Performance evaluation of three solar concentrating cookers

Three solar concentrating type cookers meant for domestic use were tested for their thermal performance and cooking abilities. Stagnation temperature, water heating and cooking tests were conducted. During the tests, the operational ease and problems in each cooker were evaluated.     

Multiple use communal solar cookers

Solar cooking in boarding schools and communal centres in isolated areas demands the heating of large quantities of food. It is generally done in large pots of 30–40 litres. In a previous paper (Saravia et al., Energías Renovables y Medio Ambiente, ASADES, 1999, 6, 7–16), the solar cooker presented consisted of two separate units: a concentrator on one side and an insulated box containing the pot on the other. In this paper we introduce some changes which improve its working capacity. At present we can count on three different kinds of absorbers, which have been optimised to fulfill different functions in a concentrator of an area of 2 m². These alternatives allow the possibility of satisfying the needs of a communal dining centre, cooking for up to 30 children, once each concentrator has been installed.     

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.     

太阳灶在印度的推广和应用

20多年来太阳灶在印度得到了成功的发展，已经被人们所接受。印度的太阳灶除了应用于炊事方面外，还在其它许多新的领域得到了应用，例如：处理污水，食品加工业，海水淡化，生产蒸汽，农产品干燥；空调和制冷。[编者按]     

The economics of box-type solar cookers

The economic feasibility of using a simple box-type solar cooker has been studied following simple engineering economics. The results of some typical numerical calculations are presented graphically and discussed.     

浅析太阳能灶在宁夏地区的发展

一引言 宁夏太阳能资源丰富,大部分属于太阳辐射一类区.据资料统计,宁夏每年太阳能辐射量为5781MJ/m2,其空间分布特征是北部多于南部,南北相差约1000 MJ/m2,灵武、同心最大,达6100 MJ/m2以上.宁夏的太阳能辐射量以直接辐射为主,散射辐射少,对宁夏太阳灶的开发利用十分有利.     

Thermal test procedure for box-type solar cookers

Some guidelines are provided for thermal evaluation of box-type solar cookers. Suitable thermal tests have been proposed and appropriate parameters identified, which pertain to the solar cooker and are relatively independent of the climatic variables as well as the products cooked. These parameters have been combined into two figures of merit.     

Heat loss coefficients for box-type solar cookers

The top and overall heat loss coefficients for the entire feasible operating range of box-type solar cookers are evaluated experimentally and presented in a graphical form as a function of the difference between mean plate temperature and ambient temperature with wind velocity and number of glass covers as parameters.

The range of plate temperatures considered is from 50°C to 180°C. While the wind velocity is varied from 0 to 3.33 m/s, and the number of glass covers considered are from 1 to 4.

Based on these experimental results, a correlation for the determination of top loss coefficient in terms of optical properties of cooker, the spacing between glass cover and absorber plate, wind velocity and number of glass covers, is derived and presented in the paper.     

聚光式太阳灶的设计与制作(Ⅰ)--抛物面聚光太阳灶是怎样工作的

一关于抛物线与抛物面 1什么是抛物线 抛物线是我们在抛出一个物体时,物体在抛力与重力的作用下所运行的路线.如你掷出一个小石子,它飞行的这一段轨迹,就是一条抛物线.抛力的大小不同,抛出的角度不同就会得到不同的抛物线,可惜你通常看不到这条线,我们可画出一条抛物线来先熟悉一下.图1为一个人抛出一颗石子,石子运行的轨迹,就是一条抛物线.     

聚光式太阳灶的设计与制作(Ⅶ)--太阳灶模具的制作

（三）反光材料 聚光太阳灶实用效果的优劣，除了设计和制作工艺对太阳灶的影响之外，在很大程度上取决于反光材料的性能。选用反射率高、寿命长的反光材料，能提高太阳灶的热效率。在功率相等的情况下可以使反光面做得小一些，从而有利于操作，也有利于降低成本。     

聚光式太阳灶的设计与制作(Ⅵ)--太阳灶模具的制作

（二）太阳灶灶壳的材料和制作 太阳灶材料可分为灶壳材料、反光材料和支架材料三大部分。由于灶壳材料是关键，我们将重点加以介绍。水泥太阳灶、玻璃钢太阳灶、铸铁太阳灶、菱镁太阳灶等称谓，大都是指灶壳的制作材料而言的，太阳灶灶壳的制作材料对所制作出的太阳灶的特点和优劣以及工艺可行性起到了决定性作用。     

聚光式太阳灶的设计与制作(Ⅷ)--太阳灶技术要求和测试方法

作为一种产品,我们需要采用科学的方法对它进行检测,以评价它的各项技术指标的优劣.聚光型太阳灶行业标准(NY219-2003),系统地归纳了我国十余年来在聚光型太阳灶方面的科研成果和生产推广经验,提出了太阳灶的设计、型号、规格和测试方法,规定了太阳灶的技术要求、结构检测和性能试验方法,是世界上首次提出的太阳灶标准.为方便读者掌握和应用,我们把标准的主要内容介绍如下.     

聚光式太阳灶的设计与制作(Ⅳ)--选一选太阳灶的支架

针对太阳灶的使用对象主要为农牧民的特点，在满足太阳灶所应具备的功能的前提下，尽量考虑到便于使用和操作，同时还要尽力降低成本。     

聚光式太阳灶的设计与制作(Ⅲ)一一算一算要多大面积画一画灶面轮廓

人们在设计工作中首先遇到的问题，是要做多大面积的太阳灶，让我们首先研究这个问题。     

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.     

Financial feasibility analysis of box-type solar cookers in India

A framework for financial evaluation of a box-type solar cooker, using cost functions for its capital cost, has been developed. The annual benefits accrued to the user are quantified in terms of number of meals cooked per year and monetary worth of the fuel saved per meal. Expressions for some financial performance indicators have been derived and results of typical numerical calculations are briefly presented.     

聚光式太阳灶的设计与制作(V)--太阳灶模具的制作

我们在前面的章节里主要是围绕着抛物面的设计原理与作图法以及结构设计等方面介绍的，现在进入了具体制作阶段，将应用前面学到的知识。     

聚光式太阳灶的设计与制作(Ⅱ)--记一记几个设计参数

一台太阳灶的优劣，同设计参数的选取有着直接的关系，确定合理的设计参数，选择适当的约束条件，是达到优化设计的关键。事实上，太阳灶的设计工作，往往要经过数次参数的调整才会得到令人满意的结果。这些设计参数，在以后还要提到，现在先明确它的含义、选取思路、计算方法及参数间的关系。     

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.