cooking stoves and space heating in the people's republic of china by hang zhu

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COOKING STOVES AND SPACE HEATINGIN THEPEOPLES REPUBLIC OF CHINA

WA S H I N G TO N - UN V PLSAINT LO UI S , M I SSO URI 63 1 30

BYHANGZHUREPORT NUMBER

THA/CDT 8 3 / 1

VAY)1983

r


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DEPARTMENTOF TECHNOLOGY AND HUMAN AFFAIRSANDCENTERFOR DEVELOPMENT TECHNOLOGYWASHINGTONUNIVERSITY

SAINT LOUIS'M I S SO U R I6 31 30

Report NumberTHA/CDT-83/1 M a y , 1983

COOKNGSTOVES AND SPACE HEATINGIN THEPEOPLES REPUBLIC OF CHINA

HANGZHU

The m a t e r i a l s i n t h i s r e p o r t w e r e t a k e n f r o m a M as t e r s t h e s i se n t i t l e d H o us e ho l d E n er g y C on su mp t i on i n t h e P e o p l e ' s R e p u b l i co f C h i n a b y H an g Z hu . C o n c l u s i o n s a n d v i e w s ex p re s se d i n t h i sr e p o r t a r e t h o s e o f t h e a u t h o r an d d o n o t n e c e s s a r i l y r e p r e s e n tt ho se o f t h e D e p ar t me n t o f Te c h n o l o g y a n d Human A f f a i r s , t h eC en te r f o r D e ve lo p me n t Te c h n o l o g y , o r W a s h i n g to n U n i v e r s i t y .


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PREFACE

This re po rt contains in form at io n on cookstoves andspace heat in g i n th e People's Republ ic o f China which,to my knowledge, i s gen eral ly n ot w ide ly avai lab l e e ls e-where. H a n g Zhu was abl e t o assemble t h i s inf orm at i onas pa r t o f h i s master 's th es i s s tu dy, "Household EnergyConsumption in th e People's Republ ic o f Ch ina." O t h e rpor tions o f th is the s is have been publ ished i n Energy:The In te rna t iona l Journ a l . W e hope th i s r ep or t w i l lprove usefu l t o those in te res ted i n t he to p i c as we l las those who seek t o fo st er good rel at io ns between thepeople o f China and the people o f th e Unite d States .I t was i n t h i s s p i r i t t ha t t he s t udy was under taken.

Robert P. MorganDirectorCenter f o r Development Technology


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Copyright 0 by Hang Zhu


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iv

TABLE OF CONTENTS

LIST OF TABLESLIST OF FIGURES

Page

vi

ChapterI. STOVE DESIGNS FOR COOKING IN URBAN AREAS 1

1.1 Bi tu mi no us Coal Cookstoves 21.2 B r i q u e t Cookstoves 31.3 Comb-Shaped Coal Cookstoves 81.4 I m pr o ve d Comb-Shaped Coal Cookstoves 1 31.5 Medium-Btu Town Gas Cookstoves 2 1References and Footnotes 2 4

II . STOVE DESIGNS FOR COOKING IN RURAL AREAS 2 52.1 A g r i c u l t u r a l Residue Cookstoves 2 62.2 F i rewood Cookstoves 2 92.3 S o l a r Cookstoves 3 12.4 B i o g a s Cookstoves 3 5References and Footnotes 4 6

I I I . HOUSEHOLD ENERGY CONSUMPTION FOR SPACE HEATING 4 83.1 Space Heating i n Urban Areas 4 83.2 Space Heating i n Rural Areas 5 43.3 Solar Heated Homes and Solar Water

Heating Systems 5 9References and Footnotes 6 8


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LIST OF TABLES

Pageable

1.1 T h e r m a l E f f i c i enc y Tes t Res ul t s o f I mprovedComb-Shaped Coal Cookstoves 1 9

3.1 T h e Results o f a Compar ison o f Steam-Boi ler andWater B o i l e r Systems 5 2


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LIST OF FIGURESFigure Page1.1 Bituminous CoalCookstove 41.2 Iron Sheet Bri qu et Cookstove 61.3 Comb-Shaped Coal Cookstove 91.4 AS imple Mechanical Devi ce f o r Making Comb-ShapedCoal 111.5 Improved Comb-Shaped Coal Cookstove w i t hDownward Combustion 141.6 Improved Comb-Shaped Coal 171.7 J801 Type Improved Comb-Shaped Coal Cookst ove 201.8 Medium-Btu Town Gas Cookstove 222.1 Agricultural Residue Cookstove 282.2 Firewood Cookstove 302.3 Improved Chinese Firewood Cookstovewith a Bellow Box 322.4 Solar Cookstoves Manufac tured i n ShanghaiNo. 15 Radio Manufacturing Plant 342.5 Recent Chinese Biogas D ig es te r Designs fr omthe People's Republ ic o f China 372.6 Diagram o f Chinese Small-S cale Biogas Di ge st erUsed i n th e Ru ral Household 392.7 Earthen Biogas Cookstove wi th Mixi ng Groove 412.8 Biogas Cookstove Used i n Chinese Rural Household 422.9 Safety Pressure Gauge . . . . . . . . . . . . . 443.1 Cast I r o n Coal Cookstove Used i n t h e Wi nt er f o rHeating 553.2 Structure o f Chinese Bed - - Kang wi th aStove a t i t s Base 57


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Figure Page3.3 S t r u c t u r e o f Chinese Kang w i t h anImproved Heating System 5 83.4 C l o s e d Loop So lar Water Heating System Ut i l i z in gAnti freeze 6 33.5 S o l a r Water Heating System (300m2) w i t h C a p a c i t yfo r Supplying Hot Water f o r 1,000 People t o 6 4take Showers3.6 S o l a r Water Heat ing System Used in Apar tmentBui ldings 6 53.7 S o l a r Bathhouse i n L inmingy ing Produc tion Br igadeo f Changzi yi ng Commune Dax ing Count y, Be i j i n g 6 6


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CHAPTER I

STOVE DESIGNS FORCOOKING IN URBAN AREAS

Af te r h is t r i p to China, Marco Po lo no t on ly no t i ced theChinese noodle, which he l a t e r made in t o spa ghe t t i , b u t he al sospoke o f the extensive use o f a k i nd o f black ston e dug f rom mountainsand burned l i k e f i rewood a l l ove r Cathay. S t o n e coal was i n use i nChina be fore the Chr is t ian e ra . A f t e r two thousand years, t heChinese are s t i l l us ing i t as the major fue l a t home.

Barring medium-Btu co al ga s a nd comb-shaped c oa l, whic hsupply 10 perce nt and 31 perc en t o f urban households w i th cookingfue l resp ec t i ve l y , about 37 .5 percent o f t he urban househo lds s t i l luse b i tuminous coal f o r cooking; 15 percent use coal br iq ue t te s .The e f f i c ien c ie s o f coa l stoves used i n t r ad i t io na l ways have no tincreased s ig ni f i ca nt ly through the years . T o maximize the ov era l le f fi c i en c y o f c ookin g f u e l u t i l i z a t i o n , t h e t he rmal e f f i c i e n c y o f acookstove i s an impor tan t parameter. T h e overa l l e f f i c ie nc y o f fue lu t i l i z a t i o n i s a l s o c l os e l y as sociat ed w i t h t he c hoi ce o f f ue l usedin the s tove , and the spe c i f i c heat o f t he mater ia l o f wh ich thecookers are made. O v e r the past t h i r t y years , th e Chinese haveattempted t o improve t he ov e ra l l e f f i c i e nc y o f f ue l u t i l i z a t i o nthrough the improvement of cookers, using aluminum instead of castiron t o make cookers and pressur e cookers, by changing th e cookin gpatterns and by improving th e thermal e f f ic ie nc ie s o f cookstoves.

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Because o f t he way in which fue l i s u t i l i ze d i n the coal cookstoves,requiring about 30 percent o f fuel t o bank up the f i r e between cookingtimes and through the n ig ht , t h i s attempt did n ot reach the desiredgoal t o increase the end-use eff ic ien cy gr eat ly.

Most o f the designs and technica l improvements o f cookstovesin China over the past t h i r t y years were based on the f ollowingrequirements: .

1) t h e need to use avai lable local f u el ;2) t h e need to increase the thermal eff i ci en cy o fcookstoves;3) t h e need to manufacture cookstoves a t low cos t;4) t h e need to popularize the stoves eas il y.The improvement o f the thermal e ff ic ie ncy o f a cookstove deals

only wit h one aspect o f the problem and does not address th e en ti reproblem of maximizing the overal l ef f ici en cy of fuel u t i l i za t i on .Also, because o f economic li mi ta ti on s , China was no t able to makerapid progress i n increasing the overal l ef f ic i enc y of fuel u t i l i -zation by f u l l y developing medium-Btu coal gas o r by u t i l i z i n g someother fue l in stead o f coal i n the home.1.1 Bituminous Coal Cookstoves

Apopular type o f bituminous coal cookstove i s usual ly b u i l tof bri cks wit h a combustion chamber at i t s top and an opening a t i t sbase which serves t o provide coal breeze* drainage and a i r fl ow.

*A substance l e f t when coke or charcoal i s burned, used as a f i l l e rfor concrete, et c.

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Normally i t i s loca ted i n the kitchen and the chimney o f the stove goesthrough the kitchen ro of to the outside. F u e l i s added from the topopening o f the combustion chamber, and coa l breeze and ashe are drainedfrom the opening a t the base of the stove. ( S e e Figure 1. 1) Becausethe bituminous coal has a lower energy content than t he an th ra ci ti ccoal and th e design o f the bituminous coal s tove has no t been broughtto a stage of high ef f i ci en cy, almost twice as much fue l i s used i na bituminous coal cookstove as i s used i n a br ique t cookstove. Amongall coal cookstoves, t he bituminous coal stove has the lowest thermalef f ic iency, about 15 percent. ( 1) T h i s low ef f ic iency is pa rt l yassociated with the 30 percent of fuel used for banking up the firebetween cooking times and through th e ni ght .

