Microcontroller PIC 16F877A standard based on solar cooker using PV—evacuated tubes with an extension of heat integrated energy system

The unavailability of sunlight during nighttime and cloudy weather condition has limited the usage of solar cookers throughout the day. This study will attempt to engineer a solar cooker with PV (photovoltaic panel), evacuated tubes with CPC reflectors, battery, and charge controller using the microcontroller PIC 16F877A. A mathematical model is developed to predict the electrical power (Ep) required during cloudy weather condition and nighttime as well as the temperatures occurring at different parts of the cooker. The proposed model is validated against experimental observations gathered for one of the typical working days of the system. The cooker is tested for various cooking loads to find the cooking time, and it is proven that the proposed cooker can be utilized over 24/7 without interruption.


Introduction
Solar cookers have immense intensity to make food for smaller and larger communities, which include hospitals, colleges, and industries. Commercial box-type solar cookers are limited to use due to their non-functionality during cloudy weather and nighttime. These limitations have been slowly overcome making efforts to introduce electrical backup by solar panel with heating coils to supply auxiliary heat during daytime and storage of electrical power in the battery whose charge can be extracted to supply for the heating coil during nighttime and cloudy weather for cooking. Researchers carried out experimental work with their proposed cookers with electrical backup and heating coil to supply heat energy for cooking. Results of the study have been documented for the welfare of the researchers in the respective field. The solar cooker technology is clean and efficient with a wide range of possible applications in eliminating pollution (Thamizharasu et al. 2020). Since the amount of solar box cookers is fixed, many scientists are trying to develop efficient solar cooking systems . The exploitation of technological developments (Palanikumaret al. 2021), including numerical simulation (Bhavania et al. 2019), is an important approach that precedes experimental work to reduce the waste of time, effort (by Bhavani et al. 2021), and money (Palanikumar et al. 2019). Since solar cooking gathered a lot of attention, a brief survey of previous studies on this subject is now presented (Bhavaniet al. 2018). Palanikumar et al. (2021) studied a stepped solar cooker using a bar plate with SiO 2 /TiO 2 nanoparticles at different concentrations equal to 10 and 15%. The experimental results confirmed that solar cooker efficiency reaches 37.69% for a 10% concentration of SiO 2 /TiO 2 nanoparticles and 49.21% for a 15% concentration. Rakesh Kumar et al. (2001) have designed a community type solar cooker using 5 evacuated tube solar collectors. Thermal analysis has been done and simulation results confirmed the possibility of cooking of several batches.
Mohammad Hosseinzadeh et al. (2020) fabricated portable evacuated tube solar cooker and analytically studied it using Taguchi analysis. It was found that the maximum operative parameters are solar radiation and absolute pressure of vacuum tubes. Arunachala and Kundapur (2020) presented a thorough review of solar cookers with and without reflectors, panels, funnels, etc. highlighting the findings of the various studies. Omara et al. (2020) reviewed the usage of different phase change materials in solar cookers: they highlighted the results obtained by the researchers and mentioned the optimal quantity of PCM to be used. Masum Ahmed et al. (2020) studied the performance on a solar cooker using parabolic reflectors. Results demonstrated the maximum reflection of solar radiation by mylar tape reflector. Devan et al. (2020) reviewed solar cookers with tracking mechanism. The review emphasized the tracking system using