Author: C. Y. Kuo/ S. C. Shen, Department of Systems and Naval Mechatronic Engineering, National Cheng Kung University

Saury fishing is one of the primary fisheries in the Northwest Pacific; saury fishermen use incandescent lamps to attract shoals of fish to catch them. Although the cost of using incandescent lamps is relatively low, the efficacy and water penetration of such lamps are low, so a large amount of power is required to attract shoals of fish. In Taiwan, an average distant water saury fishing voyage consumes 700 kL of fuel, costing approximately US$ 400k, which is half of the operating cost of a voyage. The incandescent lamps alone consume 38% of this fuel, costing approximately US$152k per voyage [1], which brings a heavy financial burden to fishermen.

Light emitting diodes (LEDs) have a wide range of applications; they are energy efficient, light, and durable with low startup voltage, quick response, and excellent shock resistance. They are more durable than incandescent lamps [2], and research has already examined their use in fishing contexts. Based on the literature studies, this research employed ray tracing to design a set of secondary lenses, and adopted intelligent controller to construct a LED fishing lamps. The intelligent LED fishing lamps were installed on a saury fishing boat for fish catching experiments, comparing fuel consumption and capture efficiency. The intelligent LED fishing lamps are show Fig 1. The experimental boat’s light field on the sea surface as show Fig.2.

Simulation of the luminous power, maximum irradiance, and average irradiance of the effective fish gathering range was designed using optical software. Table III presents a simulation comparison of the optical projection over the surface of a fishing net from the whole boat. The optical simulation was divided into four modes: 72IL; 72LoL; 72LL; and24LL+48IL, where is (a) Incandescent lamp (IL); (b) LED without lens (LoL); and (c) LED with lens (LL). As shown in Table III, the maximum irradiance of 72IL was 12.03 W/m2, recorded 1 m from the starboard side of the boat. The irradiance decreased with distance from the starboard: the irradiance at 10 m from the starboard side was only approximately 1 W/m2, and the average irradiance was 6.72 W/m2. The maximum irradiance with 72LoL was 9.04 W/m2, which was lower than that of 72IL (75.1%) and occurred 1 m from the starboard of the boat. The irradiance decreased with distance from the starboard, with similar properties to the light distribution as those seen with 72IL; however, the average irradiance was 5.03 W/m2, which was still lower than that of 72IL (74.9%). Nevertheless, the light distribution projected by 72IL and 72LoL were essentially equal. However, because the irradiance of 72LoL was only 50% of 72IL, the performance remained limited, despite its greater photoelectric efficiency.

The light distribution of 72LL differed from that of 72IL and 72LoL.The maximum irradiance was 18.91 W/m2, recorded 3 m from the starboard side of the boat. Additonally, the irradiance at 1 m to 5 m from the starboard was greater than 30 W/m2, and the average irradiance was 9.61 W/m2. 72LL was better than 72IL and 72LoL on irradiance. However, after considering the limitations of the boats to be used in the experimental stages in terms of fitting LED lamps, a combination of 24LL+48IL was simulated. The results revealed that the maximum irradiance was 13.46 W/m2, which was 71.2% of 72LL, and the average irradiance was 7.66 W/m2, which was 79.7% of 72LL an acceptable distance. Additionally, the light distribution projected was similar to that of 72LL: the area with over 30 W/m2 irradiance was 4-m-long, aided by the supplementary light of the IL poles. Considering the usage habits of saury fishing boats, the subsequent experiments were conducted using the 24LL+48IL setup.

The experiment was conducted using the 24LL+48IL setup. A total of 24 out of the 72 IL poles on the boat were replaced with 24 LL lamp poles so that the IL and the LL were arranged alternately on the starboard side and port side. A 10×50 m2 area was marked on the land, and a measurement point was marked every 5-m along the 50-m long and every 1-m along the 10-m-wide for a total of 55 measurement points. The photometer was used to measure the irradiance, with the sensor head placed horizontally on the ground while taking measurements. Therefore, once we determined that the illumination distance on land and sea were the same, we measured the light distribution on land.

