Performance and testing of large-size solar water heater cum solar cooker

The performance of a novel device has been tested. The device can be used as a collector cum storage type solar water heater during the winter, and, with minor adjustments, it can be used as a hot-box solar cooker. The device can provide hot water at 50–60°C in the evening, which can be maintained at 40–45°C until the following morning. It can also be used for cooking food for about 40 people. The efficiencies of the device as a solar water heater and as a solar cooker have been found to be 67.7% and 29.8%, respectively. The payback period varies between 1.64 to 5.90 years depending on the fuel it replaces. The payback periods are of increasing length with respect to the fuels firewood, coal, electricity, LPG and kerosene.     

Mathematical model of the thermal performance of box-type solar cookers

A mathematical model of the heat transfer processes involved with a box-type solar cooker, containing food, was developed. Solar radiation, including that from a flat reflector, enters the box and heat transfer within and out of the box was considered. Using small increments of time, the computer model finds the temperature of the air, food, interior walls and top cover as the solar flux varies throughout the cooking period. Sample results are presented, giving the food temperature as affected by latitude, month, wind, clouds, mass of food, thermal resistance of the box walls and adjustment of the box while cooking.     

Design and development of a solar cooker cum drier

A solar cooker cum drier has been designed and developed. In designing this unit, optimum booster-collector geometry has been considered in order to eliminate the requirement of sun tracking. Tilting arrangements have also been provided to capture more solar energy. This dual purpose device has been found useful for cooking food and dehydrating fruit or vegetables.     

Experimental investigation of high temperature congregating energy solar stove with sun light funnel

A solar stove which uses a light funnel to guide light and congregate solar energy has been designed. Its structure and operation principle have been introduced. The performance tests under the real weather have been carried out and the graphic lines of experiment have been given. The experimental result shows that the maximum temperature inside the stove is as high as 250 °C under the condition of 1.5 m² of lighting area, 70% reflectivity of reflecting aluminum foil inside surface of concentrator and no load (without water inside the coil pipe). When reflectivity is 86% the heat collecting efficiency of the device is about 43%. The collecting power that the stove receives can be up to 500 W. It is an ideal medium and high temperature solar energy congregating device suitable for industrial usage or cooking and other domestic usage.     

A truncated pyramid non-tracking type multipurpose domestic solar cooker/hot water system

For impressive dissemination of the solar thermal gazettes, it is imperative to keep on changing the device design features so as to cater to the different demands of diverse section of the society. Domestic solar hot water systems are not suitable for cooking and the capacity of domestic solar box type cookers for water heating is very low. We report truncated pyramid geometry based multipurpose solar device which could be used for domestic cooking as well as water heating. The device is designed, fabricated and tested. Cooking tests approved by Bureau of Indian Standards were performed in different seasons and the device was found to meet the requirement stipulated on two figures of merit. The performance of the design was also evaluated as a hot water system and the maximum efficiency was found to be 54%. The day-time and average night-time heat-loss coefficients were found to be 5.7 W/°C m² and, 3.74 W/C m², respectively, which are comparable to those of flat-plate collector based solar hot water systems. A simple economic analysis illustrate that this kind of multi-purpose design could be financially viable and physically useful.     

Design, construction and study of a hybrid solar food processor in the climate of Costa Rica

During the last 25 years, the author has designed, constructed, studied and promoted solar oven, hybrid solar/electric oven, solar oven cum drier, solar cooker cum water heater and solar still. In different parts of the world, solar cookers have been made, studied, patented, however, their real uses are very limited due to many reasons—unstable climate, economic, cultural, social and single use, etc. In order to overcome part of the problems mainly the last one, author has recently designed one hybrid food processor (multi-purposes device) and studied various technical and practical aspects. It has been used for cooking, heating/pasteurizing water (to inactivate microbes) and distillation of small quantity of water (to remove different minerals) and drying domestic products (fruits, vegetables and condiments/herbs, etc.). For more than three years of use, author has found this to be a useful device, mainly from convenience, fuel saving, economic and also from ecological point of view. This device can be used at any time and for different uses but with the reduced consumption of conventional fuel.     

Parametric model of solar cooker performance

This paper presents a model for prediction of the cooking power of a solar cooker based on three controlled parameters (solar intercept area, overall heat loss coefficient, and absorber plate thermal conductivity) and three uncontrolled variables (insolation, temperature difference, and load distribution). The model basis is a fundamental energy balance equation. Coefficients for each term in the model were determined by regression analysis of experimental data. The model was validated for commercially available solar cookers of both the box and concentrating types. The valid range of model application includes most of the feasible design space for family-sized solar cookers. The model can be used to estimate the cooking capacity of existing box type and concentrating type solar cookers. It can also be used to find the combinations of intercept area and heat loss coefficient required to cook a given quantity of food in a given climate.     

Technical feasibility assessment of a solar chimney for food drying

Solar dryers use free and renewable energy sources, reduce drying losses (as compared to sun drying) and show lower operational costs than the artificial drying, thus presenting an interesting alternative to conventional dryers. This work proposes to study the feasibility of a solar chimney to dry agricultural products. To assess the technical feasibility of this drying device, a prototype solar chimney, in which the air velocity, temperature and humidity parameters were monitored as a function of the solar incident radiation, was built. Drying tests of food, based on theoretical and experimental studies, assure the technical feasibility of solar chimneys used as solar dryers for agricultural products. The constructed chimney generates a hot airflow with a yearly average rise in temperature (compared to the ambient air temperature) of 13 ± 1 °C. In the prototype, the yearly average mass flow was found to be 1.40 ± 0.08 kg/s, which allowed a drying capacity of approximately 440 kg.     

