Design, Simulation, Construction and Performance Evaluation of a Solar Box Cooker

Design, Simulation, Construction and Performance Evaluation of a Solar Box Cooker

Chapter One

Aim and objectives

The aim of the project is to design, simulate, fabricate and carry out the performance evaluation of box solar cooker using three plane reflectors to achieve cooking under Zaria metrological condition.

Specific objectives are to:

Carry out design analysis to determine the dimensions of solar cooking system.

Simulate the design and evaluate performance of the collector under Zaria metrological condition

Construct and carry out performance evaluation of the solar cooker.

CHAPTER TWO

LITERATURE REVIEW

 Solar Energy and Its Application

Solar energy is the energy transmitted from the sun in the form of electromagnetic radiation, which requires no medium for its transmission. The earth receives about one – half of one billionth of the total solar output. Among all the nonconventional energies, solar energy is the best option if it can be used in a cost effective manner because the technology is also environmentally friendly. As the solar energy intercepted by the earth in one year is ten times greater than the total fossil resources including undiscovered and unexplored non-recoverable reserves (Meduguet al., 2013). It is expected that the present worldwide research and development program on solar energy will help to solve the future energy crisis of the world (Meduguet al., 2013). Solar radiation otherwise known as insolation is the amount of energy from the sun reaching a specific location on the surface of the earth at a specified time. Due to the interference of the atmosphere, solar energy hits a horizontal plane on earth in direct and diffuse forms. The direct form is the parallel rays from the direction of the sun while the diffuse forms is radiation scattered in many directions by matter and gases in the atmosphere. The diffuse radiation are caused by the reflection and scattering by the atmosphere (Ogbuisi, 2010).

The Application of Solar Energy is as follows:

1. Residential Application Use of solar energy for homes has number of advantages. The solar energy is used in residential homes for heating the water with the help of solar heater. The photovoltaic cell installed on the roof of the house collects the solar energy and is used to warm the water. Solar energy can also be used to generate electricity. Batteries store energy captured in day time and supply power throughout the day. The use of solar appliances is one of the best ways to cut the expenditure on energy (www.solarpoweryourhouse.com, 2008).
2. Industrial Application Sun‟s thermal energy is used in office, warehouse and industry to supply power. Solar energy is used to power radio and TV stations. It is also used to supply power to lighthouse and warning light for aircraft (solarpoweryourhouse.com, 2008).
3. Remote Application Solar energy can be used for power generation in remotely situated places like schools, homes, clinics and buildings. Water pumps run on solar energy in remote areas. Large scale desalination plant also use power generated from solar energy instead of electricity (solarpoweryourhouse.com, 2008).

Solar Spectrum and Solar Constant

The distribution of solar radiation as a function of the wavelength is called the solar spectrum, which consists of a continuous emission with some superimposed line structures. The Sun‟s total radiation output is approximately equivalent to that of a blackbody at 5776K. The solar radiation in the visible and infrared spectrum fits closely with the blackbody emission at this temperature. However, the ultraviolet (UV) region (<0.4 micrometer) of solar radiation deviates greatly from the visible and infrared regions in terms of the equivalent blackbody temperature of the sun. In the interval 0.1–0.4 micrometer, the equivalent blackbody temperature of the sun is generally less than 5776K with a minimum of about 4500K about 0.16 micrometer (Goody and Hu, 2003). The deviations seen in the solar spectrum are result in emission from the non isothermal solar atmosphere (Goody and Hu, 2003).

Solar Cookers and Their Types

Solar cookers are devices that cook food using only solar radiation and can save conventional fuels to a significant amount. It is the simplest, safest, most convenient way to cook food without consuming fuels or heating up the kitchen (Mohammed, 2015). Several factors including access to materials, availability of traditional cooking fuels, climate, food preferences, and technical capabilities affect people‟s perception of solar cooking (Ismail and Isah, 2013).

