Battery Power - September/October 2012 - (Page 16)

FEATURE PEM Fuel Cell Systems – Reliable Backup Power Source for Remote or Extended Run Power Outages Kathy Fosberg IdaTech In today’s world, on-demand communications is needed 24/7/365, businesses, individuals, emergency systems and governments rely on their instant access to voice, data and/or video through their wireless devices to be able to function effectively. In order to provide customers with instant communications anywhere in the world, wireless telecom companies have to construct and maintain cell phone towers, radio relay stations, etc., at times in remote areas where the grid reliability is marginal. Despite grid outages, telecommunications engineers must keep these sites operating without interruption to retain customer loyalty and avoid the high cost and potentially lifethreatening situations that would arise from a wireless communications failure. In anticipation of grid outages, most wireless telecom sites have backup power systems, traditionally consisting of valveregulated lead acid (VRLA) battery strings and/or gensets. These traditional solutions aren’t always appropriate for sites requiring extended run times (days vs. hours), and they don’t always work effectively. A battery string can be expected to provide anywhere from one to four hours of backup power, but battery functionality can be impacted by age, temperature, deterioration of charge during down time and corrosion. In addition, there are environmental problems with the disposal of batteries. A diesel or propane generator, on its own or in combination with batteries, provides longer backup. A generator’s run time is based on how much fuel is available for the generator and how much power is needed to replace the electricity lost from the grid outage. The problem with generators is that they are noisy, produce noxious emissions and since they have several moving parts, need a lot of maintenance, repair and lubrication. In recent years, an alternative to the traditional backup electric power for telecom installations has become commercially available. It is the fuel cell. A fuel cell produces electricity through an electrochemical reaction. The science behind fuel cells is not new. It was discovered by Welsh lawyer-turnedscientist William Robert Grove in 1838, but it wasn’t until the mid 20th Century that the design and building of fuel cells with commercial potential was explored. The type of fuel cell commercially available today and most appropriate for use with wireless telecommunications sites is the Proton Exchange Membrane (PEM) fuel cell. These fuel cells are compact, durable, reliable, quiet and operate at peak efficiency in a wide range of climates (-40°C to 50°C) and adverse weather conditions. In addition, they have few moving parts (thus needing minimal maintenance), come in sizes ranging from 250 W to 250 kW, can readily adjust their electronic output to meet shifting power demands and offer a high energy density. Also, fuel cells are fast starting and can begin delivering electricity within seconds of activation. The typical run time for one of today’s fuel cells operating on six bottles of hydrogen (one bottle = 1 T-cylinder) is 10 hours at 5 kW of output power. For longer run times, additional bottles of hydrogen can be hotswapped into the hydrogen storage cabinet. However, there can be limitations as to how much extended backup run time can be achieved by hot swapping bottles of hydrogen. The extended backup run time can be limited by the amount of space for 16 Battery Power • September/October 2012

Table of Contents for the Digital Edition of Battery Power - September/October 2012

PRBA Battery Proposals Adopted By UN Transport Sub-Committee
The Use of Lithium-Ion Batteries in Uninterruptible Power Supplies
Monitor Your Battery Cells for Superior Reliability
Juicing Up the Battery: Cutting Edge Research Delivers Battery Enhancements
PEM Fuel Cell Systems – Reliable Backup Power Source for Remote or Extended Run Power Outages
Why Your Next Renewable System Should be Built Around Energy Storage
ICs & Semiconductors
Charging, Testing & Monitoring
Power Supplies
Industry News
Calendar of Events

Battery Power - September/October 2012