[RE-wrenches] Two Load Questions

[frenergy]

Alan,

        It seems like a full load analysis is a requirement for off-grid.  If you're simply encouraging a customer to do a load analysis you may as well hand them a tail and hope they find the donkey.  Granted it's easy to slide on it as it represents a great deal of time and most customers don't really "get it". It's the most difficult part of off-grid.

        Fairly large?.....Hmmm, 20-25 CF? I would figure 1.7 KWhr/day.  With a freezer being a constant load and winter having less solar, of course your idea of having the freezer outside would help.  Though you're having to cool more in the summer, there is more solar to do so.

        Will a DC-to-DC converter run a DC freezer?  

        Yes, I think 55 watts is a good number for the "typical" 48", slow-med speed AC ceiling fan.  They certainly have their place but there goes another 1.3 KWhrs/day as people tend to leave them on all the time.

Bill


  ----- Original Message ----- 
  From: Allan Sindelar 
  To: RE-wrenches 
  Sent: Monday, December 10, 2012 8:12 PM
  Subject: [RE-wrenches] Two Load Questions


  Wrenches,
  We still try to encourage prospective off grid customers to do a full load analysis as an initial step in the system design process. To the point:

  1) What is a good watt-hours/day figure to use for a typical, modern, new, carefully chosen, fairly large conventional AC chest freezer, if kept in a heated indoor location? Assume 65 degrees and seldom opened.

  I will encourage that the freezer be located in a shaded, protected outdoor location, in order to greatly reduce winter energy consumption, but I need a good base figure to work with. 

  The proposed system will most likely be 48Vnom, so a Sundanzer or similar DC freezer is out.

  2) Same question for a ceiling fan, for general slow circulation of winter heat. The energystar.gov list gives relative cfm efficiency but not wattages. Is 55W still a good figure to use as a default?


  I have attached a condensed energystar.gov list for the freezers, but wonder what other off grid Wrenches typically use. Also, I'm not sure that Wrenches posts allow attachments, so this may not appear with my message.

  Thank you,
  Allan

  -- 
  Allan Sindelar
  Allan at positiveenergysolar.com
  NABCEP Certified Photovoltaic Installer
  NABCEP Certified Technical Sales Professional
  New Mexico EE98J Journeyman Electrician
  Founder and Chief Technology Officer
  Positive Energy, Inc.
  3209 Richards Lane (note new address)
  Santa Fe, New Mexico 87507
  505 424-1112
  www.positiveenergysolar.com 







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