Why is "Tour de Sol" trending?

Wikipedia Overview

The Tour de Sol in Switzerland was the first rally for solar powered vehicles. It was carried out annually from 1985 to 1993. The first event started on June 25 in Romanshorn on the Lake of Constance, and finished on June 30 in Geneva. 72 vehicles started in two classes; over 50 finished. The vehicles were powered exclusively by direct onboard solar power in addition to an initial charge of the onboard accumulators. The second class also allowed direct human power with pedals. The rally was conceived as a kind of race with the winners being those using the least time to travel the set course each day. The course was on unclosed public roads and the drivers were required to adhere all traffic rules and speed limits. The first events were very popular with thousands of spectators lining the roads and visiting the camps where the vehicles stopped each day. In later years the fastest vehicles also raced on round-circuit closed-off courses each day after arriving at the stops. From 1990 the organisers also held separate events called Tour de Sol Alpine. These included closed courses on frozen lakes and snowy roads and on unclosed mountain passes.