[RE-wrenches] DC, or not DC, Dat is Da question (Two Load Questions)

[Chris Daum]

The Sundanzers can be converted for AC use at the factory for a nominal
cost, and they claim it affects efficiency very little.
Chris Daum
Oasis Montana Inc.
406-777-4309
406-777-0830 fax
www.oasismontana.com 
   


  _____  

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Larry
Crutcher,Starlight Solar Power Systems
Sent: Tuesday, December 11, 2012 11:56 AM
To: RE-wrenches
Subject: [RE-wrenches] DC, or not DC, Dat is Da question (Two Load
Questions)


Why would one specify DC voltage appliances or lighting for off grid systems
today when we have sub-buck-a-Watt PV solar power?  If you have space, you
can make the added power that conventional AC appliances draw for very low
cost. It could even be argued that the cost for DC items, wiring,
distribution gear and labor will cost much more than simply adding more PV
solar and staying all AC. 

I don't like wasting resources and I understand old school thinking when PV
modules were very expensive, but with high efficiency AC appliances and low
cost inverters and PV modules, does it still make any sense? Shine some
light on my thinking. 

Larry Crutcher
Starlight Solar Power Systems





On Dec 10, 2012, at 9:12 PM, Allan Sindelar wrote:

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
 <mailto:Allan at positiveenergysolar.com> 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
 <http://www.positiveenergysolar.com/> www.positiveenergysolar.com 






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