The Chinese have l i t t l e experience i n converting bituminouscoal in t o coke or other forms at su ff i ci en t l y low cost to be used f o rcooking in households. F o r t h i s reason, bituminous coal cookstovesare s t i l l used quite extensively i n urban households, especi ally inthe northeastern and cent ral pa r ts o f China, where bituminous coalis used as t he major fu el f o r cooking i n households. A 1981 survey

of 44 urban households conducted i n Shenyang o f Liao ning prov inceas pa r t o f th is s tudy in d icate d th at b i tuminous coal consumpt ionfor cooking i n these households ranged f rom 150 kg t o 275 kg pe rmonth.

1.2 B r i q u e t CookstovesThe Chinese have used briquettes for several decades. About

45 years ago, an American scholar, Rudolf P. Hommel returned fromChina and wrote a book cal le d China A t Work, i n which he described

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Figure 1.1. Bituminous coal cookstove

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how the Chinese were making br ique ttes and using them a t thattime. (2)

"The Chinese solved i n the i r own pecul ia r way the pr o-blem o f how best t o use t h i s f u e l , as I had many oppor-tun iti es t o not ice i n Chekiang and Kiangsi. T h e powderedcoal i s mixed with clay and with t he addit ion o f water thewhole mass is formed int o a paste. I n th is moist condit ioni t is put upon a woodf ire where i t readi ly ign i tes. I tburns very slowly wit h a red glow and gives o f f a powerfulheat. I n some places, notab ly i n Kweichow, Szechuan andPeking, a s im il a r mixture i s placed i n to molds whence i tissues as b riquettes i n the shape of truncated cones.These af te r being dr ied i n the sun are ready to be usedfor fue l . "

5

Today, t he Chinese s t i l l use the same concept t o make briquetteswith diff er en t machinery. Br iq ue tt es are usually made o f a nth rac it i ccoal. Powdered anthracite is sent to a mixer with water and clay theni t is t ransported t o a br iquet-forming machine. A f t e r the b r iq uet tesare formed, they are delivered to a drier using belt machines. Thef inal step i s to dis tr i but e them throughout coal shops t o di f f ere ntresident ial areas f o r sale.

The conventional b r iq ue t cookstove i s a non-bank-up f i r e type.I t has a shor te r combustion chamber than t ha t o f a bank-up f i r ebriquet s tove. T h e combustion chamber has a tapered shape, wi th asmall opening a t the top and lar ge opening a t the bottom. T h e bodyof the br iquet cookstove i s made o f ir on sheet and looks l i k e apaint can. A f t e r the f i r e is started, i t usual ly takes 50 minutes toone hour f o r the f i r s t to be ready t o cook a meal. Because o f th isinconvenience o f using a non-bank-up f i r e br iq ue t cookstove andbecause of the depletion o f firewood i n the c i t y and subci ty areas,these stoves are being replaced by bank-up f i r e bri que t stoves. ( S e eFigure 1.2) These two kinds of stoves are somewhat similar. However,


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: I r's .- -- -. -- -- ---------15?

I-I

Figure 1.2 I r o n sheet briquet cookstove

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the bank-up f i r e br iq ue t stove has a lon ger combust ion chamber whichcan hold more fue l t o keep the coals ho t throughout the n ig ht . T h echamber of a bank-up f i r e br i que t s tove i s usu al l y 25 cent imers (cm)in depth, 9 cm in d iameter a t i t s top end o f the chamber and 23 cmin d iameter at i t s bot tom end. T h e main body of the bank-up f i r ebr iquet stove i s made e i th er o f i ro n sheet o r cas t i ro n w i th a longchimney p ipe . T h e i r on sheet b r ique t s tove i s used so le ly fo rcooking, wh i l e th e cast i r on , w i th the long chimney p ipe , can beused both f o r cooking and space heat ing i n w i nte r . T h e ins ula t io nmater ial u s e d between th e w al l o f th e chamber and th e main body i sc lay mixed wi th r i c e husks. T h e opening a t the bot tom of the s toveserves as the p r imary a i r i n l e t and the ou t l e t f o r coa l ash dra inage.The cos t o f t he i ro n sheet br iq uet s tove i s about 5 yuan ($3 U.S. )and the cos t o f t he cas t i r on one i s about 10 yuan ($6 U .S. ) . T h ei ron sheet br iqu et s toves are u sual ly used i n southern regions o fChina, whi le the cast i r on ones are used i n nor thern and cent r a lpar ts . Ac co rd in g t o tes ts us in g a quench f i r e method per formedby Yang Fuqiang, th e bank-up f i r e br iq ue t stov e has a thermale f f i c iency o f about 20 .5 percent . ( 3 )

Briquet tes have less con tac t sur face w i th the f i r e thancomb-shaped coal s. T h e y ar e p i l e d i n th e combustion chamber i n sucha way as t o b lock the a i r f l o w dur ing the burn ing p rocess. T h i scauses incomplete combust ion, and pr oh ib i t s th e conversion o f harmfulcarbon monoxide i n t o carbon d iox ide . A f t e r burn ing , t he b r i que tash s t i l l has 1 ,200 t o 1 , 500 k c a l / k g energy con t en t . T h i s i s one o fthe major reasons why the thermal e f f ic ie nc y o f the br i que t cookstoveis s t i l l l o w.

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A1981 sur vey o f 67 urban households i n Shanghai as p a r tof t h i s s tudy revealed t ha t br i que t consumpt ion i n these householdsranged fro m 25 kg t o 100 kg p er month. O n an average, t h e householdswhich used br iq uet tes as cooking fu el consumed 31 per cent le ss fu elthan an urban household using bi tuminous coal n o t i n br iq ue t form.1.3 Comb-Shaped Coal Cookstoves

Except f o r th e combustion chamber, t h e comb-shaped coalcookstove i s very s i m i la r i n des ign to the b r iqu et s tove . T h e chambero f the comb-shaped coa l s tove i s no t tapered, bu t i s cy l i nd r i ca l i nshape, about 25 cm in depth and 12 cm i n diameter. Be caus e th eformed shape o f the co al l oo ks l i k e a honeycomb wit h 12 hol es, twol ines o f four -ho les a t m idd le and two l in es o f two a t each s id e , i tis ca l l ed comb-shaped coal . A piece o f comb-shaped coal norm al l yweighs about one pound; thr ee o r fo ur pieces ar e enough f o r a f am i l yto cook one day 's meals . T h e fu el shape permi ts a i r to moveeas i l y th rough the smal l ho les , a l low in g th e fue l t o burn morecompletely and inc reasing i t s thermal e f f i c i en cy over b r iquet s toves .Acomb-shaped coal sto ve has about a 2 8 percent thermal e f f i c i e nc yas measured by Yang. ( 4 )

Af ter burn ing, t he ash o f comb-shaped coal has as l i t t l eas 200 t o 300 k c a l / k g ene rgy c on ten t. I t m igh t s t i l l be pos s ib le t oreduce th i s amount fur th er and increase the thermal e f f ic ie nc y byenlarging the con tact surfac e o f a pi ece o f comb-shaped coal by makingmore ho les i n i t . Bec aus e o f t he re l a t i v e l y h i gh t he rmal e f f i c i e nc yof comb-shaped co al , many urban households have s hi f t e d from usin gbriquet cookstoves t o comb-shaped coal stove s du r in g t he 1 9 7 01s .See F igure 1.3 ) Br iq ue t t e s now account f o r about 30 percent , andcomb-shaped coals account f o r 70 percent o f co al f u e l pro duc ts.

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Figure 1. 3. Comb-shaped-coal cookstove

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In addit io n t o the higher thermal eff ic ie nc y o f a comb-shaped coal cookstove, making comb-shaped coal requires less energyin the manufacturing process than f o r brique ttes. M o s t o f energyconsumed i n the manufacturing process f o r comb-shaped coal i srequired t o make a powder from the an th raci tic coal. T h e formingprocess can be done by hydro-pressure, which requires l i t t l e energy,and the drying process can u t i l i z e sun lig ht o r normal room temperature.Comb-shaped coal can be even made a t home by two types o f simplemechanical devices. One of these will now be described.

Asimp le mechanical device f o r making comb-shaped coal co n-s is ts o f four par ts: 1 ) base plate - a p iece of s tee l p la te wi th12 steel ba rs extending upwards; 2 ) sleeve - a length o f steeltubing th a t f i t s over t he 12 bars, th e sleeve has two handles onei ther s ide, and a l i t t l e c i r cul ar shoulder inside a t the bot tom;3) bottom washer - a round stee l p la te wit h 12 holes t h a t match the12 bars; 4 ) to p washer assembly - round stee l p la te comparable tothe bottom washer, t o which an impact nu t has been welded on t hetop. (S e e Figure 1.4) W i t h th is device, i t i s easy to make comb-shaped coal a t home. F i r s t se t the base pla te on the f l a t groundand cover the 12 bars w it h the sleeve; t hen place the bottom washerinto the sleeve, which rests on the l i t t l e c i r cul ar shoulder at thebottom insi de o f the sleeve. Th en , pu t t he we ll mixed anthra citepowder in to the sleeve, cover wit h th e top washer assembly and h i tthe impact nut with a hammer. A f t e r the coal i s formed, l i f t thesleeve by the handles. T h i s l i f t s th e bottom washer and formed coalfrom the bars o f the base pl ate . T u r n the sleeve 45 degrees such

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3) bott om washer

2) sleeve

4) top washer assembly

Figure T.4 . A simple mechanical device f o rmaking comb-shaped coal

I ) base plate

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that the so li d par t o f the bottom washer rests on the 12 bars, andpush th e sleeve down. T h i s forces th e comb-shaped coa l from t hesleeve.

Survey results from this study indicate that a comb-shaped coa l s tove usua ll y consumes 10 t o 15 percent less cookingfuel than a briquet cookstove. Because comb-shaped coal stoveshave a simple st ruct ure, are convenient t o operate wi th inexpen-sive fue l, have a f a i r l y high thermal eff i ci en cy, and are easy t omake a t home wi th simple devices, comb -shaped coa l stoves mightbe suit able f o r other t hi rd world countries i n which peopleu ti li ze coal as cooking fu el a t home and have anth rac ite coalavailable.