The measurement light distribution results of the 72IL are shown in Table IV. The average irradiance was 6.45 W/m2, which was a difference of 4.2% reduce to the simulation result of 6.72 W/m2. The maximum irradiance was 12.84 W/m2, which was a difference of 6.3% increase to the simulation result of 12.03 W/m2. The measurement light distribution results of the 24LL+48IL are shown in Table V. The average irradiance was 7.3 W/m2, which was a difference of 5.0% reduce to the simulation result of 7.66 W/m2, which was 1.14 times of 72IL. The maximum irradiance was 14.76 W/m2; which was a difference of 8.8% increase to the simulation result of 13.46 W/m2.

Numerous differences were observed between the two modes along the vertical axis. The largest difference between 72IL and 24LL+48IL was between 5 and 8 m, where the difference was over 30%. Specifically, the largest difference was at 7 m. The difference was smallest at 10 m because this range exceeded the irradiance center of the LEDs. The irradiance at the center of the net was higher for 24LL+48IL than 72IL, highlighting the spotlight advantages of this setup. Compared with 72IL, the LED lamps effectively trapped the light at the center of the net; this would cause fish shoals to gather in the center of the net and avoid loss of catch due to insufficient illumination. Therefore, the lens design was adopted for the LED lamps to decrease the LED’s light-emitting angle. This created fuller and more uniform illumination within the illumination range, diminishing the LED energy loss.

ENERGY EFFICIENCY AND CATCHING EFFICIENCY EXPERIMENT

For the catch experiment, three voyages were conducted in the Northwest Pacific over a total of 1018 operated days, consuming 3716 kL of fuel and yielding 11,114 MT of catch. Boat A and Boat B had a displacement tonnage of 1000 tons, and they were saury stick-held dip net boats with 50 crewmembers and a 50-m-wide and 10-m-long saury stick-held dip net. The boats had 72 lamp poles and cold storage with a capacity of 600 MT. Each voyage included the operations at sea (i.e., catching, rest, and transportation) but excluded the 20 days of travel back and forth the fishing ground. Each day was a full 24 hours, including night-catching operations, and stopping for rest during the day. The catching method was as follows: after dark, the fishing lights were deployed to gather the fish; then, after the fish had gathered for 1–3 hours, the stick-held dip net was used to catch the fish. These were repeated until dawn. Catch experiment are on Table VI.

Fuel consumption was calculated as follows: First, subtract the remaining amount of fuel at the end of the voyage from the amount of fuel before the start of the voyage. Then, add the amount of fuel received from an oil barge during the voyage. Finally, subtract the amount of fuel consumed travel to and from the fishing ground (the data source was the measurement of the fuel consumption of onboard oil tank). Fuel value was US$667/kL. Catch information was provided by the National Fishermen Association, Taiwan, after purchase and weighing of the catch. The experimental results of voyage fuel consumption and catch efficiency were obtained through the following analyses and evaluations: (1) fuel consumption analysis; (2) lamp pole efficiency evaluation (daily average catch/lamp number), in which the daily average catch volume for each lamp pole was evaluated; (3) fuel efficiency evaluation (daily average catch/daily average fuel consumption), in which the catch volume per day per kiloliter of fuel used was evaluated; and (4) Fuel cost (fuel costs/catch volume), in which the fuel cost required per ton of catch volume was evaluated.

(1) Fuel consumption analysis: The fuel consumption of Boat A was analyzed in relation to the 755 kL of fuel consumption in the Voyage I. In the voyage II and III using 24LL + 48IL, Boat A used only 510 kL and 596 kL of fuel, denoting savings of 26.3% and 20.6%, respectively. The fuel consumption of Boat B was also analyzed in relation to the 670 kL of fuel consumption in the Voyage I. In the III voyage using 24LL + 48IL, the fuel consumption of Boat B was 565 kL, representing a saving of 13.7%. Therefore, the voyages with LED fishing lamps provided a saving of 20.2% greater fuel efficiency than did those with conventional lamps.

(2) Lamp pole efficiency evaluation: For the voyage I, II, and III, the lamp pole efficiencies of Boat A were 0.16, 0.15, and 0.14 MT/lamp, whereas those of Boat B were 0.15, 0.14, and 0.15 MT/lamp. These results revealed no significant differences in lamp pole efficiency among the different voyages and boats. Therefore, the daily catch volume was the same regardless of whether 24LL + 48IL or 72IL was used.

