Hi William,
In off grid applications, you want to have sufficient RE to keep up with
load demand
and only run the generator when RE cannot keep up. However, having too
much RE is a waste because it will
result in energy not harvested (if regulating), however, diversion
controllers can allow the excess energy to be utilized
(i.e. water heating).
Running the gen up to the bulk level replaces approx 80% of capacity, and
maximizes fuel consumption, allowing RE to get the
batteries charged the last 20%. Automatic gen start capability with
staggered start voltages allow you to target 50% discharge
more accurately, and minimizes user interaction. Try to calculate the
total daily kWhrs and match the demand with RE as
closely as possible.
Hope that helps,
Rgds,
_____________________________________________________________________________________
Eric Bentsen | Schneider Electric | Solar Business | UNITED
STATES | Technical Support Representative
Phone: +(650) 351-8237 ext. 001# |
Email: eric.bent...@schneider-electric.com | Site:
www.schneider-electric.com/solar | Address: 250 South Vasco Rd.,
Livermore, CA 94551
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From:
Jay Peltz <j...@asis.com>
To:
RE-wrenches <re-wrenches@lists.re-wrenches.org>
Date:
08/16/2013 02:01 PM
Subject:
Re: [RE-wrenches] PV Assist
Sent by:
re-wrenches-boun...@lists.re-wrenches.org
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" <will...@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-boun...@lists.re-wrenches.org [
mailto:re-wrenches-boun...@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" <will...@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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