According to tests by Yang, the thermal efficiency of abriquet stove i s about 20 percent and a comb-shaped coal stove has28 percent thermal eff ic ie nc y. However, i n actu al ly da i ly use, th efi r e i s banked several t imes a day; ther efor e, th e da il y averageefficiency o f coal cookstoves i s much lower than t es t re su lts .According t o tests made by the Boi le r Hot-Working Teaching andResearch Section i n Shanghai Mechanical Engineering I ns t i t u t e , t heactual eff iciency of coal use in a bank-up fire coal cookstove isgenerally reduced by 30 percent from i t s tes tin g e ff i ci en cy. ( 5 )Although the fue l used f o r banking up the f i r e could contrib ute t oheat the room in the winter, i t is s t i l l wasted in the other threeseasons. F u r t h e r improvements o f coal cookstoves s t i l l have twocr i t ic al problems to solve:

1) t o el iminate the fuel used to bank-up the f i r e ;2) t o reduce pollu tants generated from the coalcombustion.

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1_4 Improved Comb-Shaped Coal CookstovesSince the ear ly 1 9 7 01s ,i m p r o v e dc o m b -s h a p e dc o alc o o ks t o ve s

with downward combustion have been developed i n China. Such stoveseliminate the fuel which i s used to bank up the f i r e between cookingtimes and throughout th e nig ht i n the tr ad it io na l comb-shaped coalcookstoves. Th e y also provide a possible way to u t i l i z e l ig n it e andbituminous coal a t su ff ic ie nt ly low cost and generate less po llu tio nthan any othe r coal cookstoves. Impr ov ed comb-shaped coa l cookstoveshave a f a i r l y high thermal e ff ic ienc y of between 45% and 54%. (6 ,7 )According t o Li u Bo and Mang Hu ix in, these improved stoves use15% to 20% less fue l than t ha t used i n conventional comb-shaped coalcookstoves (8), while according to Wang Zhihao, they use 40% to50% o f fu el less t han th a t used in conventional stoves. ( 9 )(See Figure 1.5)

The improved comb-shaped coal cookstove looks very similarto th e conventional one from the outside, b ut several c r i t i c a limprovements have been made: 1 ) e ig h t secondary a i r i n le t s areut il iz ed t o th e improved comb-shaped coal s tove which are equall ydispersed a t the top pa r t o f the combustion chamber. Th ese secondarya i r i n le t s provide oxygen which converts carbon monoxide generatedfrom the combustion i n t o carbon dioxid e through continuous burning .2) A thermal focusing plate is added at the top opening of thechamber. T h i s thermal focusing pl at e i s made o f cement wit h ei gh tsmall holes dispersing equally around a la rge hole a t t h e middleof the p late . I t serves two funct ions : f i r s t , when a f i r e i sstarted a t t he to p i gn it io n la ye r of a piece o f comb-shaped coa l, th edoor of the primary a ir in le t i s closed, the thermal focusing pla tecovers th e t op opening o f the chamber and provides a i r flowing fromtop t o bottom o f th e chamber. T h i s makes downward combustion

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f t rx ttr

t 6 r04 i . t

,

Top view o f the improved comb-shaped-coal cookstove

Figure 1.5. Improved comb-shaped-coal cookstovewith downward combustion. (1 0)


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Combustion chamber Top vi ew o f th e combustion chamber

Thermal f o cu s in g p l a t e T o p v ie w o f th e t he rm al f o cu s in g p l a t e

Too v iew o f c as t i r o n T o p v iew o f th e bottom l i n i n g o f t hestove

Cast i ron grate The bottom l i n i n g

Figure 1. 5. Im pr ov ed comb-shaped-coal cookstovewith downward combustion. ( 1 0 )(continued)

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possible. Second, a f t er the f i r e burns to the coal layer at thebottom of a piece of comb-shaped coal, the primary inlet will beopen and provides the air flowing from the bottom to the top of thechamber. A t th is t ime, t he thermal focusing pla te is used to pre-vent harmful monoxide emissions to t he a i r and makes i t burn wi thoxygen supp lied from the secondary a i r i n le t s . 3 ) The combustionchamber of the improved stove is about 15 cm which is shorter thanthat o f a conventional comb-shaped coal cookstove. B e t t e r ins ula tio nmaterials are employed i n the improved stove. T he re fo re , th etemperature outside the stove body is reduced from 230C in con-ventional comb-shaped coal stoves t o 90C i n th e improved one. ( 11 )

These techn ical improvements ce r ta in ly help t o increase t hethermal eff ic ie nc y o f the improved stove, b ut the major step o fincreasing the overal l ef f ic ienc y of fuel ut i l iz at io n i s associatedwith improvement o f the comb-shaped coal which makes i t possib le t oeliminate the fuel used f o r banking up f i r e , and which increases theoverall ef f ic ie ncy of fuel ut i l iz at io n by a t l east 30%. Improvedcomb-shaped coal i s made by combining the ign i t ion ma te ri al , t hemater ial to k indle the f i r e and the coal i t s e l f a l l i n one piece.Normally, a piece of improved comb-shaped coal consists of threelayers; the ig ni t i on la yer a t the top, the kindl ing layer at themiddle and the coal lay er at the bottom. (S e e Figure 1.6) B u t i tcan be also b u i l t with two layers - - the i gn it i on laye r and coal la ye r-- o r even with one lay er. T h e siz e, shape and weight o f a piece o fimproved comb-shaped coa l i s almost t he same as tha t o f conventionalcomb-shaped coal. The controll ing factor is the ignit ion layer; nomatter what ki nd o f combustion-supporting mater ial o r how manylayers are used, the content o f vo la ti le components i n the ig ni t i onlayer must be between 30% to 40%. T h e combustion temperature o f

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CC)CDC:3'..::7**..\\

CD C > C : 7 C P0

Cj c:D c Dc>c >. .. .- ,woo/

Figure 1.6 Improved comb-shaped coals

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this la ye r must reach from 220C t o 240C and the moisture conten tmust be less than 3%. (12)

There is no unified formula for manufacturing improved comb-shaped coa ls. T h e mater ials used f o r making such coals should bethose which are lo ca ll y avai labl e. Sawdus t, carbonized sawdust,residues o f petroleum products, wax and rosi n can be used ascombustion-supporting materials. B itum inou s c oa l, an th ra ci ti c coaland l i g n i t e can als o be used. Wang Zhihao made improved comb-shapedcoal i n Jiangxi province wi th 19 holes contained 30 percent o fpowdered bituminous coal, 40 percent of powdered anthracitic coal,14 percent of clay, 15 percent of sawdust and 1 percent of lime.These mater ials were mixed wi th some lime water i n t o a kind o f paste.After th e coal was formed, i t was waxed with about 15 grams o fwax. (13 ) T h i s comb-shaped coal w i th 19 holes has been experimentallyused in th e J801 type o f improved comb-shaped coal s tove . I t showedfairly high thermal eff iciency of between 50.6 percent to 61.4percent. T h e average thermal ef fi ci en cy was about 54.43 percent(see Table 1.1). J801 type of improved comb-shaped coal stove hasanother advantage i n th a t secondary a i r in le ts are located outs ide o fthe combustion chamber wa ll and upward along t he chamber wall t o th etop o f the chamber. T h i s pre-heats the a i r i n the secondary ai rinlets and allows to burn the coal completely into carbon dioxide.(See Figure 1. 7) T h e cos t o f such an improved comb-shaped coal st oveis about f i ve yuan, which should be widely a ffordab le.

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1.5 Med ium-Btu Town Gas CookstovesChina st ar te d t o produce medium-Btu town gas a t th e end o f th e

1 9 4 01s .Atthattime,thetotalannualsupplyoftowngasforh

holds i n ten l a rge c i t i es was less than 40 mi l l i o n cub ic meters.By 1980 t he produc tion o f medium-Btu town gas reached 1,955 m i l l i o ncubic meters supply ing cooking fue l f o r households i n s i x t y lar geand medium size c i t i e s . Tow n gas i s us ua l l y produced f rom cokingp lants o r f rom ve r t i ca l cont inuous carboniz ing reac tors . A b o u t 500Bt u/ f t 3 of town gas has an energy value o f up t o 4,455 kcal /m3.Besides town gas, there are about 590 mi l l ion cubic meters of naturalgas and 290 thousand metr i c ton s o f l i q u i f i e d petroleum gas which areused fo r cook ing fue l each year . Tog e th e r , these t hre e forms o f gassupply 16.5 percent o f t he cooking fu el f o r urban households i nChina, most ly i n the concent rated, cen t ra l c i t y areas.

A ty p i ca l Chinese town gas cookstove i s b u i l t w i t h two gasburners s ide by s ide , p laced on top o f a cab ine t . T h e body pa r t o fthe gas st ov e i s e l l i p t i c a l i n shape and i s made e i t he r o f c as t i r o nor o f ceramics . ( S e e F igure 1 .8 ) T h e dens i t y o f town gas i s about0.59 kg/m3 a ts t a nd a r dt e mp e ra t ur eandp ressu re ,(1

pressure o f town gas i n t h e gas b ur ne r i s between 80 mm and 120 mm o fwater. (17 ) T h e gas s tove has a thermal e f f i c i en cy o f about 50percent . (18 ) Su rv ey re su l t s o f 82 urban households, conducted i nGuangzhou, Guangdong provi nce, a s p a r t o f th i s stu dy in di ca te t h a tmedium-Btu town gas consumption f o r cooking i n th ese householdsranged between 9 cu bi c meters t o 102 cu bi c meters each month.

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Figure 1 . 8 . Medium-Btu town gas cookstove

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23

One process o f in te re st f o r possible fu tu re development overthe next twenty years i s the gas if icat ion o f coal. C oa l g asif ica t ionis o f in te re st because i t may prove t o be an eff ec ti ve way of producinga re la ti ve ly clean cooking f u el , employing poor q ua lit y coals andincreasing the overal l ef f iciency of fuel ut i l izat ion. Whether costswi ll p rove t o be low enough remains t o be seen. I n 1964, a demonstra-tion siz e gas if ic atio n pl an t was b u i l t i n Shenyang, Liaoning province.The ga si f i er i s 1.4 meter i n diameter, operating a t condit ions o f20 to 25 kg/cm2 pressure, 850 to 1050C temperature, and a gasificationthroughput o f 1000 to 1600 kg/m2-hr. T h i s gas if i e r consumes 20 to36 metric tons o f north Shenyang li g n i t e coal a day, which i s poorin qu al it y with 22.2 percent o f moisture and 21.8 percent o f ash, butsatisfactory results have been obtained through this practice.Table 3. 6 shows th e components o f products gas from pressurized ga si -f ica tion o f n orth Shenyang l i g n it e . ( 19)

The Chinese view ga si fi ca ti on t o produce town gas as essent ialfor improving people's l ivel ih ood, f o r increasing the eff ic ienc y ofcoal u t i l i z a ti o n and protecting the environment. A t the presentstage, t he medium-BTU town gas cookstove has the highest thermaleffi ciency among a l l t he cookstoves used i n th e urban areas ,over 50%.


