Solar cookers--part I: cooking vessel on lugs

A large number of papers have been published on the topic of solar cookers, but hardly any have discussed the role of the vessel inside the cooker. The heat has to penetrate the vessel and cook the food in a uniform pattern. The bottom surface of the cooking vessel and the lid are ineffective in the heat transfer process to the food. Raising the vessel by providing a few lugs will make the bottom of the vessel a heat transfer surface. This change improves the performance of the system by improving the heat transfer rates in both heating and cooling modes. The times for reaching saturation temperature and cooking were noticeably reduced. Raising the vessel above the base plate of the cooker is recommended for universal adoption.     

Development of a domestic concentrating cooker

A Fresnel type domestic SPRERI concentrating cooker was designed and developed. The cooker has an aperture area of 1.5 m² and a focal length of 0.75 m and was found to provide an adequate temperature needed for cooking, frying and preparation of chapatis. The cooker was found capable of cooking food for a family of 4 to 5 persons. Details of development of this cooker and the tests conducted are given in this paper.     

A new solar cooker design

This paper deals with a new box-type solar cooker design with a single reflector at the hood. In this design, the base of the oven acts as the lid, unlike the conventional box-type solar cooker. With the introduction of this concept of the lid as the base of the oven, we solve the problem of preheating, as faced in the conventional box-type solar cooker. Thus, the performance of conventional box-type solar cookers can be appreciably improved by having the lid at the bottom of the oven and not at the top. It has been observed that, having cooked once, the preheating time for further cooking is greatly reduced as compared to the conventional box type. Hence, cooking twice a day by this cooker becomes easier, unlike cooking by the conventional one.     

Experimental study of a double exposure solar cooker with finned cooking vessel

A comparative experimental study of a box type solar cooker with two different cooking vessels was conducted, the first one conventional and the second one identical to the first in shape and volume but its external lateral surface provided with fins. Fins are shown to improve the heat transfer from the internal hot air of the cooker towards the interior of the vessel where the food to be cooked is placed. This reduces the cooking time considerably. The tests were carried out on the experimental platform of the Research Unit in Renewable Energies in Saharan Medium of Adrar, located at 27°53′N latitude and 0°17′W longitude in the Algerian Sahara.     

Design optimization of solar cooker

Various designs of solar cookers have been theoretically investigated with a view to optimize their performance. Starting from a conventional box type cooker, various combinations of booster mirrors have been studied to arrive at a final design, aimed at providing a cooker, which can be fixed on a south facing window (for countries of northern hemisphere, mainly situated near the tropic of Cancer). This cooker, with a rear window opening, may provide higher cooking temperature for a fairly large duration of the day. Two or three changes in positions of the side booster mirrors, without moving the cooker as a whole has been proposed. The new design has been experimentally implemented and compared with a conventional box type solar cooker. Besides the convenience of a rear window opening, the cooker provides temperatures sufficiently high to enable cooking two meals a day.     

Studies on a new combined concentrating oven type solar cooker

This paper describes a combined concentrating/oven type solar cooker. The device can be used for cooking, boiling and roasting of foods on clear days. The cooker makes use of both concentrator and flat-plate collector principles, wherein the sunlight entering the cooker is reflected onto a hood which is provided with a selective solar absorber coating which houses the cooking vessels. Hence, the cooker makes use of both direct and diffuse solar radiation. The important part of this new device is a stationary mode and maximum capture of energy through improved design. The new cooker has been found to be more practical in comparison with either the simple hot box type solar cooker or concentrator type cookers where one needs to direct it to follow the sun. The cooking trial shows that the new device can be used twice a day, even on winter days.     

Multi-criteria evaluation of cooking energy alternatives for promoting parabolic solar cooker in India

The policy formulation for cooking energy substitution by renewables is addressed in multi-criteria context. A survey is conducted to know the perceptions of different decision making groups on present dissemination of various cooking energy alternatives in India. Nine cooking energy alternatives are evaluated on 30 different criteria comprising of technical, economic, environmental/social, behavioral and commercial issues. Preference Ranking Organization METHod for Enrichment Evaluation (PROMETHEE), a multi-criteria decision making method of outranking nature is used to rank the alternatives. It is found that liquefied petroleum gas (LPG) stove is the most preferred device, followed by kerosene stove, solar box cooker and parabolic solar cooker (PSC) in that order. A sensitivity analysis is also carried out for identifying potential areas for improvement for PSC. On the basis of results, strategies for promoting wide spread use of PSC are formulated.     

A novel advanced box-type solar cooker

An advanced version of the box-type solar cooker is presented: a fixed cooking vessel in good thermal contact with a conductive absorber plate is set into the glazing; the results are improved thermal performance, easier access to the cooking vessel and less frequent maintenance due to protection of all absorbing and reflecting surfaces. Outdoor tests show that 5 L of water per sq m of opening surface can be brought to full boiling in less than one hour. A finite element simulation model of the advanced box cooker is presented. It is shown that the most decisive parameters are absorber-to-pot heat transfer and absorber conductivity. Field tests in Ethiopia and India are under way, local production in India has started.     

