All wind measurement systems require a power source. The leading power supply options for instrumented towers are described below.
Household Batteries
The newest generation of loggers employ low-power electronic components whose operation can be sustained by common household batteries (D cells, 9-volt, and others) for six months to a year. This may be adequate for a tall tower equipped with the standard wind speed sensors. However, although the systems are generally reliable, data will nonetheless be lost if the batteries fail. In addition, household batteries are not sufficient for towers with heated sensors, sonic anemometers, or other special power needs. To address these issues, the logger batteries are often augmented by another power source.
Solar-Battery Systems
For more reliable long-term operation as well as for meeting larger power needs, the most common 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 significantly affecting their energy storage capacity, and they can hold a 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 in a gel or paste to prevent spills, called non-spillable or gel batteries, be used.
The solar panel should 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 seven 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. Further, it must include a voltage regulator to supply a voltage compatible with the battery and to prevent overcharging during months with the most sunlight. Most logger vendors offering solar-battery packages will advise on the proper size for your location.
AC Power
Alternating Current (AC) power is not normally required for wind monitoring systems. Moreover, it is unusual (except for communications towers) for a tower to be close enough to a source of AC power to make connecting to it worthwhile. Nevertheless, where AC power is conveniently at hand, the instrumentation loads are unusually large, or solar panels are not practical, then AC power can be the right choice. It should be used only to trickle-charge a storage battery, not to power the logger directly. A surge/spike suppression device should be installed to protect the system from electrical transients. In addition, all systems must be properly tied to a common earth ground.
Other Power Options
Other power sources that may be used in some circumstances include small wind systems, wind/solar hybrid systems, diesel or gasoline generators, and fuel cells. Small wind and wind/solar hybrid systems can be a good choice where there is plenty of wind and solar radiation is limited (in arctic environments, for example), or where solar panels are likely to be blocked by trees or other obstacles much of the time. Diesel or gasoline generators are sometimes used for remote sensing systems, but are usually overkill for tall towers without heated sensors. Fuel cells powered by methanol, propane, or other fuels are available for applications where large, continuous power is required. They are usually more expensive than generators, but are quieter. They can be used to power autonomous remote-sensing systems where increased power draws due to system heating or cooling are expected. Partnerships with local or regional universities or companies may yield some interesting opportunities.
Lighting
In some regions, towers taller than a certain height may need warning lights. This should be checked with the appropriate regulating agencies. The position of the lights should be considered in the monitoring design to minimise interference with anemometers and other sensors. Also, the need to power the lights should be considered in the choice of power supply. Where there is no grid power, warning lights can be operated by a photovoltaic-battery system.