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CHAPTER I REFERENCES AND FOOTNOTES

1) Ha n Xiaowo, "Developing Coal Processing I s an Importan t P ol ic yof Energy Conservat ion i n Coal Ind us tr y" , Energy, No. 3 , June25, 1981, P. 2 . ( I n Chinese)2) R u d o l f P. Hommel, China a t Work, an I l l us t r at ed Record o f thePr imi t ive Indus t r ies o f China 's Mass, Whose L i f e Is To i l , andThus an Account o f Chinese C i v i l i z a t i o n , The John Day Company,New York , 19 37, pp . 275- 276 .3) Yan g Fugiang, "Thermal E f f ic ie nc y Tests f o r th e Cookstoves Usedin the Rural Areas o f China", Energy, No. 3 , June 25, 1981, p . 47.(In Chinese)

4) I b i d , p . 47 .5)Ibid,p.48.

6) L i u Bo and Mang H uix in, "An In tro du ct i on o f Downward-CombustionComb-Shaped Coa ls and Improved Comb-Shaped Coal Cook stov es ",Environmenta l Pro tec t ion , No. 6 , 1981, p. 10. ( I n Chinese)7) Wang Zh ihao , " An In tr od uc ti on o f Improved Comb-Shaped CoalStove and Downward-Combustion Comb-Shaped Coals w i t h 19 Ho le s" ,

Energy, No. 6 , December 25, 1981, p . 38 . ( I n Chinese)8) L i u B o and M an g H u i xi n , op . c i t . , p . 1 0 .9)WangZhihao,op.cit.,p.3

10) L i u Bo and Zhang Hu ix in , op . c i t . , pp . 9 -10 .11) I b i d . , p . 1 0.12) I b i d . , p . 8 .13) Wang Zh ihao, op. c i t . , p . 37 .14) I b i d . , p . 3 8.15) I b i d . , p . 3 7 .16) J i a Wunyu, "The Ap pl i cat ion o f Aim Jet Without Blaze Gas Burne r,"Energy, June 25, 1981, No. 3 , p . 41 . ( I n Chinese)17 ) I b i d .18) Br i a n Tay lo r , Le Feure 's Domestic Ut i l i za t i on o f Gas, Ernest BennLimited, London, 1973, p p. 195-197.19) Wang Yinrer, "Status of Coal Gasif icat ion Research in China andR&D Out look f o r 19 80's", I n Proceedings o f th e 1981 In te rn at io na lGas Research Conference , September 28 - Octo ber 1 , 1 981 .

(In Chinese)

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CHAPTER I I

STOVE DESIGNS FORCOOKING I N RURAL AREAS

There has been r ap id and dramatic development o f small hy dr o-e le c t r ic power pro j ec ts and smal l -scale coal mines i n th e r ur a l areaswhich have had s i gn i f i c a n t impact s on i r r i g a t i o n , ag r i c u l t u ra l p ro -ducts manufactur ing, smal l in du st r i es and the economy in th e r ur alareas. However , ov er the past th i r ty - t wo years t h i s development hascontr ibuted very l i t t l e to household cooking fue l consumpt ion i nrural a reas . M o s t o f t h e househo lds s t i l l use f i rewood, charcoal andagr ic u l tura l res idu es which have been used f o r cook ing f ue ls f o rhundreds o f thousands o f years i n China. C o a l used as a cooking fu elin the r u ra l househo lds cont r ibu tes about 10 percent o f t he to ta l .Biogas accounts fo r about 1 percent . ( 1 ) S o l a r energy u t i l i z ed f o rcooking represents about 0.008 percent ; therefore, about 88 percent ofthe cook ing fu el comes f rom ag r i cu l tu ra l res idues and f i rewood.

Accord ing to Chinese s tat is t ics , the tota l household fuelconsumption in the rural areas during 1979 was some 3.2 x 108 metrictons o f coa l equ iva len t ( inc lud ing coa l , f i rewood, agr icu l tu ra lresidues, and animal and human wastes). ( 2 , 3 ) P e r cap i ta consumptionin th at year on the average was about 0.3 me t r ic tons o f coal eq ui -va lent . Thoug h t he amount o f fu e l consumed i s sub sta nt i a l , people i nmany ru ra l areas o f China s t i l l need to co l l ec t f i rewood and leavesin o rder t o ma in ta in th e i r da i l y fu e l consumption . I n some reg ions ,

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people lack cooking fue l f o r ha lf of the year. T h e low thermal e f f i -ciency o f cookstoves i s one o f the major reasons f o r the fu el shortagein the rur al areas o f China.2.1 Agricultural Residue Cookstoves

There are many kinds o f ag ri cu lt ur al resid ue cookstovescurrently i n use i n China, the eff i cie nci es o f which vary with stovedesign and fuel type. Ge ne ra l l y, ef f ic ien cie s o f agr icultura lresidue cookstoves range from 10 to 15 percent, which i s much lowerthan th at o f the stoves used i n t he urban areas. I n th is sectionseveral of the most popular types of agricultural residue cook-stoves w i l l be examined.

In Rudolf P. Hommelrs book, China At Work published i n 1937,the author describes a kitchen stove which i s s t i l l popularl y usedin the southeastern portion o f China today. ( 4 ) T h i s stove i sre la ti ve ly lar ge, about 1 .6 meters long and 0.8 meters wide, wi thtwo large cast i r on woks b u i l t side by side at the top surface o fthe stove. A wal l i s b u i l t t o separate the f ro nt par t ofthe stove , which people use t o do t h e i r cooking, from the backpart of the stove, where the fuel i n l e t i s located. T h i s typeof stove does not have an a i r opening; normally fi re -t ongsare used to put the f ue l a t the bottom of the stove and to s t i r e t hefuel t o l e t the a i r go through. Compared to the present design o fkitchen stoves, the re are on ly sl ig ht differences, bu t the changeswhich have been made ce rt ai nl y do improve the thermal e ff ic ie ncy o fthe stove. F i r s t , one of the woks is now of a small siz e, and is

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usually used to do the da il y cooking. Second, a c ast ir on water potis b u i l t i nt o the stove between two woks near the back edge o f thewall. Th er ef or e, th e remaining heat o f the stove can be used to warmthe water rather than being released from the combustion chamber tothe chimney. No rm al ly, a kitchen stove requires two people t o do th ecooking; one prepares the meal a t the fr on t pa rt and the othe r onesi ts at the back to tend the ki tchen f i r e . I t takes about 20 to 30minutes to cook a meal.

Results o f a survey as pa rt o f the study o f 44 rur alhouseholds which use t h i s sp ec if ic design o f kitchen cookstovesin Wansui Commune, Jiangsu province reveal t h a t ag r ic ul tu ralresidue consumption used i n these households f o r cooking ranged

fuel consumption among a l l t he survey data .from 798 t o 3027 kg a year, which represents t he highest cooking

The ag ri cu ltu ra l resi due cookstove used i n th e northernand cent ra l pa r t s o f Ch ina i s qu i te d i f f e re n t f rom the des ign o fthe k i tchen s tove descr ibed above. T h e major d i f f e rence i s th a tthe f ue l and a i r i n l e t o f t he ag r i c u l t u ra l r es idue c ooks tove i slocated i n th e f r o nt pa r t o f the s tove and i n many cases onl y onewok i s b u i l t a t t he t op o f t he s t ove . ( S e e F igure 2 . 1 ) Ac c o r d ingto Yang, the spe cif ic design o f the agr icul tura l res idue stove whichhe used f o r h i s t he rmal e f f i c i enc y t e s t has an a i r and f ue l i n l e tof 29 cm in heig ht and 21 cm i n width. ( 5 ) T h e bi g wok weighs 9.8kg and the small one is 6.65 kg in weight. The chimney of this typeof stove i s usua lly connected t o the kahg which i s a Chinese bed

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Figure 2.1. A g r i c u l t ur a l residue cookstove.

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bu il t wit h bric ks and wood frame a t the t op. T he re for e, th e rejectedheat from the stove can be used to heat the kang during the wintertime. Regardless of the rejected heat from the stove used forheating, i t onl y has a thermal eff ic ie nc y between 9. 4 and 10 per -cent. (6)2.2 Firewood Cookstoves

About 7 percent o f ru ra l households are using firewood ascooking f ue l. Th es e ru ra l households are mostly located i n mountainareas such as i n Fu jian province, Xizang autonamous regi on , Anhuiprovince and Heilongjiang province. T h e r e are var ieti es o f f irewoodcookstoves used in ru ra l areas o f China. I n what follows, twopopular types of firewood cookstoves will be discussed. The tradi-tional firewood cookstove used in China looks l i k e a p ai nt can withoutchimney pipe attached t o the body o f the s tove. T h e body o f thestove i s made of cl ay. A t the base o f the stove, th ere i s an openingwhich serves both f o r fuel ing t he stove w ith firewood and as an a i rinle t. T h e top opening f i t s a wok. T h i s type o f f irewood cookstoverequires firewood which should be dry ; th erefo re , i t generates lesssmoke. T h e design of the tr ad it io na l firewood stove i s much simplerthan many of the designs of improved firewood cookstoves which havebeen used in China or in other developing countries. However, thethermal eff iciency of this type of stove is usually only about 10percent. (7) (See Figure 2.2)

The improved firewood cookstove i s us ua ll y employed wit h abellow box which i s used to supply a i r t o support combustion. T h e

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Figure 2.2. Firewood cookstove