Types of Solar Cookers

There are three types of solar cookers:

• Panel Solar Cooker

• Box Solar Cooker

• Parabolic Solar Cooker

Panel Solar Cooker

Figure 2.1 is the pictorial view of a panel solar cooker. The panel cooker is the least expensive type of solar cooker. It is designed to reflect sunlight over the entire surface of a lightweight. Cooking pot is said to be coated with black colour on the outside with non-toxic paint. They are unstable in high winds and do not retain as much heat when the sun is hidden behind the clouds (SCP, 2015)

Figure 2.1: Panel Solar Cooker (SCP, 2015)

Box Solar Cooker

Figure 2.2 is the pictorial view of a box solar cooker. Solar box cookers (sometimes called solar ovens) are the most common and inexpensive type of solar cookers. This type of solar cooker consists of an insulated box made of cardboard, wood, metal or plastic.It is painted black on the inside and has a large glass or Plexiglas window on top to let in sunlight. Just like panel cookers, box cookers can be left unattended in the sun for hours to cookfood and pasteurize water. There is no danger of burning the food. Box solar cookers only need a slight adjustment to track the sun every few hours. Some solar box cookers have aluminium reflectors on the outside to direct even more sunlight into the box (SCP, 2015).

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CHAPTER THREE

MATERIALS AND METHODS

Description of the solar cooker

The system consists of an insulating material (fibre glass) in between theinner and outer casing to minimize heatloss. The casings were made with ply wood to further minimize heat loss and to serve as barrier to prevent any environmental effect to the solar cooker. An angle iron helps in tilting the two opposite small size reflectors and the big sized reflector is fixed which helps the two opposite small size reflector in boosting the solar radiations into the cooking chamber. The reflector handle is used in opening and closing the cooker when out of use as shown in figure 3.1. Inside the cooking chamber is an aluminium plate coated with a non toxic matte black colour to achieve high absorption coefficient. The cooking pot is situated 40mm above the bottom absorber plate. Light rays inpinging on the system are two: direct and reflected rays. Direct rays come directly from the sun into the cooking chamber through the glazing while the reflected rays hit the reflector and the reflected back to the cooking chamber through the glazing.

 Working principles

Figure 3.1 shows a pictorial view of the three reflectors box solar cooker. Sunlight both direct and reflected enters the solar box through the glazing and turns to heat energy when absorbed by the dark absorber plate and cooking pot. This heat input causes the temperature inside of the solar cooker to rise which result to solar heat gain. Temperature sufficient for cooking food and pasteurizing water are easily achieved through this means.

CHAPTER FOUR

RESULTS AND DISCUSSION

The Variation of Solar Insolation with time

Figure 4.1 shows the average solar radiation incident on surfaces at different time intervals for the 4 conservative days. The fluctuations indicate the effects of cloud cover after each 10 minutes to know the average intensity of the sun from 10:00am to 2:00pm. The curve line is a regressional line showing line of best fit for the co-efficient of determination (r²) which was found to be 91.87 .

This is the curve; it shows the graph for the four days along with the polynomial curve for the average of the four days.

CHAPTER FIVE

SUMMARY, CONCLUSIONS AND RECOMMENDATIONS

Summary

A solar cooker with reflectors was designed, simulated and constructed at Ahmadu Bello University Zaria, Nigeria. The system designed was modelled using TRNSYS, EES and Microsoft Excel.

At the initial stage, the typical metrological year (TMY) solar data of Zaria obtained from www.solar analytical.com was processed to obtain the monthly average daily solar resources of Zaria using the solar radiation and weather data processor TYPE 109 component of TRNSYS 16 software. The month with the least average daily solar radiation was considered as the design month. The result shows that the month of August has the least solar radiation and therefore, considered as the design month.Secondly, the solar cooker was constructed at Ahmadu Bello University, Zaria Mechanical Engineering Workshop using various tools for cutting and machining.Thirdly, the solar cooker was tested at Mechanical Engineering Department of ABU between 28^th and 31^st of October, 2016. During the course of the testing, it was observed that in general the performance of the cooker was so encouraging because it cooked rice within an hour.Finally, the results were analysed and performance of the cooker was evaluated using (ASAE S580, 2013) standard. The cost evaluation of the system was carried out.

