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Telecommunications

Today's telecommunications networks demand backup power solutions that provide highly reliable, cost-effective power for extended periods of time . As such the availability and reliability of backup power sources are a major concern not only in the United States, but also globally. With over 220,000 cell sites nationally and increasing cell and internet traffic, weather conditions and a fragile power infrastructure have caused blackouts across the country, and making customers and service providers look for backup power solutions that offer durability and flexibility at a reasonable cost. More recently, the realization that our power generation and distribution system may be vulnerable to interruptions due to terrorist and natural disasters has increased this need significantly.

According to a national U.S. survey commissioned by Emerson , power outages resulting in downtime are common.Forty-seven percent of survey respondents said their large businesses experienced a power outage that resulted indowntime in 2005. Of those, 44 percent were without power for at least 8 hours during the longest outage. Yet, more than 20 percent of large U.S. businesses have not budgeted to prepare for and maintain operations during natural disasters, according to the same study. Major network operators have taken a critical look at the power needs of their networks. In their own words, "Critical cell sites should be equipped with backup generators with a week's worth of fuel, backup battery power, and monitoring 24 hours a day, seven days a week."

As a result of the report of the Katrina Panel, issued in June, 2006, the U.S. Federal Communications Commission issued order FCC 07-107, requiring 24 hours backup for central office equipment and 8 hours for remote equipment, including cell sites, DLCs, and similar equipment. While the effective date of this Order has been extended, the importance of adequate reliable power and backup power continues to receive consumer, corporate and government attention. As they implement their site hardening plans, network operators have multiple methods and technologies available to them to meet their backup power needs. These include VRLA (valve regulated lead-acid) and wet cell batteries and mechanical generators, but also include fuel cells.

The Case for Fuel Cells

Behind every smoothly running network is an increasingly fragile power infrastructure. The rapid deployment of new wireless products is straining the network capacity, even as reliability and quality requirements remain high. These conditions demand wireless networks that are optimized in every respect, including backup power. Yet in the scramble to meet these demands, traditional solutions for backup power, valve-regulated lead acid (VRLA) batteries, are insufficient for the outside plant (OSP) wireless environment. That leaves wireless operators searching for new backup power sources that satisfy multiple requirements - reliability, flexibility, and durability - at a cost that makes sense for cost-conscious companies. Fortunately, several candidates have emerged.

Why Traditional Solutions Won't Work

In traditional indoor settings, like a central network switching office, traditional solutions provide reliable backup power. Flooded lead acid batteries typically achieve useful life spans of 20 years. Maintenance techniques for these and other widely used sources, such as engine-generator sets, are proven and easily implemented. Onsite personnel can monitor loads, equipment condition, and provisioning requirements for these indoor solutions. The key word, however, is indoors.

As wireless networks deploy their equipment and backup power sources in remote outdoor environments, the traditional solutions work far less effectively. VRLA batteries have proved short-lived, overly sensitive to temperature, too heavy for many outdoor applications (like rooftops), too laden with environmental issues, and unable to keep up with the increasing energy and duration demands of OSP wireless technology. With wireless sites scattered across wide geographic areas, preventive maintenance for all these units becomes a serious issue. Some of these shortcomings can have dramatic consequences: the short operating life of batteries, for instance, has been implicated in the failure of backup power to wireless networks during the famous Northeast Blackout. Over the last few years, researchers have made some advances in adapting the traditional technologies to the OSP environment. Even so, alternative technologies may gain the advantage in the race to serve wireless networks in the new distributed landscape.

In considering diesel electric generators, they are increasingly difficult to install on-site due to significant noise and emissions, low part-load efficiency, and have high maintenance requirements. As such wireless operators are actively seeking more efficient and environmentally friendly solutions.

New Batteries Emerge

Among these alternatives are several that also use battery technology. Even the most promising among them, however - the lithium-ion battery - is not without its hurdles. Lithium-ion batteries have expected lifetimes of more than 10 years in extreme environments. They offer substantial weight and space savings over both traditional lead-acid and nickel-cadmium storage systems. Their other benefits - no ventilation requirements, better cycling characteristics, and more flexibility of form factor - fulfill many OSP requirements. Unfortunately, those distinct advantages come at a cost: currently at 8-10 times the expense of VRLA batteries, lithium-ion batteries require a higher initial capital outlay than many companies are prepared to make. As with other innovations, cost will come down as the technology matures, but network administrators are under pressure to come up with solutions now. Moreover, the scarcity of the elements used in the battery will likely keep the cost somewhat high over the long term.

