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They also explain the different ways they washed the vegetables that they grew at the farm.  
They also explain the different ways they washed the vegetables that they grew at the farm.  
*For root crops: They soaked them in buckets or sinks of water, then they held them by the tops and hosed them off with a high pressure spigot. The roots were then bunched and boxed.  
*For root crops: They soaked them in buckets or sinks of water, then they held them by the tops and hosed them off with a high pressure spigot. The roots were then bunched and boxed.  
*For leaf crops:They dunked entire waxed boxes of lettuce, chard, or spinach in cool water in a large sink. Then they let the boxes drain thoroughly and covered exposed areas with freezer or packing paper to prevent desiccation. This method does tend to deteriorate boxes if they are re-used often; to counteract this problem they began using re-usable plastic field totes instead of cardboard boxes. After processing, the produce was either immediately brought to campus for the CSA pick-up or stored temporarily in a cooler."<ref>http://www.specialtycrops.colostate.edu/CSU_CSA/SCP_csu_csa_growers.htm#washing</ref>
*For leaf crops:They dunked entire waxed boxes of lettuce, chard, or spinach in cool water in a large sink. Then they let the boxes drain thoroughly and covered exposed areas with freezer or packing paper to prevent desiccation. This method does tend to deteriorate boxes if they are re-used often; to counteract this problem they began using re-usable plastic field totes instead of cardboard boxes. After processing, the produce was either immediately brought to campus for the CSA pick-up or stored temporarily in a cooler.<ref>Colorado State University (2006). "CSU CSA (Community Supported Agriculture)Information for Growers." <http://www.specialtycrops.colostate.edu/CSU_CSA/SCP_csu_csa_growers.htm#top> (Feb. 10 2010)</ref>


==References==
==References==

Revision as of 02:29, 14 February 2010

Template:305inprogress

Background

The Arcata Educational Farm is a CSA (Community-Supported Agriculture establishment) that provides local organic produce for members/shareholders and hands-on agricultural education for local students and residents. Adjacent and connected to the farm is the upcoming Bayside Community Garden, a place for residents to grow their own produce and learn how to farm organically and sustainably.

As part of our ENGR305 class, our team was asked to fix the solar water heater system there (the previous one developed a leak, presumably from the winter freeze and subsequent cracking) . We would like to improve the new system by winterproofing it and also by integrating its output into an efficient vegetable-washing system that could potentially double as a rudimentary shower for workers.

Opportunity Definition

Who
ENGR305 Spring 2010 students Melissa Pawson, Kristy Lindquist and Roger Tuan are assisting Phil Lucas, our client at the Arcata Educational Farm.
What
Retrofit, repair, and improve the solar hot water system at the farm.
  • Water Heater / Storage Tank - We know it's a Reliance 606 series heater, but we still need the exact model number.
  • Solar Collector:
    • Colt, Inc. Model C-141C solar collector. An UNVERIFIED guess is that it's actually a closed-loop system meant to be filled with glycol and not water, but this needs to be confirmed.
  • Piping: The piping from the previous system is still mostly intact and can hopefully be reused after a check for cracks and leaks.
  • Vegetable washer / shower: We'll need to track down a flexible hose and washer/shower head and perhaps improvise a shower stall. We'll also need to research various methods of effective vegetable washing and design the station accordingly.
Why
We were asked to fix the solar hot water system so the farm will once again have access to hot water. This could be useful for future community events held throughout the year!
When
Our project will take one semester, approximately 15 weeks in duration and ending around May 15th.
Where
The Arcata Educational Farm is located at 930 Old Arcata Road in the Sunnybrae neighborhood of Arcata.

See Also

Literature Review

Solar Hot Water Heater

  • A Flat Plate Collector

Flat plate collectors are the most commonly used collector in the world for domestic solar water heating. They are durable and effective and have an operating rang of zero degree Fahrenheit - 180 degrees Fahrenheit.[1]

  • Installing, Plumbing and Wiring Your Collectors

Solar installation is carpentry, plumbing and electrical work all mixed together.

