Solar charging-personal versus central etc.

scott at scott at
Thu Jul 31 00:47:20 EDT 2008

On Thu, 31 Jul 2008, Stan. SWAN wrote:

> Scott- thanks for the informative reply.

No problem.

> I've long been an enormous PV
> fan- you couldn't really ask for a better technology-

I concur.

> and have become
> even more so with global energy hikes, & the arrival of  CIS/CIGS PVs.

The uni-solar us-64 thin films we have deployed in the field are doing
great.  I am very encouraged by the recent significant advances in PV.
This for example is great:

> Low voltage,long life & rugged ultrabright white LEDs are now
> threatening to make CFLs obsolete too.

Like these?  LED's are the right choice, I think.

> Your "20 years of electricity"
> comment needs qualifying,

When one purchases solar panels, they are buying an approximate given
number of kikowatt hours at a fixed price, doled out mostly evenly over
the lifetime of the panels.  When I say 20 years I mean they will get 95%
or better of rated output 20 years down the road, and they can plan on
getting those kilowatt hours every day for 20 years.

> as with just ~10 years of storage battery
> life means at least one battery bank replacement in that time = $$$$
> extra.

And a $ number that is difficult to quantify.  How much does 1600Ah @
12VDC cost 10 years from now.  How much does it weigh.  What does it look
like?  I seriously doubt it will be lead acid by then, even though we use
vented lead acid batteries now for the best Ah/$ ratio.

> I favour both centralised AND personal solar power,

In general, I agree, and its great if there is a microfinance option for
those who choose to install personal power production.  In some cases the
central charging station will be these individuals first exposure to solar
power, or computers.

> as it's all too
> easy in many communities to get "off side" with the guys controlling
> resources.You know how these things can go no doubt, especially when
> tribal issues arise. A supply fuse my inconveniently "blow" just when
> you want a top up...


> Additionally XO use surely means colossal inconvenience having to walk
> into the village (with all it's distractions) & wait 3 hours just to
> charge the battery.

I was thinking more they leave for home with a full charge, every time.

> At weekends especially kids could be helping at
> home & have a simpler & slower (maybe loaned) personal solar charger.

thats lots if charge controllers and panels getting less than full

> I'd be very focused on a SLA battery being initially PV charged too,
> as having to leave an XO itself out in the sun may mean theft,
> accidental damage or even ruination by rain/wind. Personal chargers
> are achievable right now & proof of concept tweakable, while larger
> centralised ones require much planning & huge finance.

I'm not arguing against personal chargers if people want them.  Ideally
the central power system encourages people to add their own PV systems at
home.  The shared system ultimately has cost benefits over many smaller
units, which is important when introducing a technology.

> Long range WiFi? I modestly point to my celebrated =>
> which outlines  field work & cost
> effective enhancements. Almost ANYTHING in the LOS path of 2.4GHz
> signals will attenuate them. Are you factoring this in?

Yep.  Thats what the 50' of LMR-400, the 12dB omni, and the 400mw radio
are for.  Repeaters and directionals as necesary, of course.

> To conclude- lets not forget laptop power needs are falling
> drastically! Intel Atom powered "netbook" offerings are increasingly
> thick on the ground,& many run for 6-8 hours per charge.

VIA's new one is pretty good too.  The turion X2 machine we use as the
server for the SolarNet is around 20 watts or so.

> Laptop
> charging energy may decrease at much the same rate as have cell phone
> power needs over the last 15 years. My first calculator in 1973 ran
> for 3 hours per charge, yet most modern offerings (infinatly more
> powerful) run for months/years on a few AA cells.

That would be nice, wouldn't it, for all types of applications.  Solar
powered vehicles, PV and wind storage, mobile devices...


>  Stan
> ---------------------------------------------------------------------------------------------------------------
> Stan. SWAN - Educator/writer/consultant (ICT-Electronics-Sustainable Energy)
> EMAIL: => stan.swan at & (Work) => stan.swan at
> CELL: (64)-021-672-958 HOME: (64)-(4)-562-7494 GST Reg: 36-921-021
> POSTAL: 24 Tuatoru St, Eastbourne-L.H., Wellington 5013, NEW ZEALAND.
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