Research Article
2018, 2(2), Article No: 25

## Performance Evaluation of Waste Heat Recovery in a Charcoal Stove using a Thermo-Electric Module

Published online: 13 Mar 2018
View: 841

# Abstract

Charcoal stoves have widespread use among the poorer households and outdoor food vendors in Nigeria. In order to improve the efficiency of charcoal stoves, various researches have tried integrating a thermoelectric module in the charcoal stove. The researches, however did not exploit the performance of the thermoelectric modules at different ambient temperatures. To evaluate the performance of thermoelectric integrated charcoal stoves in the sub-Saharan Africa, a self-powered, forced air induced thermoelectric charcoal stove experiment was carried out at five different ambient temperatures of 36ºC, 33ºC, 32ºC, 30ºC and 29ºC and an average fuel hotbed temperature of 1023.75ºC. The thermoelectric charcoal stove generated a maximum voltage of 5.25V at an ambient temperature of 29ºC. The least maximum voltage was generated at the highest ambient temperature of 36ºC. It was observed that the maximum voltage increased with decreasing ambient temperature, this could be attributed to the ambient air being used to cool the thermoelectric generator. Therefore, it could be said that the performance of a forced draft thermoelectric charcoal stove increases with decrease in ambient temperature.

# INTRODUCTION

Charcoal is widely accepted as fuel for cooking especially in Sub-Sahara Africa and other developing nations. Given that large numbers of people still use inefficient charcoal stoves (E+Carbon, 2009), it is necessary to design low-cost efficient charcoal burners.

For cooking stoves, the amount of the heat content of the charcoal transferred to the load/cooking vessel determines the efficiency. Equation 1 gives the formula for calculating the efficiency of the stove;

 $NG_{s} = \frac{\text{Heat transferred to the load}}{\text{Heat content of fuel}}$ (1)

Currently, a great deal of efforts have been put into making low-cost efficient charcoal burners. According to Toyola Energy Limited, their charcoal burner ToyolaCoalpot is 33% more fuel-efficient than traditional charcoal burners (E+Carbon, 2009). This is achieved by the introduction of a ceramic liner inside the combustion zone, which increases combustion efficiency and retains heat. The ceramic liner is said to have a potential to improve fuel efficiency by up to 50% (E+Carbon, 2009). Also, to achieve improved energy efficiency with low-cost, a prototype charcoal stove has been built using principles of combustion and heat transfer to improve stove efficiency (Milind, 2009).

A unique method of increasing efficiency of the charcoal burner is by recovering the waste heat; this can be done through the use of a thermoelectric module. The concept of thermoelectric generator (TEG) integrated stove research was first done by J.C Bass and Killander in 1996 (Killander and Bass, 1996). The main objective was to make the stove very affordable and efficient for rural people and others devoid of electricity.

Nuwayhid et al studied the possibility of using a proportion of the heat from 20-50kW wood stove, to provide a continuous 10-100W electric power supply (Nuwayhid et al., 2003). In a first prototype, they used a cheap Peltier module for their TE generator. The maximum power for a module was found to be very low (1W) mostly because of the limited temperature difference due to the maximum temperature supported by the module. It is also because of the geometry, which was optimized for cooling and not generating power. In addition, natural air was used to cool the cold-side of the module. In a subsequent prototype their TE generator used 1, 2 or 3 commercially available low-cost power generator modules (Nuwayhid and Hamade, 2005). The cold side of the TE modules was naturally cooled with the surrounding air. They got a maximum power of 4.2W for one thermoelectric module and they showed that the output per module decreased when the number of thermoelectric modules in the thermoelectric generator increased (Nuwayhid and Hamade, 2005). This is as a result of the decrease in temperature difference between opposite sides of the thermoelectric module.

Nuwayhid in one of the tests used heat pipes for the heat sink (Nuwayhid and Hamade, 2005). The maximum power obtained was about 3.4W. Lertsatitthanakorn replicated the same experiment with a commercial TE module made of bismuth telluride based materials to the stove’s side wall, thereby creating a TE generator system that utilizes a proportion of the stove’s waste heat, while also using heat pipes at the cold side to maintain a temperature difference across the module (Lertsatitthanakorn, 2007). The results show that the system generates a power output of approximately 2.4W when the temperature difference is 150°C. His economic analysis indicated that the payback period was very short.

At the ETHOS 2005 congress, Mastbergen and Wilson presented a prototype of a thermoelectric generator with a forced-air cooling for the cold side with a 1W fan (Mastbergen et al., 2005), 4W of net power was produced by the thermoelectric generator and it was able to power an array of high intensity LEDs.