microcontrollers, manual tracking, and thermal and parabolic systems. Mawire et al. (2020) used two cooking pots with sunflower oil-sensible heat storage fluid and erythritol phase change material for cooking during on/off sunlight, which is an experiment showing that sunflower grease cooking vessel has better performance with lesser heat utilization efficiency. Coccia et al. (2020) tested a solar cooker provided with dual penned container filled by phase change material of 2.5 kg of erythritol. Experimental results proved the extension of load cooling time by 351.16%. Thirugnanam et al.'s (2020) obtainable comprehensive evaluation on phase change materials used a solar cooker and mentioned that the quality requirements of PCM are used in designing the solar cooking unit. Bhave and Kale (2020) used a phase change material solar salt and proved the possibility of frying and cooking in the shade inside the kitchen. Nokhosteen and Sobhansarbandi (2020) adopted the resistance network (RN) model to predict the performance on solar collectors using heat pipe-evacuated tube. Results of a model were in excellent agreement with the experimental work with a minimum error of 10%.
Very recently, Hosseinzadeh et al. (2021a) designed and tested a solar cooking unit incorporated with solar collector and used thermal oil-based nanofluids. It is observed that SiC-oil nanofluid dominates other nanofluids (TiO 2 -oil and SiO 2 -oil) on the overall energy efficiency of the system. Hosseinzadeh et al. (2021b) have studied a solar cooker as using multi-walled carbon nanotube oil nanofluid in an indirect solar cooker with collector and cooking unit. The study revealed the enhancement of the model. Further, Apaolaza-Pagoaga et al. (2021) have designed two new funnel cookers with and without glass enclosures. Experimental results revealed that cooker with glass enclosure has shown better cooker opto-thermal ratio than the cooker without glass enclosure. Tawfik et al. (2021) have tested a new tracking type solar cooker incorporated with parabolic reflector beneath the cooking vessel. Performance is compared with cooker without reflector. Results have shown that cooking time reduced by 44% by the cooker with the reflector. Thamizharasu et al. (2021) have attempted to incorporate a bar plate with nanomaterial layer to enhance the performance of solar cooker and used online sequential learning machine (OSELM). It has been observed that the efficiency of 49.21% is obtained for the usage of 15% volume fraction of nanoparticles. Gautama Hebbar et al. (2021) have designed a solar cooker with evacuated tubes and phase change materials for offshine hours cooking. Heat transfer fluid is allowed to transfer heat energy to the cooking vessel which is arranged with two hollow concentric cylinders of stainless steel. The performance of the cooker is better than that of conventional solar cooker.
Current work, as a solar cooker with PV, evacuated tubes, charge controller PIC 16F877A, nichrome heating coil, and battery, has analyzed and studied an analytical model. The goal is to predict the concert with a design. Mathematical expression derived an electrical power (E p ) based on the heat transfer process mechanisms which are used to design an evacuated tube collector, nichrome coilwounded cooking vessels, charge controller, solar panel, and a battery. The cooker is integrated with thermal and photovoltaic power to make it possible for cooking over 24/7 without interruption.
The article is drafted with three sections in which the first section tracks the inconveniences of the existing conventional solar cooker and second section focused on the design of solar cooker with evacuated tubes and PV to overcome the inconveniences. The third section concentrated on the theoretical model, simulation, and validation of the model with the experimental observations. Finally, the concluding remarks of the observations are drawn from the study.

