Performance test of a box‐type solar cooker: effect of load on the second figure of merit

In this paper thermal performance test experiments for first figure of merit (without load) and second figure of merit (with load) of a box‐type solar cooker were conducted as per Bureau of Indian Standards. The values of second figure of merit (F₂) were determined for different loads of water and the results show that F₂ depends on the quantity of water loaded in a solar cooker. Therefore, it is recommended that the performance test method should specify the amount of water which is to be taken. Copyright © 1999 John Wiley & Sons, Ltd.     

Performance analysis of a solar cooker in Turkey

A box‐type solar cooker is designed and its thermal performance is analysed experimentally. The cooker tracks the sun in two axes, altitude and sun azimuth, by hand control for hourly periods. The experimental results show that the tested cooker may be assumed suitable in some cooking processes for specific country conditions. Copyright © 2002 John Wiley & Sons, Ltd.     

Experimental investigation of energy and exergy efficiency of masonry-type solar cooker for animal feed

The performance of a masonry animal feed solar cooker was evaluated in terms of energy and exergy. It is a low-cost cooker made of cement, bricks, glass covers and a mild steel absorber plate. The energy and exergy efficiencies of the animal feed solar cooker were experimentally evaluated. The energy output of this cooker ranges from 1.89 to 49.4 kJ, whereas the exergy output ranges from 0.11 to 2.72 kJ during the same time interval. The energy efficiency of the cooker varies between 1.12% and 29.78%, while the exergy efficiency varies between 0.07% and 1.52 % during the same period.     

An exergy based test protocol for truncated pyramid type solar box cooker

Developing a test standard/protocol for solar box type cookers has drawn a considerable interest among the researchers throughout the world. Recent publications on solar cookers emphasize the need of introducing the thermal performance indicators determined through exergy analysis. In the present paper, the time variation of instantaneous exergy output and energy output as function of its temperature and also of the instantaneous ambient temperature have been reported for truncated pyramid type solar box cooker and compared with those of box type cooker. Further, variations in the exergy lost with temperature difference have been depicted for the selected water temperature range from 60 °C to 95 °C. Based on this study, quality factor, exergy temperature difference gap product, and heat loss coefficient are determined and are proposed as benchmark parameters of solar cooker’s thermal performance.     

Performance evaluation of a hot‐box reflector solar cooker using a microcontroller‐based measurement system

The performance of a low‐cost compound box‐reflector solar cooker designed and constructed by the department of Mechanical Engineering, at the University of Zimbabwe, was investigated and evaluated using a microcontroller‐based measurement system over a period of 3 months. Solar radiation and temperature measurements are sent directly to the computer for monitoring and subsequent analysis using a spreadsheet program. The system is connected to the computer through the RS232 port. Temperature was measured by LM335 temperature sensors, whereas solar radiation was measured by a Kipp & Zonen CM3 thermopile‐based pyranometer that was initially calibrated against the Eppley Precision Spectral Pyranometer. Peak temperatures of about 90°C for the food can be attained in about 5 h on a clear day in Bindura, Zimbabwe (18°S, 31°E). A standardized cooking power of 11 W and an overall efficiency of 15% were found for this cooker. Copyright © 2008 John Wiley & Sons, Ltd.     

Optimization of the parabolic mirror position in a solar cooker using the response surface method (RSM)

The main objective of this study is to develop and improve the thermal and radiative performance of solar cookers. A solar cooker has been designed, constructed and experimentally analyzed to achieve this goal. The designed system contains three narrow, adjustable flat mirrors that are mounted on a parabolic curved substrate in order to concentrate the reflected solar beam onto the absorber plate. The efficiency of this system depends on many variables that were kept fixed with the exception of the parabolic mirror position and operation time. The response surface method was used as the basis of the design and analysis of the experiments. The analysis of the results provided the mathematical function of the effective and overall efficiencies based on the experimental variables that can be adopted to optimize the mirror positions at any given time. As a result, a new system was developed with adjustable mirrors that yields 32.07% and 35.5% increase in the effective and overall efficiencies, respectively. The results have been validated by variance analysis and comparing theoretical and experimental efficiency. The experiments were carried out in Mashhad, Iran at latitude 37, longitude 54, and a height of 985 m above sea level.     

