Food dehydration by solar energy

Solar driers that are currently being investigated for drying of agricultural products can be divided into two major divisions, depending upon how they transfer the incident solar energy to the product to be dried. These two divisions are direct and indirect drying, with some work also being done on combination drying procedures. In direct solar driers, the product to be dried is usually either inside a tent, greenhouse, or a glass‐topped box, where the product to be dried is heated by the direct rays from the sun and the moist air is removed by ambient wind movement. These dryers do accelerate moisture loss rate and the product is usually safe from inclement weather. These dryers usually do not require fans for forced air circulation. With indirect drying, the opposite is true, where most require powered fans for forced air circulation. With this type of dryer, both flat‐plate and inflated tube solar heat absorbers are used, with each offering certain advantages. Also, combination dryers have been built that utilize both direct and indirect principles. Product evaluation of solar dried foods indicate that in most cases the physical properties, flavor, and vitamin A and C retention were as good as, or better than, conventional dried foods. The economics of the solar systems indicate that most drying procedures are economically feasible for use in small‐scale operations only, with the exception of grain drying.     

Temperature control in a solar kiln

Realizing the effect of venting on temperatures in a solar kiln, average kiln temperatures were measured in a solar kiln with automatic vent control. These temperatures were found to be less than 2°C above ambient with the wood above fibre saturation point and increased to about 10°C when the wood reached 12% moisture content. The effect of these relative small differences between kiln and ambient temperatures on the drying rate were investigated as well as methods to increase the average temperature in a solar kiln.     

Abiotic production of methylmercury by solar radiation

Methylmercury [MeHg(I) in the aerobic surface water of lakes is thought to be rapidly degraded, but contrary to expectations, we show that MeHg(I) concentrations often increase during sunlight hours or remain relatively constant. We hypothesized that there were water column processes that generated MeHg(I) and that these processes were linked to dissolved organic matter (DOM) and solar radiation. A 2-day diurnal pattern of MeHg(I) in surface water with corresponding bottled controls was assessed for two contrasting lakes in Kejimikujik, Nova Scotia, Canada. Following this study, a tangential ultrafiltrator was used to size-fractionate and generate a concentration gradient of DOM from four different lakes located near Lac Berthelot, Quebec, Canada. The watersheds of two of these lakes were not substantially logged whereas the other two had been extensively logged. Different size fractions of DOM as well as different concentrations of DOM were exposed to sunlight for varying periods of time. We observed that, in Keiimikujik, the concentration of MeHg(I) in surface waters peaked in the early afternoon. Furthermore, this also occurred in bottled water for one of the lakes, Puzzle, eliminating the possibility that in-lake mixing played a role in this pattern. The formation of MeHg(I) was found to be dependent on the size fraction and amount of DOM present in the water. Specifically, DOM less than 5 kDa or between 30 and 300 kDa generated MeHg(I) when exposed to sunlight, but larger fractions did not. Furthermore, although data are limited, we found that water from lakes with logged watersheds generated MeHg(I) when exposed to sunlight, whereas water from lakes with low levels of logging in the undisturbed watersheds did not. Our results demonstrate that MeHg(I) can be formed in freshwaters of certain lakes in response to solar radiation. This photoproduction of MeHg(I) is dependent on DOM concentrations and type, with the importance of water chemistry not yet clear. The significance of this process to freshwater lakes and the mechanism responsible for MeHg(I) photoproduction is still unclear, but a correction in the conventional wisdom that MeHg(I) is rapidly photodegraded is timely.     

木材太阳能干燥技术的研究

简述了太阳能用于木材干燥行业的优缺点,介绍了太阳能-热泵联合干燥的组成和基本工作原理,新型热能回收技术振荡流热管在木材干燥上的应用,指出了太阳能在木材干燥应用上的发展前景。     

葡萄酒厂屋顶上的太阳能

近日,美国光能公司(PowerLight Corporation)在加州葡萄酒厂又安装了一套太阳能发电系统,这套新的光电(PV)设备安装在加州纳帕山谷Carneros酒庄新建的黑比诺葡萄酒厂的屋顶上,面积约为9,400平方英尺。据该公司称,这套功率为120千瓦的发电设备是美国葡萄酒厂最大的太阳能光电设备。这套太阳能设备日间发电量相当于120个家庭的用电量,大大减少了Carneros酒庄的生产费用。目前,该设备已经投入运行,可为Carneros酒庄及其黑比诺酒厂提供40%的用电需求。这套设备采用日本三洋公司的高效光电技术,不仅有助于产生干净的能量,而且还可以大大的节…     

The photodegradation of wood during solar irradiation

The photodegradation of wood is essentially a surface phenomenon, and although in practical terms it has no effect on strength properties, it does have serious consequences for the surface technologist. A principal concern is photodegradation of the timber surface underlying clear and lightly-pigmented finishes—a problem which can lead to early failure of the coating and to expensive remedial measures. Recent thinking is directed towards the development of pretreatments which could stabilise the timber surface against photodegradation. However, in the absence of detailed investigations on the wood-degrading capabilities of different regions of the solar spectrum such developments have so far been restricted. In this paper, thin strips of Scots pine and lime were irradiated behind filters which transmitted selected regions of the ultraviolet and visible spectrum. Tensile tests on irradiated strips show that ultraviolet light is highly active in degrading wood, but indicate that the visible part of the spectrum also contributes significantly to loss of strength. Throughout the exposure period, samples were taken for SEM observation. The loss of strip strength is associated with a light-induced depolymerisation of lignin and cell wall constituents, and to the subsequent breakdown of the wood microstructure.     

