Specifications
AT 50
will even send a notification to your PC via
USB), and ought to keep your equipment
running long enough to save your work,
disconnect the power board from the inverter
and connect it to mains power. Conveniently,
this allows all of your equipment to remain
connected to the same power board; changing a
single plug determines whether your equipment
is running from solar or mains power. You
won’t be making green notes when running
from mains power, but it’s reassuring to know
that your commitment to solar power won’t be
compromising your creative flow.
The first step in choosing a solar power system
is to calculate the total power that your audio
technology requires. Start by finding out how
much power each individual device consumes,
then add up all the individual values to
determine the total power requirement.
The power consumption of each device can be
found in the specifications of the equipment,
and sometimes it’s printed on the back of the
equipment itself. For devices that are powered
by AC adaptors, the power rating is often
printed on the adaptor.
Power is the product of voltage and current, and
is usually rated in ‘Watts’ (abbreviated to ‘W’),
although some devices will specify it as ‘VA’
(Volt Amps) or even simply as a voltage (Volts or
V) and a current (Amps or A). If it is specified
as VA, it can be considered the same as Watts
for this purpose. If it is specified as a separate
voltage and current, multiply the two together
to determine the power in Watts (i.e. Watts =
Volts x Amps). If you’re not sure how to find
this information, ask an electrician or electronics
technician for help.
The following example calculates the total
power requirement for a laptop-based system
built around an IBM ThinkPad T43 with a
Seagate Barracuda 3.5 inch external hard drive
(500GB, 7200rpm), an MBox 2 Pro audio
interface, and a pair of Dynaudio BM5A active
nearfield monitors.
Laptop: 60W
External hard drive: 10W
Audio interface: 6W
Active monitors: 30W per monitor (two
monitors)
This recording system requires 60W + 10W +
6W + 30W + 30W = 136W of power to operate.
Because this power will be supplied from the
battery via the inverter, we must allow for the
inverter’s efficiency, which is typically 90%. So,
the total power required from the battery equals
136W / 0.9 = 151.11W, which we can safely
round down to 150W.
To assemble a solar power system for this
laptop-based system, we need to know two more
things: how long the system needs to provide
power for between recharges (also known as
the system’s ‘autonomy’), and how many hours
of ‘peak sunlight’ are available for recharging
(peak sunlight is required for the solar panel
I put my first solar power
rig together in November
2006, before venturing out
on a recording expedition
into the Himalaya. I
needed a highly portable
system with folding or
rollable solar panels that
could be hung across the
back of a pack animal (e.g.
a yak, mule or horse) to
take advantage of the high
altitude sunlight while
trekking.
Although I wanted to buy
locally, I could not find
an Australian supplier
who catered for my
needs. Looking off-shore,
I found an excellent
system from a US
company called CTSolar. It
consists of a 32W folding
solar panel, a charge
controller/regulator
and a 16A/h battery, all
neatly packaged in blue
rip-stop nylon. Landed
cost was around $850
AUD (including priority
delivery). Because it is
only intended for charging
batteries, a simple 150W
modified sine wave
inverter from Jaycar ($50)
added the finishing touch.
It’s more than enough
to keep the batteries
charged on my recording
equipment. The solar
panels collect the solar
energy during the day’s
trekking, and the charge
controller stores it in
the battery. The stored
energy is transferred to
the recording equipment
overnight, so I start each
day with fully charged
batteries.
When it’s not trekking
with me, the system earns
its keep in my Nepalese
fiancé’s remote village
in the foothills of the
Annapurna ranges. Her
younger brother goes to
school in the morning and
spends the rest of his
daylight hours working in
the fields, so he has to do
his homework by firelight.
My solar power system
gives him electric lighting
to study by, and runs a
portable cassette/radio so
he can enjoy his favourite
Nepali and Hindi pop
songs at the same time.
– Greg Simmons
Greg Simmons watches
as Dil Gurung and the
horse handler fit the
solar panels onto the
back of a horse. The
battery and charge
controller are in a saddle
pack. Pic: Mikhael
Valeman
The complete trekking
solar power system
(folding solar panels,
charge controller/battery
pack, and inverter)
recharging the Nagra
V’s internal batteries in
a Nepalese village. Pic:
Rafaelo Porter