The raft was equipped with a 60 cm LED lamp (AlumiGlo
SuperBrite 2400-DC GREEN, Fishing Lights Etc, LLC) which produced a green light of 2400 lumens and had a power consumption
of 2.5 Ah. The lamp was placed underneath a curved piece of inox
(65 × 20 cm) that acted as a reflector and was hung onto one side of
the raft with two inox arms, so as to be just above the water surface
(Fig. 1). This design fulfills the Greek legislation which prohibits the
use of underwater lighting in fishing. It must be pointed, however,
that during swell and swinging of the raft, the lamp did enter (or
was splashed by)the water. This was not an issue for the particular
lamp as according to the manufacturer it is suitable for underwater
use.
The electric circuit inside the Styrofoam box was simple and is
presented in Fig. 2. In daylight the PV charged the battery (BAT)
through a controller (C) that protected the battery from overcharging (max 13.85 V), but also from deep discharging due to the lamp’s consumption (min 11.40 V). A digital voltmeter (V) to measure the battery’s voltage was connected to a switch (S) and fixed with silicon into the top cover of the Styrofoam box. The lamp was powered by the controller via a digital timer (T), which was programmed to turn it on and off at specific times. To enable external charging of
the battery (without the use of the PV), a waterproof plug (P) was
fixed into the wall of the Styrofoam box with silicon to allow connection with an external 220 V charger. This plug was connected
to a double switch (MS), which was also the master switch for the
entire electric circuit. The MS was placed into a plastic housing
with a screwed cover to ensure waterproofness and the unit was
fixed with silicon into the top cover of the Styrofoam box. The final
weight of the fully-equipped lamp raft was 48 kg and the total cost
was 750 Euros. The cost of each component is presented in Table 1.