Daniel Champier et al were able to produce 9.5W of electric power in a forced draft stove using bismuth telluride (Champier et al., 2011). Ice was used to maintain a temperature of under 100°C at the cold side and therefore a temperature difference across the module. They were able to show that the performance of the thermoelectric generator was influenced by the heat transfer through the modules and especially by the thermal contact resistances. The aluminum surface of the heat sinks used was reduced to a flatness of 25 micrometers (standard deviation of height). Mastbergen highlighted the role played by thermal contact resistances in thermoelectric generator performance (Mastbergen et al., 2005). According to him, the thermal resistances at the interfaces between the module and the heat sinks are also important to keep to a minimum, and recommended very flat surfaces of within 0.001”. Daniel Champier et al suggested that a resistance of 500kPa was sufficient to minimize the contact resistance for the thermoelectric (Champier et al., 2011). In another experiment, Daniel Champier made use of four (4) TE modules in series and tried two different cooling systems (Champier et al., 2011):

1. A heat fins exchanger being placed on the cold side with a 10W air fan; and

2. A water tank directly put on the cold side of the TE module.

The amount of water contained in the tank applied a pressure of 10 kPa. A weight placed on rods above the fan applied the same pressure on the cell. By comparing the evolution of the temperature of the two cooling devices, it was learnt that for equivalent temperatures on the hot side, different temperatures on the cold side were reached. The cold-side temperature reached 117°C when the air fan was used, whereas, it was only 65°C with the use of ice; therefore, cooling with the air fan was not as efficient as with ice. In the experiment, a total power of about 7W was produced with a temperature difference of 160°C between the two sides of the generator. Measuring each cell independently to ascertain their individual performance, it was found that the maximum power reached by each module varied between 1.7W and 2.3W for a temperature difference between the sides of 160°C. It was also verified that the efficiency of a TE module is proportional to $$\text{ΔT}$$ which is reasonable, as the output power is proportional to $$\text{ΔT}^{2}$$ and heat flux to $$\text{ΔT}$$. For a temperature difference of 60°C, the efficiency of a thermoelectric module is about 0.6% and the heat flow through the module is around 100W. However, a thermoelectric module efficiency of about 2% is obtained when computer simulation is done with a temperature difference of 200°C (Champier et al., 2011).

A commercially available biomass stove in the U.S., BioLite, uses a thermoelectric generator to create clean, efficient cooking with a forced-air draft fan (BioLite, 2015). Additionally, it has a 5W outlet powered by the TE generator that can be used to charge/power various electronic devices.

Rinalde et al were able to generate a maximum electrical power of 10W through the use of a heat pump, which certainly decreased the available output power (Rinalde et al., 2010). Their laboratory prototype used an electric heater for the heat source and forced water cooling system to maintain a temperature difference across the thermoelectric module.

O’Shaughnessy et al used a single Seebeck optimized thermoelectric module with forced air cooling and heat pipes applied at the cold side of module to convert a small portion of heat from a stove to electricity (O’Shaughnessy et al., 2013). The electricity produced was used to charge a single 3.3V lithium–ion phosphate battery and drive a low power fan, as well as some other auxiliary features. The airflow produced by the fan was used in conjunction with a commercially available heat pipe heat sink to maintain an adequate temperature difference across the thermoelectric module. From experiments in the laboratory, a maximum TEG power output of 5.9W has been obtained. On average, 3Wh of energy was stored in a battery during a typical 1hr long burn. Three 1hr long burns produced sufficient energy to fully charge the battery.

After going through various literatures, it has been found that the voltage generated by the thermoelectric module using natural and forced air cooled induction at different operating temperatures has not yet been exploited, this study therefore aims to fill in the gap.

# OBJECTIVES

The objectives of this research was to retrofit a conventional charcoal burner with a thermoelectric generator to recover heat. After which, data from the system will be obtained detailing the electromotive force generated by the thermoelectric generator at different operating temperatures of the burner, and evaluation of the voltage generated by the thermoelectric generator of the charcoal stove at different ambient temperatures

# MATERIALS AND METHODS

## Materials

A TEG1-127-2.0-1.3 thermoelectric module manufactured by EVERREDtronics was bought online from Amazon store. The hot and cold sides of the module were identified. A silicon-based adhesive thermal grease, HT-GY260, with thermal conductivity greater than 1W/m.K and thermal impedance less than 1.36ºC-cm2/W was applied on the both surfaces of the thermoelectric module. This was done to obtain reasonable heat transfer and interfacing of the thermoelectric module with heat sinks. Two extruded aluminum heat-sinks of dimensions 28 x 28 x 20mm were obtained online from Amazon, and their top drilled to allow for insertion of type-J thermocouples. With thermal grease serving as the interfacing material, the thermoelectric module was placed in-between the two heat sinks to form the thermoelectric generator (TEG).

A low-permanence magnet DC driven fan of rated voltage 0.5-5 V and rpm of 3800 was placed at the fin side of the heat-sink attached to the cold-side of the thermoelectric module to force draft to cool the TEG. The electrical terminals of the fan were joined with the terminals of the thermoelectric module, so that the fan could be powered from the power generated from the module.

A charcoal stove was obtained from a local store in Ibadan, Oyo State. Its combustion section was an inverted truncated square pyramid of base side 7.8cm, top side of 22.1cm, and height of 16.1cm giving a volume of approximately 3870cm3. Charcoal was sourced locally from the market in Kaduna, Nigeria. The charcoal was used as fuel in the charcoal stove. The thermoelectric generator was placed in a cut-out section of the wall of the combustion chamber of the charcoal (see Figure 1).

Type-J thermocouples were placed in the holes drilled in each of the heat-sinks, and a voltage sensor was placed was connected in parallel to the electrical terminals of the thermoelectric module. The type-J thermocouples and voltage sensors were hard-wired to an Arduino micro-controller.

