[RE-wrenches] Sandia study

[Joel Davidson]

Allan, thank you for this important information.

Tom Hund, Bob Hammond, and others at the DOE brought scientific discipline 
to our work, but they lacked the field experience that Wrenches have. John 
Wiles, Ward Bower, Bill Brooks and others are better grounded in the 
real-world and make valuable contributions to our work. This Wrenches group 
is the closest thing the RE industry has to real-world peer review which 
makes this list a "must read" for anyone actually doing RE.

Michael, is there a way to know how many non-members visit RE-wrenches?

Joel Davidson

----- Original Message ----- 
From: "Allan Sindelar" <allan at positiveenergysolar.com>
To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
Sent: Friday, December 04, 2009 9:42 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
> Allan at positiveenergysolar.com
> 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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