By Stu Bartsch, Product Manager for Copper Solar and Building Wire at General Cable
Environmental concerns and the need for energy independence are catalyzing the growth of solar power. Not only can solar transform the way the world generates electricity, but these systems are extremely versatile with the ability to place solar photovoltaic (PV) panels in a variety of environments — from small-scale distributed generation systems on rooftops, to utility-scale solar energy plants in fields and deserts.
Recent trends surrounding solar energy are focused on ensuring that these systems remain economically viable. As such, technological developments in the cable that make up solar power generation, transmission and distribution systems are aimed at improving efficiency, reducing cost and ensuring long-term reliability and performance. Simultaneously, the industry is striving to establish codes and standards for best practices and safe design of cabling systems. These trends are driving developments in cable technology, while also introducing key challenges for manufacturers.
Economically generating electricity from renewable sources requires a cabling system engineered to optimize efficiency and minimize line losses. This allows more of the generated power to reach substations where it is transmitted to the grid. To optimize efficiency, cables used at the point of solar power generation offer a higher voltage range of up to 2000V versus the standard 600V rating for conventional applications. Medium-voltage cables used between transformers and substations are being re-engineered to provide better efficiency over the life of the cable through cooler operation and lower line loss.
Cables used in solar generation differ from those used in wind generation in that they must be designed to withstand long-term exposure to sunlight. To maintain long-term performance and reliability, solar cables have been developed to resistant UV, ozone and water absorption, as well as provide excellent flexibility for sub-zero conditions and deformation resistance during prolonged exposure at high temperatures.
Given the often-extreme installation environments for solar power systems, coupled with the need to save time and ensure reliability, pre-connectorized cable solutions have been developed. Ideal for utility-scale generation systems, these solutions enable fast, easy connections, simplifying installation while removing the inconsistencies associated with field termination. Along those same lines, DC feeder cables for connecting combiner boxes to inverters are now offered as all-in-one metal clad cables that increase reliability and eliminate the need to install conduit. PV cables are also being engineered in a full array of colors to easily identify source, output and inverter circuits without the need for time-consuming marking tape or tagging cables.
Despite the promising growth of solar power and related cable developments aimed at ensuring its economic viability, this emerging market is not without challenge. Codes and standards are struggling to keep pace with new technologies and applications, while a relatively new contractor base is in need of continuous on-going training to stay one step ahead of evolving installation practices. As such, the industry has seen a variety of cable designs and practices, many of which may not necessarily support long-term solar needs. Application-specific cables and contractor certification are paramount to ensuring the economic viability of solar power systems.
Cable manufacturers are challenged with balancing up-front costs with long-term reliability while continually meeting evolving requirements and trends, from developing cables for new micro inverter technology where DC power is converted to AC at the panel, to meeting more stringent fire ratings, test methods, UL and CSA standards, National Electric Code requirements and global standards for halogen-free, fire-retardant and low-corrosive gas emissions. To meet these advancing trends and standards, develop application-specific cables, and ensure the performance and reliability to support the long-term needs of solar applications, manufacturers must be committed to solar energy with significant investment in R&D efforts and a strong presence in the market through continued participation with standards bodies, utility regulators and renewable developers.