Design of the cooker
The compatible solar cooker developed in this study has four components: • Evacuated tubes with high vacuum (P < 5 × 10 −3 mbar) enclosed in rectangular wooden box with parabolic trough reflectors • Solar photovoltaic panel (2 × 100 W) • 12 V 75AH Battery • Stove with two vessels for cooking A compatible solar cooker with photovoltaic panel and evacuated tubes (Solar Chulha) has been designed and fabricated. Evacuated tubes with high vacuum (P < 5 × 10 −3 Pa) have been used in the proposed cooker, and the system is used for producing hot water at about 75 °C for cooking. Parabolic trough reflectors are designed and the evacuated tubes have been fixed on the focal line of the trough near obtain determined a solar energy. A copper tubes carrying heat transfer fluid (water) is made to run through an evacuated tube near except temperature received by a tube's performance is higher. Photovoltaic panel of power output 200 W has been used to charge 12 V 75 AH battery. The charge from the battery is used to heat the heating filament (nichrome) covering the cooking vessel. Hot water from the evacuated tubes is further heated up to the boiling point and food is cooked easily. Furthermore, DC electrical power from the panel is stored in the battery during daytime and can be used during night. Figures 1, 2, and 3 show the photograph of the solar cooker and its different components.

Thermal model of the solar cooker
Five evacuated tubes are mounted on the focal line of the CPC reflector and are enclosed in a rectangular box made of plywood. Glass wool insulators are introduced in the gap between the CPC reflectors, and glass cover of thickness 3 mm has been used to cover the rectangular box. The evacuated tubes have length of about 490 mm, while the inner and outer diameters of each tube are 33 mm and 44 mm, respectively. Copper tubes of diameter 3 mm are made to run through the evacuated tubes continuously from the first evacuated tube to last evacuated tubes, which are arranged in a sequence inside the rectangular box. Cooking liquid allowed near movement complete a copper pipe through an inlet first evacuated tube using a valve to control the movement amount on cooking liquid.
Performance collector determined through finding the total energy absorbed and utilized by the collector and the first law of thermodynamics used an energy balance equation as: where E ab is the energy absorbed or transferred to the collector and E ut is the energy that increased the temperature levels (fluid acts); useful energy utilized by the collector is: where: m − Mass flow rate of working fluid water(kg) C pw − Specific heat capacity of water J kgK T out − Output temperature of water(K) T in − Inlet water temperature(K) The energy effectively collected by the system is: where: Q col − Total energy collected by the collector; A col − Area of the collector(m 2 ); F R − Collector efficiency factor; I t − Solar radiation (W/m 2 ); ( ) e − Effective transmittance absorptance product; Hence, efficiency can be expressed as: Figure 4 shows a schematic representation of the displaced pipe with a copper pipe running it. Copper tube is shaped as a U tube and inserted in the displaced pipe. Copper tube which is an outlet from the first displaced pipe is an inlet to a second displaced pipe and so on. Solar energy entered complete a transfer material is absorbed onto the evacuated tubes. Heat energy is connected to the copper tube where fluid water inside is moved to the working process. A cooking fluid (i.e., working fluid water flowing out through the outlet of the fifth evacuated tube) reaches a maximum temperature. The flow rate of water through the copper tube is maintained in such a way to absorb enough thermal energy from the copper throughout its passage through the tube till it reaches the outlet. The design of an outer glass cover used an energy balance equation (i.e., the covering glass for the evacuated tube collector) as follows: Covering glass cover: Outer glass tube of the evacuated tube: Inner glass tube of the evacuated tube: Copper tube: Water: Equations (6) through (9) have been solved for the temperature of the outer glass cover (T og ), for T eog is an outer glass tube of the evacuated tube, as T eig is an inner glass tube of the evacuated tube, and T c is a copper tube. The evacuated tube water is used in a solar collector that solution of the Eq. (10) is obtained and it gives the outlet temperature (T out ).
Outlet cooking fluid temperature from the evacuated tube collectors reaches a maximum of 80 °C and is hence introduced into the cooking vessel, which is fitted in a wooden enclosure. The sides and bottom of the cooking vessels are well insulated using glass wool insulator with thermal conductivity of 0.0038 W/mK. The cooking vessel is made of aluminum and provided with an aluminum lid. Nichrome coil is wounded on the sides of the cooking vessel to provide the electrical backup. The energy of about 330 has been extracted from nichrome heating coil for the convection of heat energy to the cooking fluid in the cooking vessel.
The hot cooking fluid output in the displaced pipe accumulator is introduced in the cooking vessel to cook food. Copper tube running through the evacuated tube collector receives the thermal energy and transfer the energy to the cooking fluid flowing through the copper tube effectively.
Hot water temperature is T out from an evacuated pipe collector and used for cooking fluid the energy again equations base of a cooking vessel can be written as: Similarly, the energy balance for the sides of the cooking vessel is stated as: The outlet water from the evacuated tube into the cooking vessel absorbs the thermal energy supplied by the nichrome heating coil surrounding the base and sides of the cooking vessel. The cooking fluid temperature increases due to the absorption of energy from electrical back up and thus food items in the vessel can be cooked. Since the preheated water is allowed to flow inside the cooking vessel and the evacuated tube collector is fixed at the top of the system, the hot water must flow from top to cooking vessel beneath the collector. Therefore, some of the energy lost to the surroundings and the temperature of the water when it reaches the cooking vessel is 75 °C. Therefore, the temperature of cooking fluid (T cf ) can be balanced with respect to that of the absorbed energy using the relationship: where a and f(t) are constants that can be determined from the equations relative to temperature components of the evacuated tube collector, nichrome heating coil, and cooking vessel respectively.
At t = 0, T cr = T cf0 and due to the initial condition from Eq. (13). We are writing as: where α is a constant of a cooker with a different heat transfer coefficients by a system.
As an electrical power is supplied due to the conversion of absorbed solar energy by the panel of power 200 W, it is indispensable to consider the incoming solar energy by the aperture of the panel in the respective interval of time. It is also considered that the charge controller is capable of charging the battery and supplying electrical power to the nichrome heating coil without any interruption. Therefore, the input energy for the cooker with electrical back up can be written as: The energy output of the cooker is given by: From the two Eqs. (15) and (16), the thermal energy efficiency by a system is Therefore,

