[RE-wrenches] Two Load Questions

[penobscotsolar at midmaine.com]

Alan,
   Ditto to Bills last post. I always require a load evaluation as it
imposes a certain amount of personal responsibility on the part of the
off grid customer. Two years from now when they call you and tell you
they think there's something wrong with their system you can take that
load form on your site visit and show them that the toaster oven,
window air conditioner, Mr. Coffee and dishwasher were noton the
original load form.
   We use Nextekpower's (formerly TCH Fanworks) DC ceiling fans in our
office and in my home. They are about 18 watts at high speed. A 48-24
volt DC to DC converter is the customers key to big energy savings here
for both the freezer and ceiling fans.
   An argument could be made that with the current price of solar panels
that it is less expensive to simply use more power than to buy a
Sunfrost freezer, but that means needing more room for panels,possibly
another charge controller, more wire, racking. etc as well.

Daryl



> 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
>
>
>
>
>
>
>
> ------------------------------------------------------------------------------
>
>
>   _______________________________________________
>   List sponsored by Home Power magazine
>
>   List Address: RE-wrenches at lists.re-wrenches.org
>
>   Options & settings:
>   http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
>   List-Archive:
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
>   List rules & etiquette:
>   www.re-wrenches.org/etiquette.htm
>
>   Check out participant bios:
>   www.members.re-wrenches.org
>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Options & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive:
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out participant bios:
> www.members.re-wrenches.org
>
>