## Experimental Method

The temperature of the ambient where the experimental rig was setup was recorded. The coupled thermoelectric generator was placed on the hot path of the combustion product. Type-J thermocouples were used to measure the temperature difference across the generator, while the voltage transducer is used to record the generated voltage. The micro-controller collects the various data every 10 seconds and logs the data unto a computer. The handheld digital multi-meter was used to take measurements of the current and recorded by hand.

The thermoelectric charcoal stove was run at five different ambient temperatures of 36ºC, 33ºC, 32ºC, 30ºC and 29ºC with an average fuel hotbed temperature of 1023.75ºC. Figures 2 and 3 show the thermoelectric charcoal stove in operation with the data being collected on a computer. The data were saved as text files and analyzed using R programming language.

## Calculating Efficiency of Cookstove

Firepower is the energy released by the burning fuel per unit time. Therefore, for any combustion phase, firepower can be calculated as follows (Chen et al., n.a):

 $\text{Fire power}\left( W \right) = \ \frac{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}}{\text{time}}$ (2)

where:

P = power (W)

Mci = initial mass of charcoal in the cook stove (g)

Mcf = final mass of charcoal in the cook stove (g)

Hc = energy content of charcoal (29000J/g)

Time = time of combustion phase (s)

Using the time it takes to boil water by a specified amount of the fuel, efficiency becomes the ratio of energy transferred to the water in the cooking pot to energy released by the burning fuel. Since the energy transferred to the water are in two phases – i.e. energy required to raise the temperature of water and energy required to evaporate the water – the efficiency will be calculated in two phases; hi-power phase (during temperature change of the water) and low-power phase (evaporation of the water). The following formulas which were gotten from literature (Chen et al., n.a), will be used in calculating efficiency,

During hi-power phase (conventional stove):

 $Efficiency (\%) = \frac{M_{w} \times C_{w} \times (T_{f} - T_{i})}{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}}$ (3)

During hi-power phase (thermoelectric integrated stove):

 $Efficiency (\%) = \frac{M_{w} \times C_{w} \times \left( T_{f} - T_{i} \right) + (V_{\text{av}}I_{\text{av}}t)}{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}}$ (4)

During low-power phase (conventional stove):

 $\text{Efficiency}\left( \% \right) = \frac{H_{w} \times (M_{\text{wi}} - M_{\text{wf}})}{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}}$ (5)

During low-power phase (thermoelectric integrated stove):

 $\text{Efficiency}\left( \% \right) = \frac{H_{w} \times \left( M_{\text{wi}} - M_{\text{wf}} \right) + (V_{\text{av}}I_{\text{av}}t)}{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}}$ (6)

where:

Mw = average water mass in the cook pot from pre-start to finish

Cw = heat capacity of water (4.184J/gºC)

Tf = temperature of first boiling (ºC)

Ti = initial temperature of the water in the pot (ºC)

Hw = heat of vaporization of water (2260J/g)

Vav = average voltage generated during operation

Iav = average current generated during operation

T = time

# RESULTS AND DISCUSSION

The charcoal stove was operated at an average fuel hot-bed temperature of 1023.75°C and run at five different ambient temperatures of 29ºC, 30ºC, 32ºC, 33ºC and 36ºC. Readings were taken every 10 seconds for a total of 15 minutes. Natural air-cooling was used until the voltage generated by the thermoelectric module reached 0.5 V after which it was able to power the fan to force draft to cool the TEG.

## Case 1: At Ambient Temperature of 36ºC

A maximum voltage of 3.01 V was achieved, and this occurred at a temperature difference of 54ºC and a hot-side temperature of 136ºC. The value of voltage increased linearly with the temperature difference before reaching its peak, after which it started forming a downward curve (Figure 4). The mean voltage generated was 0.9964 V and the median voltage value is 0.36 V. The mean temperature difference is ∆Tmean =23.84ºC, while the maximum temperature difference is 150ºC with a corresponding hot side temperature of 241ºC and voltage of 2.61 V. The graph of voltage generated against the hot side temperature is shown in Figure 5. Voltage increases linearly with increase in hot side temperature, after which it starts to form a downward curve. At a voltage of 0.5 V, where the powering of the fan by the TEG starts, gives a hot side temperature of 64ºC and temperature difference of 10.

Table 1 provides a summary of the parameters operating at 36ºC ambient temperature. The data used can be seen at appendix A.1

Table 1. Summary of parameters at 36ºC ambient temperature

 Voltage Hot side temp (T1) Temperature difference, ∆T Min. 0.000 45.00 2.00 1st quartile 0.078 49.00 6.00 Median 0.355 57.50 9.00 Mean 0.996 79.41 23.84 3rd quartile 2.293 112.25 45.25 Max. 3.010 241.00 146.00

## Case 2: At Ambient Temperature of 33ºC

Here, maximum voltage of 3 V was achieved at a temperature difference of 72ºC and hot side temperature of 136ºC. The voltage increased linearly up to 2.7 V before it started it started curving downwards Figure 6. The mean voltage obtained is 1.15 V with the median voltage value at 0.73 V. The mean temperature difference is ∆Tmean=25.81ºC, while the maximum temperature difference (∆T=103ºC) (see Figure 7) occurred at a hot side temperature of 176ºC and gave a voltage of 2.74 V. At the voltage of 0.5 V, where the fan starts to be powered, the hot side temperature and temperature difference were 63ºC and 14ºC respectively.