Results and Discussion
The evacuated tube collector was tested separately with a temperature component, which is measured along sun rays and ambient temperature intermittently using solar radiation monitor. The measured data (solar radiation and ambient temperature) relative to one of the typical experimental days was used for calculations as shown in Fig. 5. The variation with a glass cover temperature an evacuated tube solar collector has been respected to the time allows one liter water, which is allowed to flow over the copper tube as shown in Fig. 6. The glass cover temperature influences the temperature of 62 °C in 50 min as the glass cover covering the enclosure of the evacuated tube collector has larger aperture to receive the sun energy. The temperature of the glass cover of the evacuated tube collector has significant impact on the performance of the evacuated tube collector for the production of hot water which is preheated. Energy balance equation of a solution from Eq. (6) is obtained and a glass cover temperature for the theoretical value is also determined. It is showed from Fig. 6 that theoretical and experimental values have practically the same trend throughout time. Therefore, the analytical solution for the glass cover can be used for the simulation model in any other similar location having the same climatic conditions. Since the thermal energy absorbed is not fully utilized for cooking during daytime but some of the energy is used to charge the battery. Stored energy in the battery can be utilized for cooking during nighttime. Nearly 440 W of thermal power has been saved and utilized for cooking during nighttime.  outer glass with an evacuated tube received a thermal energy from the trapped heat energy and the remaining amount of energy is sent to the path of the temperature component of the system. An inner glass tube with an evacuated tube in various temperatures was calculated by solving Eq. (8), and the numerical values were plotted along with the experimental observations in Fig. 8. Heat energy reaching an internal glass pipe is trapped due to evacuation, which is an inner glass tube temperature as gradually increases with beginning and abruptly increased due to evacuation. It appears from the figure that theoretical predictions and experimental observations agree very well throughout the working time due to the exact evaluation of the component which created an energy balance equation.
A copper tube (evacuated tube) has been inserted into the U-shaped pipe where an output is first provided, the input is the second, and so on. The copper tube receives the heat energy from an inner glass tube, which is trapped inside the tube energy without much loss.
A copper tube is showed in Fig. 9 with a variation's temperature by deference near period; analytical results created solution where an energy balance equation was obtained from Eq. (9). The thermal energy is absorbed by the copper tube with flowing water throughout its path. It reaches the outlet of the displaced pipe collector where fluid temperature becomes maximum.
The water temperature increases in every step (i.e., every evacuated tube) and water outlet from the last evacuated tube reaches the maximum temperature. It was solved energy equations determining a water temperature with an outlet to a collector, when the results were evaluated. Figure 10 is valued an experimental data and analytical results are plotted with respect to time. An outlet of evacuated tube collector with temperature reached the maximum of 96 °C.
Furthermore, the theoretical outcomes have been closed the contract by an investigational explanation. It is possible to get low pressurized steam if the flow rate of water through the copper pipes was adjusted and an intermittent steam may be produced with optimum movement amount of an aquatic.
Results discussed above indicated that simulation model developed in this study predicted the temperature components of the system with very small errors. Therefore, for the evacuated tube collector, the model can be used to simulate the collector for any location and it may be possible to optimize design parameters for community-based installments.
The outlet water was introduced into the cooking vessel seeing that the water itself has to move through a certain distance in open environment and flow into the cooking vessel. Hence, an evacuated tube collector water temperature through an outlet is decreased by some extent before it reaches the cooking vessel. During its path, some energy was lost to the surroundings and water temperature through an inlet of a cooking vessel decreased to 74 °C. Therefore, after the introduction of hot water into the cooking vessel, auxiliary heat energy is supplied by electrical backup.
The base and sides of the cooking vessel receive heat energy from electrical backup as well as via convection Theoretical Experimental two components was obtained and it is plotted along with experimental observations as shown in Fig. 11 and Fig. 12 a directive that confirm to the model. It is variations of temperature in base, for side cooking vessel with respect to the working hours. The theoretical results were moral contract by an experimental observation. Therefore, thermal simulation model developed in energy process of a temperature component gives precise results and can be used for portraying the system behavior. An evacuated tube collector allowed the flow of hot water into cooking vessel, thus supplying the cooker liquid. A cooking fluid temperature at the cooking vessel is nearly 74 °C, and auxiliary heat is supplied to the cooking fluid by the nichrome coil wounded over the sides in cooking pot. As the fluid of a cooking temperature rises, the food is cooked. An analytical solution for the cooking fluid temperature is used to calculate a cooking fluid temperature at any instant period with Eq. (14). An experimental observation and the theoretical calculations done for cooking fluid temperature are associated with Fig. 13. It can be seen that theoretical and experimental results are as expected and agree very well with small deviations. This is due to the intermittent nature of cooking fluid temperature which is incorporated to a food item.
The thermal model developed for determining temperature elements of the cooker is moral arrangement by an investigational consequence. Cooking fluid temperature is used to find the energy output of the proposed system with electrical backup. Energy output with electrical backup was calculated then which is experimental follow of water fever from an evacuated pipe collector was 75 °C and it is fed into the cooking vessel. The temperature was further increased to 96 °C by utilizing the electrical backup for a time period of 15 min. The temperature of the cooking fluid should be sustained for 45 min to cook 1 kg of rice. The electrical backup required to sustain the temperature of the cooking fluid was found to be 0.15 unit of electricity with power of 160 W. Energy input to the cooker can be calculated using Eq. (15), and the efficiency of the cooker is estimated with the energy output and energy input using Eq. (18). The validated results revealed that during the peak sunny hours, the level of solar radiation is sufficient enough to activate the process of cooking. The ratio of useful energy delivered to the available energy is found to be 0.72 in which almost ¾ of the available energy is utilized for cooking and found to be stable.
The resulting efficiency of the proposed system with a load of 1 kg of food stuff was found to be 36.52%. This was achieved by using the electrical backup supplied by the nichrome heating coil. The system was used to cook different food stuff and is tabulated in Table 1.