Piping and Pipe Insulation

Copper tubing is the best kind of pop to use for the solar loop because it can withstand a temperature range from 300 degrees Fahrenheit to - 30 Fahrenheit, it is durable and easy to install. [2]

Testing the System

To check for leaks you can use air pressure or water pressure. [3]

  • Types of Flat Plate Collector Systems:
1. A Thermosiphon System

The system is the simplest of all open loop, flat plate systems. There is no need for pumps or electrical controls. Water heated in the collector becomes less dense and rises into the storage tank, while cooler, denser water falls from the tank and enters the collector, all in a continuous cycle that lasts as long as the sun delivers enough energy. With no electrical controls and no antifreeze fluid. a collector in this system has no build-in freeze protection except for the protection of installing it behind glazing within the thermal envelope of the building where it isn't supposed to freeze. [4]

2. The Drain Back System

This unpressurized closed loop system is designed to automatically drain itself whenever the pump is off without using electrically operated valves or other special components. When the differential thermostat senses that solar heat is available, the pump is switched on to draw "collector" water from an unpressurized tank and run it through the collector. When the pump stops, gravity takes over; water in the collector and the connection pipes simply drains back into the tank, A heat exchanger carrying pressurized domestic water is immersed in the upper party of the tank. When hot water is used, the water is preheated in the exchanger before it flows into the back-p water heater and out to points of use.[5]

3. Recirculation and Drain-Down Systems

This system is made up of two flat plate systems that are protected with electrical and mechanical controls. The recirculation system works by taking a little hot water from the solar storage and pumping it through the collector array. It's good for climates that only occasionally experience just-below-freezing temperatures. The drain -down system, not to be confused with drain-back, uses a special valve that closes off the pressurized lines to the collectors and allows them to drain away that one or two gallons they and the pipelines carry. Both are pressurized open loop systems that circulate potable water between the collectors and the storage tank. [6]

4. A Fluid Freeze Protection System

This systems is closely related to the flat plate collector loop, except that antifreeze fluid replaces the water. It is a closed loop system and a heat exchanger is required. The right antifreeze fluid is important because some are poisonous, some eat away at the copper piping and all fluids don't transfer heat as well as water.[7]

  • Example: The Bread Box Design: A Passive Solar Water Heater

This system is made up of a two-tank batch-type system that provides approximately 60 percent of the annual hot water needs of a family of three at a total cost of $400. It works by sending pressurized domestic water through the tanks. The "collector" tanks preheat the water before entering the back-up water heater. [8]

Vegetable Washing Station

  • Different Ways to Wash Vegetables

Vegetables and fruits are often covered with pesticides, herbicides, fungicides or wax. To maintain freshness it is best to wash produce before use and not before storage, which can make it spoil faster.

Firm-skinned Produce

To wash firm-skimmed produce you should use a little warm water and a scrub brush if needed. It is also important to rinse produce well to remove any residual dirt. [9]

Soft-skinned Produce

To wash soft-skinned produce soak vegetables or fruit for a minutes. The temperature should be between room temperature or a couple degrees cooler. [10]

Common Disinfectants

This study was undertaken to determine the efficacy of three commonly used disinfectants in packing-houses of Culiacan, Mexico:

  • sodium hypochlorite [NaOCl]
  • trichlor-s-triazinetrione [TST]
  • thrichlormelamine [TCM])

Water samples were taken after 2 minutes of contact with chlorine-based products and tested for the particular microorganisms. TST and NaOCl were found to effectively reduce for bacterial pathogens and viral indicators. The highest inactivation rate was observed when the turbidity was low and the disinfectant was applied at 300 mg. TCM did not show effective results when compared with the TST and NaOCl. These findings suggest that turbidity created by the organic and inorganic material present in the water tanks carried by the fresh produce may affect the efficacy of the chlorine-based products. [11]

  • Example of a Washing and Processing Station

Colorado State University has assembled an Information Guide for Community Supported Agriculture Growers. Along with the plethora of useful information they include how they built an produce washing and processing station for produce. They used a hoop house structure with shade cloth over it to provide a cooler environment for cleaning, boxing, and bunching. The station was made using recycled materials. The sinks were bought at the local Habitat for Humanity thrift store and a table was constructed for them using an old metal table frame and scrap wood from a local door manufacturing company. Wooden floors were also made using this same scrap wood and lashed together with twine or nailed into a base to provide a non-muddy area to walk on. Municipal water was used to wash the vegetables with a hose.

They also explain the different ways they washed the vegetables that they grew at the farm.

