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

[toddcory at finestplanet.com]

this brings up a probably off topic subject regarding efficiency. i have always considered efficiency and conservation to be job one... especially on off grid systems... but with modules so inexpensive... does this still make sense? for example, i have an off grid customer who i suggested get a lorentz pump for his well. yes, the well produces around the same gpm as it used to, now only using about 15% of the power... but the cost to accomplish that was absurd, and that money could have been invested in more modules, which would also mean less winter generator run time... but manufacturing modules is not light in the resource consumption department either.
 
so my question is: do you other wrenches just look at the bottom line, short term costs for more efficient appliances compared to more modules to power the old inefficient gear... or do you take the added step to include embedded energy... and if so can you share the calculation process?
 
thanks,
 
todd
 
 
 
 
On Tuesday, December 11, 2012 10:55am, "Larry Crutcher, Starlight Solar Power Systems" <larry at starlightsolar.com> said:


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 [http://energystar.gov] 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 [http://energystar.gov] 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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