Novel mixed solar cooker: Experimental,energy, exergy,and economic analysis

This work focuses on the structure, working, and testing of a new mixed solar cooker using a linear Fresnel collector, evacuated tube and box-type cooker. The low-cost components used in the construction of this cooker can help it satisfy the needs of both urban and rural inhabitants who need steady cooking temperatures above 140°C. A family of five can prepare four meals using this modified solar cooker, which costs about $250. The designed solar cooker was tested by conducting no-load and full-load tests. For the no-load test, the maximum temperature of the absorber plate and oil for the new mixed cooker was recorded as 160.26°C and 172.72°C, respectively. The absorber plate of the new mixed cooker and its oil both reached their highest temperatures during the full-load test at 141.14°C and 157°C, respectively. The energy efficiency of the new cooker is 58.776%, while its exergy efficiency is 13%. The heat transfer coefficient increased to 100.16 W/m² °C. This cooker provides an additional time savings of 60 min. An improvement of 27.5% in the highest temperature reached was seen when the developed cooker's performance was compared with those reported in the literature. Additionally, the new cooker's heat-storing capability enables up to 3 h of autonomy. The Levelized Cost of Cooking a Meal for the innovative mixed solar cooker is $0.034 per meal.     

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.     

Novel solar cookers: suitable for small families

This paper presents the fabrication details and on-field experimental studies of two novel solar cookers, suitable for cooking requirements of small families; these are named as small family solar cookers (SFSC-1 and SFSC-2). Small size, good thermal performance, light weight, low-cost and short payback periods are some important features of these cookers. The values of some essential thermal performance parameters, first figure of merit (F₁), second figure of merit (F₂) and standard cooking power suggested by Bureau of Indian Standards and International Standard for box-type solar cookers, have been evaluated by experimental studies and found to be 0.116°C m²/W, 0.466, 30 W and 0.118°C m²/W, 0.488, 50 W for SFSC-1 and SFSC-2, respectively. A comparative analysis of the thermal performances of SFSCs with the solar cookers, developed by many authors, has also been presented here. The payback periods with respect to different cooking fuels for SFSCs have been found to be reasonably short.     

Simulated energy and exergy analyses of the charging of an oil-pebble bed thermal energy storage system for a solar cooker

Energy balance equations are used to model the solar energy capture (SEC) system and the thermal energy storage (TES) system of a proposed indirect solar cooker. An oil-pebble bed is used as the TES material. Energy and exergy analyses are carried out using two different charging methods to predict the performance of the TES system. The first method charges the TES system at a constant flowrate. In the second method, the flowrate is made variable to maintain a constant charging temperature. A Simulink block model is developed to solve the energy balance equations and to perform energy and exergy analyses. Simulation results using the two methods indicate a greater degree of thermal stratification and energy stored when using constant-temperature charging than when using constant-flowrate charging. There are greater initial energy and exergy rates for the constant-flowrate method when the solar radiation is low. Energy efficiencies using both methods are comparable whilst the constant-temperature method results in greater exergy efficiency at higher levels of the solar radiation. Parametric results showing the effect of each charging method on the energy and exergy efficiencies are also presented.     

