Solar panels

Wed Jan 26 23:15:18 UTC 2011

Hi all,

As always, i can offer no practical fieldwork advice, but...

Our company provides small mobile internet connected computer labs in a suitcase (or, rather, pelican case) to a number of schools in off-grid parts of Uganda.  We fit 11 netbooks with 9 cell batteries and a single loom charger.  Most netbooks are designed to draw 19V, but we have no problem at all fitting the loom directly to a 12V battery and providing DC power.  With this lab-in-a-case, we are able to provide fully internet-connected(3G/gprs/edge/sat (with a SPOT (http://www.findmespot.com/en/index.php?cid=116)) to places that have no power.  The system is able to be used for about 5 hours without a charge, but a whole day oif trickle charging from solar.  Whilst this solution works for getting everything charged at a base station where solar panels can be permanently fixed, there are also a number of really good portable options.  

Keeping in mind that the netbooks will run fine on 12V DC (as will small desktop PCs like the Eee Box which can be fitted with a DC LCD monitor), it is possible to rig a 12V folding solar panel directly to the charger of the netbook.  Suntech make small folding 60W 12V panels but they still weigh about 15kg - not great for lugging around.  ALternatively, and much better if weight is a concern, is the 20W solar-charging laptop bag (http://www.multipoweredproducts.com.au/products/Voltaic-Generator-%252d-Solar-Laptop-Charger-Bag.html).  This bag has batteries which will bring your netbook up to a full charge in a day, provided you get about 5 hours of sunlight.  It's probably not going to be enough to charge a full-sized laptop though.  It also has outputs for you to connect 5V USB devices and car-plug options.   This means you can plug in a caravan/car/camping style lamp into the case at night and give yourself plenty of power.  

Cheers,
Xavier

On 27/01/2011, at 4:06 AM, Jeremy Hammond wrote:

