Tridente-class submarine

The Tridente-class submarines, also designated as U 209PN, are diesel-electric submarines based on the Type 214 submarine developed by Howaldtswerke-Deutsche Werft GmbH (HDW) for the Portuguese Navy.

This class of submarines was acquired by Portugal to replace the previous submarines of the Albacora-class submarine, then being operated by the navy. Originally, HDW proposed the Type 209 submarine (U-209) during the competition, but decided to later enter a new proposal based on the Type 214. It is for this reason that the Tridente class is commonly designated as the U 209PN.

The class and its ships are the first to not be named after marine animals, thus breaking a tradition retracing back to 1913, when the first submarine entered service with the Portuguese Navy.

Ships
The Tridente-class submarines are wrongly classed in the "diesel-electric" class. Their propulsion is exclusively electric, with electric motors powered by batteries. These batteries may be charged while submerged by "fuel-cells" (inverse electrolysis) for which, this submarine carries a huge supply of liquid oxygen and hydrogen. Also, and solely as a second solution for recharging the batteries, this submarine carries two powerful diesel-electric generators (1,000 KVA) for use only when surfaced, or at snorkel depth.

Submerged, from Lisbon, Portugal, submarines of the class may reach the Cape of Good Hope and return, in 15 days.