Table 2 provides a summary of the parameters operating at 33ºC ambient temperature. The data used to generate the table can be found in appendix A.2

Table 2. Summary of parameters at 33ºC ambient temperature

 Voltage Hot side temp (T1) Temperature difference, ∆T Min. 0.000 41.00 4.00 1st quartile 0.295 53.25 11.00 Median 0.730 67.50 15.00 Mean 1.146 78.83 25.81 3rd quartile 2.038 98.25 36.50 Max. 3.060 176.00 103.00

## Case 3: At Ambient Temperature of 32ºC

The voltage increased linearly to up to its peak 3.49 V at a temperature difference of 86ºC (Figure 8). From Figure 9 the peak voltage occurred at a hot side temperature of about 55ºC. The mean voltage generated is 1.34 V and the median voltage is 1.15 V. The mean temperature difference is ∆Tmean = 29.04ºC, while the maximum temperature difference obtained is 86ºC, and the corresponding voltage and hot side temperature are 3.49 V and 141ºC respectively. At the 0.5 V voltage point, the hot side temperature was 60ºC and temperature difference of 17ºC.

Table 3 provides a summary of the parameters operating at 32ºC ambient temperature. The data used to generate the table can be found in appendix A.3

Table 3. Summary of parameters at 32ºC ambient temperature

 Voltage Hot side temp (T1) Temperature difference, ∆T Min. 0.000 39.00 6.00 1st quartile 0.540 60.25 17.00 Median 1.150 80.00 24.00 Mean 1.343 81.62 29.04 3rd quartile 1.873 89.00 29.00 Max. 3.490 141.00 86.00

## Case 4: At Ambient Temperature of 30ºC

Voltage peaked at 4.36 V after increasing linearly. The maximum voltage occurred at a temperature difference of 89ºC (Figure 10) and a hot side temperature of 150ºC (Figure 11). The mean and median voltages are 1.94 V and 1.950 V respectively. The mean temperature difference is ∆Tmean = 38.47ºC, while maximum temperature difference of 91ºC was achieved with corresponding voltage and hot side temperature of 4.23 V and 151ºC respectively. At the voltage point (0.5 V) of powering the fan, the temperature difference and hot side temperature were 12ºC and 61ºC respectively.

Table 4 provides a summary of the parameters operating at 30ºC ambient temperature. The data used to generate the table can be found in appendix A.4

Table 4. Summary of parameters at 30ºC ambient temperature

 Voltage Hot side temp (T1) Temperature difference, ∆T Min. 0.000 42.00 4.00 1st quartile 0.648 65.50 16.25 Median 1.950 89.00 31.00 Mean 1.944 92.64 38.47 3rd quartile 3.095 118.75 60.25 Max. 4.360 151.00 91.00

## Case 5: At Ambient Temperature of 29ºC

Voltage increased linearly with respect to temperature difference and peaked at 5.25 V with corresponding temperature difference of 92ºC (Figure 12), and hot side temperature of 159ºC (Figure 13). The mean and median voltages are 2.56 V and 2.788 V respectively. The mean temperature difference obtained is ∆Tmean = 48.13ºC, while the maximum obtained temperature difference is 106ºC, with corresponding voltage of 4.79 V and hot side temperature of 164ºC. At the 0.5 V point where the thermoelectric starts to power the fan, the hot side temperature was 62ºC and temperature difference of 7ºC.

Table 5 provides a summary of the parameters operating at 30ºC ambient temperature. The data used to generate the table can be found in appendix A.5.

Table 5. Summary of parameters operating at 29ºC ambient temperature

 Voltage Hot side temp (T1) Temperature difference, ∆T Min. 0.000 45.00 3.00 1st quartile 0.788 71.75 19.25 Median 2.785 98.00 39.00 Mean 2.560 103.78 48.13 3rd quartile 4.308 149.50 91.00 Max. 5.250 164.00 106.00

The graphs of voltage generated versus hot side temperature, T1, for ambient temperatures of 29ºC, 30ºC and 32ºC follow a similar linear pattern, however for ambient temperatures of 33ºC and 36ºC, a downward curve begins to appear at about 60ºC. Similarly graphs of voltage generated versus ∆T for ambient temperatures of 29ºC, 30ºC and 32ºC have the same pattern, while ambient temperatures of 33ºC and 36ºC take a different pattern. It can be seen that voltage generally increases with an increase in the hot side temperature for all ambient temperatures, with the highest voltage recordings being 5.25 V at an ambient temperature of 29ºC. It is observed that from an ambient temperature of 36ºC, each subsequent lower ambient temperature recorded a higher and maximum voltage values. Likewise, the mean voltage values increased with lower ambient temperature. Explanation for this phenomenon could come from the fact that since ambient air is used to cool the thermoelectric generator enabling temperature difference across the module, the lower the ambient temperature the more effective temperature difference is achieved across the module. This is substantiated from the data on temperature difference, where the mean temperature difference across the module is higher with decreasing ambient temperature. The mean temperature difference for 29ºC ambient temperature, which had the highest maximum and mean voltage readings, is ∆Tmean= 48.13ºC; while for 36ºC ambient temperature which had the lowest maximum and mean voltage readings, is ∆Tmean = 23.84ºC.

