Solar Lighting Design Guide: Sizing, Aesthetics, and More
Posted by Stephen Shickadance in Solar Lighting Design.
How to Size a Street Lighting Design
Improper design of a solar light can lead to light fixture malfunction, improper light spread, shortened component life, panels that are too large (causing more expensive shipping and higher wind load) or poor aesthetics. That’s why we’ve developed this street lighting design guide to share with you how important it is your lights are properly made.
Quality manufacturers should provide two complementary 3-D simulations of your street lighting design layout--one that is desired versus one that is recommended based upon the location. This way you can be aware of what kind of systems to select from, the proper sizing of each component, and the real-world calculations behind the full project. A common measurement for light is foot-candles, or the amount of light that hits an object 1 foot (12 inches) away from a lit candle.
Less common measurements are LUX, but your manufacturer should provide simulations in whatever units desired.
The Array-to-Load Ratio for Solar
The Array-to-Load Ratio (ALR) determines the size of electrical components and the wattage of the solar panel. This is a fundamental ratio for sizing solar lights that must be calculated by qualified lighting engineers since it constantly changes over time. Every year there are incremental improvements in power efficiency, suggesting smaller panels and smaller batteries.
An improper ALR can, once again, lead to a host of problems and the system will have to be reconfigured.
Solar Panel Wattage
The amount of solar energy in a given area depends on what’s called the solar insolation, or more commonly known as sun hours. The amount of sun hours determines the size and wattage of the panel.
Quality manufacturers measure sun hours during the winter solstice--the darkest day of the year--to determine if the location provides more energy during sun hours than the energy drained while the light fixtures are on. If there’s more energy gathered than drained, the sizing and location are optimal for “set and forget” operation.
Street Lighting Design Layout
This aspect of solar lighting design tends to be left up to the customer since it determines if the light coverage from one light floods into the adjacent light.
For instance, if lights are installed to illuminate a street, their spacing may be far apart--it isn’t necessary to have every inch of the street illuminated. But if lights are needed to illuminate a business entrance, it may be necessary to pair lights closer to get full grounds coverage. It’s important to consider the kind of traffic as well--foot traffic would need larger lights closer together, whereas auto traffic suffices with them spread further apart.
Solar Street Light Pole Design
Consider the locations of each light as they’re planned--solar panel obstructions are common in parks (trees) and metropolis areas (skyscrapers). The surroundings for a project site are not always ideal for solar energy.\
Also, “competing” light sources can be problematic. If your project location is nearby brighter light sources (car dealerships), your lights may pale in comparison. Consider what light sources are nearby so that your solar light design is best for the area.
Solar Light Fixture Aesthetics
Admittedly, one of the drawbacks of street lighting design is the aesthetics of a solar panel. They aren’t the most attractive addition to a lighting system, but that doesn’t mean you have to install ugly lights in a park or city area.
Change the Light Fixture
If aesthetics are a concern, there are options to divert attention away from the solar panels. A good manufacturer typically has several fixtures to choose from that look better than a simple cobra-head fixture. Fixtures like the Lita or Brighta series are better for parks and beautification, but if the solar panel is still too distracting from the light, there are options to change out the lights themselves for a prettier presentation.
Use the Volta
The Volta series has a unique solar street light design that incorporates the solar panel into the pole. The panel wraps around the pole so it appears as one unit instead of two separate components. If you’re interested in the Volta for your project, be sure to consult a lighting engineer as the Volta is most efficient in certain locales.
Bury the Batteries
Batteries aren’t typically buried since after 5 years they’ll need to be replaced (average timespan). However, when presentation and aesthetics are more important than component accessibility, you can opt to place the battery underground. This is also a good way to regulate battery temperature if there are extreme temperatures to consider--gel lead-acid batteries don’t fare well in extreme cold.
There are some “checkmarks” that lights need to hit in order to be considered “best” for public use or a street lighting design layout. The first is called International Dark Sky Association (IDA) Compliance. This is a set of guidelines to ensure lighting isn’t harmful to living organisms.
The IDA recommends light fixtures that do not have a “spillover” of light past the 180-degree plane of a fixtures angle. If light escapes the fixture past this plane for whatever reason, this is a telltale sign of a poor-quality fixture.
IDA compliance for lights states that the color temperature given from the light fixture should be no more than 3000 Kelvins.
Color temperature is a characteristic of light falling in the visible spectrum. 3000K (pictured above near the center of the image) is often labeled as a warm white and is very natural to the eyes. However, in manufacturing, LEDs aren’t always the same. Variations in quality for LEDs tend to slightly change the target color temperature, and so quality manufacturers adhere to the ANSI standard, a specific range for color temperature that is considered “acceptable” to look like a certain color temperature.
There are a lot of factors to consider when it comes to solar lighting design. That’s why it’s important to ensure your materials are of a certain standard and properly work for the situation you need.
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