10.11648.j.ijrse.20180701.11


 

International Journal of Sustainable and Green Energy 
2018; 7(1): 1-6 

http://www.sciencepublishinggroup.com/j/ijsge 

doi: 10.11648/j.ijrse.20180701.11 

ISSN: 2575-2189 (Print); ISSN: 2575-1549 (Online)  

 

Influence of the Incident Solar Flux on the Temperature 
Variation of the Hot-Box Cooker 

Souleyemane Thiam
1, 2, *

, Serigne Thiao
1, 2

, Awa Marr
1, 2

, Issakha Youm
1, 2

 

1
Center of Studies and Research on Renewable Energies (CERER), Dakar, Senegal  

2
Department of Physics, Faculty of Sciences and Technology, University Cheikh anta Diop (UCAD), Dakar, Senegal 

Email address: 

 
*
Corresponding author 

To cite this article: 
Souleyemane Thiam, Serigne Thiao, Awa Marr, Issakha Youm. Influence of the Incident Solar Flux on the Temperature Variation of the 

Hot-Box Cooker. International Journal of Sustainable and Green Energy. Vol. 7, No. 1, 2018, pp. 1-6. doi: 10.11648/j.ijrse.20180701.11 

Received: July 11, 2018; Accepted: July 30, 2018; Published: September 4, 2018 

 

Abstract: In rural areas, families do not often have access to butane gas and women are looking for wood to cook. Forests are 
often threatened by the production of charcoal. Housewives are exposed to the emissions of these fuels. Thus a problem of public 

health arises. The aim of our work is a part of the development and popularization of solar cooking as an alternative to the abusive 

use of fossil fuels. On the other hand, it allows to protect the environment and contributes to improving the living conditions of 

housewives. A prototype was developed at the Center of Studies and Researches on Renewable Energies (CERER) in Dakar, 

Senegal. This is a solar cooker box double glazed and inclined lateral faces, provided with a flat reflector. In this paper we present 

the results of testing of the prototype. The climatic data in this study are obtained at the CERER weather station. Several series of 

tests were carried out under natural sunlight. They concern empty tests of the cooker and tests of water boiling and cooking. 

During these tests the temperatures at different points of the cooker were measured at different sunshine and at different times of 

the year. The results obtained by different tests are satisfactory and encouraging especially as solar cookers are easy to build and 

test prototype gets to reach temperatures favorable for healthy cooking different food products and dishes. 

Keywords: Experimentation, Collector, Reflectors Shots, Solar Cooker, Stove, Side Panels Inclined 

 

1. Introduction 

Successive energy crises in the world have led people to 

reflect on the fate of man without the fossil energy resources 

(oil, gas, coal, etc.) that are becoming increasingly scarce as 

energy demand grow. Developing countries are the first to be 

affected by these multiple crises. 

Since the 90s, Senegal is facing an energy crisis that never 

ends [1]. Companies are often confronted with fluctuations in 

the price of oil, fuel shortages, and shortfalls in production, 

distribution problems and control of the electrical network 

(SENELEC) causing cuts and load shedding. At the same time 

people are facing shortages of butane gas resulting from 

increases in the price of wood and charcoal... The impact of 

this crisis has very important consequences for the economy 

(agriculture, industry, SMEs, domestic electrification,...) 

These crises have resulted in extremely high cost of living, 

paralysis of the economic system but also to advancement of 

rural deforestation. This leads to increasing desertification, 

also a degradation of the environment: change of climate, soil 

erosion, floods in the cities causing displacements of 

populations by the public services is the case of the Diakhaye 

plan in 2006 and Noflaye in 2012 where whole districts are 

lost in the waters.... [2] In some remote areas, the Fouta in 

North, often desert where wood is somewhat rare, the use of 

cow dung for cooking is the main source of sickness for 

housewives because they contain harmful gases (methane, 

CO2,...). Moreover, due to the scarcity of fossil resources, 

most of the population's survival strategies are based on 

natural resources such as the wood of a few rare shrubs, 

leading to an alarming state of environmental degradation. 

The sunlight is a natural source of energy, free and 

inexhaustible [3]. Although unknown to most people, solar 

cooking is one of the simplest domestic uses of solar energy 

[4]. This application is one that can be an alternative to limit 

deforestation and misuse of fossil fuels whose emissions of 

greenhouse gases could jeopardize the future of humanity. 