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31

bel low box i s made o f wood wi th a handle a t the f r on t and a rubber va lveat the back. ( S e e F igure 2 .3 ) T h e handle moves in a hor izon ta l d i r ec -t ion . When the hand le i s pu l led , t he rubber va lve i s opened and a i renters; when i t i s pushed, the rubber va lve c loses and a i r i s in j ec te dinto th e bot tom o f th e combust ion chamber through th e pip e connect ingthe be l low box to the s tove . T h i s t ype o f s tove i s used in many ru r a lhouseholds i n China because i t has a thermal ef f i c i e nc y o f about 20percent . ( 8 ) A c co r d i n g t o Yang Fug iang, th e f i rewood cooks tove w i t hbel low box which he tes ted f o r thermal e f f i c i en cy i n Be i j in g , has anopening f o r f i rewood f ue l o f about 28 cm i n hei ght and 20 cm i nwidth. T h e top opening on which th e wok re s ts i s about 66 cm i ndiameter. ( 9 )

Improved f ire wood cookstoves have provid ed a fe as ib le way o fincreas ing the thermal ef f ic iency of burn ing f i rewood and representone o f t he op t ions o f easing f ue l s ho r t age i n ru r a l a reas . W i t hresearch and development on f irew ood cookstoves i n China, t h e th ermale f f i c ienc i es o f the improved f i rewood s toves have been t r ip l ed . F o rinstanc e, Gan* No. 1 a nd No. 2 improved wood sto ves an d improved woodstoves No. 1, No. 2 , and No. 3 developed i n th e North Coast o f Anhuiprovince have thermal ef f ic ie nc ie s o f f rom 30 t o 35 percent . (10)2.3 S o l a r Cookstoves

Research on s o l a r cookstoves and s o l a r ovens was s ta rt ed morethan twenty years ago i n China, b ut the rap id development o f so larcookstove appl icat i ons i n the ru ra l area s has been tak in g p lace s inc ethe mid-1970's . Becau se o f lac k o f cooking fue l coupled wi t h goodsun l ight , mos t so la r cooks toves are cur ren t l y u t i l i z ed i n X izang andGansu provi nce i n th e southwest p ar t o f China.

*Gan is the shor t form for J iangx i prov ince.


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32

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The f i r s t series o f 1,000 small parabo lic so lar cookstoveswas manufactured i n Shanghai No. 15 Radio Factory i n 1974, and wasused experimental ly by peasants i n the communes and by people o fprospecting teams where there was not enough cooking f ue l o r ther ewas no cons tant cooking f ue l supp ly. (11) This type of solar cook-stove with a parabol ic concentrat ing col lec tor can boi l 3 l i t e r s o fwater in twenty minutes and cook one kilogram of rice in fifteenminutes, having b et te r performance than t hat o f a small coa l cook-stove. A f t e r several years o f research and development, th i s fa ct or y

developed a new type o f so la r cookstove wi th rec tangular shaped para-bolic concentrating c ol le ct or made of calcium-containing p la st ic i n1978. (S e e Figure 2 . 4 ) This calcium-containing p la st ic sol arcollector is easy to manufacture.

In Lasa, Xizang, research on t i l t e d so la r cookstoves and ovensis being ca rr ied out a t th e Xizang So lar Energy Research Department.The t i l t e d sola r oven uses two pieces o f parabol ic col l ector s a t i t sbottom and top f o r focusing and ref le ct in g th e su nlig ht to the i nsi debottom and top o f the oven. Acc or din g t o the te st s, even i n January the temperature insi de the so la r oven can reach as high as 240C. I tcan bake 2.5 kilograms o f cake withon one hour. (12) A so la r stovedeveloped in Losa, si mi la r to the s ol ar oven str uct ure , can boi l t enpounds o f water i n 40 to 60 minutes. (1 3 ) Th e mate rials used t obuild these so la r ovens and stoves are very common ones l i k e gla ss ,wood board, i r o n sheet and aluminium-plated polyes ter f i l m . T h ecosts f o r bu il ding them are between 30 yuan and 50 yuan, which i sbetween 20 t o 30 U.S. d ol la rs . (14) A f t e r mass production o f thesesolar cookers, the cost w i l l l i k e l y be reduced.

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In Jiangsu, a broad new type o f so la r cookstove has beendeveloped ve ry re cent ly a t the Yancheng D i s t r i c t New Energy ResearchInst i tu te. T h i s cookstove uses a f i lm negative pressure structu reprinciple in which a f i lm bag i s used as the cover over the s olarcoll ecto r. D u e to the differe nce in pressure between the two edgesof the f i l m bag, the re fl ec ti ng surface assumes th e desired shape.The temperature a t the focusing poi nt o f the so la r cookstove canreach 500 t o 700C. (1 5) T h i s so la r stove has a c ol le ct or 1.6 metersin diameter and weighs only 10 kilograms. I t was exhibited a t theWorld's Fa ir i n Knoxvil le, Tennessee, th e United States, i n 1982.

Research into solar cookstoves is not limited only to thesolar research in st i t ut e o r the univ ersi ty; i t has been carrie d on i nmany o f the ru ra l areas i n China. T h e most exci tin g development o fsolar cookstoves i s i n Yongjing county, Gansu province where wit h ina year from the s ta rt i n 1980, h a l f o f the households i n Yongjingcounty, some 12,000 households, have been using so la r s toves. T h esolar stove developed ther e uses cement concrete t o bu il d the so la rcol lector base and si lve r-p late d glass on the top as r ef l ec t in gmaterial. T h e thermal output o f the s ola r stove i s comparable tothat o f a one ki lo wat t el ec tr ic range. T h e cost o f the cement con-crete sol ar stove i s about 50 yuan to 80 yuan. (17)

2.4 Biogas CookstovesI t i s we ll known th at biogas i s normally produced by allowing

organic matter o f various kinds t o ferment i n oxygen-poor conditions;i t i s ide nti cal t o the marsh gas o f freshwater wetlands. A n y wastedorganic matte r contain ing carbon, hydrogen, and oxygen may be a su i ta -ble material f o r biogas product ion. Und er the act ion o f natu ral l y

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occurring bacterial f l o r a o f various kinds, t he very long organicchains conta ini ng carbon, hydrogen and oxygen, together wi th some othe rcompounds - i n par ti cul ar nitrogen - are disassociated f i r s t in to t he irconst itutent sugars and then transformed by another set o f bacteri ainto various alcohols and acids. F i n a l l y, some o f these alcohols andacids are converted into methane, carbon dioxide and other trace gaseswith the energetica lly useful p ar t - methane - ty pi ca ll y accountingfor 60 to 70 percent o f the to ta l biogas content. T h e biogas,therefore, has a fairly high content per volume, between 600 to 700Btu per cubic foot. (18)

Since 1975, t he smal l-scale biogas d igeste rs have beenrapidly developed. Ac co rd in g t o data published i n 1981in China, about 8.5 million small-scale biogas digesters have beenbu il t i n r ur al households since 1975. (19) A typi cal small-scal ebiogas digeste r has a volume of 6 x 10 cubic meters. I t i s made ofbricks and cement and can be e it he r i n semici rcu lar shape, i ncircular shape or i n el l i pt ic al shape. (S e e Figure 2. 5) The designof a Chinese biogas diges ter i s re la t iv el y simple; i t combines th efermentation u n i t and the biogas storage i n t o one and uses water asa material f o r covering the biogas without add itional pressure con-tr ol. T h e organic material i n l e t i s usual ly connected with a pigst yand pl as ti c pipe i s used t o del iv er biogas to the stove i n thekitchen. (See Figure 2.6)

The attractions of the Chinese drumness design of the biogasdigester are as follows:

i ) r e l a t i v e l y low to ta l cos t fo r bui lding adigester (less than $100 U.S.) (20);i i ) e l i min at i on of the problem of s teel corrosion;

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100 al00OUTLET

S E M I C I R C U L A R

37

S k i l l e d L a b o ur 8Labour 1 5Cement 4 0 0 k gSand 1 0 0 0 k gGravel 4 0 0 k gBr icks 1 5 0 n oC on cr et e R a t i o 1 : 2 3( 2 0 0 4 )

,Yoluma 8 m3

C I R C U L A RS k i l l e d L a b o u r 3Labour 1 5Cement 4 0 0 k gSand 1 0 0 0 k gGravel 9 0 0 k gBr icks 1 5 0 noC on cr et e R a t i o 1 : Z : 3( Z 0 0

,1olume 8 m3

Figure 2. 5 R e c e n t Chinese Magas Digeste r Designs f romthe People's Republ ic o f China (2 1)


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E L L I P T I C A LS k i l l e d L a b ou r 3Labour ' 15Cement 4 0 0 k gSand 1 0 0 0 k gGravel 9 0 0 k gBr icks 1 5 0 s oC on cr et e R a t i o 1 1 2 : 3(200 ,: )Volume 8 m3

Figure 2.5. R ec e n t Chinese Magas Dig ester Designs f romthe People's Republ ic o f China (21)(continued)

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i i i ) improvement in sani tat io n;i v) p r o v i s i o n o f more o rg an ic f e r t i l i z e r t o f ar m l a n d;v) increa sed end-use eff ic ienc y o f fuel

Because of these a tt ra ct io ns , biogas d igesters have beenrapidly popularized i n ru ra l households since 1975, especi ally i nsouthern parts o f China. F o r instance, 5 mi l l io n biogas digestershave been b u i l t i n one southwest province, Sichuan. Alt ho ug h simplein design and low in cost , Chinese digester s als o have some sho rt -comings. F i r s t , these digesters mainly r e l y upon the outdoor tempera-ture; therefore, t h is l i mi ts the use of the digesters i n the coldernorthern and central p ar ts o f China. Second, t her e i s no device t ocontrol the gas pressure used in the digester. T h i r d , there i s alsoan operat ion and maintenance problem. These th re e major problemscer tai nly need to be solved i n fu tu re research and development f o rdigesters.

Biogas i s a high qu al it y fue l which contains about 60 t o 70percent of CH4, 4 0p e r c en to fC O2a nd2to4p er ce ntH2,an

requires a good burning vessel t o have a complete combustion. T h ebasic stru ct ure o f biogas stoves and burners a r e si mi la r; commonelements are a nozzle, an a i r i n l e t , and a mixing chamber and thefi re sieve pl ate . T h e r e a re many kinds o f biogas stoves o r burnersused in Chinese ru ra l households. B a s i c a l l y, these stoves andburners are ei th er made of cla y which are us ual ly cal led earthenbiogas stoves, o r made of steel p ip e which loo k l i k e any other kindof th e gas burners . (See F igures 2 .7 and 2.8 )

To make the earthen b iogas stove, ye ll ow mud, re d mud o rwhite clay a re usua lly employed, mixed with a su ita ble amount o f s a l twater and ri c e hu ll ash . Th es e materials help the stove t o withstandheat and prevent cracking.

