California-based TS Conductor has developed a transmission cable with carbon nanotube (CNT) composite fibres to give the core of the cable conductive and reinforcing characteristics. The line may speed up grid upgrading and boost capacity three times above the current infrastructure.
What are Carbon Nanotubes?
CNT composite fibres serve as an additive in a different host material. CNTs exhibit exceptional electrical conductivity, which various composites can leverage. CNTs exhibit remarkable inherent strength, boasting 100 times the strength of steel while weighing only a quarter as much. However, their diminutive size limits their standalone use in various applications, particularly those that require bulk material.
Different techniques for bottom-up fabrication and spinning can facilitate the alignment of CNTs within composite fibres. As one-dimensional materials, CNTs integrate into the host and result in optimal conductive and mechanical properties. The flow of electrons is restricted to the longitudinal axis, operating within a single dimension. Aligning enhances both the elastic modulus and fracture toughness of the composite.
Carbon nanotubes can significantly bolster the strength of the host material and enhance conductivity in applications that demand high strength, such as power lines. Combining CNTs with a conductive yet mechanically weaker material like aluminium results in a more balanced array of properties for transmission line applications, eliminating the necessity for heavier steel alloying components.
CNT-Enhanced Cable Core for Transmission Lines
The core of the cable is made by mixing carbon fibre with a small number of carbon nanotubes (CNTs). This combination creates a composite that has both conductivity and strength. The core is protected for its entire lifetime against environmental deterioration, including moisture plasticisation, polymer oxidation, and UV/ozone degradation, by being enclosed in a highly conductive aluminium alloy. Optical fibres can also be embedded into the wire to make them “smart,” which could benefit digitalised smart grids. In the United States, transmission lines have been built using various design methods, each with its own requirements for structural loads. Weather events, like wind, snow, and storms, can cause loads that exceed the line’s loading standards. This can lead to corrosion, strain, friction, and structural collapse. The increase in global temperatures also impacts transmission lines. These temperatures lower the thermal rating of transmission lines, which is the maximum current for a specific temperature. As a result, the wires droop considerably, posing a risk to the grid’s stability. As a result, transmission lines made of materials that can endure greater temperatures are required to avoid sagging.
How CNT Can Improve Transmission Lines
Carbon nanotubes (CNTs) have the potential to improve transmission lines in several ways significantly:
Enhanced Conductivity:
- High Electrical Conductivity: CNTs possess exceptionally high electrical conductivity, surpassing even copper in some cases. Incorporating CNTs into the conductor material can significantly reduce electrical resistance, minimizing energy losses during power transmission.
- Increased Current Carrying Capacity: This reduced resistance allows for higher current flow through the lines without excessive heat generation, leading to increased power transmission capacity.
Improved Mechanical Strength:
- High Tensile Strength: CNTs are incredibly strong, exhibiting tensile strengths much higher than steel. This enhanced strength allows for the construction of lighter and more robust transmission lines, reducing the weight and cost of supporting structures like towers.
- Improved Resistance to Sagging: Lighter lines are less susceptible to sagging due to their own weight, especially in hot weather, improving overall system reliability.
Enhanced Thermal Conductivity:
- Efficient Heat Dissipation: CNTs exhibit excellent thermal conductivity, facilitating efficient heat dissipation from the conductor. This helps to maintain lower operating temperatures, reducing the risk of overheating and potential failures.
Reduced Weight and Size:
- Lightweight Materials: The combination of high strength and low weight enables the construction of lighter transmission lines, reducing material costs and transportation requirements.
- Smaller Footprint: Lighter lines may require fewer or less substantial supporting structures, potentially reducing the environmental impact and right-of-way requirements.
How CNTs are being integrated:
- Composite Conductors: CNTs are often incorporated into composite materials used for conductor cores, combining their electrical and mechanical properties with other materials like aluminium or copper.
- Reinforcement: CNTs can be used as reinforcement materials within the conductor structure, enhancing its strength and durability.
Challenges and Future Directions:
- Cost-effective Production: Large-scale, cost-effective production of high-quality CNTs remains a significant challenge.
- Uniformity and Dispersion: Ensuring uniform dispersion of CNTs within the conductor material is crucial for consistent performance.
- Long-term Reliability: Extensive research and testing are needed to evaluate CNT-enhanced transmission lines’ long-term reliability and durability under various environmental conditions.
CNT Cable Future
The future of CNT cables holds immense promise, driven by their exceptional properties:
Enhanced Power Transmission:
- Reduced Energy Loss: Higher conductivity reduces energy losses during power transmission, improving efficiency and minimizing environmental impact.
- Increased Transmission Capacity: Higher current carrying capacity allows for the transmission of more power over existing infrastructure, addressing the growing electricity demand.
Improved Infrastructure:
- Lighter and Stronger Lines: CNT-enhanced cables can be lighter and stronger, reducing the need for massive supporting structures and minimizing environmental impact.
- Increased Reliability: Improved mechanical strength and resistance to sagging enhance the reliability of power transmission systems, reducing the frequency of outages.
Advanced Applications:
- High-Frequency Applications: CNT cables may enable new high-frequency communication and data transmission applications due to their superior electrical properties.
- Space Applications: Their lightweight and high-strength characteristics make them ideal for space-based applications like satellite communication systems.
This results in a flexible sheet of Kapton with an aligned CNT film bonded to the surface, as shown in Fig. 4 (A). The CNT film may subsequently be printed for any application using lithography techniques typical in the industry. This results in electrical devices with aligned CNTs (Fig. 4 (B)). As a demonstration, it could be quickly and repeatedly designed devices such as co-planer waveguides, which may be used as entirely carbon radio-frequency micro-switches. In this process, we could pattern carbon nanotubes (CNTs) to fit features as small as 6 µm.
However, several challenges must be addressed:
- Cost-effective Production: Large-scale, cost-effective production of high-quality CNTs remains a significant hurdle.
- Uniformity and Dispersion: Ensuring uniform dispersion of CNTs within the conductor material is crucial for consistent performance.
- Long-term Reliability: Extensive research and testing are needed to evaluate CNT-enhanced transmission lines’ long-term reliability and durability under various environmental conditions.
Despite these challenges, ongoing research and development efforts are paving the way for a future where CNT cables revolutionise power transmission:
- Material Science Advancements: Ongoing research focuses on developing more efficient and cost-effective methods for producing high-quality CNTs.
- Manufacturing Techniques: Innovations in manufacturing processes are crucial for integrating CNTs seamlessly into existing cable manufacturing processes.
- Field Testing and Deployment: Real-world testing and deployment of pilot projects will provide valuable data for refining designs and addressing practical challenges.
In conclusion, while challenges remain, the potential benefits of CNT cables are significant. Continued investment in research and development, coupled with a collaborative approach between academia, industry, and policymakers, will be crucial to unlocking the full potential of this transformative technology.
Dr. Sujit Kumar, Assistant Professor, Dayananda Sagar College of Engineering, Bengaluru.
Dr. Anubhav Kumar Pandey, Assistant Professor, Dayananda Sagar College of Engineering, Bengaluru.
Dr. Manikanta Gopisetti, Assistant Professor, Dayananda Sagar College of Engineering, Bengaluru
