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Not all solar lighting systems are created equal. Each has its own unique qualities and benefits. Understanding system differences along with your own requirements will allow you to build the perfect solar lighting system solution for your project while working with your designer. The three strategies for designing the perfect solar lighting system below will help you best determine what you need and how to achieve the best outcome.
1. Know how much light is required
Does your lighting project require you to meet IES Standard light levels? Or are there specific lighting requirements in your area? Talking to local code enforcement will help you determine if there are any guidelines you must follow or if there are no set numbers for the type of lighting required. IES Standards are a good guideline for most projects; however, different municipalities have different variations of the standards that they can enforce.
If you are in an area where IES Standards will work for the project, letting your lighting designer know this information will help them work to determine what type of light, distribution, and brightness will be required for your project. Providing the designer with additional information, such as the length of the roadway, size of the parking lot, dimensions of the area, etc, will allow for the designer to provide additional information, such as a light layout to show uniformity and light levels across an entire project.
Another huge help to lighting designers to showcase the light levels is having an AutoCAD file or Google Earth location so the layout can take into consideration obstacles and other project-specific needs. Seeing the layout helps the lighting designer visualize medians, entrances, exits, trees, obstructions, buildings, etc. to ensure that adequate lighting is provided for each area. Having this data also helps to ensure proper lighting is in place for specialty locations, such as ADA parking spaces where higher light levels are required for compliance.
2. Understand system constraints
Depending on the installation area and system requirements, certain projects may be more viable than others. A 70 Watt LED fixture operating all night will require a much larger solar power assembly in Maine than it would in Arizona. This is due to the solar irradiance that is available in any specific location. Off-grid systems need to look at the worst-case scenario and use that data, not overall averages, to ensure the system is sized properly for the installation location.
Instead of just looking at arbitrary wattages, looking at light-level requirements should be the first step to determining what is required for the project. Decreasing the wattage and adding a pole or two, in many cases, can actually create more even illumination and a more feasible project in the end while still providing the correct light levels.
Storage requirements also vary from one location to the next. From the Tennessee / Kentucky border south, five nights of autonomy is adequate for backup power; however, the further north you go, the more storage the system will require. This is due to the depth of discharge changes in the batteries in colder climates. I would also like to point out that Lithium is not good for extreme HOT or COLD climates and should be avoided.
Also, look at local weather patterns. How many days of cloudy / overcast weather does the area typically receive? Understanding this, along with how cold an area gets, will help determine how much is adequate for backup storage to ensure system operation and longevity.
3. Determine operation schedules
Solar lighting systems can be provided with multiple operation schedules to meet the needs of the project. Determining the operation schedule when initially designing the project will help ensure that the system will operate as needed and is sized accordingly. This is best configured by looking at the traffic and usage of the space prior to sending out the request for solar. If the traffic reduces or all but stops, having the lights turn off around that time will save on the system, whereas spaces that have activity at random times throughout the night may need motion sensors to allow for full brightness when people are around.
Dusk-to-dawn operation is the most popular configuration and everyone's first choice. However, split time and dimming help reduce the requirements of the solar allowing for smaller power assemblies. Do not just assume that the fixtures will operate from dusk to dawn at full intensity unless this has been determined in the initial system design.
Many companies use control electronics that override the system to provide adaptive lighting controls that are outside the original design requirements. Instead, by working with the design team to understand the exact controls being used for the system being installed. If dimming, split time, motion, or any other operation profiles are allowed, make sure to specify this initially. If they are not, make sure the company you are working with fully understands this, and make sure they don't have some hidden controls.
Understanding these three important design requirements before getting a final system design will ensure that your system will operate the way it is required with the correct lighting levels, uniformity, operation, and sizing for the specific project. One size does not fit all in any solar application, lighting, or power and should be specific to each individual project. This ensures you will never be left in the dark.