Utility assessment of parabolic solar cooker as a domestic cooking device in India

The needs of cooking energy in households can be supplemented by parabolic solar cooker (PSC). Policy for energy substitution by renewables has to consider many conflicting socio-economic issues. To know the perceptions of decision-makers and users, a survey is conducted to evaluate nine cooking energy devices available in India. Energy technology issues, economics, environmental/social, behavioral and commercial issues are considered for the evaluation. Thirty criteria are considered under these five aspects for pair-wise comparison of the devices. Additive Multi-Attribute Utility Theory (MAUT) is employed to evolve ranking of selected devices. It is found that Liquefied Petroleum Gas (LPG) stove is the most preferred cooking device, followed by microwave ovens and kerosene stoves. PSC has occupied fifth rank amongst the devices. A sensitivity analysis is also carried out for identifying potential areas of improvement for PSC, which forms a basis for policy interventions required for its better dissemination in India.     

Fabrication of portable solar thermal bank for indoor cooking

The aim of this report is to build a portable solar thermal bank based on a Scheffler reflector that is capable of boiling-type cooking using HITEC as a thermal storage material. This report reviews the problems related to solar cooking and evaluates the novel layout of a portable solar thermal bank which includes a daily thermal storage vessel. This stove is in the shape of a cylindrical container filled with phase-changing latent heat storage material. Inside the container, we provide a small gap taking into account the volumetric expansion of the phase change material (PCM) during the melting process. The solar thermal bank is charged in the sun. It is placed directly for a few hours under the focus of a Scheffler reflector, which charges the solar thermal bank with enough thermal energy stored. After a while, the cooking process can be completed by users using that stored heat. The top cavity is used as a cooking pot in a solar thermal bank. Cooking meals do not require direct sunlight, which is typical for most solar cookers. The portable solar thermal bank is an alternative for low-income households and adapts to local traditions of indoor cooking. It is portable and can be used safely to cook indoors or outdoors. In this study, a solar cooker with a thermal storage device was developed using a PCM. The size of the stove has been calculated by calculating the energy consumption for two to three people. HITEC salt has been chosen as a phase change material for thermal storage, which will be used for cooking when there is no sunlight. It enhances the applicability of solar cooking and preserves cooking possibilities using energy stored throughout the day at low production costs.     

Thermal performance of a solar pressure cooker based on evacuated tube solar collector

This paper presents the thermal performance of a community type solar pressure cooker based on evacuated tube solar collector. The developed design of solar pressure cooker has separate parts for energy collection and cooking unit and both are coupled by heat exchanger. The paper has presented the performance results of experimental study conducted on solar pressure cooker and a simulation model has been developed for predicting the cooker performance under a variety of operating and climatic conditions. The theoretical model is validated against the experimental results. The obtained results have suggested a possibility of several batches of solar cooking on a clear sunny day under typical conditions of Delhi.     

An improved solar cooker

An improved hot box type solar cooker (SC-2) has been designed, developed and tested. It is an improvement on the solar cooker SC-1 earlier developed at the institute. The cooking chamber has properly been optimized for cooking the food for a family of five persons. A rubber gasket has been provided at the boundary of the openable door to prevent the leakage of hot air, thus increasing the pressure in the cooking chamber. Different cooking trials like boiling, roasting and baking were successfully conducted and the cooker was found useful from 8.00 a.m. to 5.00 p.m., even during a winter month. The efficiency of the cooker was found to be 41.2 per cent.     

Solar box-cooker: Part I—Modeling

Thermal models for the solar box-cookers loaded with one, two, or four vessels have been presented. The method of Taha and Eldighidy has been utilized to estimate the enhanced solar irradiance on the cooker due to the flat reflector fitted to the cooker. The coupling of the Taha and Eldighidy method with the thermal models yielded the models for the box-cookers. A great many transfer coefficients and view factors are required as the model inputs. The methods for their estimation are given. Analysis of the transfer processes, computer simulation of the cooker, and experimental data on some of the coefficients, which are peculiar to the cooker and not available in the literature are presented in the companion paper.     

Heat losses from a paraboloid concentrator solar cooker: Experimental investigations on effect of reflector orientation

The thermal performance of any focussing-type solar cooker, where an unglazed/uuninsulated cooking pot is often used, depends to a great extent on wind conditions. Moreover, these cookers need frequent adjustments to track the Sun in order to keep the focus always at the bottom of the cooking pot. The present paper reports experimental investigations on heat losses from such cooker for different orientations of the paraboloied reflector. Values of the heat loss factor for the tilted reflector are compared with those obtained with the reflector in a horizontal position. The heat loss factore for a cooker with/without reflector is determined for no-wind conditions. It is suggested that a paraboloid reflector is not required for heat loss determination in this case.     