## Calculating and Comparing the Efficiency of the Thermoelectric Charcoal Stove with a Conventional Charcoal Stove of Similar Size at the Same Ambient Temperature of 29ºC.

From Equations 2 – 6,

High-power phase Firepower

 $\text{Fire power}\left( W \right) = \ \frac{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}}{\text{time}} = \frac{138g \times 29000J/g}{17 min \times 60s/min} = 2924W$

Low-power phase Firepower,

 $\text{Fire power}\left( W \right) = \frac{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}}{\text{time}} = \frac{19g \times 29000J/g}{14 min \times 60s/min} = 656 W$

### Efficiency for Conventional Charcoal Stove of Volume Capacity 3870 cm3 at 29ºC Ambient Temperature

High-power phase:

 $\text{Efficiency}\left( \% \right) = \frac{M_{w} \times C_{w} \times \left( T_{f} - T_{i} \right)}{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}} = \frac{2652g \times 4.184J/g°C \times \left( 100 - 27 \right)°C}{138g \times 29000J/g} = 20.24\%$

Low-power phase:

 $\text{Efficiency}\left( \% \right) = \frac{H_{w} \times (M_{\text{wi}} - M_{\text{wf}})}{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}} = \frac{2260J/g \times 139g}{19g \times 29000J/g} = 57.00\%$

### Efficiency for Thermoelectric Charcoal Stove of Volume Capacity 3870 cm3 at 29ºC Ambient Temperature

High-power phase:

 $\text{Efficiency}\left( \% \right) = \frac{M_{w} \times C_{w} \times \left( T_{f} - T_{i} \right) + \left( I_{\text{av}}V_{\text{av}}t \right)}{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}}$ $= \frac{2652g \times \frac{4.184J}{g}°C\ \times \left( 100 - 27 \right)°C + \left( 2.56*0.43 \right)*(17*60)}{138g \times 29000J/g} = 20.27\%$

Low-power phase:

 $\text{Efficiency}\left( \% \right) = \frac{H_{w} \times \left( M_{\text{wi}} - M_{\text{wf}} \right) + \left( V_{\text{av}}I_{\text{av}}t \right)}{\left( M_{\text{ci}} - M_{\text{cf}} \right) \times H_{c}}$ $= \frac{2260J/g \times 139g + \left( 2.56*1 \right)*(17*60)}{19g \times 29000J/g} = 57.49\%$

Tabulating the result of the computations,

Table 6 shows the various power and efficiency values of the conventional and thermoelectric burner at 29ºC ambient temperature. The thermoelectric burner is seen to have a slightly higher efficiency than the conventional charcoal burner.

Table 6. Power and efficiency values of the conventional and thermoelectric burner

 Conventional Burner Thermoelectric burner Ambient temperature of 29ºC Ambient temperature of 29ºC Hi-power phase Fire power (W) 2924W 2924W Efficiency (%) 20.24% 20.32% Low-power phase Fire power (W) 656W 656W Efficiency (%) 57.00% 57.6%

# CONCLUSION

The development of a conventional charcoal burner with a thermoelectric generator attached to it has been achieved and tested under real-life cooking conditions in sub-Saharan Africa. The e.m.f generated by the thermoelectric charcoal stove generally increases with increase in the hot side temperature of the thermoelectric module. When using ambient air to cool the thermoelectric module, the performance of the thermoelectric module increases with a decrease in ambient temperature. This is as a result of the lower ambient temperature enabling a higher temperature difference across the thermoelectric generator.

While the improved efficiency of a thermoelectric charcoal stove over a conventional charcoal stove is not so higher, the electrical energy from it can be put to good use, such as charging batteries and powering LEDs

# APPENDIX A

Table A.1. Data at ambient temperature of 36°C and average fuel hotbed temperature of 1023.75°C

