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

[Jason Lerner]

Hello Larry,

I still install DC fridge/freezers in off grid systems for efficiency,  but also so that when the owners leave for the weekend/week/month they can turn off the inverter and all the associated phantom AC loads,  but the DC freezer is still on. When they come back, the meat in the freezer is still frozen.

Recently for a new off grid cabin we compared a Subzero 23 Cu. ft. fridge/freezer to a Sundanzer chest freezer and Sunfrost all fridge which is 51 cu ft.combined.  Using nameplate yearly KWH's, retail price tags and putting the freezer in an outbuilding we found the sunfrost/sundanzer has 2.22 times more cu ft at 60% of the subzero's energy consumption....at 66% of the cost of the Subzero.  

Adding additional PV/wiring/CC/racking to run the Subzero was going to cost an additional $2500.  The contractor building the cabin brought up the point that the Sunfrost does stick out farther into the kitchen then an "average" fridge and there was going to be a cost associated with custom cabinets to match that depth,  possibly the same amount as adding extra PV's...

Best,

Jason Lerner
Waldron Power and Light Co.



On Dec 11, 2012, at 10:55 AM, Larry Crutcher, Starlight Solar Power Systems wrote:

> 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
> 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
> 
> 
> 
> <Freezers Product List.xlsx>_______________________________________________
> 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
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20121211/e084c1a6/attachment-0003.html>