| Ultracapacitors Help P21 To Provide Fuel Cell-Based Backup Power For Telecoms Introduction P21 develops, produces, and sells fuel cell based backup systems. They are used in base station networks where conventional batteries often operate at their technical limits. With its patented, hydrogen-powered PEM fuel cells, P21 is the leading supplier of fuel cell power for use in the telecommunications industry: as backup solutions, primary supply in combination with renewable energies, energy saving systems with unattended remote control operation While fuel cells are an excellent technology for backup power, they take a few seconds to come online and provide full power. P21 therefore needed to select an energy storage technology to provide short-term "bridge" power to cover this gap. It chose ultracapacitors from Maxwell Technologies, as these provided a number of advantages over batteries for this application. Requirements for backup power in telecoms For many mission-critical installations, backup power generation equipment is essential to ensure continuous operation. The telecoms industry, in particular, needs to ensure that its mobile phone base stations have power at all times, and are able to keep functioning even if there is an interruption to the grid electricity supply. Traditionally, the technology chosen for back up power was batteries. More recently, fuel cells have been used for base station power backup. PEM (Proton Exchange Membrane) fuel cells are today highly-efficient energy conversion devices that can operate continuously for as long as hydrogen Is available. They are environmentally benign and can provide a reliable source of back-up power for many applications. They provide high reliability and savings in cost, space and weight, and can withstand harsh conditions of high temperatures and humidity. P21 fuel cell systems have advanced control and online monitoring features, to ensure they are safe in operation. Fuel cells have proven reliable in practice, with over 1 billion hours of operation over 10 years in back-up power applications. Based on a 10-15 year useful life a fuel cell based solution can be around 30% less expensive than a battery backup solution. However, a typical P21 fuel cell has a start up time of about 5 seconds to achieve full power. This means that a short-term source of bridge power is still required to ensure continuous operation. While batteries have often been used with fuel cells to provide this bridge power, they have a number of disadvantages, including relatively short lifetime, regular maintenance requirements, and poor performance in extreme temperatures. For | 