Time (sec) Voltage T1 T2 T1-T2
10 0 45 36 9
20 0 45 42 2
30 0 45 43 2
30 0 46 43 3
40 0 46 44 3
50 0 47 44 3
60 0 47 44 3
70 0 47 44 3
80 0 47 44 3
90 0 48 42 5
100 0 48 42 6
110 0 48 40 8
120 0 48 41 7
130 0.02 47 40 7
140 0.02 48 42 6
150 0.02 47 42 6
160 0.02 48 42 5
170 0.05 47 41 6
180 0.05 47 41 6
190 0.05 47 41 6
200 0.07 48 41 7
210 0.07 48 40 8
220 0.07 48 42 7
230 0.07 49 42 7
240 0.1 49 42 7
250 0.1 49 43 6
260 0.1 49 43 7
270 0.1 50 42 8
280 0.1 50 42 8
290 0.1 50 41 9
300 0.12 49 41 9
310 0.12 50 41 9
320 0.12 50 40 10
330 0.15 50 45 5
340 0.15 50 45 5
350 0.15 50 45 5
360 0.15 50 44 6
370 0.17 50 45 6
380 0.17 51 46 6
390 0.17 52 46 6
400 0.2 52 46 6
410 0.22 52 46 6
420 0.24 52 45 8
430 0.24 54 48 6
440 0.24 55 49 7
450 0.32 56 50 6
460 0.39 59 52 7
470 0.44 60 55 5
480 0.46 63 55 8
490 0.56 64 54 10
500 0.66 66 52 15
510 0.73 68 52 16
520 0.73 70 52 18
530 0.76 71 52 19
540 0.78 72 52 20
550 0.78 73 53 20
560 0.9 75 54 20
570 1.05 77 55 22
580 1.32 80 55 25
590 1.34 83 57 26
600 1.52 87 59 28
610 1.54 89 58 31
620 1.71 91 60 31
630 1.83 95 64 32
640 1.98 100 65 35
650 2.13 104 65 39
660 2.17 107 66 41
670 2.32 110 67 43
680 2.27 113 68 46
690 2.3 115 67 48
700 2.35 119 69 50
710 2.76 122 70 51
720 2.42 122 72 51
730 2.44 126 73 53
740 2.47 128 75 53
750 2.54 132 78 54
760 3.01 136 82 54
770 2.69 140 84 55
780 2.74 141 87 54
790 2.79 143 86 57
800 2.74 143 85 58
810 2.66 143 84 59
820 2.74 143 86 57
830 2.61 241 95 146
840 2.49 141 84 58
850 2.52 142 84 59
860 2.49 140 81 59
870 2.57 139 79 59
880 2.79 137 77 61
890 2.44 137 77 60
900 2.76 136 76 60

Table A.2. Data at ambient temperature of 33°C and average fuel hot-bed temperature of 1023.75°C.

Time (sec) Voltage T1 T2 T1-T2
10 0.00 41 33 8
20 0.01 41 37 4
30 0.02 42 38 4
30 0.10 43 38 5
40 0.13 46 39 6
50 0.16 47 40 7
60 0.18 48 40 8
70 0.19 50 44 6
80 0.19 50 43 7
90 0.22 52 44 8
100 0.22 53 45 8
110 0.23 53 43 9
120 0.25 53 41 12
130 0.26 52 41 12
140 0.27 52 41 11
150 0.27 53 41 11
160 0.27 53 42 11
170 0.29 52 41 11
180 0.27 52 41 10
190 0.26 51 41 10
200 0.27 51 41 10
210 0.27 51 41 10
220 0.27 52 42 10
230 0.28 53 43 10
240 0.31 54 43 11
250 0.34 56 45 11
260 0.37 60 49 11
270 0.41 62 49 13
280 0.45 63 49 14
290 0.50 63 49 14
300 0.49 62 48 14
310 0.56 63 47 15
320 0.54 64 48 15
330 0.55 63 50 13
340 0.56 63 49 13
350 0.56 64 50 14
360 0.58 64 50 14
370 0.59 64 50 14
380 0.61 64 50 14
390 0.61 64 50 14
400 0.67 64 50 14
410 0.64 65 50 15
420 0.66 65 50 15
430 0.66 66 51 15
440 0.67 67 52 14
450 0.71 67 53 14
460 0.75 68 53 15
470 0.78 69 55 14
480 0.79 70 55 16
490 0.85 71 54 17
500 0.95 72 53 19
510 0.95 72 52 20
520 0.96 73 52 21
530 0.97 74 51 22
540 0.98 74 52 23
550 1.00 75 52 23
560 1.08 76 52 24
570 1.14 77 52 25
580 1.30 79 52 27
590 1.30 80 53 27
600 1.39 82 54 28
610 1.40 83 54 29
620 1.51 84 55 29
630 1.64 87 57 30
640 1.68 90 58 31
650 1.79 91 58 33
660 1.83 93 60 33
670 2.00 96 61 35
680 2.05 99 63 37
690 2.13 102 63 39
700 2.21 106 63 42
710 2.54 109 64 45
720 2.41 110 65 46
730 2.33 113 65 48
740 2.35 114 65 49
750 2.38 116 67 49
760 2.77 119 70 49
770 2.55 122 71 50
780 2.64 123 72 51
790 2.59 125 71 53
800 2.61 126 70 55
810 2.61 126 69 57
820 2.73 127 69 58
830 2.74 176 73 103
840 2.68 128 67 61
850 2.66 127 68 59
860 2.74 128 69 59
870 2.84 131 68 63
880 2.98 134 66 67
890 2.89 135 64 71
900 3.06 136 64 72

Table A.3. Data at ambient temperature of 32ºC and average fuel hot-bed temperature of 1023.75°C.

