LED-ing the way

Conventional incandescent light bulbs are grossly inefficient. Light is produced when an electric current passes through the filament (a simple coil of wire). The wire heats up until it glows white-hot, producing light.

But it also produces heat — up to 90 per cent of the energy used by an incandescent bulb is ‘wasted’ as heat energy. Not only is that heat generally unwanted, it can easily cause a fire hazard and other damage if the bulb is not correctly insulated.

In home and office environments, these bulbs are rapidly being replaced by compact fluorescent light (CFL) bulbs. These produce relatively little heat and up to five times as much light output for the same power consumption.

CFLs have some issues, however, including toxic mercury in the bulbs and complex electronics within the unit. This makes them unsuitable for harsh marine environments, and some argue they’re bad for all environments because of the mercury.

LED REVOLUTION
The latest technology — the light-emitting diode (LED) — offers the most exciting and environmentally-friendly solution. A product of the semiconductor age, it was first demonstrated in 1962. Initial units were limited to a dim, red light, and it is only the recent development of the high-intensity LED that has moved these from the realm of the electronics enthusiast into the mainstream.

As a result of this innovation (effected by using different semiconductor materials in the construction), modern LED lights are rapidly replacing all other bulb types in marine and automotive applications. We can increasingly expect to see them around the home as well. They have everything going for them: they are cheap, simple, contain no environmentally-harmful compounds and are very efficient, converting almost all the electrical energy into light with very little heat produced.

Consider the comparison: a standard incandescent light bulb produces about 15 lumens of light per Watt of energy. Compact fluorescents produce up to 100 lumens per Watt, while the latest LED technology generates a staggering 300 lumens per Watt, although this level is not yet commercially available.

But it is not just the efficiency that makes LED lighting attractive. Semiconductor materials are subject to very little wear and tear, with lifetimes quoted in excess of 100,000 hours. A typical household incandescent bulb will usually burnout after about 1000 hours of use, and even CFLs only last 6000 to 8000 hours. To put this in perspective, an LED light could be left on continuously 24 hours a day for 11 years before it might need replacing.

Despite these advances though, LEDs still have a few drawbacks. Size is one issue — current technology only allows an individual LED to be a maximum of 5mm across. Each of these LEDs can produce up to 250 lumens, which is only the same amount of light as a 15W incandescent bulb.

Since LEDs also typically operate on 3V-DC, clustering four or more individual units allows them to operate at the usual 12V house voltage of most boats, while producing a more useful amount of light equivalent to about a 60W conventional bulb.

The other main drawback is that the light from an LED is very directional, like a tightly focused torch beam. This makes LED light extremely harsh, and various techniques are used to create mood lighting, or to avoid blinding people where it is used for direct lighting. Newer versions offer greater viewing angles, i.e. the light is dispersed more widely, although standard diffusers also help.

The enormous longevity of LEDs makes them very suitable for permanently fitting into a variety of applications. A bank of LEDs can be wired into a unit then encased in epoxy, secure in the knowledge that the LED will probably outlast the integrity of the epoxy itself. This enables the construction of maintenance-free and totally waterproof modules, such as for submersible trailer lights, exterior navigation lights and even fully-submerged hull lighting.

BOAT LED CONVERSION
So, having decided that LED is the way to go, how do you go about converting your boat to this technology? Fortunately, a number of manufacturers have created LED bulbs (i.e. a cluster of LEDs suitably packaged to fit directly into a standard bulb fitting). These will be rated at the same current as the original bulb, so it means a 3V torch bulb, a wide range of 12V and 24V marine and automotive bulbs, and even 240V domestic bulbs can now be directly replaced with an LED bulb.

It’s a simple matter of unscrewing your conventional bulbs and installing the LED cluster bulb. One caveat — unlike a conventional bulb, an LED only works if the polarity is correct. So if the new bulb does not work, try reversing the wiring to your light fitting. For 240V units, the LED unit will always have a rectifier to convert the AC to DC, so polarity is not a problem for those.

Although LED bulbs are now available in just about every possible fitting size, check that they are rated for marine use. Vibration-resistance is important, but more significant is corrosion-resistance. Units with tinned wiring, or fully-sealed units, are preferable.

When outfitting a new boat, or revising the lighting on an older vessel, it makes sense to consider LEDs throughout the craft. With the low-current requirement you can use more lights, and the thinner wiring employed in them means they can also be placed unobtrusively in places where a conventional light would be dangerous.

Most marine chandlers sell a range of LED lighting, but a specialist supplier may be more appropriate. Hella Marine is one of the foremost suppliers of marine LED units and offers a range on navigation, interior, floodlight and surface-mount lights. Its 7W LED Megabeam floodlight, typically used for lighting a boat’s cockpit, provides the same light output as a standard 55W Halogen floodlight, while using less than 15 per cent of the energy.

Since a typical deep-cycle house battery will have somewhere around an 85 to 100amp/h capacity, it’s obvious that a single night’s usage of lights alone could easily consume most of the battery’s capacity.

Add further current drain from a VHF radio or stereo, or even the GPS/sonar left on continuously for the anchor alarm function, and it is conceivable that the battery could be completely drained before the night is over.

Switching to LED lights will greatly reduce the drain, leaving a greater safety margin. They could also allow smaller house batteries to be installed, reducing the overall cost.