Just as troubling is the uncertain path of innovation and cost reduction that lithium-ion batteries will take. Most high-current research has focused on automotive applications, particularly hybrid and electric vehicles, where the potential sales volume may accelerate development. However, technology designed for mobile and backup power use may not translate directly, or even easily, into stationary applications. Even on the automotive front, several key issues remain to be resolved, among them load response and the need for intelligent systems to charge and maintain the batteries. One other disadvantage may prove troublesome for wireless networks as well: lithium's high flammability. The risk of fire only adds to liability concerns and replacement costs.

The Promise of Fuel Cells

Yet another option is the proton-exchange membrane (PEM) fuel cell. In this system, hydrogen fuel directly generates DC power, with water as the only by-product. Such a process makes fuel cells particularly adaptable to the OSP environment even as they carry the strengths of the new batteries. Fuel cells for backup applications are designed for reliable operation in a very broad temperature range. The systems provide immediate and, as necessary, extended response to power interruptions, while their generally lightweight, small footprint makes them suitable for rooftop locations. The clean process produces zero emissions and little noise, and the units are easily monitored and controlled with remote automated systems.

Topping all these benefits is the cost savings generated by fuel cells. Initial unit cost runs roughly half to one-third that of lithium batteries. While still more expensive than VRLA batteries, fuel cells carry a lower life cycle cost, with lower maintenance needs and longer life.

Fuel Cell technology has drawn widespread support within government agencies, from the Department of Defense to the National Institute for Standards and Technology. And stationary fuel cells already have a track record in the field, as such established utilities as the Long Island Power Authority have installed them to run as both a parallel and a backup power source. Nevertheless, several challenges remain. Chief among them is the logistics of fuel supply, specifically the refilling of tanks via drop-off fueling, and the corresponding concerns surrounding the storage of hydrogen.

The Case for GEI Fuel Cell Solutions

Typical backup power fuel cell systems use pressurized bottled hydrogen which powers the fuel cell stack and produces regulated DC power and clean exhaust and waste heat. Bottled hydrogen is suitable and cost effective for a range of telecom backup requirements, including eight hours or less of backup power time, lower power needs, and where convenient access to hydrogen refueling is available. Six bottles of hydrogen provide eight hours of backup power for a 5 kW load. However, in situations requiring extended backup power times, higher power needs or in situations where hydrogen delivery is difficult or impossible, compressed hydrogen is a challenge. For example, 36 hydrogen cylinders are required to provide 48 hours of backup power for a 5 kW load.

In the comparison between liquid fuel and hydrogen bottles, 60 gallons of a methanol/water fuel mixture and a fuel reformer will provide the same amount of power for the same length of time as 36 hydrogen cylinders. Alternatively, if diesel fuel is the fuel processor feed source, only 20 gallons are required. In situations where hydrogen storage is difficult due to space and weight restrictions, liquid fuel combined with a fuel reformer is the most economical solution. Additionally, at remote installation locations such as telecommunications tower sites, hydrogen can prove to be difficult, bulky and heavy to store, and maintenance to re-supply industrial hydrogen cylinders in these remotes sites is not feasible. Reforming technologies and fuel cell products that incorporate reformers exist today that eliminate these obstacles and pave the way for even broader network applications.

The GEI X5 fuel cell APU has the distinct competitive advantage of fuel diversity. As such, in addition to hydrogen, cell sites can use locally available logistics fuels such as diesel, propane, methanol, ethanol, natural gas, bio-diesel, JP10, and other bio-renewable fuels. These fuel options provide the maximum flexibility to minimize cost and maximize fuel effectiveness for each cell site owner. As previously stated, due to the characteristics of high temperature PEM fuel cells the liquid fuel processor solution is exceptionally compact, efficient, and robust. The GEI high-temperature PEM fuel cell solution enables power generation for a large range of capabilities and for critical backup power or remote power applications where no grid is available, now can run for days versus hours of backup power.

In summary, fuel cell backup power systems have numerous advantages versus traditional stand-alone battery or diesel generators. In addition to those benefits, the GEI fuel processor/PEM high-temperature fuel cell stack technology solves the hydrogen storage issue and provides virtually unlimited fuel cell backup power for mission critical and remote sites. However, if hydrogen is available and is the fuel of choice, the GEI X5 APU would still employ hydrogen as a fuel.