Time (sec) Voltage T1 T2 T1-T2
10 0.00 39 32 7
20 0.02 40 33 6
30 0.05 41 34 6
30 0.20 43 34 8
40 0.27 47 36 11
50 0.32 48 37 11
60 0.37 51 38 13
70 0.39 55 45 10
80 0.39 56 44 11
90 0.44 59 48 10
100 0.44 60 49 11
110 0.46 60 48 12
120 0.51 60 42 18
130 0.51 60 43 17
140 0.54 59 43 17
150 0.54 60 43 17
160 0.54 60 43 18
170 0.54 59 43 16
180 0.51 59 44 15
190 0.46 57 43 15
200 0.49 57 44 13
210 0.49 57 44 13
220 0.49 58 45 13
230 0.51 60 47 13
240 0.54 61 46 15
250 0.59 65 49 16
260 0.66 74 57 16
270 0.73 76 57 20
280 0.81 78 58 20
290 0.93 79 58 21
300 0.88 78 57 21
310 1.03 78 56 22
320 0.98 80 59 21
330 0.98 80 58 22
340 1.00 79 56 23
350 1.00 80 57 23
360 1.03 80 58 23
370 1.03 80 58 22
380 1.08 80 58 23
390 1.08 80 57 23
400 1.17 79 57 23
410 1.08 80 56 24
420 1.10 80 57 23
430 1.10 81 57 24
440 1.12 81 58 23
450 1.12 81 57 23
460 1.15 80 58 23
470 1.15 81 57 24
480 1.15 81 57 24
490 1.17 80 57 24
500 1.27 81 56 25
510 1.20 80 55 25
520 1.22 80 54 26
530 1.22 80 53 27
540 1.22 80 54 27
550 1.27 80 54 27
560 1.30 80 52 28
570 1.27 81 52 29
580 1.34 81 51 29
590 1.32 81 52 29
600 1.32 81 52 29
610 1.32 80 52 28
620 1.37 80 53 28
630 1.52 82 54 29
640 1.44 83 54 29
650 1.52 83 54 28
660 1.56 83 56 27
670 1.76 86 58 29
680 1.91 90 60 29
690 2.05 93 62 32
700 2.15 97 61 36
710 2.42 101 61 40
720 2.49 103 60 43
730 2.32 106 60 46
740 2.32 106 59 47
750 2.32 106 60 46
760 2.64 107 61 46
770 2.52 109 61 48
780 2.64 110 61 50
790 2.49 112 60 52
800 2.59 113 59 55
810 2.66 115 57 58
820 2.83 116 55 62
830 2.98 118 54 64
840 2.98 119 52 67
850 2.91 117 56 62
860 3.10 121 60 61
870 3.23 128 59 69
880 3.30 136 59 77
890 3.45 140 55 85
900 3.49 141 55 86

Table A.4. Data at ambient temperature of 30ºC and average fuel hot-bed temperature of 1023.75°C.

Time (sec) Voltage T1 T2 T1-T2
10 0.00 42 30 12
20 0.00 43 38 5
30 0.03 43 39 4
30 0.10 45 38 7
40 0.16 47 38 9
50 0.20 49 40 9
60 0.25 50 42 9
70 0.27 52 45 7
80 0.26 53 44 8
90 0.30 55 47 8
100 0.31 56 48 8
110 0.34 57 48 9
120 0.39 58 46 12
130 0.43 59 47 12
140 0.48 60 49 11
150 0.49 61 49 12
160 0.60 63 48 14
170 0.58 62 48 14
180 0.60 63 48 15
190 0.59 62 47 15
200 0.62 63 48 15
210 0.62 63 48 15
220 0.63 64 48 16
230 0.64 65 49 16
240 0.67 67 50 17
250 0.74 70 52 18
260 0.87 77 57 20
270 0.91 79 57 21
280 0.96 79 58 21
290 1.04 80 58 22
300 1.01 79 57 22
310 1.12 79 55 24
320 1.09 80 56 24
330 1.17 80 56 24
340 1.14 80 54 25
350 1.13 80 55 25
360 1.30 81 56 25
370 1.23 82 56 26
380 1.38 83 57 26
390 1.44 83 57 26
400 1.65 85 58 26
410 1.86 88 57 31
420 1.87 88 57 31
430 1.89 89 58 31
440 1.92 89 58 31
450 1.93 89 58 31
460 2.02 89 59 30
470 2.01 89 59 31
480 1.97 90 58 31
490 2.01 90 58 31
500 2.15 91 59 32
510 2.25 91 58 33
520 2.14 91 58 33
530 2.30 92 58 34
540 2.31 94 59 35
550 2.55 94 59 36
560 2.33 94 58 36
570 2.56 95 58 36
580 2.35 95 58 37
590 2.46 97 58 39
600 2.50 106 55 51
610 2.66 106 55 51
620 2.69 106 55 51
630 2.76 107 55 52
640 2.74 108 56 53
650 2.71 113 55 58
660 2.86 113 56 57
670 3.10 115 57 58
680 3.15 120 59 61
690 3.19 122 59 63
700 3.08 125 60 65
710 3.60 127 60 67
720 3.50 128 59 69
730 3.40 130 59 70
740 3.77 130 58 71
750 3.46 131 59 72
760 3.71 132 59 72
770 3.61 133 59 74
780 3.66 134 59 74
790 3.61 135 59 76
800 3.63 136 58 78
810 3.71 137 58 79
820 3.80 138 56 82
830 3.87 138 56 82
840 3.98 139 55 84
850 3.85 139 57 82
860 3.75 142 59 83
870 3.98 146 58 88
880 4.04 150 58 91
890 4.23 151 60 91
900 4.36 150 61 89

Table A.5. Data at ambient temperature of 29ºC and average fuel hot-bed temperature of 1023.75°C.

