This is the 5th article in a series by Kevin Conlin on solar powered billboards.  Previous articles have talked about solar basics, grid tied billboards, standalone billboards and batteries.  Today’s post will discuss solar billboard lights and controllers.

For small systems and boards with a single face, using the solar controller as a timer is the simplest and least expensive option.

Basically, the controller uses the solar array as a photo eye, and turns the lights on at dusk for a preset number of hours. It also learns when dawn occurs, and can turn the lights on for an hour before dawn if desired.

For systems with dual faces that are controlled separately, a timer or SmartLink is used. Tork builds a good 12VDC timer, and since the lights are 24V, a 24V to 12V converter is used. The Tork timer can be set for “real” (clock) time, or it can automatically turn the lights on at dusk based on latitude. This type of timer is known as an astronomical timer.

The SmartLink is also available for DC operation, and in addition to turning the lights on and off, it can automatically reduce the run time during periods of extended cloudy weather, and also alert the board owner to any light failures.

We’re finally down to the lights, and as far as the customer is concerned, it’s all about the lights. As we said earlier, the best solar system in the world can’t make up for poor lighting.

In my opinion, the two best DC lights are manufactured by Holophane and Lighting Technologies, or LTI. Although distinctly different in design, both provide even illumination of the sign face, and light levels seen with conventionally powered boards.

When wiring 24VDC lights, it’s important to use heavy gauge wire, otherwise excessive voltage drops can occur, resulting in dim lights.

One final note: All solar lighting systems, when properly designed, qualify for a 30% Federal tax Credit. This means a $10,000 solar system will cost $7,000 after taking the tax credit.

The systems also qualify for accelerated depreciation, and are exempt from property taxes in most states. To see which incentives are available in your area, go to www.dsireusa.org/

Kevin Conlin is President of Autonomous Power Solutions.    You can reach Kevin at kconlin@autonomouspwr.com or 281-202-9629.

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