[RE-wrenches] PV Assist

[Jay Peltz]

Hi William 

Thx helps a lot. 
I can only say how I do it. 
I'll give the client some options, including the change of appliances and usually the price difference makes the sale one way or the other. 

Funny reminds me of the old days, only with much smaller loads/$. 

Good luck

Jay



Sent from my iPhone

On Aug 16, 2013, at 12:49 PM, "William Miller" <william at millersolar.com> wrote:

> Jay:
>  
> There are four systems in question.  In three the loads are year round and one is summer only AC loads.  The year round loaded systems have loads day and night.
>  
> One is a highway maintenence station with at least 4 residences.
> One is a family compound with two homes with electric ranges,  water heaters, AC units (I know its stupid, lord knows I've tried to convince them to change appliances.)
> One is an animal rescue operation with heater loads.
> One is a large home with 5 very small, very new, very sophisticated and frugal AC units
>  
> I know it is silly to move these loads off-grid, but people do it and they will hire someone to work on the systems.  It may as well be me, doing the best I can to use the resources as wisely as possible.
>  
> William
>  
> PS:  It always happens like this:  I get a call from a client with problems.  Well, of course their expensive battery bank died and it died because of wasteful appliances.  The prescription is a new, expensive battery bank and, at the same time, new, expensive, efficient appliances.  They complain can't afford both and they have to have the batteries, so that is what they get.  Repeat every two years.  Sad....
>  
> Wm
>  
>  
> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jay Peltz
> Sent: Friday, August 16, 2013 12:22 PM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] PV Assist
> 
> 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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