  • For root crops: They soaked them in buckets or sinks of water, then they held them by the tops and hosed them off with a high pressure spigot. The roots were then bunched and boxed.
  • For leaf crops:They dunked entire waxed boxes of lettuce, chard, or spinach in cool water in a large sink. Then they let the boxes drain thoroughly and covered exposed areas with freezer or packing paper to prevent desiccation. This method does tend to deteriorate boxes if they are re-used often; to counteract this problem they began using re-usable plastic field totes instead of cardboard boxes. After processing, the produce was either immediately brought to campus for the CSA pick-up or stored temporarily in a cooler.[12]

References

  1. Carter, Joe (1981). "Solarizing Your Present Home." Practical Solar Heating Systems You Can Build,Rodale Press, Inc.,USA, Chapter 2 Domestic Water Heating.
  2. Ramlow, Bob (2006. "Solar Water Heating." A Comprehensive Guide to Solar Water and Space Heating Systems, New Society Publishers, Gabriola Island, Canada, Chapter 5 Solar Water Heating Systems.
  3. Ibid
  4. Carter, Joe (1981). "Solarizing Your Present Home." Practical Solar Heating Systems You Can Build,Rodale Press, Inc.,USA, Chapter 2 Domestic Water Heating.
  5. Ibid
  6. Ibid
  7. Ibid
  8. Ibid
  9. Hunter, Mason (2005. "Green Clean." The Environmentally Sound Guide to Cleaning Your Home, Melcher Media, New York, NY, Chapter 3 The Kitchen, 44-65.
  10. Hunter, Mason (2005. "Green Clean." The Environmentally Sound Guide to Cleaning Your Home, Melcher Media, New York, NY, Chapter 3 The Kitchen, 44-65.
  11. Chaidez, Cristobal, Moreno, Maria, Rubio, Werner, Angulo, Miguel, Valdez, Benigno (2003). "Comparison of the disinfection efficacy of chlorine-based products for inactivation of viral indicators and pathogenic bacteria in produce wash water." International Journal of Environmental Health Research, Vol. 13, Issue 3, p295-303.
  12. Colorado State University (2006). "CSU CSA (Community Supported Agriculture)Information for Growers." <http://www.specialtycrops.colostate.edu/CSU_CSA/SCP_csu_csa_growers.htm#top> (Feb. 10 2010)

Books of Reference

  • Keisling, Bill. (1983). “The homeowner’s handbook of solar water heating systems.” Rodale Press, Emmaus, Pa.
  • McConnell, Charles. (1977). “Plumbers and Pipe Fitters Library.” Water Supply, Drainage, Calculations. Howard W. Sams & Co., Inc. Indianapolis, Indiana.
  • Kut, David. Hare, Gerard. (1979). “Applied Solar Energy.” A guide to the design, installation and maintenance of heating and hot water services. The Architectural Press. London, England.
  • Ramlow, Bob (2006. "Solar Water Heating." A Comprehensive Guide to Solar Water and Space Heating Systems, New Society Publishers, Gabriola Island, Canada, Chapter 5 Solar Water Heating Systems.
  • Carter, Joe (1981). "Solarizing Your Present Home." Practical Solar Heating Systems You Can Build,Rodale Press, Inc.,USA, Chapter 2 Domestic Water Heating.
  • Hunter, Mason (2005. "Green Clean." The Environmentally Sound Guide to Cleaning Your Home, Melcher Media, New York, NY, Chapter 3 The Kitchen, 44-65.
  • Bainbridge, D. A. The integral passive solar water heater book. Passive Solar Institute, PO Box 722.
    • Basic design and operation, different types, solar availability across the USA
  • Chiras, Daniel D. 2006. The homeowner's guide to renewable energy. New Society Publishers, April 3. Gunerhan, Huseyin, and Arif Hepbasli. 2007.
    • Methods to deal with freezing
  • Schroeder, Daniel V. 2000. An Introduction to Thermal Physics. San Francisco, CA: Addison Wesley.
    • To better understand math and physics involved in our project

Peer-reviewed Articles

  • Chaidez, Cristobal, Moreno, Maria, Rubio, Werner, Angulo, Miguel, Valdez, Benigno (2003). "Comparison of the disinfection efficacy of chlorine-based products for inactivation of viral indicators and pathogenic bacteria in produce wash water." International Journal of Environmental Health Research, Vol. 13, Issue 3, p295-303.
  • Annous, B. A., G. M. Sapers, A. M. Mattrazzo, and D. C. R. Riordan. 2001. Efficacy of washing with a commercial flatbed brush washer, using conventional and experimental washing agents, in reducing populations of Escherichia coli on artificially inoculated apples. Journal of Food Protection&# 174; 64, no. 2: 159-163.
    • For vegetable washing information -- is a commercial agent necessary vs plain water?

Websites

External Links

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