Running high-wattage lights on solar energy is a lot more complicated than most people think. In addition to needing to be in a location with persistent sunlight exposure, operators must take battery capacity, storage, attachments, wiring and PV efficiency rates into consideration. Moreover, you have to maintain the whole system to make sure all of the essential components are working properly.
This article covers specific processes associated with battery maintenance and the application of motion sensors to offset power consumption. Before tackling these issues, you must first compute for daily energy consumption, figure out the number of solar panels you need for the system, find the right type/size of batteries and commit to a set of luminaries (preferably LEDs due to their energy-efficient properties – more on this later). All of these requirements are covered in a previous article titled Considerations for Solar Energy Systems that Owners Must Know About. Assuming you have the basics down (if not, refer to the article) and you’re ready to take on more complicated aspects of solar energy, let’s get started.
Handling and Maintaining Batteries
Consistent battery maintenance is key to ensuring long-term performance of solar panel systems. There are several factors that one must take into consideration when keeping batteries in tip-top condition. For unsealed power cells (Flooded Lead Acid [FLA] batteries), it is crucial to check fluid levels periodically. To do this, simply open the battery cap and monitor the distilled water level of the unit. Make sure that no metal lead surfaces can be seen upon opening the battery (there should be a marker that indicates optimal electrolyte levels). This process can help address over 80 percent of battery failure causes related to sulfation, or the buildup of sulfur crystals on lead plates, which hinders essential energized reactions from taking place.
Charging batteries must closely adhere to cycles that allow the units to complete the following phases:
- Float Charging (trickle charging)- Charging a set of batteries at the same rate it is being discharged to maintain a fully charged state.
- Bulk Charging– This practice involves the initial steps of charging a depleted or discharged battery, wherein voltage increases dramatically to peak levels.
- Absorption Charging– Same as bulk charging, but instead of holding voltages at peak levels, it is held constant at maximum levels then decreases slowly until the battery reaches a fully charged state.
A charge controller may be used to automate or streamline the activation/deactivation of the cycles above. If this is the route you want to take, simply setup the system according to the guidelines set by the battery manufacturer.
Battery systems that are designed to activate when power outage occurs must also be maintained consistently to ensure operation after months or years of dormancy. To keep such units functioning properly, you have to keep them in a fully charged state. Overlooking this practice will cause batteries to lose their charge. Trickle charging may be applied to keep them topped up with power. It is recommended to utilize AGM (absorbed glass-matt type of lead-acid batteries) cells when setting up a backup battery system, because they require very little maintenance.
To smash some myths surrounding battery care, you should not resort to using car batteries on solar panels. This will cause the units to prematurely fail after deep discharging, due to the presence of thin lead plates. Furthermore, one should avoid mixing new and old batteries together, as this practice will cause the new units to degrade noticeably faster.
Day/Night Sensors versus Motion Sensors
Due to the storage and power limitations of solar energy systems, it is important to only use solar-powered lights when needed. This is easier said than done for busy operators – without help from day/night or motion sensing devices. The first unit detects sunrise and sunset conditions: it keeps the lights off when the sun is out and turns the connected fixtures on when the sun is down. Day/night devices are suitable for general lighting applications that need to be always on. For high-wattage lights, this is not a good option, because it will keep the luminaries on for up to 12 hours per day (depending on your location and season). Unless you have a robust set of batteries and solar panels supporting the fixtures, it would be best to instead rely on units that activate when sensing movement.
Most motion sensors are capable to detecting activities between 7-70 feet, depending on the model. There are three types of motion sensing features that leverage different kinds of technologies:
- Infrared Sensors- Detects changes in infrared heat signatures
- Optical Sensors- The use of video cameras to compare pixels via algorithmic protocols
- Radio Wave Sensors- Beams microwave signals to sense movement
Motion sensing devices are ideal for solar panel systems with alarms and security features. They can be used to automate remote notifications to individuals on a network, while discouraging criminals from entering the premise with bright lights. They can also be applied to busy work sites, like construction, repair and outdoor events. Since there is plenty of movement in such locations, the solar energy system will remain operational and only turn off when people are taking breaks or have left the area. This offers a tighter operational period than day/night sensors.
For outdoor use, passive infrared motion sensors (PIR) perform better than active motion sensors which are perfect for indoor applications. The latter is prone to false alarms and is very sensitive to irrelevant movements, like large flying insects. PIR sensors (includes a PIR detector, infrared sensor and a Fresnel lens) use infrared radiation to monitor heat signatures in the target area. They are useful for solar energy systems, because the units consume very little energy.
Choosing the right set of lights matter in the performance of solar panels. Technically, you could run any type of luminary via solar energy – but it doesn’t mean you should. Some lights, like incandescent and metal halide lamps, consume large amounts of energy due to the wasteful conversion of heat during output (up to 80 percent). This results in limited operational times, greater power storage requirements, possibly more solar panels and etc. Additionally, such luminaries come with short lifespans (specifically incandescent lighting) and lengthy startup periods (metal halide lamps).
For large-scale lighting requirements, LEDs are the way to go. By comparison, a 12-watt LED light can provide the same level of brightness when paired with a 60-watt incandescent bulb. While a 90-watt LED light offers the same brightness as a 175-watt metal halide unit and a 250-watt high pressure sodium lamp. LEDs also come with longer lifespans and are capable of withstanding rough treatment due to their solid-state designs.