Experimental studies on solar parabolic dish cooker with porous medium

The solar cooking is the alternate method of cooking to reduce consumptions of fossil fuels. An affordable, energy efficient solar cooking technology is much need due to the fossil fuels increasing cost and it is the hottest research topic in all over the world. This paper presents an experimental analysis of the heat transfer enhancement of solar parabolic dish cookers by a porous medium made of scrap material. Using the stagnation temperature test and water boiling test are conducted on the cooking vessel with and without porous medium. Experimental results are compared for both cases in terms of thermal performance, optical efficiency, heat loss factor and cooking power.     

A parabolic solar cooker with automatic two axes sun tracking system

A parabolic solar cooker with automatic two axes sun tracking system was designed, constructed, operated and tested to overcome the need for frequent tracking and standing in the sun, facing all concentrating solar cookers with manual tracking, and a programmable logic controller was used to control the motion of the solar cooker. The results of the continuous test – performed for three days from 8:30 h to 16:30 h in the year 2008 – showed that the water temperature inside the cooker’s tube reached 90 °C in typical summer days, when the maximum registered ambient temperature was 36 °C. It was also noticed that the water temperature increases when the ambient temperature gets higher or when the solar intensity is abundant. This is in favor of utilizing this cooker in many developing countries, which are characterized by high solar insulations and high temperatures. Besides cooking, the proposed cooker could be utilized for warming food, drinks as well as to pasteurize water or milk.     

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.     

Experimental testing of a box-type solar cooker using the standard procedure of cooking power

A box-type solar cooker with one (Model I) or four (Model II) cooking pots was constructed and tested under Tanta prevailing weather conditions. Experiments were performed during July 2002 using the cooker with or without load. The obtained results were employed to calculate the two figures of merit, F₁ and F₂, as well as the utilization efficiency η_u and the specific t_s and characteristic t_c boiling times. The obtained values of F₁ indicate that the cooker can be used twice a day for consecutive cooking. F₂ was found to increase almost linearly with the mass of the cooking fluid M_f. The cooker is able to boil 1 kg of water in 15 min when its aperture area equals 1 m². Furthermore, experiments also considered the requirements for the international standard test procedure for solar cookers. The cooking power P was correlated with the temperature difference ΔT between the cooking fluid and the ambient air. Linear correlations between P and ΔT had correlation coefficients higher than 0.90 satisfying the standard. The obtained values of the initial cooking power, heat loss coefficient and the cooking power at a temperature difference of 50 °C agree well with those obtained for small solar cookers. The present cooker is able to cook most kinds of food with an overall utilization efficiency of 26.7%.     

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.     

Design and development of a solar cooker for maximum energy capture in stationary mode

An efficient solar cooker has been designed, developed and tested. The device can be used for cooking, boiling and roasting of different foods in clear days. The important part of this new device is its stationary mode and maximum capture of energy through improved design and optimum tilt of the system. This new cooker has been found to be more practical in comparison to the simple hot-box type solar cooker, 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 in winter days.     

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).     

Characterisation and design methods of solar cookers

The use of solar cookers is much needed in many regions with good solar radiation intensity throughout the world. The reasons are economical, as the price of fuel for cooking is no longer affordable by many families; ecological, as in many regions deforestation is also associated with the use of wood as an energy source; and social, as the money used to buy fuel could be used to buy food, medications and other needs to improve the quality of life. Because of the variety of solar cookers that has been presented in the literature, a general procedure to compare these cookers with one another is very complex. This article presents the general types of solar cookers, theirs basic characteristics, and experimental procedures to test the different types of solar cookers. The variables measured in these procedures are necessary to calculate parameters, which are used to compare the thermal performance of the solar cookers. In addition to these experimental procedures, a simplified analytical model is presented to design simple cooking systems. For more complex systems, results are shown and references are indicated in the text.     

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.     

Experimental investigation of solar-powered food steamer based on parabolic dish concentrator for domestic applications

Steam cooking is beneficial over other cooking techniques like boiling since it preserves more vitamins lost during other methods. In this study, a novel solar food steamer (SFS) based on a parabolic dish concentrator (PDC) is designed and constructed for domestic food preparation. A straightforward fabrication process of a 2.626 m² PDC with design calculations is also presented. The system's instantaneous energy and exergy efficiency evaluation has been examined from different tests over three consecutive days. The system's high energetic and exergetic efficiency was achieved in the case of sweet potato, that is, 72.83% and 15.14%, respectively. In the case of dried chickpeas, the maximum steaming duration of 70 min was attained, along with an energy efficiency of 47.74% and an exergy efficiency of 10.07%. In addition, an economic analysis was performed to determine the payback time in terms of cost and utility. The payback time for the proposed method is 2.4 years. The SFS may save 43 kg/month of carbon dioxide from escaping into the atmosphere; it can be considered an environmentally valuable device.     

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.