Time (sec) Voltage T1 T2 T1-T2
10 0.00 45 29 3
20 0.00 46 43 4
30 0.02 46 43 3
30 0.02 47 42 6
40 0.07 48 41 7
50 0.10 49 42 8
60 0.15 49 45 4
70 0.17 50 45 5
80 0.15 50 44 6
90 0.17 51 45 6
100 0.20 52 46 6
110 0.24 54 49 6
120 0.29 56 50 6
130 0.37 58 52 7
140 0.44 61 55 6
150 0.46 62 55 7
160 0.68 65 54 11
170 0.68 65 54 11
180 0.64 66 53 13
190 0.71 67 52 15
200 0.73 68 52 16
210 0.76 69 52 17
220 0.78 70 51 19
230 0.78 71 52 19
240 0.81 74 54 20
250 0.90 74 54 20
260 1.10 81 58 23
270 1.10 81 58 23
280 1.12 81 58 23
290 1.17 81 57 24
300 1.15 81 58 23
310 1.22 80 54 26
320 1.22 81 54 27
330 1.37 80 54 27
340 1.30 81 53 28
350 1.27 81 53 28
360 1.59 82 54 28
370 1.44 83 54 29
380 1.69 85 56 29
390 1.81 85 57 29
400 2.15 91 60 31
410 2.66 96 57 39
420 2.66 97 58 39
430 2.69 97 59 38
440 2.74 97 58 39
450 2.76 98 59 39
460 2.91 98 60 38
470 2.88 98 60 38
480 2.81 98 60 38
490 2.86 99 60 39
500 3.05 102 62 40
510 3.32 102 61 41
520 3.08 102 63 40
530 3.40 103 63 41
540 3.42 108 64 44
550 3.84 108 64 45
560 3.37 107 64 44
570 3.86 108 64 44
580 3.37 109 64 45
590 3.62 114 64 50
600 3.69 131 57 74
610 4.01 131 57 74
620 4.03 132 58 75
630 4.01 133 57 76
640 4.06 133 57 76
650 3.91 144 56 88
660 4.18 144 56 88
670 4.45 145 56 88
680 4.40 151 58 93
690 4.35 151 57 94
700 4.03 153 58 95
710 4.79 153 59 94
720 4.52 153 58 95
730 4.50 154 58 95
740 5.23 154 58 96
750 4.62 157 59 98
760 4.79 157 58 99
770 4.72 158 58 100
780 4.69 158 58 100
790 4.74 158 58 100
800 4.69 159 58 101
810 4.77 159 58 101
820 4.79 159 57 102
830 4.77 158 58 100
840 4.99 160 58 102
850 4.81 160 58 103
860 4.42 163 58 105
870 4.74 163 57 106
880 4.79 164 58 106
890 5.03 163 66 97
900 5.25 159 67 92
Figure 1. Thermoelectric generator placed in the charcoal stove
Figure 2. Experimental Rig
Figure 3. Data being displayed on the computer serial monitor
Figure 4. Voltage generated against temperature difference, at 36ºC ambient temperature
Figure 5. Voltage generated against hot side temperature, at 36ºC ambient temperature
Figure 6. Voltage generated against temperature difference, at 33ºC ambient temperature
Figure 7. Voltage generated against hot side temperature, at 33ºC ambient temperature
Figure 8. Voltage generated against temperature difference, at 32ºC ambient temperature
Figure 9. Voltage generated against hot side temperature, at 32ºC ambient temperature
Figure 10. Voltage generated against temperature difference, at 30ºC ambient temperature
Figure 11. Voltage generated against hot side temperature, at 30ºC ambient temperature
Figure 12. Voltage generated against temperature, at 29ºC ambient temperature
Figure 13. Voltage generated against hot side temperature, at 29ºC ambient temperature
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Reference: Ajah NJ. Performance Evaluation of Waste Heat Recovery in a Charcoal Stove using a Thermo-Electric Module. European Journal of Sustainable Development Research. 2018;2(2), 25. https://doi.org/10.20897/ejosdr/85187
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Reference: Ajah, N. J. (2018). Performance Evaluation of Waste Heat Recovery in a Charcoal Stove using a Thermo-Electric Module. European Journal of Sustainable Development Research, 2(2), 25. https://doi.org/10.20897/ejosdr/85187
Chicago
In-text citation: (Ajah, 2018)
Reference: Ajah, Nnamdi Judges. "Performance Evaluation of Waste Heat Recovery in a Charcoal Stove using a Thermo-Electric Module". European Journal of Sustainable Development Research 2018 2 no. 2 (2018): 25. https://doi.org/10.20897/ejosdr/85187
Harvard
In-text citation: (Ajah, 2018)
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In-text citation: (Ajah, 2018)
Reference: Ajah, Nnamdi Judges "Performance Evaluation of Waste Heat Recovery in a Charcoal Stove using a Thermo-Electric Module". European Journal of Sustainable Development Research, vol. 2, no. 2, 2018, 25. https://doi.org/10.20897/ejosdr/85187
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Reference: Ajah NJ. Performance Evaluation of Waste Heat Recovery in a Charcoal Stove using a Thermo-Electric Module. European Journal of Sustainable Development Research. 2018;2(2):25. https://doi.org/10.20897/ejosdr/85187
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