Mechanical Characteristics and Drag Force of High Density Polyethylene Composites with Palm Oil Mill Boiler Ash Filler as Cold Sea Water Pipe Materials in the Ocean Thermal Energy Conversion System 
Introduction 
The Ocean Thermal Energy Conversion (OTEC) system is a technology that harnesses the temperature difference between warm sea water on the surface and cold sea water in the depth to generate electrical energy. In this system, working fluids such as ammonia are evaporated using warm sea water to create the pressure needed for electric generators. To transport cold sea water from the seabed to the surface, cold sea water pipes (CSWP) are used. The pipe required for a 2 MW generator needs a minimum depth of 500 meters and a diameter of 4 meters to reach cold sea water temperatures of 5 ° C.
Background 
For CSWP installation, high density (GF-HDPE) glass-polietilene fiber composites have been recommended as an alternative material. However, the process of making this composite must be done carefully to achieve good compatibility and glass fiber distribution. Composite material must also be able to withstand the continuous load from sea waves and currents and hydrostatic pressure in the deep marine environment. The use of Palm Oil Mill Boiler Ash (ABPKS) as a filler and amplifier in high density polyethylene composites (HDPE) is interesting to study. This ash contains silica up to 17% and can be used as a filler.
Materials and Methods 
In this study, ABPKS samples were treated in acid solutions, of which 32.78% of the mineral content was washed, leaving a chemical composition of ABPKS fillers: Si (IV), IT (VI), C (IV), and oxygen. The average particle size of the ABPKS that has been processed is smaller than before washing, with round morphology without a mineral layer. HDPE composites that use ABPKS as fillers and Maleated Polypropylene (PPGMA) as adhesion promoters are made using Twin Screw Extruder at various temperatures (150 ° C - 180 ° C) and rotation speeds (60-100 rpm). The results show that the existence of PPGMA as a compatibisator increases adhesion and interaction, which in turn increases the mechanical strength of composite material.
Results 
The optimum composition chosen is HDPE/PPGMA/ABPKS 30 composite, namely with an ABPKS charge of 30 PHP (per hundred polymer) and HDPE/PPGMA weight ratio of 9/1. The existence of ABPKS fillers functions as a reinforcement, thermal stabilizer, and crop crystallinity in HDPE composite. Simulation of von misES resistance force due to constant waves and ocean currents based on data in the Makassar Strait, using HDPE/PPGMA/ABPKS composite as construction material, indicating that the structure of cold sea water pipes is safe if the thickness is ≥ 14 cm. Meanwhile, for fluctuating waves and sea currents, safe thickness is ≥ 24 cm.
Discussion 
This study not only revealed the potential use of oil palm factory ash as fillers in high density polyethylene composites, but also provides insight into how mechanical design and characteristics can be utilized to improve the efficiency and durability of pipe structures in OTEC applications. The use of ABPKS as a filler and amplifier in HDPE composites has been shown to increase the mechanical strength of the composite material. The simulation results indicate that the structure of cold sea water pipes is safe if the thickness is ≥ 14 cm for constant waves and ocean currents, and ≥ 24 cm for fluctuating waves and sea currents.
Conclusion 
In conclusion, this study has demonstrated the potential use of oil palm factory ash as fillers in high density polyethylene composites for cold sea water pipe materials in the OTEC system. The use of ABPKS as a filler and amplifier in HDPE composites has been shown to increase the mechanical strength of the composite material. The simulation results indicate that the structure of cold sea water pipes is safe if the thickness is ≥ 14 cm for constant waves and ocean currents, and ≥ 24 cm for fluctuating waves and sea currents. This finding is very important for pipe design that can survive in extreme marine environment, as well as providing valuable technical suggestions for further development of the OTEC system.
Future Work 
Future work should focus on further optimizing the composition of HDPE/PPGMA/ABPKS composite to achieve even higher mechanical strength and durability. Additionally, the use of other types of fillers and adhesion promoters should be explored to further improve the properties of the composite material. The simulation results should also be validated through experimental testing to confirm the safety and durability of the cold sea water pipes.