Conclusion
The paper described a novel solar cooker design including photovoltaic panels, evacuated tubes with CPC reflectors, battery, and charge controller using the microcontroller PIC 16F877A. An analytical model was established with a simulation of the thermal performance on the cooker; it is validated against experimental measurements. The subsequent inferences have been strained from this study: (i) Figure of Merit (F 1 ) and Figure of Merit (F 2 ) for the cooker have been found as 0.1197 and 0.4018, which met the value of the Bureau of Indian Standard. (ii) As the cooking vessel is well thermally insulated using glass wool of thermal conductivity 0.0038 W/ mK, the temperature attained using the electrical backup can be maintained for a time long enough to cook food. (iii) The water output temperature of an evacuated tube reached a maximum of 75 to 80 °C within a short interval of time with optimum movement amount to the inlet of an evacuated pipe. (iv) Validation of the thermal simulation model demonstrated the usability of the model for optimizing design parameters. Furthermore, the model can be utilized for large-scale installations. (v) The thermal efficiency of the cooker is 36.52% and the cooker can be used over the 24-h cycle as it is provided with a battery to store the charge rather than the 32% of efficiency in the case of conventional solar cooker.
(vi) The cooker can be used for cooking as well as frying food stuff as it is provided with electrical back up of 160 W. (vii) The cooker is affordable to a common man as the cost of the cooker is INR 10,500 only.   Availability of data and material The designed solar cooker and data of results of characterization are available.

Declarations
Ethical approval The research work is ethically complied.

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All the authors give their consent to having participated in the current work.

Consent for publication
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Conflict of interest
The authors declare no competing interests.