2.2.1. Modifications Made to TECs in Order to Perform Automated Maneuvers

The GIT-ERM research group designed the gravity-based first generation TEC presented herein in order to enable it to perform automatic emersion/immersion maneuvers. This is done by using small guide wires and controlling the ballast water inside the device [24,25]. The control of the ballast water permits the implementation of a closed-loop depth and/or orientation control, which, in turn, allow(s): (i) the extraction of the main power generation unit from its normal depth of operation (on the seabed) to the surface of the sea, and (ii) it to be returned from the surface to its base on the seabed. Figure 8 illustrates the shape of a gravity-based first generation TEC capable of performing automated maneuvers and its distribution equipment. The main differences between the gondola of the TEC illustrated in Figure 3 (designed for manual maneuvers) and the gondola of the TEC depicted in Figure 8 (designed for automated maneuvers) are the following: (a) the places in which the ballast tanks and their associated pumping system are located, and (b) the shape of the gondola, which has been modified in order to attain neutral buoyancy when the ballast tanks are half full. In the system depicted in Figure 8a, the gondola has been increased longitudinally as opposed to increasing its diameter. This has been done so as to optimize its hydrodynamic performance [37]. A detailed description of the design modifications and the behavior of the modified gravity-based TEC, along with interesting laboratory experiments, can be found in [23–25,37].

**Figure 8.** First generation TEC designed for automated maneuvers: (**a**) shape of the gondola and (**b**) distribution equipment.
