops is great for eliciting communityparticipation and awareness. Piloting: One should select leaders from the community to helpwith piloting the stove, creating awareness, and as a source of anoverview of the community feedback based on which the designcould be improved. Scaling Up: Training youth, women, artisans, masons and so on,in the construction and maintenance of good stoves would helpscale up their demand and supply. By creating linkages andconverging with various agencies, funds from governments, donorsand other organizations can be accessed. This would also helpdisseminating the stove over a large area and expanding demand.
  100. 100. Understanding Stoves 91 Monitoring: Monitoring the performance of the stoves should bea continuous effort. Therefore, maintenance and related servicesshould be offered by trained local people. Achievements / Results: Documentation of the number of goodstoves being adopted by communities, by location. Recognition: Recognizing all the stakeholders involved directly orindirectly in the promotion of good stoves – members of the targetcommunity, facilitators, donors, other support organizations,scientists and institutional partners involved in the process. Escalating prices of a stove for the sake of business or schemes affects the purchasing power of the poor
  101. 101. 92 Understanding StovesInstitutional Stoves Institutional stoves, alsocalled community stoves, aredesigned for large scale cooking.Domestic cooking stoves, on theother hand, typically meet thecooking needs of a family. A majority of the institutional Picture 69 A makeshift three stonestoves currently in use are three- stove used in a schoolstone stoves, which are highlyinefficient. These stoves require less space and can be moved easilyto any place as per convenience. In institutional stoves wood isused as fuel more often than in  On Institutionaldomestic stoves, in which stoves – preparations andhouseholds often use crop residue installation of institutional/ twigs branches / etc., very often. stoves; stoves efficiency;This type of use has potential affect and adaptation factors.on the environment.
  102. 102. Understanding Stoves 93 Even though efficient stovesfor institutional kitchens appearmore expensive initially, thesavings made on wood over aperiod make them less expensiveoverall. Picture 70 Hazardous way of lifting and bringing down the cooked food from stovePicture 71 An efficient institutional stove Picture 72 Testing an institutional stove in a school

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