(3) Fuel efficiency evaluation: For the voyage I, II, and III, the energy efficiencies of Boat A were 2.85, 3.54, and 3.03 MT/kL, whereas those of Boat B were 2.89, 2.43, and 3.33 MT/kL. The results revealed that when Boat A and Boat B used 72IL, the energy efficiencies were 2.85 and 2.89 MT/kL, respectively, demonstrating no significant differences. In the voyage II, Boat A used 24LL + 48IL, with an energy efficiency of 3.54 MT/kL. By contrast, Boat B used 72IL, with an energy efficiency of 2.43 MT/kL; thus, the lamp setup on Boat A was more energy efficient than that on Boat B. In the III voyage, both boats used 24LL + 48IL, with energy efficiencies of 3.33 and 3.03 MT/kL, respectively, demonstrating no significant differences. These findings show that the use of the 24LL+48IL lamp setup can surely improve energy efficiency.

(4) Fuel cost: For the voyage I, II, and III, the results of catch by fuel cost for Boat A were US$237, US$190, and US$231/MT, and those of catch by fuel cost for Boat B were US$233, US$269, and US$194/MT. No significant differences were observed between Boat A and Boat B during the Voyage I when both boats used 72IL. In the voyage II, the costs of Boat A were only 70.63% of those of Boat B, confirming that the costs of Boat A equipped with LED fishing lamps were lower than those of Boat B using 72IL. In the voyage III, both Boat A and Boat B used 24LL + 48IL. The costs of Boat B were reduced to US$194/MT, which were better than those of Boat A, primarily because the catch volume of Boat B was greater than that of Boat A. In terms of the Catch by Fuel cost, Boat A was associated with savings of 19.8% and 2.5% in voyages II and III, respectively. Boat B saved 16.7% in voyage III. Therefore, the voyages with LED fishing lamps provided a saving of 13% Fuel cost than did those with conventional lamps.

Onsite observation revealed that LL could effectively compensate for the inadequate irradiance at the center of the net in the LoL and IL; the light from LL was also more concentrated, allowing for deeper water penetration. Onsite observation confirmed that the 24LL+48IL setup enabled light to penetrate deeper into the water; the water penetration of 72IL was relatively shallow, and, because of the difference in incidence angle, the amount of light reflected by the sea surface was also greater than 24LL+48IL. The captain and operating crew members also noted that the power generator output required adjustment before switching on or off the ILs due to their higher power consumption, meaning careless handling could damage the power system. Because the LED lamps consumed relatively less power, this problem was avoided. In terms of cost recovery, currently, the cost of an LED lamp pole is approximately US$3k, and complete installation of 24 LED lamp poles (24LL + 48IL) costs US$72k. Using the 13% savings calculated in the Fuel cost as a standard, the reductions in fuel consumption for each voyage can save US$59k, thus, a return on investment for exchange can be achieved by the second voyage.

CONCLUSIONS

The study employed ray tracing to design a lens and a light distribution pattern for LED fishing lights used in saury fishing. The purpose of the design was to enhance irradiance within the net area. Measurements revealed that the average irradiance of the designed LED pattern 24LL+48IL was 71.2% of that of 72LL. The test results indicated the following advantages of using LED fishing lights: (1) The use of LED lamps did not affect catch volume, and this was evident across findings for various voyages and boats; (2) the fuel efficiency evaluation revealed that the use of 24LL+48IL in this experiment resulted in significantly lower fuel consumption; (3) compared with the cost associated with use of 72IL, the fuel cost per MT of catch of using 24LL+48IL exhibited savings of 13.0%.Overall, the proposed lens enhanced the functionality of LED fishing lights for use on saury fishing boats by focusing light into the net; moreover, use of the proposed design resulted in significantly lower energy consumption.

ACKNOWLEDGMENT

The authors would like to thank Fisheries Agency, Council of Agriculture (FA.COA) for their supports to the project. (granted number: 107-AS-14.2.7–FA-F1(3))