Lithium Goes Mainstream for Cable Broadband Outside Plant

By Toby Peck, Greg Laughlin

As utility uncertainty continues to impact network resiliency, cable operators are looking for new solutions in energy storage to extend their network availability. Lithium-ion has the attention of the cable broadband industry for its advantages in high energy density and service life. To determine what is best for your network, there are several factors to consider.

Energy storage considerations for cable broadband

• Load profile — Active elements in the cable broadband outside network include traditional nodes and amplifiers, remote-PHY devices (RPDs) and more recently PON OLTs, strand-mounted Wi-Fi access points and small cell radios. These powered elements are considered constant power loads, meaning that their consumption of power does not change throughout the day.
• Runtime requirements — Utility outages have been increasing in duration and frequency, placing more responsibility on cable operators to ensure network resiliency. At the same time, operators are being challenged to reduce their overall carbon footprints. Using stored energy to increase network runtimes during extended utility outages reduces the need to dispatch trucks carrying curbside generators, saving costs while reducing carbon emissions.
• Cycling frequency — Typical cable broadband network sites only drain batteries during infrequent outages, so battery cycle frequency is not a large concern. Sites served by poor quality utility power, (e.g., power sags, surges, or noise) may benefit from an energy storage solution designed for more frequent discharging.
• Site limitations — Every unique site may have limitations such as pole weight restrictions and local government codes. Adding capacity may not be as simple as adding more batteries.
• Environmental resilience — Batteries are generally averse to extreme hot or cold environments, so choice of energy storage must consider thermal resilience.
• Safety — Safety is a key consideration, especially when considering chemistries like lithium-ion that are prone to thermal-runaway if not designed correctly.
• Recyclability — Battery recycling is not only an environmental concern; it also impacts the overall cost of ownership of the energy storage system. Some chemistries like lead-acid are highly recyclable with monetary incentives from independent recyclers. Other chemistries may not be as profitable to recyclers and will require payment for disposal.

Lithium-ion for cable broadband

While there are several emerging technologies in energy storage that hold promise for cable broadband networks, lithium-ion is commercially available, and is a promising option for extending network resiliency. Lithium-ion’s higher energy density can add significant runtime to network sites without increasing the size of existing cabinets. Lithium-ion’s high cyclability will extend the service life of the battery system, and its slow discharge rate allows operators to warehouse batteries longer without the need to recharge.

Each lithium-ion chemistry has some risk of thermal runaway. The best way to mitigate any safety concerns is in the design of the battery solution. UL (Underwriters Laboratory) has established requirements and test methods designed to minimize the risk of lithium-ion thermal runaway. While UL 1973 tests at the battery level for abusive test situations such as overcharge, drop test, crush test etc., UL 9540 and 9540A provide a much more stringent test at the energy storage system level to account for additional safety precautions. Meeting UL 9540A is the highest level of safety protection applied to lithium-ion systems and should be considered the benchmark for deployable solutions.

How do I decide what’s best for my network?

The prudent approach to deciding the most suitable energy storage solution is to consider all factors including the overall cost. Reviewing the pros and cons for each unique site can reveal the best energy storage alternative. Whether the selection is lithium-ion or lead-acid, the energy storage must carry the load to ensure continuous network operation.

Toby Peck,

EnerSys

Toby is the Sr. Director of Broadband Product Management for EnerSys (formerly Alpha Technologies). He is responsible for the definition, planning, and development for broadband products and software. He has 14 years in the cable broadband industry. In previous roles, he focused on improving operational efficiency in outside plant.

Greg Laughlin,

EnerSys

Greg Laughlin is a strategic marketing manager for broadband markets at Enersys. In his 15+ years at Enersys, formerly Alpha Technologies, Greg has served as a senior product manager for DOCSIS^® power supply communication and gateway products.

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