Permanent load shifting and UPS functionality at a Telecommunications site using the VRB-ESS™ -a case study

Abstract

Telecommunication facilities of all types from small cellular radio sites to microwave repeaters and larger point-of-presence (POP) and switching hubs, all require uninterruptible power supply (UPS) to ride through short duration interruptions. This function is supplemented by back up diesel generators for support in the event of long term outages. Conventionally the UPS functionality has been provided through the use of lead acid batteries. In many off grid or weak grid installations, diesel generation is often the only source of power, sometimes supplemented by photovoltaic power or even wind turbines. A novel concept which is being implemented at a POP facility in California at one of the USApsilas largest cellular radio network providers is to use the battery storage to provide both the basic UPS ride through function as well as to peak shave demand on a permanent basis. The system will be rated 20 kW with 9 hours of storage, 6 for permanent load reduction and 3 hours for UPS functionality. This is only possible with storage systems that can be deep cycled thousands of times without significant degradation and also where it is possible to independently tailor the storage duration to match the electricity tariff structure. The project will be discussed showing the use of a VRB flow battery and the potential economic savings for different tariffs that may result for a range of battery efficiencies.