[RE-wrenches] PV-direct electric water heating

[conrad geyser]

Hilton and Allan,

 

If the system has an Outback or any other charge controller with a diversion
load setting, the diversion to water heating or ice making can be made to
happen at a fully charged setpoint only.   I have a system set up making ice
which does this nicely - it typically comes on by 11 AM (if the
load/collection ratio hasn't been to high) and actually cycles some later in
the day.  It never takes the 24 V bank below 27.1 V(continues to float) and
leaves the system with topped off batteries and a bunch of ice at the end of
any halfway decent day.  Saves lots of battery load.  Ice lasts for a week.
Works pissah.  

 

Conrad

Cotuit Solar

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allan
Sindelar
Sent: Tuesday, May 14, 2013 11:24 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] PV-direct electric water heating

 

Hilton,
That sounds like a good idea at first glance but a bad one when you dig a
bit deeper. In essence he is sacrificing proper absorption on the batteries
and will pay the price in reduced battery capacity and life. As soon as the
batteries reach the bulk voltage setpoint, which is typically about 85% SOC
and would normally trigger the absorption stage, the charge current is
diverted to the heating element. As soon as the controller switches it over,
the battery voltage drops to the reconnect point - sort of like an old Trace
C30A, which was never a good controller. In the best case, the energy cycles
back and forth between absorption and diversion, or if the controller has
PWM, I suppose a portion would go to each.

Somehow I just can't see how it could be made to work without these inherent
complications.
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
www.positiveenergysolar.com <http://www.positiveenergysolar.com/>  

 

 

On 5/14/2013 6:22 PM, Hilton Dier III wrote:

A friend of mine lives off grid with PV and wind. He added a shunt-type
controller to his battery bank and connected it to a DC heating element in
his hot water tank. Below a set voltage the element is dormant. When the
battery bank hits a high voltage (at the end of a particularly sunny day or
during a windy spell) the element comes on. That way, instead of just a PWM
shutoff and wasted energy, he gets some benefit.

I wouldn't deliberately install PV just for hot water, but in an off grid
situation where the excess would go to waste, it makes sense.

Hilton



-- 
Hilton Dier III
Renewable Energy Design
Partner, Solar Gain LLC
453 East Hill Rd.
Middlesex, VT 05602






_______________________________________________
List sponsored by Home Power magazine
 
List Address: RE-wrenches at lists.re-wrenches.org
 
Change email address & 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/20130515/809ad06a/attachment-0004.html>