 Conclusions

The following conclusions can be drawn:

1. A solar cooking system was designed using surface collector area 0.56m²and collector length of 0.8mfor Zaria metrological condition. Third reflector was added which yield 1654.6J amount of energy. The percentage energy increment was found to be 84.5.
2. The regression line for the experiment and simulation were obtained and were used to compute the cooking power of the cooker. The experimental and simulated cooking powers were 52.8W and 54.8W respectively. This occurred at optimum collector slope of 21^ousing Zaria metrological condition.
3. The construction of the cooker was carried out at Mechanical Engineering workshop Ahmadu Bello University Zaria. The performance evaluation was carried out where the RMSE values for 30^thand 31^st October, 2016 were found to be 4.8203^oC and 2.604^oC respectively. The NSE values for 30^th and 31^st October 2016 were found to be 0.986 and 0.996 respectively. The results show little deviation of the predicted values and also a good level of fit, thereby validating the model used for simulating the solar cooker.

Recommendations.

1. The use of various oven cavity geometries should be investigated in collector design, in order to study the effect of various geometric on the performance.
2. Alternative construction materials should be explored with a view to reduce the size and weight of the cooker for easy handling and transportation.
3. Optimisation of insulation thickness should be carried out to further minimize heat loss.

 

REFERENCES

• Abdlwahid, B., Syed, A.Z., Zain, U.A. and Muhammad, Y.K.. (2015). Performance Modelling And Parametric Analysis of a Double Glazed Solar Oven. Journal of Clean Energy Technology. Vol. 4(3): pp187-191 DOI:10.7763/JOCET.2015.v4.277
• Ademola, K.A. and Joseph, C.I. (2015). Energetic and Exergetic Evaluation of Box Type Solar Cooker Using Different Insulation Materials. International Journal of Biological,Biomolecular, Agricultural Food and Bio-Technological Engineering. Vol. 9(5): pp.426-432.
• Aiden, J. (2014). Performance Evaluation of a Parabolic Solar Dish Cooker. Journal of Applied Physics. Vol. 5(1): pp. 46-50.
• Akachukwu B.E. (2011). Prediction of Optimum Angle of Inclination of Flat Plate Solar Collector in Zaria. Agricultural Engineering International: CIGR Journal. Vol. 3(4)
• Aremu, A.K. and Akinoso, R. (2013). Use of Solar Cooker in Nigeria. International Food Research Journal. Vol.20 (5): pp.2881-2886.
• ASAE S580 (2013). Testing and Reporting Solar Cooker Performance. American Society of Agricultural Engineers (ASAE). The Society for Engineering in Agricultural, Food and Biological Systems. Renewable Power Generation Committee. 2950 Niles Road, USA.
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• Basil, O.E. (2013). Performance Evaluation of a Parabolic Solar Cooker. International Journal of Engineering and Technology. Vol.3 (10): pp.923-927.
• Bello, A.M., Makinde, V. and Sulu, H.T. (2010). Performance Test and Thermal Efficiency, Evaluation of a Constructed Solar Box Cooker. Journal of American Science. Vol. 6(2): pp.32-38.
• Chinnumol, F. and victor, J.(2015). A Review on Performance Improvements in Box Type Solar Cookers. International Journal of Current Engineering and Scientific Research. Vol. 2(7): pp. 169-175.
• Dasin, D.Y. (2013). Experimental Investigations of Heat Losses from a Parabolic Concentrator Solar Cooker. African Journal of Engineering Research. Vol. 1(3): pp.90-96.
• Duffie and Bechman (2013). Solar Engineering of Thermal Processes. John Wiley and Sons, New Jersey.
• Echukwu, O.V.(2001). Design and Measured Performance of a Plane Reflector Augmented Box Type Solar Energy Cooker (Unpublished) thesis. Department of Mechanical Engineering, University of Nigeria, Nsukka.

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