[RE-wrenches] PV Assist

Jay Peltz jay at asis.com
Fri Aug 16 12:21:37 PDT 2013


Hi William

I feel it's impossible to discuss without more specifics. 

For example if the extreme loads are only every ( just run the genny) so often vs seasonal ( maybe AC coupling makes more sense vs cycling a extremely expensive battery 4 x day),  vs year round vs what is do able etc

I would be curious to know what some of the parameters are, as I'm sure others as well

Jay

Peltz power. 





Sent from my iPhone

On Aug 16, 2013, at 10:53 AM, "William Miller" <william at millersolar.com> wrote:

> Friends:
>  
> We have been receiving a flurry of requests for design of off-grid systems where the loads are enormous, relative to normal off-grid requirements.  It is obvious that the size of PV and battery arrays to power these loads is beyond what is practical.  We have dubbed these systems Generator/battery with PV assist, or PV assist for short.
>  
> These systems will cycle batteries multiple times per day.  It is my understanding that the extra battery cycels will shorten battery life.  Since generator run is expected, we are willing to increase generator run time in order to prolong battery life.
>  
> The parameters I suggest are an aggressive load start and a very high battery start parameter.  This will prevent deep discharge of the battery bank.  I know shallow discharge is not the norm, but I don't believe shallow cycling is a problem as long is it as at the top of the voltage window, i.e. the batteries achieve absorption at least once per day.
>  
> We know a load start ciuld result in an abbreviated run time, curtailing absorption period, but we are assuming there will be a battery votage start at least once per day allowing full absorption.
>  
> Has anyone else considered these issues, and what conclusions did you make
>  
> I am looking forward to a spirited discussion as usual.  I throuroughlyenjoy and beneift from them, even thought the advice is usually conflilcting.  Thanks in advance.
>  
> William Miller
>  
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