College of the Redwoods farm

Distilled water should be used for the closed loop side of a solar water heating system. The collector requires.5 to 1 gallon of water flow per minute. If pump velocity is above 5ft per second for hot water or above 10ft per second can cause turbulence which creates pinholes in the line possibly creating a leak. Water soluble flux needs to be used in the closed loop because there is little chance to flush the line once installed. Silver solder performs better at higher temperatures and doesn't contain heavy metals like antimonic. When designing a system the ratio between the collector and the tank needs to be addressed.


Depending on your climate conditions more or less tank space is required.

  • For Humboldt counties climate a.75 square foot to 1 gallon of tank space
  • Hotter climates need.5 square foot to 1 gallon of tank space
  • Colder climates need 1 square foot to 1 gallon of tank space


The drain back tank serves as an expansion tank and should not be completely filled to allow for expansion. A drain back system requires ¾ inch pipe with a 100watt pump. A Glycol system requires ½ inch pipe and a 40-60 watt pump. Ben states that a double pump system is not worth the extra electricity and maintenance to offset the benefit.

System overview
  • 2 4' x 6.5' collectors
  • 80 gallon storage tank
  • Drain back system
Energy produced
  • 64,000 BTUs per day
Cost
  • $9,000
Efficiency
  • 80%
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Authors Michael Hultin
License CC-BY-SA-3.0
Language English (en)
Related 0 subpages, 0 pages link here
Aliases Solar thermal at college of the Redwoods farm
Impact 204 page views
Created December 18, 2009 by Michael Hultin
Modified January 30, 2023 by Irene Delgado
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