During graduate school, I spent several months working at a university in Stuttg

Question

During graduate school, I spent several months working at a university in Stuttgart, Germany. I shared an office there with an engineer who was working on the design of a large-scale food dehydration system for drying foods (mostly fruit) for preservation in developing countries, where many of the resources that we take for granted (e.g., an electrical outlet, or refrigeration systems) are not available. The system was being designed for a fairly large-scale (e.g., an extended family or village). The system had not been optimized, and I have thought since then that a smaller-scale system might be useful for an individual or small family, either in a developing country or even here. Consequently, your assignment is as follows:
Design a small-scale food dehydration system, capable of operating on renewable resources (i.e., not from an electric outlet or from other non-reusable/non-renewable consumables), and suitable for drying fruits in a home-scale application.

List your design criteria (objectives and constraints) for this problem. Be quantitative to the maximum extent possible.

List at least four pieces of information would you need to gather before you could complete this design and full engineering analysis of your solutions. You do not need to actually get this info; just state what you would need (e.g., Average ambient temperature at whatever location your are specifying as your target market).

Generate and clearly communicate (with sketches) three alternative design concepts.

Utilize a decision matrix to select your best design concept.

Explanation / Answer

1) Outline : Increasing population and high cost of fuels have created opportunities for using alternate energies for post-harvest processing of foods. Solar food processing is an emerging technology that provides good quality foods at low or no additional fuel costs. A number of solar dryers, collectors and concentrators are currently being used for various steps in food processing and value addition. Society for Energy, Environment and Development (SEED) developed Solar Cabinet Dryer with forced circulation which has been used for dehydration and development of value added products from locally grown fruits, vegetables, leafy greens and forest produce. Drying under simulated shade conditions using UV-reducing Blue filter helps retain nutrients better. Its simple design and ease of handling makes SEED Solar Dryer an ideal choice for application of food processing in rural settings, closer to where the harvest is produced, eliminating the need for expensive transportation or storage of fresh produce. It also creates employment opportunities among the rural population, especially women. Other gadgets based on solar collectors and concentrators currently being used at various steps of food processing are reviewed.

2) Why not conventional?

Dehydration is one of the most important steps for preservation and value addition of food products through moisture control. Conduction, convection and radiation are the basic techniques by which water is forced to vapourise and the resulting vapour is removed either naturally or by force resulting in dehydration. Conventional convective drying is used for drying fruits and vegetables

However, this process also brings in some important changes in physical and chemical properties such as loss of color and change of texture, flavour and loss of nutrients. While high temperature used during the processing are responsible for the alterations, lowering temperature increases the time of dehydration therefore increase in cost. Since fresh fruits and vegetables contain over 80 % moisture, the process of dehydration to a desirable lower moisture content such as 5–10 % (Eg. 75 kg of water from a 100 kg sample) is very energy-consuming. The process of dehydration alone contributes up to 30 % of the total cost of processing of most fresh produce. Thus, the cost of dehydration and energy consumption and quality of dried products play very important role in choosing an appropriate drying process.

3) use renewable Energy

The process of drying in the Solar Dryer is facilitated by circulation of hot air, the spreading density of the product, the nature of pretreatment as well as the nature of the product to be dried itself. The time taken for drying is also determined by the factors such as the initial moisture content and the desired final % moisture of the product. For example, it may take 4 h to bring moisture level from an initial 4 to 0 % final in a single 50 kg load of refined wheat flour that is used in Instant Gulabjamun Mixes where as 6 h are needed to reduce moisture level from an initial of 63 % to 4 % final level from a 4 kg load of curry leaves

4)Advantages

Solar food processing brings in two emerging technologies together to solve the two major problems the world facing in 21st century, namely: how to generate energy enough for an expanding global population? and how to feed the constantly expanding world population? This has a different connotation with respect to developing countries. Growing population and unequal wealth distribution in these countries has created a section of the society being left behind and chronically poor. Lack of reliable and affordable energy sources in these parts only complicates the matter. This situation also demands search for faster, cheaper and safer methods by which food can be conserved and distributed to the poorer, usually rural populations, especially women and children. In the face of such great demand for food to feed people, it is sad to note that 30–40 % of food goes waste in India every year for lack of a systematic post-harvest processing and preservation. The food processing industry in India accounts for only 2.2 % of the total.

The International Energy Agency in its 2011 Solar Energy Perspectives: Executive Summary (SEP 2011) states that “Solar energy offers a clean, climate-friendly, very abundant and inexhaustible energy resource to mankind, relatively well-spread over the globe. Its availability is greater in warm and sunny countries—those countries that will experience most of the world’s population and economic growth over the next decades. They will likely contain about 7 billion inhabitants by 2050 versus 2 billion in cold and temperate countries (including most of Europe, Russia, and parts of China and the United States of America)”. Thus there is an urgency in addressing the twin problems of energy and hunger facing world in this century.

The present review tries to summarize some of the solar technologies available for food processing where solar energy can and is playing a key role, possible strengths and drawbacks in the current practices and put-in some suggestions for moving forward.

Recent studies indicate that while post-consumer food waste accounts for the greatest overall losses among affluent economies, food wastes are much higher at the immediate post-harvest stages in developing countries and wastage of perishable foods is higher across industrialized and developing economies alike. Food losses at various processing steps are quantified and presented in Table 1 along a generic food supply chain (Parfitt et al. 2010).

5) what you would need ?

a) Food waste within food supply chains: Quantification and potential for change to 2050

b)Comparison of various drying methods

c) Structure of food processing industry , where we want to set up

d) Solar radiation map

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