Over The Horizon

Mariners' Microlight

Porirua company Vega Industries is cashing in on the upgrading of the US Coast Guard's 106 lighthouse stations.

Two years ago the Coast Guard issued an ambitious specification for a totally new beacon which would use only 10% of the energy used by existing lights, which produce a beam visible over 40 kilometres away. The aim was to reduce energy demand to the level where expensive diesel generators could be abandoned in favour of solar panels and batteries. This would dramatically reduce both capital and operating costs of major lighthouses.

The specification was very demanding, as the solar powered goal could only be achieved by applying the latest technology in optical systems, high-intensity lamps, motor drives, and electronic power converters.

The Coast Guard also wanted a beam no less than 1.5 degrees wide, but with an effective intensity of more than 1.3 million candelas -- with a lamp no larger than 250 watts. It was to be mounted on a turntable that consumed less than four watts of power, with an automatic lamp changer so that the light would only need to be re-lamped once a year.

Vega won the design contract against international competition, and one year later has exceeded the specification in every respect, achieving a 43-km range and using only 150 watts to power the system.

The key to this performance is in the optics. Vega designed the parabolic reflector and lens system to give the right beam width and height, with an absolute minimum of wasted light. Even the irregular radiation pattern from the lamp was turned to advantage.

Up to eight optic heads can be mounted on the turntable to give two beams and 8,000 burning hours -- over 18 months of automatic operation. The turntable is powered by a brushless DC motor designed in New Zealand, and consumes only 0.6 watts. The special power supplies to start and run the lamps were also designed in New Zealand.

The optic units are 60% smaller in diameter than the existing lights, and the whole beacon is very compact, lightweight and easily disassembled, which is very important when carrying components out to remote locations and to the top of tall towers.

The XAB-17 beacon is claimed to represent a significant step forward in the energy efficiency of major lighthouses, and should substantially reduce costs compared to current systems in use around the world.