, Vol 3, No 1 (2012)

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Continental J. Renewable Energy 3 (1): 8 - 13 2012 ISSN: 2251 - 0494

Wilolud Journals, 2012 http://www.wiloludjournal.com

Printed in Nigeria doi:10.5707/cjre.2012.3.1.8.13

 

 

PERFORMANCE COMPARISON OF A PORTABLE ROCKET STOVE WITH SOME NIGERIAN WOODSTOVES.

 

Abdulrahim A. Toyin1, Ojo B. Emmanuel1, Oumarou M. Ben1 and Liman B. Sanda1,2

1Department of Mechanical Engineering, University of Maiduguri, Maiduguri, Nigeria.

2Department of Estate and Works, National Assembly, Maitama, Abuja, Nigeria.

 

ABSTRACT

The performance of a developed rocket stove was compared with existing local woodstoves namely the Three stones and Metal cylindrical wood stoves which represent typical Nigerian woodstoves. The test results revealed that in the boiling of 3.5kg of water, the percentage heat utilized (PHU) in the three stones stove, metal cylindrical shape stove and rocket stove are 11.6%, 14.05% and 16.3% respectively, and the power dissipated(P) by the wood are 10.89kW, 7.71kW and 5.63kW respectively. The above shows that the percentage heat utilized (PHU) of the rocket stove is higher and the power dissipated (P) by the wood is lesser in the rocket stove when compared with the other stoves. The results show that the rocket stove is more effective and efficient when compared to the already existing woodstoves. The adoption of the rocket stove in Nigeria with help in reducing the increasing rate of fuel wood consumption as well reduced the heath risk associated with the usage of the common and existing wood stoves.

 

KEYWORDS: Performance, Three stones stove, Metal cylindrical shape stove and Rocket stove.

 

INTRODUCTION

The use of wood for domestic purposes is projected to have begun some 400,000 to 500,000 years ago and bio-fuels, especially wood has remained the most widely used fuel both for domestic and industrial purposes throughout the changes of history (Openshaw, 1980; Foley and Moss, 1985). With over 80% of the total wood consumption in the less developed countries, the demand for fuel wood from natural forest resources have greatly increased, the world over, due to increase in population growth (Osemeobo, 1992). Populations around the world are going to continue using biomass fuel for indefinite future as a source of domestic energy. In Nigeria, wood used for cooking accounts for nearly 80% of the energy consumption (Akinbode, 1991), and in arid-zone of the country like Borno, fuel wood has been identified as the major energy utilized for heating and cooking purposes (Malgwi and Bumba, 2003).

 

The largest strides have been made in innovations for biomass burning stoves such as the wood burning stoves used in many of the most populous countries. As concern about air pollution, deforestation and climate change have increased due to the continuous consumption of fuel wood, new efforts are been made to improve the design of stoves. Domestic woodstoves are designed to perform heating tasks such as water heating and cooking. Akinbode (1991) identified typical Nigerian woodstoves and investigated their performance under in-door and outdoor conditions. Improved woodstoves have been developed in Nigeria and a number of performance evaluations as well as comparism have been carried out (Danshehu et al., 1992; Garba and Atiku, 1996; 1997; Olorunnisola, 1999).

 

Rocket stove is also an improved woodstove with quite a number of advantages. According to Ianto and Leslie (2006, 2011), the design of rocket stove address the fundamental problems that wood and other biomass stoves have such as the consumption of large amount of fuel to produce relatively small amount of heat and the production of fumes that cause significant indoor and environmental pollutants. A rocket stove is an innovation clean and efficient cooking stove using small diameter wood fuel which is burnt in a simple high-temperature combustion chamber containing an insulated vertical chimney which ensures complete combustion prior to the flames reaching the cooking surface (Leslie, 2008). Fuel savings may not only be the driving factor in the adaptation of rocket stove, it also saves children from the dangers of burns from the open fire, reduce respiratory diseases and burn clean and free of soot. Rocket stove has been used for cooking in many third-world localities (notably Rwandan refugee camps) as well as for space and water heating.

 

Abdulrahim A. Toyin et al.,: Continental J. Renewable Energy 3 (1): 8 - 13 2012

 

 

In Nigeria, Rocket stove is not yet common despite its various advantages. The present study is therefore aimed at carrying out performance evaluation of a developed Rocket stove as well compare its performance with some traditional local wood stoves.

 

MATERIALS AND METHOD

Materials

The materials used for this study include developed Rocket stove (Fig. 1), Three stones stove and Metal cylindrical shape stove as showed in Fig. 2. Others are Scale Weigh machine, Mercury in glass Thermometers, fuel woods, Water, Aluminum pots, and Stop watch.

The main components of the rocket stove are the following:

i.                     Fuel Magazine: A cavity into which the unburned fuel is placed and from where it feeds into the combustion chamber.

ii.                    Combustion Chamber: Is located at the end of the fuel magazine where the wood fuel is burned.

iii.                  Chimney: A vertical chimney above the combustion chamber to provide the updraft needed to maintain the fire.

iv.                  Heat Exchanger: To transfer the heat to where it is needed.