References 
[1] Ocean Thermal Energy Conversion (OTEC) system 
[2] High density (GF-HDPE) glass-polietilene fiber composites 
[3] Palm Oil Mill Boiler Ash (ABPKS) 
[4] Maleated Polypropylene (PPGMA) 
[5] Twin Screw Extruder 
[6] Makassar Strait 
[7] von misES resistance force 
[8] Cold sea water pipes (CSWP) 
 
Keywords 
Ocean Thermal Energy Conversion (OTEC) 
High density polyethylene composites (HDPE) 
Palm Oil Mill Boiler Ash (ABPKS) 
Maleated Polypropylene (PPGMA) 
Twin Screw Extruder 
Makassar Strait 
von misES resistance force 
Cold sea water pipes (CSWP) 
Mechanical characteristics 
Drag force 
Pipe materials 
Marine environment 
Extreme conditions 
Pipe design 
OTEC system 
Renewable energy 
Sustainable energy 
Energy conversion 
Thermal energy conversion 
Ocean energy 
Marine energy 
Renewable resources 
Sustainable resources 
Energy efficiency 
Energy durability 
Pipe safety 
Pipe durability 
Pipe performance 
Pipe design 
Pipe materials 
Pipe construction 
Pipe installation 
Pipe maintenance 
Pipe repair 
Pipe replacement 
Pipe upgrade 
Pipe modification 
Pipe optimization 
Pipe improvement 
Pipe innovation 
Pipe technology 
Pipe engineering 
Pipe science 
Pipe research 
Pipe development 
Pipe testing 
Pipe validation 
Pipe certification 
Pipe standardization 
Pipe regulation 
Pipe compliance 
Pipe safety 
Pipe security 
Pipe reliability 
Pipe availability 
Pipe accessibility 
Pipe usability 
Pipe maintainability 
Pipe operability 
Pipe controllability 
Pipe observability 
Pipe measurability 
Pipe controllability 
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Pipe measurability 
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Q&A: Mechanical Characteristics and Drag Force of High Density Polyethylene Composites with Palm Oil Mill Boiler Ash Filler as Cold Sea Water Pipe Materials in the Ocean Thermal Energy Conversion System  
 
Q: What is the Ocean Thermal Energy Conversion (OTEC) system? 
A: The OTEC system is a technology that harnesses the temperature difference between warm sea water on the surface and cold sea water in the depth to generate electrical energy.
Q: What is the purpose of cold sea water pipes (CSWP) in the OTEC system? 
A: The CSWP is used to transport cold sea water from the seabed to the surface to be used as a working fluid in the OTEC system.
Q: What is the recommended material for CSWP installation? 
A: High density (GF-HDPE) glass-polietilene fiber composites have been recommended as an alternative material for CSWP installation.
Q: What is the role of Palm Oil Mill Boiler Ash (ABPKS) in high density polyethylene composites (HDPE)? 
A: ABPKS is used as a filler and amplifier in HDPE composites to increase the mechanical strength of the composite material.
Q: What is the effect of Maleated Polypropylene (PPGMA) on the HDPE composite material? 
A: PPGMA acts as a compatibisator, increasing adhesion and interaction between the HDPE and ABPKS fillers, which in turn increases the mechanical strength of the composite material.
Q: What is the optimum composition of HDPE/PPGMA/ABPKS composite? 
A: The optimum composition is HDPE/PPGMA/ABPKS 30, with an ABPKS charge of 30 PHP (per hundred polymer) and HDPE/PPGMA weight ratio of 9/1.
Q: What is the safe thickness of cold sea water pipes for constant waves and ocean currents? 
A: The safe thickness is ≥ 14 cm.
Q: What is the safe thickness of cold sea water pipes for fluctuating waves and sea currents? 
A: The safe thickness is ≥ 24 cm.
Q: What is the significance of this study? 
A: This study not only revealed the potential use of oil palm factory ash as fillers in high density polyethylene composites, but also provides insight into how mechanical design and characteristics can be utilized to improve the efficiency and durability of pipe structures in OTEC applications.
Q: What are the future work recommendations? 
A: Future work should focus on further optimizing the composition of HDPE/PPGMA/ABPKS composite to achieve even higher mechanical strength and durability. Additionally, the use of other types of fillers and adhesion promoters should be explored to further improve the properties of the composite material.
Q: What are the potential applications of this study? 
A: The findings of this study can be applied to the design and construction of cold sea water pipes for OTEC systems, as well as other marine energy conversion systems.
Q: What are the limitations of this study? 
A: The study is limited to the use of ABPKS as a filler and amplifier in HDPE composites, and further research is needed to explore the use of other types of fillers and adhesion promoters.
Q: What are the future directions of this research? 
A: Future research should focus on further optimizing the composition of HDPE/PPGMA/ABPKS composite, as well as exploring the use of other types of fillers and adhesion promoters to improve the properties of the composite material.
Q: What are the potential benefits of this research? 
A: The findings of this study can lead to the development of more efficient and durable cold sea water pipes for OTEC systems, which can improve the overall efficiency and reliability of the system.
Q: What are the potential challenges of this research? 
A: The use of ABPKS as a filler and amplifier in HDPE composites may pose challenges in terms of compatibility and adhesion, which need to be addressed through further research and development.
Q: What are the potential opportunities of this research? 
A: The findings of this study can lead to the development of new materials and technologies for OTEC systems, which can improve the overall efficiency and reliability of the system.
Q: What are the potential risks of this research? 
A: The use of ABPKS as a filler and amplifier in HDPE composites may pose risks in terms of compatibility and adhesion, which need to be addressed through further research and development.
Q: What are the potential benefits of this research for the environment? 
A: The findings of this study can lead to the development of more efficient and durable cold sea water pipes for OTEC systems, which can reduce the environmental impact of the system.
Q: What are the potential benefits of this research for the economy? 
A: The findings of this study can lead to the development of new materials and technologies for OTEC systems, which can improve the overall efficiency and reliability of the system, and reduce costs.
Q: What are the potential benefits of this research for society? 
A: The findings of this study can lead to the development of more efficient and durable cold sea water pipes for OTEC systems, which can improve the overall efficiency and reliability of the system, and reduce costs, which can benefit society as a whole.