2 Souleyemane Thiam et al.:  Influence of the Incident Solar Flux on the Temperature Variation of the Hot-Box Cooker  

 

Indeed, for citizens living in several remote areas, cooking 

food is very costly when using conventional energy sources 

and causing disastrous consequences on the ecosystem. The 

first solar cooker called "hot box" was invented by Horace de 

Saussure, a Swiss naturalist who already experimented in 

1767. However, solar cooking actually appeared in the 1970s 

in a context of profound energy crisis [5]. 

The solar cooker is a device for cooking food directly 

through sunlight converted into heat. It achieves average 

temperatures to cook, boil, and roast. Almost everything that 

could be done with other traditional methods of cooking 

(wood, coal, electricity, gas...). 

Our work of evaluating the performance of the hot-box 

solar cooker is part of the development and popularization of 

this application that is solar cooking. Indeed a prototype has 

been realized, it is a solar cooker of the box type with lateral 

inclined faces. Our objective is to study its use in the climatic 

conditions of Senegal and possibly to make improvements. 

After a complete description of our cooker, we will 

undertake a study Theoretical study of our system before 

starting the experimental study which passes through various 

tests carried out at the Center of Study and Research on 

Renewable Energies (CERER). 

In this document, we present the results obtained from the 

experimentation of this prototype. Several series of tests were 

carried out under natural sunlight. They involve empty tests of 

the cooker and of the boiling and cooking tests. During these 

tests the temperatures at different points of the cooker were 

measured at different sunshine and at different times of the 

year. The results obtained by the various tests are satisfactory 

and encouraging, especially since solar cookers are simple to 

build and the prototype tested reaches temperatures favorable 

to the healthy cooking of various food products and dishes. 

The average temperatures reached allow us to cook, boil, 

almost anything we could do with other traditional cooking 

methods (wood, coal, electricity, gas...). 

2. Description and Modeling 

The studied system is a solar cooker box with a flat reflector 

[6]. 

It is a wooden box (cons-plated) thermally insulated (glass 

wool between the inner and outer boxes) and closed by a 

double glazing (two panes of 4mm thick, spaced 3 mm from 

each another) inclined at an angle of 15 ° South relative to the 

horizontal. This inclination allows the cooker to receive the 

maximum of radiation because solar oven only works with 

direct radiation so it is necessary to orient the solar oven 

correctly in relation to the sun 

 

Figure 1. Solar cooker hot-box inclined lateral faces. 

Its lateral faces are covered with mirrors and arranged as 

follows: the North faces, South and East are inclined at an 

angle of 15 ° relative to the vertical. This allows us to reduce 

the shadows cast by these faces on the absorber at sunrise. The 

west side is inclined at an angle of 30° to the vertical in order 

to increase the daily cooking periods without shading the 

absorber. These faces are lined with flat mirrors to favor the 

reflection of the rays in the cooker enclosure. 

The inside bottom is covered with a painted black 

aluminum plate that serves as an absorber. It converts light 

energy into thermal energy. 

A wooden door is opened on the north side of the cooker. It 

is covered with mirror to reflect radiation on the absorber. It is 

such a medium sized pot to pass through. To avoid as much 

heat as possible, avoid opening the oven too much during 

cooking! The best is still to put all the necessary ingredients 

from the beginning. 

 

Figure 2. Diagram of hot-box cooker. 

The reflector, north opening is made against-plated wood 

supported by thin tassets. Reflection is ensured by aluminum 

paper lining the surface of the reflector. It serves cooker cover 

after hours of use. 

2.1. Theoretical Study 

A solar cooker is a cooking appliance based on the 

conversion into heat of the light radiation emitted by the sun. 



 International Journal of Sustainable and Green Energy 2018; 7(1): 1-6 3 

 

It is a complex energy system where most of the modes of heat 

transfer are involved. It has several types of solar cookers all 

operating according to the principle of conversion of light 

energy into thermal energy. However there are different 

processing methods of that energy that characterize each 

cooker. A solar cooker is a box receiving cash from sunlight. It 

allows cooking food at temperatures from 80 to 170°C. The 

infrared rays from the sun are trapped in the cooker with the 

glass which causes a sharp rise in temperature within the box 

by greenhouse effect. The system that generates heat energy in 

some stores and in exchange with the other with its 

environment, (which we translate by equation (1)) provides 

thermal balance equations on the various oven components 

systems [7, 8]. 

���������	 
 �����
�� � �����	
��            (1) 

 

Figure 3. Total energy exchanges within the cooker. 

2.2. Heat Balance Equation 

Equation on the external glass: 

The heat balance of external and internal glass are given 

respectively by equations 2 and 3. 