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m ixi ngchamber

Fine sieve plate

Earthen biogas cooks tove

01

Biagi's spurt holes

Biogus-airiMet

Air inlet

Biogas inlet

Figure 2 . 7 . E a r t h e n b iogas cookstove wi thmixing groove ( 2 3 )

Biogas-airmixing groove

Air inlet

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Figure 2.8.

Steel pi pe biogas burner

Biogas cookstove used i n ChineseRural Household (29)

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The nozzle i s a ho llow tube made o f bamboo, gla ss , o rplast ic. T h e nozzle hole i s the size o f a needle point (0.5 mm indiameter), so th at the biogas can spu rt out under the high pressure.The biogas and a i r must be mixed i n a cer ta in proport ion t o enablethe flame t o blaze and produce a powerful hea t (normally 1:10 i nvolume). (24)

Because no device to con tro l th e gas pressure i s usedin the biogas digeste r, a saf ety pressure gauge i s usu all y usedwith biogas stoves. ( S e e Figure 2.9 ) T h e safety pressuregauge i s a simple dev ice made o f two g lass tubes and a hose i n aU-shaped tube f i l l e d wit h colored water. Tu b e A i s connected tothe gas o ut le t o f the biogas di ges ter through a Y-shaped tube, andtube B i s open t o the atmosphere. T h e heights o f the water columnsof the pressure gauge vary when pressure i s created by th e pr o-duction o f biogas insid e t he biogas pla nt. (25)

Most o f th e designs and technical improvements o f biogascookstoves i n China over the past f i v e years were based on thefollowing requirements:

1) t o increase the thermal eff ic ien cy;2) t o burn in a stable condit ion;3) t o reduce emission o f monoxide to l ess than

0,05 percent in the smoke;4) t o reduce the co st o f biogas cookstoves.According to national tests of thermal eff iciency of

biogas stoves, i t has been found th at two- thir ds o f the biogas stoves

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Connected to the gas pipe

Usable biogas

Figure 2 .9 . S a f e t y p ressure gauge (26 )

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45

used in ru ra l households have a thermal e f f ic ie nc y over 55 percent ,but on ly a f ew o f them have met th e standard formonoxide emission(0.05 percent ) . (2 7) C u r r e n t l y , more and more ru ra l households usethe biogas stoves made of e i th er cast i r on or ceramic . Ya ng Fuoiangdid thermal ef f i c i en cy tes t i ng o f b iogas cookstoves made o f casti ron and ceramic i n Shun Yi County, B ei j i ng . T h e te s ts showed th atthese biogas stoves had a thermal e ff i c i e n c y between 51% and 59,1%.(28)


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15) Z i a o Kuan-ken, " So la r Cookstove", People's Da i l y , December 27,1981, P. 3 .16) "C h i na ' s P ic t u re " , No. 1 , January 1978, p . 44 .17) H e Dong J i un , "The Secretary o f the County Popula r iz ing S ol arCookstoves", Peopl e's Da i l y , February 28, 1982, p . 3 .18) Elizabeth Cecelski, Joy Dunkerley, and Wil l iam Ramsey, HouseholdEnergy and th e Poor i n th e T hir d World, Resources f o r th e Fu ture,Washington, D.C., Research Paper F-15, 1979, pp. 35-36.19) a ) Si ma Chen, " Fu l l y Develop Biogas i n China t o Solve EnergyProblems i n Rural Are as" , Energy, August 25, 1981, p . 39 .(In Chinese)

b) F u l l y Popularize Biogas i n China wi th a Good Planning, "Guang Ming Da i l y , J u l y 13, 1980, p. 3 . ( I n Chinese)

20) L i N ian-guo, the respondent of PRC, "W i l l th e Energy Si t uat ionin t he Developing World Get Be t t er o r Worse i n th e Years Ahead?,"VITA News, J u l y 1981, Maryland , USA, p . 5 .21) S . L . Maskey, "Bio gas Research Center a t Shanghai, Chi na ,"Biogas New sle tte r, No. 10 , Autumn 1980, Nepal, p . 5 .22) "Pr obl ems i n Popula r iz ing Biogas Program i n Nepal, " BiogasNewslet ter, No. 2 , Autumn, 1978, Nepal, p. 1 .23) M icha e l G. McGarry and J i l l S ta in f o r th (Ed i to rs ) , Compost,F e r t i l i z e r and Biogas P rod uct ion fro m Human and Farm Wastesin th e People's Republ ic o f China, Ottawa, Canada, 1978, p p.69 and 93.24) I b i d . , p . 6 8.25) I b i d , p . 6 3 .2 6 ) I b i d .27) Zhang Rongl in, "The Designs o f Biogas Stoves and Increase o f th eThermal Ef f ic iency," Energy, No. 4, August 25, 1981, p. 39.(In Chinese)28) Yang F uc iang , op . c i t . , p . 46 .29) a ) S . L . Maskey, o p . c i t . , p . 4 .

b) "Chan ge Wastes I n t o Treasures and th e Harmful I n t oBen ef i c ial , " Biogas Newslet ter, NO. 10, Autumn 1980, p. 2.

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CHAPTER I I I

SPACE HEATING

3.1SpaceHeatinginUrbanAreas

Household energy consumption used f o r space hea tin g accou ntsfo r 58 x 106 met r i c tons o f coa l equ iva len t o r about one-ha l f o f t hetota l c oal consumption i n the household sec tor in China ( 1 ) , onethe l eas t e f f i c i e n t and most po l l u t i ng o f f ue l c onve rsions . U pto now, o th er sources o f fue l used f o r res id ent ia l space heat ing ,such as e le c t r ic heat ing o r gas heat ing have been a lmost n eg l i g i b l e.There ar e no space heati ng systems ava il ab le on a commercial bas isother than s team-boi ler systems. W h i l e only a few s tudies havebeen done on the subjec t of res ide nt i a l space heat ing over the pastthree decades, sever al in te re st in g papers have appeared re ce nt ly.Using a few such works and othe r a vai lab le mater ia ls , we w i l l pr o-ceed to examine t h e space hea tin g problem.

China 's l a t i t ud in a l pos i t i on corresponds a lmos t exac t l y w i ththa t o f t h e Uni ted Sta tes . Tw o major r i v ers the Ye l low R iver(Huanghe) and Yangtze (Changj iang) t r i s e c t China i n t o thr ee majorb el ts : I ) t h e r e gi on t o t h e n or t h o f t h e Ye l lo w R i ve r f ro m l a t i t u d e35'N t o 50'11., 2 )t h er e g io nb e tw e entheY e

River spanning the la t i t ud es 40 'N t o 3 0N ; 3 ) t h er e g i o ns o u t ho f

the Yangtze River ex tending south t o the 28 'N la t i tu de . T h e Chinesegovernment has designated the northeast region, that is , the area

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49north o f the Yel low River, as a "winter heated region." I n addit ion ,winter heating i s allowed i n most o f the reg ion between the Yellowand Yangtze riv er s. T h e region south o f the Yangtze River i s cl as -sif ie d as a "non-heated regio n", even i n the wint er.

According to the above government stipulations, the additionalfunds required f o r heating and fu el w i l l be provided by th e governmentthrough various i ns t i tu t i on s, such as fact orie s, univ ers i t ies andother government enterpri ses t o each individual household i n th ewinter. F ees f o r household heating vary with the region and theperiod o f win ter when heat needs t o be provided. I n northermostHeilongjiang province, the government supplies each governmentemployee t h i r t y yuan per month f o r the s i x month period from 10thOctober to 10th Ap r i l. I n Shanxi province, t he government onl y giveseach government employee f our yuan p er month on a th re e month basis.In some othe r regions, the government provides a dd iti onal coaldi re ct ly to government employees f o r heating purposes. T h e coalconsumption for heating the household space varies with the mechanismby which heat i s provided. F o r instance, a medium-size fam ily o ff ive t o si x people i n nort her ly Heilongjiang province, using abituminous coal stove, could consume as much as 1.5 to 2 metric tonsof coal i n the winter. I n general, the funds or fuel are given onlyto households which do not use central heat ing systems. A greatmany households in the c i t y areas are provided heat d ir ec tl y i n thewinter through centra l heating systems; e it he r steam-boiler systemsor waterbo iler systems.


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50

The steam-boiler heating system, which has a generat ing capa-c i t y o f t he one or less than one met r i c ton o f steam a hour, i s usua l l yused f o r suppl ying hea t t o about 500 households depending upon th eneeds and phys ica l locat ions of the households . Current ly , there areabout 150,000 s team-boi lers i n use i n China. ( 2 ) T h e therm ef f i c i en cyo f t h i s k i n d o f s t e am -b o il er i s a b ou t f i f t y p e r ce nt . T h e i n t e r m i t t e n theating method i s of t en used fo r supplying heat , t h e e f f i c i en cy o fwhich would be 10 to 20 percent lower than t ha t o f the constantheating method, ( 3 ) because in te rm i t te nt heat ing requi res mu l t ip leheating o f w a l l s . Ve r y o f ten the room tempera ture f a i l s t o reachthe des ign- requ ired po i n t . U su a l l y , t h e room tempera ture a f t e rheat ing i s a bout 16C to 18C (60F t o 6 4F ) . ( 4 ) B e c a u s es t e a m -boi ler he at ing does no t reuse condensed wate r, t h e rej ect ed he ataccounts f o r more than one- th i rd o f the heat in pu t . M ore ove r ,because the stea m-boi ler he av i l y p ol l ute s th e surrounding environment,i t has t o be b u i l t some dis tance away f rom the areas t o be heated,thus increas ing heat los s f rom the p ipel ines. T o overcome th i sproblem, pi pe l i ne in su la t i on would be an important means t o preventheat loss . Acc or d in g to tes t s conduc ted in China on two p ipe l ines i nthe same area us ing d i f fe re nt in sul at i on methods, th e heat los s o fone p ipe l ine was on ly 1 .2 percent, w h i l e the loss i n the o ther wasabout 7 . 7 pe rc en t. ( 5 ) F r o m t h i s i t i s e v id e n t t h a t p i p e l i n e i n s u l a -t ion can be a s i gn i f i c an t fa c to r in the conserva t ion o f househo ldheat ing fuel .

