Solar Power and Modern Lighthouses
The Energy Problem in Remote Places
Lighthouse keepers spent a significant part of every working day managing the energy supply of their stations. Coal had to be shovelled, oil had to be measured and pumped, acetylene cylinders had to be ordered and exchanged, mains electricity required a connection to the national grid that was impossible on an isolated rock twelve miles from the nearest land. The energy question was never trivial. The Eddystone lighthouse, 14 miles south of Plymouth in the English Channel, ran on paraffin vapour through most of the twentieth century, its supply delivered by Trinity House tender. Breakdowns in the supply chain, storms that delayed the tender, or mechanical faults in the vaporising burner could all threaten the continuity of the light.
Solar power, first applied to lighthouse buoys in the 1970s and to manned stations from the 1980s onward, dissolved this problem for a large proportion of the world's aids to navigation. A correctly sized solar panel array, combined with a battery bank and a low-power LED source, can keep a lighthouse operating through months of overcast weather and seasons of darkness at relatively modest cost. The capital investment is repaid within a few years by the elimination of fuel deliveries, keeper salaries and the maintenance demands of rotating machinery.
The Transition from Acetylene to Solar
Before solar power, the preferred energy source for isolated and unwatched lights was dissolved acetylene. An acetylene buoy or minor lighthouse could run for months on a single cylinder of gas, and the burner apparatus was mechanically simple and reliable. The system was introduced in the late nineteenth century by Gustaf Dalén, the Swedish engineer who won the Nobel Prize in Physics in 1912 partly for his invention of the AGA regulator — a device that automatically extinguished an acetylene light by day and re-lit it at dusk using the sensitivity of the rod to solar radiation.
Acetylene served well for seventy years, but it carried risks. The gas is explosive if the cylinder leaks in a confined space, the supply chain required trained handlers, and the carbon footprint of producing and transporting cylinders to remote sites was considerable. When silicon photovoltaic cells became commercially available at acceptable prices in the mid-1970s, the lighthouse authorities of Scandinavia, Canada and the United States began replacing acetylene systems with solar-charged batteries as fast as budgets allowed.
The Swedish Lighthouse Authority automated the Kullens lighthouse on the Skagerrak coast in 1979 using an early solar installation alongside a wind generator. The combination worked through the short winter days of the Swedish coast, and the experiment was judged successful enough to guide subsequent installations. Within a decade, solar power had become the default solution for any isolated light whose position could receive meaningful sunlight for at least part of the year.
How a Modern Solar Lighthouse Works
A complete solar-powered lighthouse installation has four main components: the photovoltaic panels, the charge controller, the battery bank and the LED lamp unit. The panels collect solar energy during daylight and feed it through the charge controller — which prevents overcharging and deep discharge — into a bank of sealed lead-acid or lithium-iron-phosphate batteries. The batteries power the LED lamp during the night and during periods of overcast. A properly designed system provides a safety margin of several days of battery reserve, so that a prolonged cloudy period does not extinguish the light.
The LED lamp unit itself is where the greatest technical change has occurred. The xenon flasher tubes and rotating optics of the early automated era gave way to solid-state LED arrays from the mid-2000s onward. A modern marine LED light requires between 10 and 100 watts to produce a flash visible at 10 to 20 nautical miles, compared to the kilowatts consumed by a heated filament or discharge lamp to achieve similar results. This reduction in power consumption is what makes the solar system feasible at high latitudes and during extended cloud cover. The Skervuile lighthouse off the west coast of Scotland, rebuilt as an automatic solar LED station in 1994, draws so little power that its battery bank can sustain the light for two weeks without any solar input at all.
Arctic and Subarctic Applications
The apparent paradox of solar power at high latitudes — where winter days are short and sunlight weak — has been resolved partly by the compensating long days of the arctic summer. In the Norwegian archipelago of Svalbard, latitude 78 degrees north, there is continuous daylight for approximately four months of the year. A battery bank charged to capacity during the summer can, in theory, carry the light through the polar night, though in practice the combination of solar panels with wind generators is more reliable.
