Panasonic PT-DZ12000U Operating Instructions Manual page 150

D. Solar Power
Solar power panels can be an effective way to power a
remote air monitoring system.
If you want to operate the system continuously you need to
add a battery system. Use previous guidance from the
section on battery systems to determine the required size of
the battery system.
Solar cells produce 5 to 15 watts per square foot of panel
depending on the quality of the panels, orientation of the
panels, geographic location, and season of the year. The
purchase cost of solar power panels ranges from about $7
per watt to $10 per watt. The installation cost of your system
must also be considered.
Example: You have a vacuum pump that uses 750 watts per
hour. Your sunlight availability at the location is 6 hours per
day. You want to continuously operate your vacuum pump
and you want to plan for a lack of useable sunlight for only
one day. You need a battery system that will operate the
vacuum pump for 36 or more hours, but then you must also
size the solar panel system to generate enough power to
operate the vacuum pump and recharge the battery system.
You need 750 watts per hour times 24 hours or 18,000 watt-
hours per day from your solar panels. You also need to store
a minimum of 18 hours in the battery system in order to
operate your air sample pump when there is no sunlight.
Your battery system needs to store 750 watts times 18 hours
or 13,500 watt-hours just to operate overnight. You must
double that battery storage capacity if you need to operate for
an extra day without useable sunlight for you solar panels.