Lighthouse tech

Leaving Flåm and en route to Bergen I could not help notice numerous automatic lighthouses sprinkled across the fjords and on tiny land-masses. Traditionally the concept of a light house springs to mind the manned nature of these navigation aids with a resident keeper. But the rugged and weather challenged Scandinavian coastline demands sophistication.

In 1896 while studying at the Polytechnische Hochschule under Prof. Aurel Boleshaw Stodola, Nils Gustaf Dalén, son of a farmer and a Swedish mechanical engineer became acquainted with Stodola and Adolf Hurwitz’s work on automatic control systems.1

He returned to Sweden in 1897 and began as an entrepreneur. His significant contribution, together with his partner Henrik von Celsing, was in applying acetylene combustion to lighting fixtures and heating devices. Much brighter than petroleum gas, acetylene, a popular method of street lighting (a.k.a gas-lighting) offered significant advantages for lighting or heating in remote locations, mobile installations, in railways, and in automotive vehicles before the wide-spread access to electricity.2 Acetylene lighting proved to be a great application for lighthouses and light-buoys along the coastlines and shipping routes. But there was a problem: the acetylene’s explosive nature during transportation (in pressure vessels) inhibited its adoption in such applications. Dalén and his partners turned their attention to this problem.

By 1895 it had been discovered that acetylene could be prepared from calcium carbide on a commercial scale. But attempts to store it in light buoys and have acetylene escape under the action of water supplied automatically had proven to be inconvenient, unreliable, and unworkable in cold weather. Two French chemists, Claude and Hess discovered that acetylene could be dissolved in large quantities in acetone and the resulting solution wasn’t unstable to be explosive. It could further be transported safely if it was compressed in a porous and sufficiently-elastic mass inside pressurized shipping containers. Dalen discovered and patented such a mass and named it after his company, AGA. The aga mass is an artificially developed porous substrate, described thus in the patent:

The mass embodying the invention consists, broadly speaking, of lumps formed of porous material bound together by means of a suitable binding agent or cement, such, for example, as good Portland or hydraulic cement, a cement consisting of a mixture of zinc oxide and zinc chloride, etc., the voids between which are filled with a porous fibrous material or with a powdered or granular material.

The result was one of extreme fuel efficiency. For example, when used in maritime lighting, petroleum gas had to be burned in flashes lasting about six seconds, and with the valve-system available at the time, one litre of gas generated 50 flashes. In comparison Dalén’s system delivered several thousand short but brilliant flashes for a litre of acetylene. The increased number of flashes enabled a larger coding alphabet for navigation signals. Not to be done with he further designed a special Sun valve (Solventil) in 1907 that turned the apparatus off at sunrise and back on when sunlight disappeared. Using an arrangement of four metal rods inside a glass cylinder — three highly polished, surrounding the fourth dark rod, he invoked differential expansion and contraction of rods to release & cut gas supply as the rods absorbed heat from Sun at dawn & cooled at dusk respectively. The gas would be lit by a small, always burning pilot light.

Before Dalén’s system, a lightship in Sweden cost Kr 200,000 with an annual maintenance cost of Kr 25,000. An automatically operated signal buoy costing Kr 9,000 with an annual maintenance of only Kr 60 could now replace this. In 1911 AGA Company was contracted to provide lighthouse system for the entire Panama Canal, and by 1912 an increasing number of coastal installations in Sweden and several parts of the world had installed the super-efficient and automatic Dalén lighting system.

Blockhusudden lighthouse, Stockholm
Blockhusudden lighthouse, Stockholm.

As we cruised along Djurgarden this August, we saw the Blockhusudden lighthouse (above), which was one of early AGA lighthouses. It operated uninterrupted from its installation in 1912 until electrification in 1980, having consumed 1.8 million liters of acetylene and emitting 400 million flashes in 68 years!

Dalén, for his work on the Dalén light and revolutionizing lighthouse technology, received the Nobel Prize of 1912 (in the category of gases), but not before permanently losing his sight in an accident involving acetylene explosion.

Despite this, there is no shortage of books, articles and people in the scientific community who think he was unworthy or least qualified to receive Nobel prize. I find this troubling. As the land of the midnight sun, with six months of darkness, Scandinavia is no less harsh or unforgiving today. I cannot imagine what it must have been in the early 1900s for its largely fishing communities — living remotely without power source, communication or navigation support, not to mention life-threatening. One really needs to traverse the rugged islands and scattered landmasses between fjords to realize its topographic severity. As an engineer and inventor whose work was immediately realized, unlike some potentially distant disruptive theory for future applications like quantum mechanics for instance, Dalén’s invention was very much in Nobel Prize’s vein “for the greatest benefit to mankind”, and I think it was very well deserved.

  1. Robert N. Clark, Historical Perspectives – Nils Gustaf Dalén (1869-1937): Inventor, Experimenter, Engineer, and Nobel Laureate, IEEE Control Systems Magazine, August 2003. 

  2. Dalén is also credited to introducing acetylene use for welding in Sweden in 1902, although it did not come into general use until much later.