Solar panels

[Tom Honeyman]

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