Solar cooker with latent heat storage systems: A review

Cooking with the sun has become a potentially viable substitute for fuel-wood in food preparation in much of the developing world. Energy requirements for cooking account for 36% of total primary energy consumption in India. The rural and urban population, depend mainly, on non-commercial fuels to meet their energy needs. Solar cooking is one possible solution but its acceptance has been limited partially due to some barriers. Solar cooker cannot cook the food in late evening. That drawback can be solved by the storage unit associated with in a solar cooker. So that food can be cook at late evening. Therefore, in this paper, an attempt has been taken to summarize the investigation of the solar cooking system incorporating with phase change materials (PCMs).     

A new design for an economical, highly efficient, conical solar cooker

In this paper, the concept of the conical focus is revealed, and the design of a solar cooker is explained. The cooker was practically tested for grilling both white and red meat in a record time. A method for obtaining real boiling of water (100°C) using a solar heater is described. The cooker was also tested for oil frying and for cooking beans.     

A review of the thermal performance parameters of box type solar cookers and identification of their correlations

One of the many thermal performance parameters such as efficiency, cooking power, figures of merit etc. are used to evaluate a solar cooker (including box type) based on test procedures which are non-identical. In the absence of an interrelation between the different performance parameters, it is very difficult to compare the cookers’ performance reported by different researchers and establish the criteria required for selection of a cooker which can accomplish cooking successfully and satisfactorily. In this review paper, some of the performance parameters and the related test procedures have been reviewed for box type solar cooker. Further an attempt has been made to identify common links between the different performance parameters in terms of a few objective parameters. This provides an enabling tool to the researchers to compare and correlate the different performance parameters. Three such objective parameters have been identified for box type solar cookers.     

Thermal efficiency improvement of an LPG gas cooker by a swirling central flame

The present study proposes a swirling central flame technique to improve the thermal efficiency of a conventional open‐flame atmospheric gas cooker which is now widely used as a domestic appliance. More extensive studies were done in an effort to improve the thermal efficiency of the cooker by reducing thermal inertia of the pan support and using the proposed porous medium technology to recover heat from flame radiation to preheat the secondary air entrained from the bottom of the burner. The experimental results showed that the thermal efficiency of the swirling central flame burner with conventional support is approximately 15 per cent higher than that of the conventional radial flow burner. This can be attributed to the higher heat transfer coefficient between hot flue gas and vessel surface of the swirl burner than that of the conventional one. By replacing the conventional support of the developed swirl burner with a lighter one, whose mass was reduced by a factor of 3.7, the thermal efficiency could be increased by about 3 per cent. By using the proposed preheating secondary air support instead of the light support, the thermal efficiency could be further improved by 3 per cent. The predicted thermal efficiency obtained from the proposed model showed good agreement with the experiment. Copyright © 2001 John Wiley & Sons, Ltd.     

Thermal performance of a solar cooker based on an evacuated tube solar collector with a PCM storage unit

The thermal performance of a prototype solar cooker based on an evacuated tube solar collector with phase change material (PCM) storage unit is investigated. The design has separate parts for energy collection and cooking coupled by a PCM storage unit. Solar energy is stored in the PCM storage unit during sunshine hours and is utilized for cooking in late evening/night time. Commercial grade erythritol was used as a latent heat storage material. Noon and evening cooking experiments were conducted with different loads and loading times. Cooking experiments and PCM storage processes were carried out simultaneously. It was observed that noon cooking did not affect the evening cooking, and evening cooking using PCM heat storage was found to be faster than noon cooking. The cooker performance under a variety of operating and climatic conditions was studied at Mie, Japan.     

Evaluating the optimum load range for box-type solar cookers

This paper introduces a new concept of Optimum Load Range (OLR) for solar cookers. OLR gives the load values for which cooker preferably shows good thermal as well as good cooking performance; it may be considered a crucial parameter for solar cookers. This OLR concept is based on the dependence of rate of rise of load temperature on different heat transfer processes between load and cooker interior. This concept illustrates solar cooking in two simple steps. The total time required to complete these steps puts an essential constraint for cooking of any load amount. The maximum value of load (upper limit of OLR) till which cooker shows satisfactory cooking may be determined from this constraint. This constraint requires determination of two OLR parameters which are t_{step I} and t_{step II}. The load for which cooker remain almost 30% efficient, may be referred as lower limit (minimum value) of OLR. For the verification of OLR, experimental studies have been conducted with a solar cooker named SFSC. The OLR parameters along with different thermal performance parameters (TPPs) (second figure of merit (F₂), utilization efficiency (η_u) etc.) suggested by different researches for solar cookers in water load condition have been computed from the measured thermal profiles of different loads (0.8–3.0 kg). From the curve analysis of different TPPs with load, the existence of upper limit of OLR is observed. The values of rate of rise of load temperature at water temperatures 80, 85 and 90 °C for different loads also confirm the same. The OLR of SFSC is found to be 1.2–1.6 kg.