 

As the fuel burns within the combustion chamber, convection draws new air into the combustion chamber from below ensuring that any smoke from smoldering wood near to the fire is also drawn into the fire and up the chimney. The chimney is insulated to maximize the temperature and improve combustion. From the chimney, heat passed into a suitable heat exchanger to ensure the efficient use of the generated heat. The developed Rocket stove is shown in Fig. 1.

 

Figure 1: Developed Rocket Stove

 

Method

The three stoves were loaded with measured mass of fuel woods and ignited with fire. Once the fire is going down, it was tended regularly, as well as adding new wood as the fire burns, it is also of important to constantly push burning pieces of wood all the way into the combustion chamber. Three aluminum pots filled with measured volume of water were placed on each of the stoves. The heating processes were carried out at outdoor conditions. The initial Temperatures of the water were measured using the mercury in glass thermometer and left on the stoves for the water boiling tests. Subsequently, the water Temperatures were taken at 5minutes

Abdulrahim A. Toyin et al.,: Continental J. Renewable Energy 3 (1): 8 - 13 2012

 

 

interval. After boiling, the final temperatures of the water were measured, the time taken as well as the leftover woods for each of the stove was also measured. The experimentation set-up is as shown in Fig. 2.

 

Figure 2: Experimental set-up for the Water boiling tests Showing Rocket, Metal cylindrical shape and Three stones wood stoves.

 

The following expressions were used to analyze the performance of the three stoves in order to obtain their efficiencies comparatively.

 

The percentage heat utilized (PHU) in boiling is (Akinbode,1991):

(2.1)

 

Power (P1) dissipated by wood during boiling (Akinbode,1991):

..... (2.2)

 

Equivalent wood consumed after boiling (Akinbode,1991)

. (2.3)

 

where;

B0 = Weight of wood in kg at the beginning of boiling.

B1 = Weight of wood in kg remaining after boiling.

C1 = Weight of wood/charcoal remaining after boiling.

BS1 = Equivalent wood consumed after boiling.

M0 = Initial weight of water.

M1 = Weight of water remaining after boiling.

T0 = Initial temperature of water.

MV = Weight of pot.

TE = Time taken by water to boil.

CW = Calorific value of the wood (14680kJ/kg) (Akinbode,1991)

X = Relative humidity

 

Abdulrahim A. Toyin et al.,: Continental J. Renewable Energy 3 (1): 8 - 13 2012

 

 

RESULTS

The results obtained are presented in Tables 1 and 2 for the measured parameters during the experiments, and the calculated values of the performance indicators are presented in Table 3.

 

Table 1: Temperature variation with time when the three stoves are loaded with 2kg of wood for boiling 4 litres of water.

 

Time (min)

Metal cylindrical shape stove

Three stones stove

Rocket stove

Temperature (0C)

Weight of wood used (kg)

Temperature (0C)

Weight of wood used (kg)

Temperature (0C)

Weight of wood used (kg)

0:00

34.0

0.0

34.0

0.0

34.0

0.0

0:05

39.0

_

41.0

_

37.0

_

0:10

45.0

_

44.0

_

47.0

_

0:15

60.0

_

57.0

_

69.0

_

0:20

69.0

_

67.0

_

92.0

_

0:25

86.0

_

81.0

_

100.0

_

0:30

99.0

1.3

97.0

1.5

_

0.9

 

Table 2: Temperature variation with time when the three stoves are loaded with 2.5kg of wood for boiling 4 litres of water.

 

Time (min)

Metal cylindrical shape stove

Three stones stove

Rocket stove

Temperature (0C)

Weight of wood used (kg)

Temperature (0C)

Weight of wood used (kg)

Temperature (0C)

Weight of wood used (kg)

0:00

35.0

0.0

35.0

0.0

35.0

0.0

0:05

45.0

_

40.0

_

42.0

_

0:10

56.0

_

49.0

_

62.0

_

0:15

74.0

_

65.0

_

87.0

_

0:18

87.0

_

82.0

_

100.0

_

0:20

97.0

_

89.0

_

_

_

0:21

100.0

_

96.0

_

_

_

0:23

_

_

100.0

-

_

_

After boiling for 30min

98.0

1.8

96.0

2.0

100.0

1.4

 

 

 

 

Abdulrahim A. Toyin et al.,: Continental J. Renewable Energy 3 (1): 8 - 13 2012

 

 

 

Table 3: Summary of the comparative efficiencies of the three stoves

 

Type of Stove

 

PHU for Boiling (%)

Power dissipated by wood (kW)

 

 

 

 

Three stones stove

 

11.6

10.89

 

 

 

 

Metal cylindrical shape stove

 

 

14.05

7.71

 

 

 

 

Rocket stove

 

16.3

5.63

 

