Part 3 of the solar lighting design guide is about choosing an operation profile. Not all applications require dusk to dawn operation. Understanding exactly what you require for your project will help determine exactly how much power is required to complete your project.
Dusk to dawn is the most popular operation profile for lighting applications. This is from the old mindset of grid-tied lighting since there is no worry about the amount of power usage. Since grid lights will operate as long as there is power, there is little difference in cost for adaptive lighting. With solar, using adaptive lighting techniques can provide for a smaller solar and battery system.
The second popular system is dusk activated for a set number of hours or split time operation. For example, if a business closes at 10 pm and most people/customers are gone by 11 pm, having the lights shut off around midnight will reduce the solar sizing. If this same business opens again at 6 am, the lights can come back on an hour or two before dawn, making the system split time. The only time the lights are off is during the times the light is not required. For security during those off periods, the light power can also be reduced for adaptive lighting.
Other options include a real-time clock for specific hours of operation. These systems operate till a set time at night and then turn off, and can also be set to come on again in the morning before dawn. These clocks are great for some applications, but it must be noted that they cannot account for daylight savings time. This means that a light set to go off in the summer at midnight will only operate till 11 pm in the winter unless the programming is changed.
If midnight is the required time, but 1 am in the summer is okay, then set the system to a program of midnight in the winter will automatically operate the system till 1 am in the summer. Remote real-time clocks can be used for remote mounting the clock if changes are required more frequently.
Other operations include:
Electronic time computers for specific operations can be programmed, up to 365 days and are typically used for traffic flashers, work shift programming, and other applications where calendar control is required.
Motion-activated infrared detectors or occupancy sensors for areas where the light only needs to operate when there is someone in the area. These can either bring light on or to a different intensity during the activation periods and then off or reduced wattage for the rest of the time.
Switches such as a remote actuated switch or spring-loaded timers are used when the lights are only required during certain times or for short spurts of time.
Each type of operation profile will be a factor in sizing up the correct solar power assembly to operate the chosen light fixture at the wattage required. Sometimes by looking at a project with a more set schedule of operation and not just opting for dusk to dawn can make or break a project. Understand exactly what the operation requirements are when working with the solar lighting specialist to design the system.