The wate r-bo i ler heat ing system i s a l so an opt io n f o r use i nres identia l a reas . U s u a l l y , water - bo i le r heat ing sys tems are d iv ided


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in to h igh- temperature and low- temperature hot water . C u r r e n t l y , th er eare about 30,000 water -boi lers i n use i n China, most o f which are usedin i ndu s t r i a l app l i c a t i ons . ( 6 ) T h e wa t e r -bo i l e r uses t wen t y t oth i r t y percent o r sometimes even f i f t y percent less f ue l t ha n t ha tused in the s team-boi ler . The water temperature in water-boi lerheating systems usua l l y reach 9 5 / 7 00C * , 1 0 0 / 7 0 C ,1 3 0 / 8 0 Co r1 5 0 / 9 0 C

in China. T h e maximum temperature o f th e Chinese design standard f o rthe water -bo i le r a t t he h o t water supp ly s ide i s 150C, bu t in mos t o fthe cases the ac tua l water temperature i n fac to r ies o r res id ent ia lprac t ices is lower than 100C. (7) Because the water-boi ler heat ingsystem is a c losed- loop sys tem, los s o f re jec ted heat i s re la t i ve lys ma ll . I n t he m iddle 19 601s , s o m ef a c t o r i e si nt h en o r t h ea s tp a rt

of China sh i f t ed f rom s team-boi ler heat ing sys tems t o wate r-b oi l erheat ing systems wi th good res ul ts i n fu el saving s and improvement i nheating qu a l i t y . Ta b l e 3 .1 shows the resu l t s o f a comparison o f thesteam-boi ler heat ing system and the wat er -b oi ler heat ing system innortheast China. Al th ou gh the c losed- loop water -bo i ler heat ing systemhas gr ea t advantages over t he st eam-bo i ler heat i ng system, i t i ss t i l l no t very much used f o r heating app l i ca t ions i n Ch inese res iden-t i a l a reas.

Studies o f methods t o apply rej ecte d h eat f rom thermal powerplants to pot ent ia l h eat ing space have la t e l y taken on great impor-tance. Ma ny proposals and suggest ions have been reported f o r several

51

*The f i r s t number ind icates th e hot water supply s ide temperature, thesecond number represent s t he temperature o f recovered h ot wat er,a f t er i t i s u sed i n t h e r a d i a to r s .


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cr>

co

,-...cc. v )C _.0 s _ .

- E-.--CU

-1=3ce

,c t

1--cri0L) - I - ).-Cr)

a l C CC)= .-c r: /C c c i .cc; v ) ..ct

V)SCU.Cci ' r -1 0_CICD I> E0 r t IE WCU-1-)S- cr)

Cr)WE.) 0S- 0- C S -- Pa) CUcn . - -0 ,-1. 0u _0

.-rci00 -P E(0 C cZ)= . .-CDc > . C)ft; (r) 0,1

a)S- S -CU =_w 4._).13 0:$ c - )s-cu c )-

I-)CL.

0 E= CUI

C)C ICDcri

CDr---.

C>criC)Cr.ts,Q

i..0criCD,,

toC

C)c,-->ocs....---- 1 - - _ - ..---CU

U-

CDLs) 1--re)

S-W_ 4 ., q

0 -, - S -CO 0 =I t o 0S-0-_=

CU a l - - ,4-) Li cricc; E ,..__..

-----rs..IEcri = ,C C D,- .----.,=)CO 4

-)rofl

C,..)rCSC)CD

.3., S_ t. r)- = c o . - -'--- - - -

S- S -0) a )o 1 - -. . - CO 0 CO 0. CO . CO/ I I I1--- s - E--- ECU r oczi -I-) 0 CUC ( C 3 4-)Ca) I ( r )

S-S- Cl)cu ,--CD-I- I . -C ( 0 00 3 -a l

C)r-- (. 01in

---,>1 s_1&.. 4-) _ ,E a.) ,- - - rri , L i 0cl) 9- co - =4-> 0 SD- cs,-)

V) CO azi Ec--)c\-1 t=i

cr)1s _E a )fO .0 0 ) . .-3 4-) 04--) Li l i n

.-CU t i lS- . EC O0 0 04 - - 0 S -Cr)ICC)

(I)(cu-t--s_04-)0.111-

Cr)=!-5-=4-1cr) Li >-, r- C a l S --CI 1- 4

- 05-S - = -I-)Cl.) (IZS C u.1l CU iTS cCI= no m 1-1-

cr)=1-s- cu s-cu > =rcl 9--P

= 4-1 L) >-,0 m i 5. -. .-E4-0

= 0 = +. )c r L ) = L ) r- 0 r c i M ScZT ) .e.... 1--)...

Cr)=-,--->) =S-4-)

cu L) >-,C 0 rC5 S -CC1- - (I - -0

r,,.-C=4->

, Li = L icri a l 11, t c .CZ1 = 1-1-

. >1 + - )0 I - >1 =0) s- -P= cLi L i > )cc) C ( t ) S.->, e 4- 0C -_= n -i-)cu c-) = L i-C CO a:S ccsV

./=MLT-

cr)=-=Cs) 4 - )= c ) > -,rC. S - (1:1 S -> , CU 4 - 0= 3 C 4-)

CU 0 C L I-= r o rioV ) CC L . -

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areas and reg ions i n Ch ina. I n Be i j in g , th e B e i j i ng No. 1 and No. 2Thermal Power Plants suppl y heat t o 14 percent o f the to ta l muni c ipalcons truct ion space in w in t e r . ( 9 ) S i m i l a r app l i ca t ions have occurredin Buxin c i t y , L iaon ing prov ince i n 1981. T h e Buxin P lan t i s alarge-size power plant with an annual product ion of 45 x 108 kwh of

53

e l ec t r i c i t y . I n the pas t , va s t amounts o f heat were re leased f romthe p lant and ser iou s ly po l lu te d th e surrounding envi ronment . I n1981, th e munic ipal Commit tee o f Buxin c i t y proposed bui ld in g aheating system and us ing t he re jec t ed hea t as t he win ter heat ingsource. T h e pro jec t was budgeted fo r about 9 .1 m i l l i on yuan. T h i spro ject was f in ish ed two and h a l f months be fore the ar r i va l o f w in te rin 1981. To d a y, th e to ta l p i pe l i ne system measures 56 k i lometersin length and br ings " re jec ted heat " t o heat 560,000 square metersof co nst ru ct i on space in cl ud in g 50,000 households and 160 governmentent erpr is es . A s a r es u l t , 135 s ma ll bo i l e r s p rev ious l y used f o rspace heati ng have been shu t down. T h i s saves an est imated 50,000metr i c tons o f coa l each w in t e r . ( 10)

Recovered heat f rom thermal power pla nts would be i n su f f ic i en tt o s upp l y a l l t h e res iden t i a l a reas i n Ch ina. I n t he subu rbs, t hehouseholds which a re f a r removed from th e heat ing systems u su al lyre ly on coa l s toves f o r heat ing . Th es e coa l s toves are designed f o rboth cooking and heat i ng. T h e y can be fu ele d by bi tuminous co al ,brique ttes o r comb-shaped coal accor ding t o t h e i r combustion chambers.Such stoves are us ua l ly made of cas t i r o n , wi th lon g chimney pipesattached t o relea se smoke and carbon di oxi de outs i de th e house. U s eof coa l s toves bo th f o r a l l - ye ar cook ing and heat ing i n the w in te r


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54

maximizes the thermal eff ic ie nc y o f the stove; nevertheless i ts t i l l has lower thermal eff ic ien cy than the steam-boi ler or water-boiler used so le ly f o r space heating. Furthermor e, these coalstoves produce large amounts of coal ash, coal dust and carbondioxide, SO2p o l l u ti n gt hea ir .P re se n tl y ,thereisnomeansof

control ling such pol lutants. F ig u r e 3.1 i l lu st ra te s the cast i roncoal stove used f o r space heating and cooking i n ordin ary householdsin China.

Recently newer means o f household heating have been introducedto the c i t y areas, such as long-wave inf rar ed heaters and el ec tr icheaters, but these s t i l l account f o r only a ver y small amount of thetotal space heating applications.3.2 Space Heating I n Rural Areas

Most o f the ru ra l areas i n China need heating i n the win tertime, except i n areas l i k e Guangdong and Guangxi i n th e Extreme southand Shanghai i n th e southeast. T h e fu el used f o r space heating i nthe rura l areas i n China are a l l drawn from loc al sources. T h egovernment provides ne ither funds o r fuel f o r space heating i n ru ra lhouseholds. I n general, th e required fuels are supplied by the l oca lproduction teams according t o th e numbers i n th e given household.The fa ci l i t i es fo r heating are therefore t ied to the ava i la bi l i t y o ffuels i n the various regions and are used i n th e simplest ways f o rheating purposes such as kangs*, cookstoves with chimnies and even

*Kang i s a bed made of br ick s wi th a wood frame a t the to p, and a smallstove bu i l t at i t s base for heat ing the kang in the win ter.


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Figure 3.1 . C a s t i r on coal cookstove used inthe w in te r fo r heat ing

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56

open- f ires. T h e fue l consumpt ion fo r heat ing i n t he r u ra l a reas o fChina var ies accord ing t o the ch arac ter i s t i cs o f t he reg ion o r t hearea. T h e survey da ta f o r th is s t udy , ind ica tes t ha t i n t he ex tremenor thern ru ra l a reas o f He i longj iang prov ince , a fami ly o f t h ree tofour people consumes 1.5 metr ic to ns o f wheat st ra w f o r he at ing i na wi nt er wh il e a fa mi ly wi th s i x t o seven members would consume atleast 2.5 met r i c tons o f wheat s t raw. I n some regions , th e householdheating f ue l consumption i s as much as t h e annual household cookingfuel consumpt ion. Because o f the fu e l shor tage i n the ru ra l a rea s ,heating i s sometimes l i mi te d to onl y p ar t o f the house, the bed o rsmall device s used f o r warming hands and f e e t .