DISCUSSION

From the results obtained in Table 1, it shows that the rocket stove gets to a boiling state of 100in 25min using 0.9kg of wood to boil 4litres of water while the three stones stove and the metal cylindrical shape stove gets to a boiling state of 97in 30min using 1.5kg of wood and 99in 30min using 1.3kg respectively to boil 4litres of water respectively. From Table 2, it could be observed that the temperature of the 4 litres of water remained constant even after keeping the water for continuous boiling for another 30 minutes in the rocket stove, whereas in the three stone stove and the metal cylindrical shape stove the temperature of the same quantity of water reduces, this is due to the quantity of wood remaining in their respective combustion chambers and the heat transfer processes in the stoves. From Table 3, it can be observed that the percentage heat utilized by the rocket stove is higher when compared to the three stones stove and the metal cylindrical shape stove. The rocket stove also uses a lesser power dissipated by the wood during the boiling process. Comparing the efficiency of the woodstoves from their evaluation tests, the rocket stove is found to have the highest efficiency, the insulation capacity of the rocket stove might accounts for its high efficiency as well as effective heat transfer processes between the combustion chamber and the pot among others.

 

From observations during the experimentation, it was noticed that the three stones stove and the metal cylindrical shape stove produces more smoke due to incomplete combustion. Also, during the boiling tests they experience a heat loss due to external air draft from the environment, but for the rocket stove it produces less smoke at the initial stage of the wood burning and subsequently produces quite lesser smoke which shows a sign of a complete combustion and good air circulation. For the Rocket stove, there was no problem getting enough air into the fire or having smoke back out of the combustion chamber. This makes starting a fire very easy, there were a little ashes left over. The wood burned hot and combusted completely.

 

CONCLUSION AND RECOMMENDATIONS

The rocket stove took lesser time and used lesser wood for the heating operations when compared to the other type of woodstoves namely the metal cylindrical shape and the three stones wood stoves. In boiling 3.5kg of water, the percentage heat utilized (PHU) in the three stones stove, metal cylindrical shape stove and rocket stove are 11.6%, 14.05% and 16.3% respectively, and the power (P)dissipated by the wood are 10.89kW, 7.71kW and 5.63kW respectively. These results show that the effectiveness of the rocket stove by the percentage heat utilized (PHU) is higher and the power (P) dissipated by the wood is lesser when compared with the performance of the metal cylindrical shape and the three stones wood stoves. In-door boiling and cooking tests are recommended for the three wood cooking stoves.

 

REFERENCES

Akinbode F.O. (1991). Testing the efficiency of Nigerian woodstoves. Nigerian Journal of Renewable Energy, Vol. 2, No. 1, pp. 43-48.

 

Danshehu B. G. Sambo A. S. and Musa, M. (1992). Comparative performance of Saw-dust and Wood-burning Stoves. Nigerian Journal of Renewable Energy, Vol. 3, No. 1, pp. 50-55.

 

Foley G. and Moss P. (1985). Improved cooking stoves in Developing Countries. Technical Report, No. 2 IIED (Earthscan) for Energy Information Programmes, London, 177.

Abdulrahim A. Toyin et al.,: Continental J. Renewable Energy 3 (1): 8 - 13 2012

 

 

Garba B. and Atiku A. T. (1996). Studies of the Mechanical Properties of some construction materials for improved wood-burning Stove. Nigerian Journal of Renewable Energy, Vol. 4, No. 2, pp. 19-25.

 

Garba B. and Atiku A. T. (1997). Thermal Studies on some Tropical Tree Species and their performance in improved wood-burning Stoves. Nigerian Journal of Renewable Energy, Vol. 5, No. 1&2, pp. 16-20.

 

Ianto E. (2008). Rocket stove to Heat cob buildings, Cob Cottage Company.

 

Ianto E. and Leslie J. (2006). Rocket Mass Heater: superefficient woodstoves you can build, Cob Cottage Company.

 

Ianto E. and Leslie J. (2011). Book Review-Rocket Mass Heater, Cob Cottage Company.

 

Malgwi D. I. and Bumba U. M. (2003). Fuelwood Exploitation from the Natural Ecosystem in Borno State, Nigeria: Socio-Economic and environmental Implications. Nigerian Journal of Renewable Energy, Vol. 11, No. 1&2, pp. 33-40.

 

Olorunnisola A. O. (1999). The Efficiency of Two Nigerians Cooking Stoves in Handling Corn-Cob Briquettes. Nigerian Journal of Renewable Energy, Vol. 7, No. 1&2, pp. 31-34.

 

Openshaw K. (1980). Wood fuel A time for reassessment. In: V. Smil and W.E. Knowland (eds.), Energy in Developing World: the Real Energy Crisis. Journ. of UN in Energy, Minerals and Water Resources, Vol. 3, No. 1, pp. 72-81.

 

Osemeobo G. J. (1992). Fuelwood Exploitation from Natural Ecosystem in Nigeria: Socio-Economic and Ecological Implication. Journ. of Rural Dev. Vol. 11, No. 2, pp. 141-155.

 

Received for Publication: 05/06/2012

Accepted for Publication: 23/08/2012

 

Corresponding Author

Abdulrahim A. Toyin

Department of Mechanical Engineering, University of Maiduguri, Maiduguri, Nigeria.

Email: engrabdulrahimat@yahoo.com