Île de Ré's Baleines lighthouse, a reminder of energy transitions

Every summer, the population of the island of Ré increases tenfold, from just over 17,000 in winter. Holidaymakers flock to the beaches and 110 km of cycle paths.

Christian de Perthuis, University of Paris Dauphine - PSL and Boris Solier, University of Montpellier

One of the must-do vacation activities is a visit to the Phare des Baleines (Whale Lighthouse). Located on the north-western tip of the island, the building was named after the whales that once came ashore on the beach below.

From its 57-metre height, this construction offers a unique panorama to the daredevils who climb the 257 steps to the summit. Its history is also that of the many innovations that have made it possible to project light ever further.

The Phare des Baleines is thus an excellent marker of past energy transitions, analyzed in a recent study by the Climate Economics Chair.

From whale oil to electrification

The story begins under Louis XIV. Construction of the Tour des Baleines, located between the current lighthouse and the coastline, was commissioned by Colbert, then Secretary of State for the Navy, and completed in 1682 under the supervision of Vauban.

Originally, the tower burned fish and whale oil, which had a low light output and reduced efficiency, as the burning oil tended to burn out the lantern's glass panes. Whale oil was the fuel of choice at the time, so much so that the world's lighting needs dangerously accelerated the hunting of this now-protected marine mammal.

As early as 1736, coal was substituted for whale oil as a fuel. It was burned in a stove topped by a dome to reflect the light. This change improved lighting efficiency, but required large quantities of coal to be transported. Records from the Cordouan lighthouse, located at the mouth of the Gironde, reveal that the keepers had to bring up between 100 and 150 kg of coal every day to fuel the fire. That's why coal was later replaced by kerosene, before switching to electricity in the early ^20th century.

The switch from whale oil to coal improved lighting performance. For the same mass, coal's calorific value - i.e. the amount of energy produced during combustion - is far greater than that of whale oil. Similarly, the substitution of oil for coal subsequently increased lighting efficiency.

The mobilization of increasingly dense primary energy sources is one of the major characteristics of the energy transitions analyzed by Vaclav Smil. Using a historical approach, the author shows that this densification has led to an unprecedented worldwide increase in energy consumption and_CO2 emissions of fossil origin.

Leveraging efficiency gains

In addition to improvements in the energy sources used by the lighthouse, there were innovations in energy transformation and light diffusion techniques, thanks firstly to the invention of the stepped lens by French engineer Augustin Fresnel (1822), and then to the electric bulbs invented by Joseph Swann (1878) and Thomas Edison (1879).

The old Baleines tower, deemed to have insufficient range, was replaced in 1854 by the current lighthouse, which is twice as high. It was one of the first to benefit from the Fresnel lens system, still in use today, giving it a range of around 50 km.

In 1904, a steam power plant replaced the previous combustion systems. The Phare des Baleines was not connected to the electricity grid until the 1950s. With electricity, the lighthouse's range was multiplied once again, thanks to the efficiency of light bulbs in transforming energy into light.

Technical advances in the conversion of energy into light were even more decisive in increasing the range of the lighthouse than were increases in the quantity and quality of the primary energy used. Here we return to the conclusions of Fouquet and Pearson 's work showing the major role of efficiency gains in lowering lighting costs over the past two centuries.

A more general lesson for energy transitions: as much as the mix of energy sources on which debates often focus, the chain of transformation of these sources into end uses is a decisive link in energy systems and their transformations.

From light to satellites

The etymology of the word "lighthouse" comes from the Greek Pharos, the name of the island where the famous Alexandria lighthouse stood, which disappeared over 700 years ago. Modern lighthouses have not disappeared, but most of them are now listed as historic monuments, their operation, use and purpose having evolved considerably since their construction.

The arrival of electricity initially paved the way for the automation of lighthouses. The Baleines lighthouse saw its last keeper leave in the early 2000s, when its operation was fully automated.

Advances in satellite-assisted navigation, which now equips the majority of boats, have subsequently drastically reduced the usefulness of lighthouses, to the point where some are now for sale. The Lighthouse of the Whales will certainly continue to sweep the ocean with its beams of light for a long time to come, even if its original purpose - navigational guidance - is now somewhat obsolete.

Descending the lighthouse's 257 steps, visitors are sure to wonder about the current energy transition. Has the switch from lighthouse to satellite guidance of ships reduced the need for fossil fuels, and consequently_CO2 emissions?

It's probably the opposite: the primary energy used by information technologies is not directly visible, like whale oil or the coal hoisted to the top of ancient lighthouses. But it is high, because satellite imagery involves a whole infrastructure that consumes grey energy. Above all, satellite guidance enables a multiplication of end uses and contributes to the very rapid growth of maritime navigation: one of the sources of CO₂ the fastest-growing market in the world!

Christian de Perthuis, Professor of Economics, founder of the Climate Economics Chair, Paris Dauphine University - PSL and Boris Solier, Senior Lecturer in Economics, research associate at the Climate Economics Chair (Paris-Dauphine), University of Montpellier

The original version of this article was published on The Conversation.