太阳能干燥设备在食品原料干燥中的应用

综述了太阳能干燥设备在食品原料干燥领域的应用,分别分析了各种太阳能干燥设备的结构、用途和干燥效果,从自然对流和强迫对流两种不同空气流动方式的角度上,探讨了国内外各种太阳能食品干燥设备的研究进展,着重对便携、储能、废热回收等一般太阳能干燥设备所没有的方面展开分析。介绍了如便携式干燥设备、太阳能辅助干燥设备、太阳能储能干燥设备等适用于食品干燥的太阳能干燥设备的性能及优点,并提出太阳能干燥设备都是向节能和智能化方面,并辅助其他形式的设备一起使用,实现干燥设备可连续作业等观点。      

Design and testing of a solar kiln simulator

The solar simulation system as previously described (Steinmann 1990) was used to simulate an actual drying run in a solar kiln. Adjustments necessary to compensate for difference in scale are described. The simulated weather conditions were in close agreement with the actual weather. The conditions in the solar kiln simulator and the solar kiln were so similar that the drying rates were virtually identical. Repeatability of runs in the simulator was good and it was concluded that valid results on solar drying could be produced in the solar simulation system.     

Design and testing of a solar kiln simulator

To overcome the need for repeatable weather conditions when investigating solar wood drying, a solar simulation system was designed consisting of a climatic chamber for producing ambient wet and dry bulb conditions, a solar energy simulator to simulate the solar energy falling on the collector, and a small solar kiln to fit inside the climatic chamber. A fully automated control system, as used in an experimental solar kiln, controlled the simulation system. The design parameters, construction, and control logic of the system are discussed in Part 1 while the testing and performance of the system will be discussed in Part 2.     

一种家用小型太阳能堆肥箱的设计

针对目前市场上常见的厨余垃圾堆肥箱不易保温、堆肥时间长、沥水效果差、臭味重等问题,设计一种家用小型堆肥箱,该装置包括太阳能集热板、太阳能电池板、通风管路、投料口、沥水筛网、尾气处理等多个模块。通过对堆肥箱空间结构进行设计和优化,使其更好地满足高温好氧堆肥工艺的需求,同时由于引入了太阳能为整个系统的保温和通风供能,大大降低了能耗。该装置与自然堆肥相比缩短了堆肥时间,且整个系统移动搬运方便,不受放置地点限制,十分适合庭院内使用。     

光伏太阳能硅片切割用钢丝生产

切割钢丝一般选用碳质量分数为0.80%～0.92%的专用盘条,对钢材冶炼水平尤其是各类非金属夹杂物的数量、尺寸等有较高质量要求。介绍常用规格切割硅片用钢丝的生产工艺流程,给出切割钢丝的主要规格及相应的技术指标。分析对切割钢丝质量有重要影响的因素:半成品钢丝热处理采用水浴淬火,焦磷酸盐电镀铜,硫酸盐电镀锌,并通过热扩散形成黄铜组织;盘条及中丝的拉拔采用直进式拉丝机,最终热处理后冷拉采用水箱拉丝机;水箱拉丝机成品拉拔前1～3道次选用聚晶模,其余选用硬质合金模具,并严格控制润滑液的成分,将润滑液温度控制在最佳温度区间。生产直径小于0.100 mm的金刚石线锯是切割钢丝未来的发展方向。     

矿卤日晒扩大试验研究

通过台北盐场5万吨矿卤日晒项目扩大试验,获得了准确的矿卤日晒生产工艺参数,为100万吨的规模化生产提供决策依据。     

基于太阳能利用的发热服装研究

介绍了利用太阳能进行发热的服装的应用现状。按其构成原理,将太阳能发热服装分为太阳能蓄电电热服和太阳能蓄热服两类。详细阐述了实现太阳能蓄电的关键元件———太阳能电池板在服装上的应用,以及电热服的实现途径,尤其是碳纤维在发热服装中的应用;关于太阳能蓄热服,分析了太阳能蓄热保暖材料的研究进展及其在服装上的应用。同时,探讨了太阳能发热服装可能存在的热学问题,并分别阐述了国内对太阳能蓄电电热服和太阳能蓄热服的研究状况。