Development of new solar exergy maps

In this paper, we develop a solar exergy map concept and conduct a comprehensive case study to show how it is utilized and how it is significant for practical solar applications. Based on the exergy content of the solar radiation, the performance of a photovoltaic thermal (PV/T) system is evaluated for different Indian cities, namely Bangalore (latitude 12°58′N, longitude 77°38′E), Jodhpur (latitude 26°18′N, longitude 73°04′E), Mumbai (latitude 18°55′N, longitude 72°54′E), New Delhi (latitude 28°35′N, longitude 77°12′E) and Srinagar (latitude 34°08′N, longitude 74°51′E) for a year and for different cities of U.S.A., namely Chicago (latitude 41°50′N, longitude 87°37′W), Las Vegas (latitude 36°10′N, longitude 115°12′W), Miami (latitude 25°46′N, longitude 80°12′W), New York (latitude 40°47′N, longitude 73°58′E), Portland (latitude 43°40′N, longitude 70°15′W), San Antonio (latitude 29°23′N, longitude 98°33′W), San Francisco (latitude 37°47′N, longitude 122°26′W), Tucson (latitude 32°7′N, longitude 110°56′W) and Tulsa (latitude 36°09′N, longitude 95°59′W) for different months of January, April, June and October. For the first time, the development of exergy maps for the exergy of solar radiation as well as the exergy efficiency of PV/T system is done for the above‐mentioned Indian and American climatic conditions. It is found that the predicted exergy efficiency is in good agreement with the experimental results for the climatic conditions of New Delhi, India. It is observed that the average exergy efficiency is highest in Bangalore from January (28%) to April (32.6%) and from September (32.5%) to December (32.4%) and it is highest in Srinagar from May (29.5%) to August (26.8%) for Indian climatic conditions and for American climatic conditions, the PV/T system gives the best performance in terms of exergy efficiency in Las Vegas (32%) and Tucson (32.5–31.5%) in April and June. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

Estimation of design parameters for thermal performance evaluation of box-type solar cooker

The paper presents a simple test procedure for determination of design parameters to predict the thermal performance of a box-type solar cooker. A series of out-door experiments were performed on the double-glazed solar cooker of aperture area 0.245 m² with a fibre body to obtain two figures of merit, F₁ and F₂. The necessary design parameters—optical efficiency, F′η_o and heat capacity, (MC)′ of the cooker are calculated using the linear regression analysis of experimental F₂ data for different load of water. Based on the experimental results, a correlation for F₂ as a function of quantity of water (load) is proposed. The close agreement between experimental and calculated F₂ indicates the validity of the correlation. The proposed procedure is then applied to predict the heating characteristic curves of the solar cooker for different load of water. The predicted heating characteristic curves are validated by comparing with the experimental data from a series of cooker testing experiments. The results of present study reveal that F′η_o and (MC)′ are the critical design parameters required for the prediction of thermal performance of the solar cooker.     

Analysis of the exergetic performance of the reverse-side absorber-plate shallow solar pond

Results of exergetic performance analysis of three shallow solar pond (SSP) types – the CSSP, the RASSPgc, and RASSPins – are presented for the first time. The study shows that the highest irreversibilities are encountered in the components of the RASSPgc and that better exergetic performances in SSPs may be obtained by improving the surface properties: absorptivity, reflectivity, and transmissivity. Steady-state analysis also shows that exergy ‘losses’ in the SSPs due to irreversibilities in their water masses are significant and result from the direct absorption of solar radiation. Transient analysis reveals that the RASSPgc achieves the highest overall exergetic efficiency (4.37%), followed by the RASSPins (3.96%) and then the CSSP (2.87%). At the end of a 24 h operation, the exergy content of the water masses in the RASSPgc and the CSSP is negligible, whereas the water mass in the RASSPins retains 0.057 MJ of the exergy accumulated during daytime heating.     

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.     

Exergy‐based performance analysis of packed‐bed solar air heaters

This paper presents an experimental investigation of the thermal performance of a solar air heater having its flow channel packed with Raschig rings. The packing improves the heat transfer from the plate to the air flow underneath. The dimensions of the heater are 0.9 m wide and 1.9 m long. The aluminium‐based absorber plate was coated with ordinary black paint. The characteristic diameter of the Raschig rings, made of black polyvinyl chloride (PVC) tube, is 50 mm and the depth of the packed‐bed in flow channel is 60 mm. Energy and exergy analyses were applied for evaluating the efficiency of the packed‐bed solar air heater. The rate of heat recovered from the packed‐bed solar air heater varied between 9.3 and 151.5 W m^?2, while the rate of thermal exergy recovered from the packed‐bed solar air heater varied between 0.04 and 8.77 W m^?2 during the charging period. The net energy efficiency varied from 2.05 to 33.78%, whereas the net exergy efficiency ranged from 0.01 to 2.16%. It was found that the average daily net energy and exergy efficiencies were 17.51 and 0.91%, respectively. The energy and exergy efficiencies of the packed‐bed solar air heater increased as the outlet temperature of heat transfer fluid increased. Copyright © 2004 John Wiley & Sons, Ltd.     

