I have always wondered about that statistic, and figured it had to be
something wrong with the survey - that pretty much confirms it.
It makes sense, but to add another skew to it: From Jan 2008 until now, we
have sold around $1.6 million in batteries. Of those, not a single one was
purchased from an RE distributor. Ever single one was purchased from 3
different battery (not RE) distributors. Why? - Well because most are local,
thus low or no shipping, and because they are cheaper. We are lucky in that
4 of the 5 major battery brands we sell all have local distributor
warehouses in our area and shipping to us is usually free on all but very
small quantities. We have been buying from the same distributors locally for
close to 20 years, so I am sure that none of those ever showed up in the
statistics you refer to.
..................................................................................................
Northern Arizona Wind & Sun - Electricity From The Sun Since 1979
Solar Discussion Forum: http://www.wind-sun.com/ForumVB/
..................................................................................................
----- Original Message -----
From: "Allan Sindelar" <[email protected]>
To: "'RE-wrenches'" <[email protected]>
Sent: Friday, December 04, 2009 10:42 PM
Subject: Re: [RE-wrenches] Sandia study - WAS Strings and series ofbatteries
with reverse return linkup
There's an interesting "back story" to the 1996 battery study you cite,
Joel. It illustrates the pitfalls that can occur when you don't ask the
right questions of the right people.
I reviewed that study a few years later, and was surprised to read that
Mr.
Hund's survey suggested that 64% of batteries used in PV systems were
VRLA.
From that study:
"Table 1 presents a preview from the battery survey listing total flooded
and VRLA
battery sales from the 21 PV system integrators for 1995. The data
indicates
that
64% of the PV batteries sold are VRLA with a dollar value of $3.4
million."
My own observation suggested that this number was way off: I knew of
virtually no one who used sealed batteries for typical residential
off-grid
homes.
I had the opportunity to question Mr. Hund about this at some technical
forum. When he explained that this number came from a survey of RE
wholesalers' battery sales, it all made sense. Sealed batteries can be
shipped; flooded batteries are generally delivered by trucks operated by
battery wholesalers. If you only ask RE distributors what they sell, the
answer will reflect this reality. Mr. Hund asked the wrong people, and
drew
an erroneous conclusion from the answers he received.
A year or two later I was talking with someone in tech support at
Morningstar; I think it was about how easy it was to default the charge
voltage setting on an early ProStar controller to the VRLA setting. If you
ever disconnected battery DC to the controller, it repowered up at the
lower
VRLA voltage, and must be reset each time to the higher settings needed
for
flooded batteries. The technician defended the structure by referring to a
Sandia study that found that nearly 2/3 of batteries in PV systems were
VRLA. When I explained the fundamental flaw in the study that led to that
conclusion, the Morningstar technician was pretty surprised. A year or two
later, the second-generation ProStar was released, that is still in
current
production, with a rotary switch setting that is set once and returns to
the
same setting - gel, VRLA, or flooded - when powered up.
I have long remembered this as a good lesson in how poorly crafted
research
can result in unintended consequences.
Allan Sindelar
[email protected]
NABCEP Certified Photovoltaic Installer
EE98J Journeyman Electrician
Positive Energy, Inc.
3201 Calle Marie
Santa Fe, New Mexico 87507
505 424-1112
www.PositiveEnergySolar.com
-----Original Message-----
Here's some good info:
http://photovoltaics.sandia.gov/docs/battery1.htm
or
http://www.osti.gov/bridge/purl.cover.jsp;jsessionid=CC366D87BBE1C7C3BCBEEAF
D87A3D0D7?purl=/402426-htwdT8/webviewable/
or
http://www.osti.gov/bridge/purl.cover.jsp?purl=/125071-E7W1qQ/webviewable/
Joel Davidson
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