The Norwegian Coastal Administration has operated solar-wind hybrid systems on Svalbard since the early 1990s. The Bjørnøya lighthouse, on Bear Island at latitude 74 degrees north, uses solar panels for summer charging and a wind turbine as the primary source during the dark months. The combination has proven more economical than maintaining a diesel generator and fuel supply on one of the most isolated islands in the Barents Sea.
At the other extreme, the lighthouses of tropical coasts receive abundant solar energy year-round, and in these regions the transition to solar power was both technically straightforward and economically compelling. The lighthouse authorities of Australia, New Zealand and the Pacific Island nations automated most of their remote lights with solar installations during the 1980s and 1990s, with results that confirmed the technology's reliability in marine environments.
Trinity House and the British Programme
Trinity House, the general lighthouse authority for England, Wales and the Channel Islands, undertook a systematic programme of automation and conversion to solar power between 1980 and 1998. By the time the last attended lighthouse — North Foreland, on the Kent coast — was automated in November 1998, almost all of the authority's 66 major lighthouses had been converted from kerosene or mains electricity to solar-powered LED systems where their power requirements permitted, or to mains-supplied LED where a grid connection already existed.
The Bishop Rock lighthouse, the westernmost lighthouse in England, standing on a rock eight miles beyond the Scilly Isles, was automated in 1992. Its original first-order Fresnel lens was removed and replaced with a modern optic drawing power from solar panels mounted on the tower's exterior. The light character — two flashes every fifteen seconds — was preserved, but the power consumption fell to a fraction of its previous level. The saved operational costs were substantial for a station that had previously required relief keepers to be landed by helicopter due to its isolation.
LED Optics and Light Character
The shift to LED sources has not merely changed the energy economics of lighthouses; it has altered the character of the light itself in subtle ways. The classic rotating Fresnel lens produced a flash whose duration and intensity varied as the lens revolved, creating the smooth rise-and-fall appearance that experienced mariners learned to associate with particular lights. An LED array with an electronic flasher produces a crisp, square-edged flash — instantaneous onset and cutoff — that looks different in character even when the period matches that of the old lens.
Light authorities have taken different approaches to this change. Some have accepted the new character as the effective standard. Others have programmed the LED controllers to produce a gradual rise and fall in intensity that better resembles the classic rotating-lens flash. In either case, the essential identifying information — the period, the number of flashes, the colour — is preserved, and the light remains correctly identified in the relevant light list.
The Future of the Lighthouse Signal
Solar-powered LED lighthouses are now the global standard for new installations and for the modernisation of existing structures. The International Association of Marine Aids to Navigation and Lighthouse Authorities, known as IALA, has published technical guidelines for solar power system design that are used by lighthouse authorities worldwide, covering panel sizing, battery specification, charge controller requirements and the minimum battery reserve appropriate for different latitudes and weather conditions.
The AIS transmitter, which broadcasts a lighthouse's identity, position and light character in digital form on the marine VHF band, is increasingly fitted alongside or in place of the traditional optical signal. Many modern lighthouse installations are in effect dual-mode: they emit an optical flash for vessels without electronic aids, and an AIS signal for those equipped with modern navigation systems. Both functions draw from the same solar-charged battery bank.
Open the map to explore active lighthouses around the world and see which stations have been modernised with solar and LED technology.
What Has Been Lost and What Remains
The lighthouse keeper is gone from the great majority of the world's lighthouses. The discipline, the isolation, the careful management of fuel and light that defined the keeper's life have passed into history. What remains is the light itself: still flashing, still exactly on character, still visible at the same range as when a keeper climbed the stairs each evening to start the lamp. The technology has changed completely, but the function — a fixed, reliable, precisely characterised signal in the darkness — is unchanged. Solar power and LEDs have made that signal cheaper and more reliable than it has ever been.