Solar Power for Alvarion Equipment by Dave Clelland
When you size solar power, you have to calculate a few things
first.
1. Each BreezeACCESS 2.4 AU, BreezeNET Pro.11, and BreezeNET DS.11
access unit, or access point consumes about 11 watts of continuous
power.
Each BreezeACCESS LB will consume about 38 watts of continuous
power.
Add
up the watts of continuous power consumption that your planned
site
will
use. Remember to include any hub, switch or router that may be
installed
in the site as well.
2. Multiply watts consumed by 24. This will give you the
watts/day of power required.
3. Find out the average number of
hours of daylight during the winter in your location. You need to
generate 24 hours worth of power in the number of hours of
daylight you have during the shortest days of the
year.
Here in Edmonton, we have 7 hours of daylight in the winter, so a
solar
array that I would build must completely recharge my batteries in
those
7
hours. Again, an example:
a. Suppose I have 2 BAII AU's, back hauled with a
DS11 system. This means my radios will consume 33 watts of
power.
In
one day I will consume 792 watts. In my area, I have 7 hours of
daylight
in the winter, so my solar panels need to provide 792/7 = 113.1
watts
per
hour round that up to 120 watts per daylight hour.
4. Go to your local solar panel distributor. They will have
panels based on 20 watt, or 40 watt increments. Connect the right
number of panels in parallel to make up the correct wattage  in
our example we might use 3 40 watt panels at our site. a. A 40
watt Siemens panel is about 4ft by 2ft., and puts out about 12
volts. You need to make sure you have a regulator,
and
a low voltage disconnect on your panels and between your batteries
and your load. b. For all Alvarion equipment, I recommend
inverting the DC power to AC, then using standard 120vAC to power
the radios,
and
any switch, or other network device you might use.
5. Size the batteries such that one 24 hour period without sun
will only draw the batteries down about 5%. This does not mean
you have 20 days worth of backup power, but you do not want the
voltage to drop
too
much when a day with heavy clouds obscures the sun.
a. In our example, we are using 33 watts of power. Batteries are
sized in amp hours, so we need to convert our watts to
amps
(Power = volts X amps, or Power / volts = amps). 33/12=2.75 amps
of current. In one hour, we would drain 2.75 amp hours of energy
from
the
battery. We would use 66 amps per day. Using the 5% rule, I
would install a battery set capable of delivering at least 1300
amps / day,
or
55 amp hours of energy. Your local battery specialty shop, or a
company
that provides standby power will be able to help you purchase the
correct
batteries for your area.