> Hi All,
> 
> I am pretty much in agreement with Tom and have being successfully doing a
> similar setup for the past 3 years in Vanuatu. I also buy lead acid
> battery in-situ but am considering getting a solar-specific one this year
> if I can find it in Port Vila. I'll just add 3 points.
> 
> 1. Buy a universal battery charger. They are great and means you can
> really cut down on the amount of chargers you have to take (I.e.
> phone/Camera/AA/video/AAA/USB are all doable with mine). Here is one
> http://www.solartechnology.co.uk/shop/camcaddy-cc1005.htm but there are
> different brands/models. You can buy them at most camera stores. I just
> have two of these for all my charging needs (plus my laptop charger of
> course).
> 
> 2. Consider getting solid panels. If you have easy enough access to your
> fieldsite and have a long term relationship with them then it is an easy
> process to take it there and set it up on a roof etc. I usually take a
> solid 50W panel with me each time I go so that now I have around 150W
> which should be above 200W this coming year. They are super strong, and
> great long term value. Plus now I leave them there setup with LEDs on the
> battery so that people there can use the light at night, even when I'm not
> there.
> 
> 3. While tom suggested the "workman's" light and they are good, if you are
> electrically handy then making your own LED setup is really inexpensive
> and easy. There are some great yellow ones that are good for
> reading/working by as well. On that note as Tom said, test your setup but
> also understand how it works. Get a friend who knows something about
> electronics to explain it to you and when things go wrong, you will be in
> a much better position to fix it.
> 
> Jeremy
> 
> 
> -------------------------------
> Jeremy Hammond
> Syntax, Typology and Information Structure Group
> Max Planck Institute for Psycholinguistics
> P: +31-24-3521171
> E: Jeremy.Hammond at mpi.nl
> W: http://www.mpi.nl/people/hammond-jeremy
> 
> 
> 
> 
> 
> 
> 
> On 26/01/11 7:27 AM, "Tom Honeyman" <t.honeyman at gmail.com> wrote:
> 
>> Hi Jeff,
>> 
>> Despite the negative "reality check" at the end of the paper Pat
>> mentions (thanks Pat!, also the paper supersedes the blog posts, but
>> thanks Peter!), I am now quite happily using solar power for fieldwork
>> in Papua New Guinea.
>> 
>> My current setup (well actually I've dropped/genericised/forgotten a
>> few items to simplify!):
>> 
>> 1 low power netbook (they're all almost exactly the same)
>> 2x DC adapter for netbook, but also adapters to charge USB devices,
>> mobile phones etc also very good
>> 2x Li-Ion battery pack chargers (for camera, video camera etc... can
>> be very handy)
>> 1x DC-DC adapter with multiple plugs (very handy for powering all
>> sorts of things if you know what you're doing)
>> DC plug adaptors (so I can plug in many things at once)
>> 50W foldable solar panel
>> charge regulator with load cut-off
>> 10x AA NiMH AA batteries
>> 8x AA NiMH AAA batteries
>> 1x AA/AAA battery charger (charges 10 batteries at once, each
>> individually)
>> 1x AA/AAA battery charger (charges 4 batteries in pairs - this can be
>> a pain if you have a device that uses 3 batteries!)
>> Head torch and mag-lite - make sure they work with rechargeables!
>> Often they don't work well with them.
>> 12v/DC workman's light, fluro or LED based, low power consumption
>> (these are really good for a lot of light!)
>> All the regular equipment otherwise (recorders, speakers, mike,
>> cameras, etc), but make sure they work well with rechargeables).
>> 
>> And then I also pack the following for fixing stuff (but only if you
>> know what you're doing):
>> 
>> fuses, glass and blade with several spares for each device that has one
>> pack of alligator clip wires
>> Gaffer tape (often available in country)
>> digital multi-meter
>> pocket knife
>> jeweller's screw driver set
>> super glue (often available in country)
>> 
>> I tend to buy a (preferably deep cycle) lead acid battery in country.
>> 
>> This let me work for a few hours a day on the laptop, use torches/
>> flashlights at night, and put on a "movie night" once a week. Every
>> now and then an activity might come along (like a big recording
>> session, or very rainy weather, or on one occasion my roof blowing
>> off!), which would drain the battery too much. Then I'd have a day or
>> two not using the laptop (far and away the most power hungry).
>> 
>> 4 things I'd recommend:
>> 
>> (a) check _everything_ beforehand. There are many "single points of
>> failure" in a solar setup. That's why its good to have backups, or
>> multiple ways of achieving the same thing.
>> 
>> (b) get a charge regulator with a load cut off. This magical box will:
>> - ensure that the battery is charged properly, dropping the power as
>> it approaches a full charge and cutting the power entirely when the
>> battery is full
>> - stop power flowing back into the panel at night (this is often
>> redundant depending on the panel)
>> - cut the power to your devices when the battery is too low
>> Basically this will let you safely run your equipment, but it'll
>> ensure that the battery doesn't fail because you've drained it too
>> much... this is something that is _very_ easy to do. If you know what
>> you're doing then you can drop this, but you'll spend more time
>> managing your power setup and less doing work.
>> 
>> (c) try to eliminate using AC power. This is costly. I guarantee that
>> you will not have enough power to do all the things that you'd like to
>> do. So this means do not use "wall adapter" plug equipment, use "car
>> adapters" for all of your equipment. The DC adapters for charging a
>> laptop can often power other equipment. The DC-DC adapter is extremely
>> useful for powering low power equipment. Having these flexible, multi-
>> plug adaptors can be very useful for unexpected scenarios like
>> powering a cassette recorder you've borrowed because your audio
>> equipment fell in the river. Or powering your recorder directly
>> because your batteries or battery chargers have failed for some reason.
>> 
>> (d) check that the AA/AAA powered equipment works, and works well with
>> rechargeable batteries. Rechargeables operate at a lower voltage than
>> Alkaline batteries. A lot of equipment is designed for use with
>> Alkaline batteries, and even though initially they may work fine,
>> later in the field you may discover that they have a (seemingly) short
>> life. Digital cameras often are designed to work with rechargeables
>> these days (sometimes they last longer with rechargeables), but
>> torches/flashlights for instance are often not.
>> 
>> Hope this helps,
>> 
>> Tom
>> 
>> On 26/01/2011, at 3:48 PM, Patrick Hall wrote:
>> 
>>> Hi,
>>> 
>>> Honeyman also coauthored a paper with Laura Robinson on this topic in
>>> LD&C which might be of use:
>>> 
>>> Honeyman, Tom & Laura C. Robinson. 2007. Solar power for the digital
>>> fieldworker. Language Documentation & Conservation 1(1): 17-27.
>>> 
>>> It's available online:
>>> 
>>> http://hdl.handle.net/10125/1722
>>> 
>>> cheers,
>>> Pat
>> 
> 

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