Security Applications for Solar Lighting

You might think it surprising, considering their lack of brightness in other applications, that solar lights are now being engineered for security applications, using large arrays of bright white LEDs to provide illumination. Solar security lights that include motion detectors are available from many sources, while bright floodlights designed to remain on all night are still a specialty item used for yard security and commercial sign illumination where line power is not available.

The main benefits of using solar lights for security lighting are the generous savings in electricity costs, the long life of LEDs, and the ease of installation where 120V line power cannot be provided. Challenges of meeting the requirements for security lighting make security lighting systems more expensive than other types of solar lighting, however.

Differences from other outside lighting uses

Security lighting is a very different application from the traditional uses of outdoor solar lighting – path, landscape and party lighting – and has different requirements. Chief among these is that security lights must flood an area with bright light, either when set in motion by an intruder or all night, and the lights’ operation must be reliable.

While path lighting needs to be bright enough so that a visitor can safely follow a walkway or driveway, it is usually sufficient that that the path or drive be marked rather than brightly illuminated. If necessary, path marking can be supplemented with a brighter level of LED lights when a visitor comes along and triggers a built-in motion detector.

Landscape lighting is designed for aesthetics rather than safety or security. While highlighting a façade requires a reasonable level of light, it is not usually essential for the lighting to last more than a few hours, and high reliability is not a factor. In any event, using line voltage may provide greater flexibility when lighting a facade.

Party lighting is used primarily to provide a fun atmosphere. If ambient light is needed, the solar light will need to be supplemented by another type of lighting. Low cost is eessential, and buyers will usually buy extra lights to provide spares or more atmosphere. Often party lights will be used just once.

Buyers of these various types of outside solar lights want style that fits their aesthetic desires, and they want it at low cost. They may or may not want to pay for durable materials and will rarely look at the specs of components (which are rarely provided by vendors anyway). Manufacturers may or may not use the high-quality/high-capacity components that will provide for night-long lighting, since most consumers don’t demand it.

Requirements and guidelines for security lighting systems

Security lights has specific requirements that don’t involve style or low cost.

They must adequately illuminate an area.
If triggered by a motion detector, they must stay lit as long as the motion continues and, after resetting themselves, do so again and again if necessary. If they have no motion detector, they must remain lit for 8-10 hours or more of darkness.
They must work reliably night after night.

Guidelines for lights with PIR motion detectors:

To fulfil the illumination requirement, a light must use multiple LEDs, as many as 80 high-brightness white LEDs to produce the equivalent of a 45-watt bulb.
To fulfill the night-long requirement, they should have an array of several photovoltaic cells in their light-converting PV panel, at least 3 watts. They must have a battery with enough capacity to store the electicity to run all those lights, a 6V sealed lead-acid battery rated at 2 amps/hour.
To work reliably night after night, they should be sealed against moisture. While LEDs may last for 20 years, batteries need to be replaced from time to time. A battery should be replaced every 2-3 years.

Guidelines for lighting systems that must stay lit all night long:

To fulfil the illumination requirement, a light must use multiple LEDs, 108-144 high-brightness white LEDs, to produce the equivalent of a 100-150 watt incandescent bulb.
To fulfill the night-long requirement, they should have a large array of photovoltaic cells in their light-converting PV panel, at least 10 watts in the southern US and 20 watts in the north. They must have a battery with enough capacity to store the electicity to run all those lights, one or two 12V sealed lead-acid batteries rated at 4 amps/hour.
To work reliably night after night, they should be sealed against moisture. While LEDs may last for 20 years, batteries need to be replaced from time to time. Batteries should be replaced every 12-18 months.

Having overcome the limitations of limited brightness and short lighting duration with the systems described above, the initial cost of the investment in equipment is a main disadvantage, though this will be offset in time by savings in electricity costs.

Costs of solar security lights

Estimated costs:

An 80-LED security light system with PIR motion detector that meets the above specs would cost about $80-90.
A 108-LED security light system designed to stay lit all night would cost about $400 with a 10W PV panel (suitable for the south) and a single 12-volt battery.
A 144-LED security light system designed to stay lit all night would cost about $1000 with a 45W PV panel (suitable for the north) and two 12-volt batteries.

Styles of solar security lights

A well-designed security light system includes the light array, which is usually wall-mounted but may be clamped to a flag pole or fence post or ground-staked; a wired remote PV panel that can be mounted in a sunny location; and a battery pack of 6 or 12 volts. A 6V battery is usually mounted with the light array; a 12V battery, if supplied in its own container, might be attached by cable. The remote PV panel, mounted outdoors, enables the light to be used indoors – in a garage or shed. The cable is usually 12 or 16-feet long.

Security lights have manual on-off switches, and lights with motion detectors can be adjusted for sensitivity and length on before rechecking for motion.

Materials are ABS plastic, aluminum, or some combination, along with a silicone gasket for keeping water out of the light housing.

Lights with motion detectors are available from local big box and hardware stores and from several sources on the web. Be sure the specs of the system you are considering meet the requirements described above.

All-night security lights are generally not available at local hardware stores, though you may find them at an electrical supply house. There are a few sources on the web. Again, be sure the specs of the system you are considering meet the requirements described above. Some suppliers of commercial systems charge a restocking charge if you find the light unsuitable after you get it home.

Solar security lighting can be justified primarily by the need to install it where a 120V line is not available or where line installation would be difficult. That said, there are multiple-LED solar lighting systems available now that are suitable for security applications.