Cutting all the wires: Solar power in the field
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by Matt Blair
Posted: 8/25/2004
For the past few years, HumaniNet has been working to
find the most inexpensive, easy-to-use technology for humanitarian
teams who need to communicate from anywhere, to anywhere.
Satellite modems, like the RBGAN, have become a
proven solution because they can be used in remote locations,
independent of any local telecommunications infrastructure.
These remote locations are also frequently "off-grid",
away from wired power grids, or energy infrastructure of
any kind. Laptops, PDAs, cell and satellite phones all
have batteries, and even the RBGAN can operate on its internal
battery for short periods of time. But in a truly off-grid
situation, how can you recharge? Once you've cut the communication
wires, how can you cut the electrical wiring, and attain
true independence of movement?
Using a generator or continuously running a vehicle engine
is impractical because it provides far more power than
most electronic communication devices need. At the same
time, recharging many electronic devices can take hours,
so charging them from a vehicle battery is not always advisable.
Most car/truck batteries are designed to maintain a relatively
high charge, and deep, frequent discharges will dramatically
shorten the life of the battery, and/or diminish its performance.
For these reasons, we have had our eye on solar power,
and believe it is an interesting option worth considering
in many remote locations.
I recently attended a seminar and several exhibits at
the American Solar Energy
Society's
SOLAR 2004 convention in Portland, Oregon. Most of the
solar equipment on display was designed for fixed, long-term
installation, but in talking with vendors, and through
subsequent research, HumaniNet has discovered several systems
which may be of use in the field. The following examples
could be quickly deployed with minimal technical hassle
and cost.
The Portable
Energy System by Sunwize is designed specifically for laptops, satellite
phones, cell phones, GPS units, and 'gadgets' of similar
size and power requirements. It is slightly larger (10.5
by 15.5 inches, or 26.7 by 39.5 cm) than the average laptop
computer, but less than 2 cm thick and weighs only 2.5
lbs (about 1.1 kg). Despite its low weight, this is a solid,
well-reinforced panel. It provides power output up to 8.5
watts with a variety of DC outputs from 3-12 volts. There
is also an add-on panel available, called the System Doubler,
that can increase the power output.
If you need something less rigid, literally, take a look
at the PowerFilm line by Iowa Thin Film Technologies. These flexible solar
panels can actually be rolled up for storage and transport,
and there are a variety of adapters available to charge
batteries or provide a 'cigarette lighter' connection to
your electronic devices. The panels are about a foot wide
(about 30.5 cm) and vary in length from 21 to 73 inches
(about 53 to 186 cm). The weight of the longest panel is
1.9 pounds (0.88 kg). When rolled, even the longest panel
is about the size of a compact sleeping bag.
Iowa Thin Film's informative website provides details
about using these panels to charge
batteries and to directly
power electronic devices.
Each page provides a chart that translates the technical
specifications into real-world charge times and "application
run times" for several scenarios.
The same company has also integrated this flexible panel
technology into a series of 'army
tents' that provide shelter
and power at the same time.
The solar-equipped tents can generate between 200 watts
and 1 kilowatt of power, which would be stored in a bank
of batteries, and could then provide power for a variety
of applications, including mobile communications.
If your ambitions for solar go beyond charging batteries
or powering a single device, putting a system together
can require detailed research into inverters, charge controllers,
line conditioners, deep-cycle batteries, etc. The EN-R-Pak is an all-in-one 'compact power center' that eliminates
a lot of that complexity. It includes a solar panel and
a single battery unit (18 by 14.5 by 12 inches, or about
46 by 37 by 30 cm) that integrates a battery and everything
else you need to provide up to 200w of 110v AC power or
15-amps of 12 volt DC in one single unit. When fully-charged,
it can provide 40 watts of AC power for twenty hours of
operation. The total weight of the panel and the battery
unit is 115 lbs, or just over 52 kg.
During the solar conference, I also attended the "Basics
of Using Solar Energy in a Disaster" seminar. A few
key points of the presentation were:
- Negotiating mutual aid agreements, "push-button" contracts,
and MOUs with other organizations in advance, before
deploying to the disaster area, is vital. This can include
sharing of equipment, staff, logistics support, communications,
and other resources.
- Training, drills, exercises, and
prior planning are essential to an effective response.
Don't plan to figure out how to use solar in the field.
- Carefully
consider the lifecycle cost of solar versus gas/diesel
generators during a disaster. While the initial cost
of solar may be higher, what effect will the disaster
have on the price of fuel needed to run the generators?
We hope this article will encourage more discussion of
mobile power solutions among humanitarian teams. If you
have any experiences with solar in the field, or would
like to partner to explore solar projects, please let us
know by sending email to info@humaninet.org.
For additional information on portable power, see the
Power
Options section of Vern Gillespie's Mobility Portal.
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