MONITORING STATION INSTRUMENTATION AND MEASUREMENTS - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 53

4.7 POWER SOURCES
All electronic data loggers require a power source, which should be sized to meet the
total power requirements of the monitoring system. The leading power options are
described below.
4.7.1 Household Batteries
The newest generation of loggers employ low power electronic components whose
operation can be sustained by common household batteries (D cells, 9 V, and others)
for 6 months to a year. Although the systems are generally reliable, if the batteries fail,
data collection stops. In addition, the power is not sufficient for towers with heated
sensors or for other special power needs. To address these issues, logger batteries are
often augmented by another power source.
4.7.2 Solar Battery Systems
For more reliable long-term operation and for meeting larger power needs, the most
popular choice is a rechargeable lead-acid battery coupled to a solar panel. Packaged
solar battery systems are offered by most logger vendors for this purpose.
Lead-acid batteries are a good choice because they can withstand repeated discharge
and recharge cycles without greatly affecting their energy storage capacity, and they
can hold charge well in cold temperatures. Caution should always be used when
working with large batteries like these to avoid a short circuit between the battery
terminals. It is also recommended that newer battery designs which encapsulate the
acid into a gel or paste to prevent spills, called nonspillable or gel batteries , be used.
Although long-lived, lead-acid batteries subjected to many charge and discharge cycles
eventually lose capacity. It is important to take this decline into account when sizing
the battery if it is intended to last in the field for several years.
The solar panel must be large enough to operate the monitoring system and keep
the battery charged during the worst expected conditions (usually in winter). To avoid
outages that may cause data loss, it is recommended that the solar and storage system
be designed for at least 7 days of autonomous operation (without recharging). The
solar system must also be reverse-bias protected with a diode to prevent power drain
from the battery at night. In addition, it must include a voltage regulator to supply a
voltage compatible with the battery and to prevent overcharging during months with
the most sunlight.
Logger vendors offering solar battery packages can advise on the proper size for
any location.
4.7.3 AC Power
Alternating current (AC) power is not normally required for wind monitoring systems.
Moreover, it is unusual (except for communications towers) for a met mast to be close