Evaluation of solar cooker thermal performance using different insulating materials

This paper summarizes very briefly the thermal performance of solar cookers with four different insulations readily available in rural areas. A comparison of each one of these is made with the performance of glass wool. This experiment is performed to minimize the cost of the cooker with a view to enhance its widespread application in the rural Indian environment.     

Design and measured performance of a plane reflector augmented box-type solar-energy cooker

The design philosophy, construction and measured performances of a plane-reflector augmented box-type solar-energy cooker are presented. The experimental solar cooker consists of an aluminum plate absorber painted matt black and a double-glazed lid. The bottom and sides are lagged with fibreglass wool insulator. The reflector consists of a wooden-framed commercially available specular plane mirror which is sized to form a cover for the box when not in use. Provision is made for four cooking vessels, each capable of holding upto 1 kg of water. Results of thermal performance tests show stagnation absorber plate temperatures of 138°C and 119°C for the cooker with and without the plane reflector in place respectively. Boiling times of 60 min (3600 s) and 70 min (4200 s) for 1 kg of water, for the cooker with and without the plane reflector in place, respectively, were recorded. The solar cooker performance has been rated using the first figure of merit (F₁) on the no-load test and the second figure of merit (F₂) on the sensible heat tests. Predicted water boiling times using the two figures of merit compared favourably with measured values. The performance of the cooker with the plane reflector in place was improved tremendously compared to that without the reflector in place.     

An investigation into sky temperature estimation,its variation,and significance in heat transfer calculations of solar cookers

The determination of sky temperature assumes great importance in engineering applications such as radiative cooling of buildings. Many studies that involve a radiative exchange with the sky employ different reported models of sky temperature interchangeably. However, until now, hardly any systematic study has been done to quantify the errors/variations that might be encountered in calculating this radiative exchange employing these different correlations. In the current paper, first, a thorough analysis has been presented on the sky temperature correlations and a possible range of variation in sky temperature based on the estimation of sky emissivity is computed. Both diurnal‐nocturnal variation in sky temperature and seasonal disparities in sky temperature have been reported. Next, the case of a box‐type solar cooker has been taken up for investigation with respect to the possible influence of the sky temperature estimation in predicting its performance parameter, first‐figure‐of‐merit on a daily, seasonal, and climatic basis. Our observations show an enormous difference in sky temperature depending upon the expressions of emissivity from which it is derived. The variability of sky temperature has a nominal influence on the prediction of first‐figure‐of‐merit, although a marked discrepancy is observed across the seasons at the same location.     

A solar ejector air‐conditioning system using environment‐friendly working fluids

In this paper, the performance of the solar‐driven ejector air conditioning with several environment‐friendly working fluids is studied. The effect of the fluid nature and operating conditions on the ejector performance is examined. This performance is calculated using an empirical correlation. Thermodynamic properties of functioning fluids are obtained with a package REFPROP7. It appears that the refrigerant R717 offers the highest coefficient of performance (COP). For generator temperature T_B = 90°C, condenser temperature T_C = 35°C and evaporator temperature T_E = 15°C and with R717, the COP of ejector air‐conditioning system is 0.408. Using a meteorological data for the city of Tunis, the system performance is computed for three collector types. The air‐conditioning season and period were taken for six months from April to September. The daily period is between 8 and 17 h. For the solar air‐conditioning application, the COP of the overall system varied from 0.21 to 0.28 and the exergy efficiency varied from 0.14 to 0.19 with the same working conditions and total solar radiation (351–875 Wm^?2) in July. Copyright © 2008 John Wiley & Sons, Ltd.