Solar panels

[Jennifer Teeter]

Dear Jeff

I consulted with the director of Greenheart Project, and he gave me this
answer. I hope that this information is useful in some way. Good luck!
Jennifer


> I've managed portable solar systems 'in the field' before, yes, but never
> as small as for a single laptop and light bulb.  Here's a formula:  1)
> calculate your weekly power requirements [laptop consumption in Watts times
> # of hours use per week, plus light bulb in Watts times # hours use per
> week, plus power demand of inverter to change battery DC into laptop AC =
> total power requirement per week].  Then numbers of hours and quality of sun
> exposure per week will indicate what size collector you will need to meet
> that demand.   Double that array size, and get a battery bank that can store
> that doubled demand.   Consider also 'field' conditions and the cost and
> weight (esp, if portable) and time required to protect all gear from  the
> elements.  Consider hand crank generation alone for lighter loads and/or
> many hands.  Consider also notebook/ziplock/greasepencil & penlight system
> for ease of use in adverse, dark, wet, and extreme 'fields'
>


On Wed, Jan 26, 2011 at 3:27 PM, 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
>>
>
>


-- 
Greenheart Project
www.greenheartproject.org
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