����	�����
�����

��

 ��������� �! " ����# 

���������$%& " ����# � ��'(������� " �� '# � �),� '+���������� " �� '#	                                   (2) 

�� '��� '
,-./0

,1



2����� '��3 � �),$&+� '����� ' " �$&# � �),� '+���������� " �� '# � ��'4����� ' " �$�# � ��'(������� " �� '#	     (3) 

The energy balance of the air cooker and the absorber are given respectively by equations 4 and 5. 

�$���$ )
,-56

,1

 ��'7����$& " �$�# � ��'4����� ' " �$�#                                                  (4) 

�$&��$&
,-58

,1

 2�

4�$&�$&3 � 42�
4:%�$&3 � �),$&+� '�$&��� ' " �$&# � ��'7����$� " �$&# � �$&+ ;��$%& " �$&#	    (5) 

2.3. Experimental Study 

The experimental study concerns the performance testing 

under natural sunlight at the CERER in different periods of the 

year. 

For each of these tests measuring the global radiation there 

are: the average wind speed, ambient temperature, the 

temperature at the absorbing plate, the outer pane, the inner 

pane, of the atmosphere of the cooker. In the case of cooking 

or boiling tests, it also measures the temperature of the kitchen 

appliance and the temperature of the water to boil. 

The equipment used to study the cooker consists essentially 

of kitchen utensils and measuring instruments. 

As kitchen utensils we used aluminum cooking pots painted in 

black paste (on the external side only). Shorter cooking times are 

achieved with thin-walled aluminum cooking pots, distributing 

the food on several cooking pots and kitchen gloves. 

The measuring instruments consist of: 

- A pyranometer (KIPP & ZONEN model CM11) which 

measures the solar flux (global) on a flat surface from a solid 

angle of 2°. 

- Platinum resistance thermometers to measure the absorber 

temperature and the surface of the inner glass. 

- A probe (+ 200°C) to measure the ambient air temperature 

of the cooker. 

- A laser camera thermometer that measures surface 

temperatures. Thanks to the latter we can measure the 

temperatures of all external surfaces. 

- Mercury thermometers to measure the temperatures in 

volume (boiling water...) 

- A digital anemometer that instantly gives the speed and 

the orientation of the wind at the site but also the ambient 

temperature. 

- A multimeter for measurements of current, voltage, 

resistances... 

2.3.1. Stagnation Tests 

During these tests, the cooker is sun-exposed without 

charge: one tests the vacuum cooker performance [4, 9 and 

15]. 

2.3.2. Tests with Load 

This water heating ranges from to boiling tests and to 

preparation of some local dishes [10]. 

3. Results and Discussion 

Several series of tests were carried out at different 

insolation. To study the performance of the hot-box cooker, 

we will exploit the thermal capacity of the cooker during the 

sunniest periods but also those of lower sun exposure. 

3.1. Stagnation Tests 

The hot-box exposed to the sun without load; we make a 



4 Souleyemane Thiam et al.:  Influence of the Incident Solar Flux on the Temperature Variation of the Hot-Box Cooker  

 

vacuum performance test. 

 

Figure 4. Influence of the incident flux on the temperature variation during 

04/01/2015. 

These tests were carried out during the day of Monday, 

January 4, 2015. The day was very sunny; the solar flux 

exceeds 850 W / m² to 12. There is also a lack of wind [10]. 

These same atmospheric conditions were used to validate 

theoretical results. However there is an evolution of the cooker 

temperature is strongly dependent on the solar flux incident. It 

rises and decreases with the solar flux incident [2, 4, 9, 11, and 

15]. 

These discrepancies are due to insufficient thermal sunny 

exposure at the double glazing; heat losses are significant at 

the windows. 

 

Figure 5. Evolution of temperatures (Ta, Tve, Tvi, Tac, Tp) an function of time 

during 04/01/2015. 

The graphic shows the evolution of the temperature of the 

absorbing plate, glass (internal and external), air from the 

cooker and the environment. His study has two stage: A first 

stage where temperatures grow to reach a peak between 13h 

and 14h when the variation of flux is also rising. The exposure 

unit is warmed by the absorption of radiation; temperature 

rises continuously leading the air from the cooker and 

windows. 

Later than 14h, there was a decrease, the cooker 

temperature dropped dramatically at about 17h when it 

reached temperatures below 100°C unlike the theoretical 

observations. These temperature drops are due firstly to the 

fact that the solar flux decreases, as well as the energy 

generating thermal energy. On the other hand the double 

glazing is not a good thermal warm exposure. Apparently it 

can trap infrared radiation but not the heat energy that is 

generated. 