The kang is the major device used in the rural households ofChina, espec i a l l y in nor theas t o r cen t ra l pa r t s o f Ch ina. F i g u r e 3 .2shows th e str uc tu re o f the convent ional Chinese bed, t he kang whichhas been used in China for centur ies, but has rapidly disappearedwherever modern c i t i es developed owing t o i t s in su i ta b i l i t y fo r thenew condi t ions o f urban l i f e . T h e kang i s a bed made of br ic ks andwood f rame at th e to p, b ut h ol low in s ide . A kang i s about 3 meterslong, 2 .5 meters in w id th and 2 .5 f ee t h ig h , and i s o f ten b u i l t underthe window fac ing south. I t used to be heated f rom a smal l s tov eat i t s base, b u t now i t i s more commonly heated by means whichut i l iz es th e waste heat f rom th e cookstove. T h e chimney p ipe f rom thecookstove in the k i t chen i s b u i l t t o pass th rough the kang i n ahor iz on ta l d i r e c t i o n bef o re r i s i ng t hrough t he roo f . I n o rde r t oreduce the heat l oss o f the chimney p ipe, th e cookstove i s usu al l yas near to th e kang as poss ib le . F i g u r e 3 . 3 i s a d iagram o f the


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Figure 3 .2 . S t ru c t u re o f Chinese bed - - kangwith a smal l s tove a t i t s base

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58

SucueoCnkwhamohnsem


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improved heat in g system of a kang. T h e br ic ks o f the kang ar e ableto absorb a l ar ge amount of waste heat f rom t he cookstove i n th ek i tchen, prov id in g a warm place t o s i t dur ing t he day and a warmplace to s leep a t n igh t . A s a method o f inc reas ing the overa l le f f i c i enc y o f f ue l u t i l i z a t i o n i n t he househo ld , t he kang repres en tsa ra the r ingenious invent ion o f the Chinese people.3.3 S o l a r Heated Homes and So la r Water

Heating SystemsChina s ta r te d s ol ar energy research and i t s appl icat ions i n

the l a t e 1950s , du r i ng wh ic h t ime a t t en t i on was l im i t ed t o s o la rcookstoves. N o w China has 150 so la r energy research in st i tu t i o n sand un i ver s i t i es a t var ious lev e ls w i th more than 1,000 sc ie n t i s t sand technical sp ec ia l i s t s work ing f o r th e development of th is newenergy source fo r a var ie t y o f ap p l i ca t ions . ( 11)

Solar energy research and development in China ranges fromhighly technical s tudies to pract ica l development and appl icat ion.In th e f i r s t ca tegory a re photovo l ta ic improvements, p r im ar i l y i ns i ng le c r y s t a l s i l i c o n c e l l s , Se lec t i v e s u r f ac e app l i c a t i ons onglass and meta ls , and evacuated tub ul ar co l l ec to r des ign and f a b r i -ca tion. I n the ap p l i ca t ion area are improvements i n so l a r waterheaters , ac t iv e and pass ive heat ing development , the sol ar s t i l lf o r d is t i l l a t i o n o f sea water and so l a r cooks toves. I n commercia lproduct ion and use are so la r water heat ing col le c t or s , b iogasdigesters and smal l ph oto vol ta ic power un i t s f o r communication ands igna l ing . O t h e r so la r research and deve lopment a c t i v i t i e s inc lude

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60dry ing o f v a r ious p roduct s w i t h s o la r hea ted a i r , s o la r r e f r i g e ra t o rs ,non-convective s ol ar ponds and so la r heat storage.

Vast i n a rea , Ch ina i s a count ry where two- th i rds o f i t s landcan have more than 2,000 hours o f sunshine each year. L a s a (Lhasa ),which i s us ua l l y c a l l e d " s un l i gh t c i t y " , t he c ap i t a l o f X izang(T ibet ) , has an average of 3,006 hours o f sunshine a year . B e i j i n ghas 2,700 hours o f sunshine each yea r. I t would appear the ref orethat th e northern and northwestern pa rt s o f China and th e Qinghai-Xizang p lateau w i th t h e i r dry and c l ea r a i r have ext remely goodnatural condi t ions f o r harnessing sol ar energy.

The appl icat ion of solar energy for space heat ing purposeshas made progress i n rece nt yea rs, bu t most o f the app l ica t io ns havenot ye t reached th e commercial s tag e. M o s t o f th e so la r heated homesare b u i l t i n Quinghai prov ince and Gansu prov ince, bot h i n th esouthwest pa r t o f Ch ina. Acc ord in g t o an ar t i c l e i n the Peop le 'sDai ly, a res ide nt i a l so la r heat ing home was b u i l t i n Ounhuang county ,Gansu province in 1980 using a t rombe-wal l air- f lowing passive solarspace-heating sys tem. A f t e r a month o f tes t in g , the res u l t s werefa i r l y sa t i s fac to ry . When t he ou ts ide tempera ture was 8.26C,the maximum room temperatu re o f th e s o l a r heated home reached 20Cand minimum room temperatu re was 15C. T h e average room temperatur ewas 16.77C. I n th e Dunhuang county a rea , t h e usual room temperaturew i thout heat ing i n the w in te r t ime was about 7 .9C. A f t e r conventiona lheat ing, t h e room temperature could reach 16.3C, which was s t i l l0.47C lower than the average room temperature of the solar heatedhome. (1 2) Tw o oth er so la r heated homes were b u i l t i n 1978 i n Gansu


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As ol ar water-heating system was f i r s t used i n Lasa, Xizangin the 19 601s ,m o s t lyf o rb at hh ou se san

Since then, more than 2,000 square meters of solar water-heatingcollectors have been b u i l t i n Lasa. (15) T hos e sol ar c olle cto rs canraise th e water t o a maximum of 70C. S o l a r water-heaters have als obeen in st a ll ed i n many hote ls, ba th houses, and barber shops i n

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province, which showed almost the same res ul ts as the room temperaturein the Dunhuang experiment.

Another published account of a solar heated home applicationis i n Xining c i t y, Qinghai province. Th er e a 700 square meter portionof a f iv e-sto ry of f ice bui ld ing, the tota l f lo o r space of which wasabout 3,000 square meters, was heated by so la r energy. A f t e r ayear's use, th e r esul ts were very good. (13) A p a r t from theseexperimental models, th e f i r s t series o f pr ac ti ca ll y used passivesolar heated homes, to t a l l i n g f if t e en , have now been b u i l t i n Gansu,Inner Mongolia, Gingha i, T ian j i n , Shenyang, Be ij in g and Shijiazhuang.These app lica tions are being made both i n houses and f iv e-st o rybuilding apartments. (14 ) Unf ort un ate ly fu rt he r information aboutthese so la r heated homes, th e mater ials used f o r bu il ding them,technical features , t he c ost and pay-back period i s s t i l l unavailable.I t i s possib le th at so la r heated home app lications can be expandedto many part s o f China, espe cia lly to those ru ra l areas which requi reonly a s l i gh t bolstering o f the heat supply i n winter. T h i s amountof heat can be provided through e it he r so la r heated homes o r theimprovement o f insu la ti on o f the windows, doors and wa ll s o f thehouse.


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Xingjiang and Beijing since the 19701s . A c c o r d i n gt o a na r t i c l ei n

People's Da il y, more than 100,000 square meters o f so la r water-heating coll ecto rs have been b u i l t in China, about h al f o f which arein use i n Bei j ing. (16 ) (S ee Figures 3.4 and 3.5 ) Lo cated at 40degrees nor th l at it ud e. A n average o f 1 square meter o f s unl igh tharnessed at Beijing can heat 100 kilograms of water daily totemperatures from 40C to 60C. S o l a r water-heating col lect ors canbe u t i li zed s i x t o seven months o f each ye ar, and each square meterof sola r co lle cto r could save up t o 200 to 300 kilograms o f coalannually. (17)The most si gn if ic an t p oi nt o f such so la r water-heaterapplications i s th a t t hey are beginning t o be used in households i nrural as well as urban areas. I n Daxing county, Bei j i ng , s ol arwater col lec tor s have been b u i l t with the capacity to supply 15,000people with showers each day. A t t e n t i o n has al so been direc ted t othe Linmingying Production Brigade where every household has b u i l ta so la r bath house. (2 0) ( S e e Figure 3 . 6 ) So la r water-heaters havealso been installed in some of the apartment buildings in Beijing.(See Figure 3.7) This type of solar water-heater uses a closed-loop system wi th a co ll ec to r area o f 1 square meter and water storagecapacity of between 70 to 100 l i t r e s , su ff ic ie nt fo r the hot watersupply f o r a household.

In recent years, Hebei and Henan provinces, and mun ic ipali tie sof Beijing and Shanghai have built many kinds of solar water-heaters.Now China has more than t h i r t y fa ct or ie s and companies i n f i f t e encit i es and provinces manufacturing d iff er en t types o f sola r


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Figure 3.5. Solar wate r he at in g system (300m2)w ith capac i t y f o r supp lying ho twater f o r 1,000 people t o takeshowers. (19)

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Figure 3.6 . S o l a r water heating system usedin an apartment bui ldi ng . (2 1)

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4 . : 4 Wrc.0

v i gk

'

Figure 3 . 7 So la r bathhouse i n LinmingyingProduction Brigade of ChangziyingCommune Daxing Cou nty, B e i j i n g . ( 2 2 )

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67water-heaters w it h an annual production capacit y o f 50,000 squaremeters of solar collectors. (23)

Although data on the cost of these solar water-heatingsystems i s scarce, t he information ava ilab le seems t o ind ica te th atthe cost o f buil ding so la r water-heaters i n China i s much lower thanthat in the Uni ted States. Gene ral ly th i s low cost ref le cts thecheap lab or cost i n China and the selection o f inexpensive materials .Atype o f shallow tank sol ar water-heater without water storage wasmanufactured i n Nanjing. E ach square meter o f so la r co ll ec to r con-sumes about 20 kilograms o f metal materi al s and costs about 40yuan. (24 ) Ot he r information suppl ies clues t o the cost o f the sola rwater-heating system i n the Be iji ng Science and Education F ilmStudio. T h i s stu dio uses a so la r water-heating system wit h vacuumtube collec tor s, inste ad o f a conventional water bo il er fueled bypetroleum, t o sup

cooking stoves and space heating in the people's republic of china by hang zhu

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