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.     

Enhancement the solar box cooker performance using steel fibers

The use of fossil fuel and wood for cooking poses health, environmental, and economic challenges, especially with the growing population. This has led to an increase in the trend towards the use of clean and sustainable cooking sources, including solar cookers. This experimental study aims to contribute by enhancing the performance of a solar box cooker (SBC) according to the concept of porous media via adding steel fibers inside the box as a modified SBC and comparing it with a conventional SBC. The stagnation test to determine the first figure of merit and the load test to determine the second figure of merit, standard boiling time, and cooker optothermal ratio were conducted under the outdoor conditions of Baghdad city. Also, an energy and exergy efficiency analysis, and calculating the rate of heat loss by three water loads heating and cooling tests. The results revealed that the modified SBC has a higher thermal performance than the conventional SBC.     

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.     

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.     

Theoretical analysis of the thermoelectric figure of merit

A theoretical analysis of the thermoelectric figure of merit is presented based upon a two band conduction model for single and many valley semiconductors. The figure of merit is obtained as a function of reduced Fermi potential for a model system which is a close approximation to the silicon-germanium alloys currently employed in thermoelectric applications. The effect of a reduction in grain size on the thermal conductivity and consequently on the figure of merit is also discussed.     

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.     

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.     

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.     

Performance evaluation of a small‐scale sodium carbonate salt gradient solar pond

In this study, thermal performance of the salt gradient solar pond (SGSP), which of density gradient is artificially with sodium carbonate solution, was tested under Karabuk prevailing weather conditions in Turkey. A small‐scale prismatic glass tank was constructed with an area of 0.45 × 0.20 m² and a depth of 0.25 m as solar pond. A series of experiments with four different density levels were conducted in July–August 2004. The variations of the temperature and density profiles were observed for each of experiment for a week. It was found that the maximum temperature difference between the bottom and surface of the pond is 21°C and maximum temperature in the lower convective zone (LCZ) has been measured as 49°C at the first experiment. The efficiency of the pond was evaluated 13.33% weekly mean radiation intensity of 524 W m^?2 for the first experiment. Copyright © 2006 John Wiley & Sons, Ltd.     

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.     

The BEPE – Break-Even Price of Energy: A financial figure of merit for renewable energy projects

Renewable energy is a fact, with more than 1580 GW installed worldwide growing up to 2350 GW expected for 2018 [1]. Driven by increasing conventional fuels prices and limited reserves, the energy mix for covering the world's demand is rapidly including renewable energy sources, providing carbon free energy as well as energy independence. Some studies claim the costs of renewable energy as one of the most important barriers to accelerate their deployment and reach a complete change in the energy model [2]. In this scenario, the cost of energy becomes one of the most important figures of merit for analyzing renewable energy projects. However, defining the cost of energy as figure of merit is not a trivial issue and most times is being done with different criteria, thus leading to different results difficult to compare. In this paper, a new figure of merit for renewable energy projects is presented alongside the methodology for its calculation. This figure of merit is not based on the cost of energy itself, but on the price at which this energy has to be sold in an energy market to result into a profitable project. The Break-Even Price of Energy, BEPE, is proposed as a financial indicator focused on renewable energy projects developers, and takes into account all the specific aspects of each legal and financial framework. This is of major importance when considering the present renewable energy scenario, with vast influence of local conditioning factors in the cost of energy depending on the project location and technology [3]. Thus, this indicator makes it possible to compare different specific renewable energy projects, and can really help developers to decide amongst different technologies, designs, locations, legal frameworks, etc.     

First and second law analyses of a typical solar air dryer system: a case study

This communication presents an experimental study based on energy and exergy analyses of a typical solar air dryer. On the basis of the experimental results, the first and the second law efficiencies are calculated with respect to the available solar radiation. It is found that the second law efficiency is much less than the first law efficiency irrespective of the mass flow rate of the circulating fluid. It is also found that both efficiencies are an increasing function with respect to the mass flow rate of the working fluid. For a particular day, it is also found that first and second law efficiencies fluctuate according to radiation. The results obtained in this article are found to be consistent with those obtained by earlier authors as given in the literature.     

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.     

太阳能半导体制冷性能改进的技术策略

本文在介绍了太阳能半导体制冷的原理及系统结构的基础上,对影响太阳能半导体制冷性能的主要因素进行了系统分析,主要有太阳辐射强度和电池板的光电转换效率、材料的优值系数、电臂的优化结构设计、热端强化散热以及半导体最优工况。其中半导体材料的优值系数和半导体制冷热端散热这两个因素是影响太阳能半导体制冷性能的关键因素。从优值系数方面讲,可以通过半导体材料的性能改进及其加工、制造工艺的完善提高优值系数,从而提高半导体制冷性能。而寻找合理的半导体制冷热端散热方式对制冷性能也有着很重要的影响,随着散热强度的不断增强,半导体制冷的性能有所提高,但最终趋于恒定。     

First and second law investigations of a new solar‐assisted thermodynamic cycle for triple effect refrigeration

This investigation is persuaded for the first and second law analyses of a new solar‐driven triple‐effect refrigeration cycle using Duratherm 600 oil (Duratherm Extended Life Fluid, NY, USA) as the heat transfer fluid is performed. The proposed cycle is an integration of ejector, absorption, and cascaded refrigeration cycles that could produce refrigeration output of different magnitude at different temperature simultaneously. Both exergy destruction and losses in each component and hence in the overall system are determined to identify the causes and locations of the thermodynamic imperfection. The effects of some influenced parameters such as hot oil outlet temperature, refrigerant turbine inlet pressure, and the evaporator temperature of ejector and cascaded refrigeration cycle have been observed on the first and second law performances. It is found that maximum irreversibility occurs in central receiver as 52.5% and the second largest irreversibility of 25% occurs in heliostat field. The second law efficiency of the solar driven triple effect refrigeration cycle is 2%, which is much lower than its first law efficiency of 11.5%. Analysis clearly shows that performance evaluation based on the first law analysis is inadequate and hence, more meaningful evaluation must be included in the second law analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

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.     

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.     

Performance evaluation of a single solar air heater with N‐subcollectors connected in different combinations

In the present communication, a generalized procedure has been described for the performance evaluation of a solar air heater with N‐subcollectors with identical collector aspect ratio connected in various combinations such as in series, parallel and series–parallel. It has been found that the performance of a solar air heating system can be improved by operating several subcollectors in series in place of a single large collector with the same total area. Results have been presented to show the effect of various design parameters, viz. collector aspect ratio, mass flow rate, etc. on the performance of solar air heater with N‐subcollectors in series, parallel and series–parallel combinations. Copyright © 1999 John Wiley & Sons, Ltd.     

Data analysis on solar irradiance and performance characteristics of solar modules with a test facility of various tilted angles and directions

We examined and evaluated the output characteristics and the deterioration lowering factors of modules installed under various conditions (module directions and tilted angles) based on the data collected at the multi-position test facility, which was produced and installed in order to conduct evaluation using design parameters (correction coefficient). This report introduces example data and the results of our evaluation.