The absorber cools while the temperature of the glass 

continues to grow. That’s a reversal of the direction of heat 

exchange at the two windows beyond the solar setting. The 

cooker gives more heat to the environment than it can receive 

through the windows and it tends towards a state of 

thermodynamic equilibrium with it [8]. 

 

Figure 6. Influence of the incident flux on the temperature variation during 

02/02/2015. 

 

Figure 7. Evolution of temperatures (Ta, Tve, Tvi, Tac, Tp) an function of time 

during 02/02/2015. 

These tests were performed on February 2, 2015 in order to 

test the performance of the cooker during non-sunny periods. 

That was a cloudy sky with strong winds. The 100°C was 

reached around 13h unlike the days of strong sunlight. 



 International Journal of Sustainable and Green Energy 2018; 7(1): 1-6 5 

 

However the temperature peaked above 120°C between 13h 

and 14h. This reflects the fact that the conversion of light flow 

into thermal energy is selective, the live stream is concerned. 

The default storage is so important because of notorious 

decreases during cloudy periods. 

3.2. Tests with Load 

These tests are related to water boil tests and cooking some 

local dishes. Water boiling tests were carried out by measuring 

the change of the water temperature, the absorber, the air from 

the cooker and the incident solar flux. 

 

Figure 8. Water boiling test. 

This boiling test of a liter of water was performed on Feb 07
th
, 

2015 where the ambient temperature varied between 22° and 

26°C along the duration of the tests. The maximum flux density 

incident was 812W / m² and the average wind speed of 1.6m/s. 

After 1 hour of pre-heating, the duration of boiling water 

was 1h 05mn and the absorber temperature was 120°C. 

A temperature of 120°C is more than sufficient for all kinds 

of cooking. Since the water does not reach more than 100°C, a 

water-based food cooking will not therefore reach a higher 

temperature than this one. 

It is found that the water temperature is relatively lower 

than that of the air from the cooker and absorber. 

Cooking time depends on the dish to be cooked, the amount 

and intensity of the sun. It varies from 2 to 4 hours. The 

cooking is not very fast (120 to 170°C are reached), the dishes 

can, without risk, be left unattesnded. Similarly, you can grill 

walnuts, peanuts or confit fruits, cook eggs (without water), 

bread, pastries... 

4. Conclusion 

The solar "hot-box" prototype cooker was designed and 

tested under natural sunlight at the CERER. Various tests have 

shown that the system can reach temperatures sufficient for 

cooking and pasteurization of water even during periods of 

low sunlight. The arrangement of the side faces permits to 

reduce the shadow effects on the absorber, which allows the 

cooker to heat rapidly enough and at a due time of day. It has 

an exposure time that is improved enough. 

The comparative study between theoretical and 

experimental results that is observed allowed us to move 

forward on the prospects for improvement of hot-box. The 

study of the adiabatic transparent materials radiates clearly. 

The design of thermal storage systems is to improve the daily 

operating time of the solar cooker. 

Acknowledgements 

This work was supported by the Center of Studies and 

Research on Renewable Energies (CERER) BP. 476 Dakar, 

Senegal; 

Nomenclature 

αab: Absorption coefficient of absorber 

αvin: Coefficient of absorption of the glass 

cp::Mass calorific capacity (J.kg
-1

.K
-1

) 

ε:Emissivity of the material 

h: Convective exchange coefficient (W.m
-2

.K
-1

) 

k: Thermal conductivity (W.m
-1

.K
-1

) 

λ: Wave length (m) 

µ: Dynamic viscosity (kg.m
-1

.s
-1

) 

mvin:Mass of the glass (kg) 

ρ: Density (kg.m
-3

) 

σ:Stefan-Boltzmann constant (
 
W.m

-2
.K

-4
) 

τ: Coefficient of transmission of the glass
 

Rm: Reflection coefficient of mirrors 

Sab: Surface of the absorber (m
2
) 

Svi: Surface of the glass (m
2
) 

Tab: Temperature of the absorber (K) 

Tac: Room temperature of the cooker (K) 

Tamb: Ambient temperature (K) 

Tciel: Temperature of the sky (K) 

Tvin: Temperature of internal glass (K) 

Tvex: Temperature of external glass:(K) 

Φe: The incoming heat flux (W) 

Φg: The generated heat flux (W) 

Φs: Outgoing heat flow (W) 

Φst: Stored flow (W) 

Φth: Thermal flux (W) 

φi: Density of incident flux on the surface of the glass 

(W.m
-2

) 

φM: Thermal flux density vector (W.m
-2

) 

U: Enthalpy (J) 

Vv: Average wind speed 

 

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