Power's Guardian Angel

A site without power is like an angel without wings.

As wireless networks add capacity and customers, reliable power becomes far more critical. Today's battery and generator solutions give service providers added assurance, serving as their sites' guardian angels against the unexpected power blips.

In the past, service providers focused on getting power from batteries. However, more companies are beginning to evaluate generators for their power supplies. These providers also are becoming highly competitive trying to offer the best services providing the most power to their cell sites.

Generator reliability and upstart are the most important considerations for wireless-service providers so they ensure that their reliability and cost-effective performance are at their peaks. Commercial customers seek the most appropriate generator for improved durability. Many generator companies offer numerous units, including medium, light-duty and portable generator sets for a variety of applications.

There are many options for wireless-service providers to supply power to their cell sites. "Generators are used as backup-power solutions for wireless-service providers," said Steve Goran, Generac Power Systems national account manager. "Most of these companies use batteries, but they don't last so long. It makes more sense to have an engine generator on site."

It's important to note the electrical requirements of a specific site before a generator is selected.

"There's a lot of sizing that goes into the electrical requirements of the site," Goran added. "Digital wireless systems go into cabinets so the power requirements drop. We are able to use 6kW generators at these sites instead of the 25kW to 50kW ones we used in the past. Then we take a look at how to fuel the generator. If natural gas isn't to be used, then liquid propane or diesel fuel would be used for engines above 100kW. Gasoline is never used because it is a poor storing fuel."

Many service providers use systems such as Generac's Guardian emergency power systems, which range in size from 6kW to 40kW. Once the output from the generator and the type of fuel to be used (natural gas or diesel) is determined, the emergency power system can be selected.

"Batteries keep most equipment up and operating by sending signals," said Brian Jewart, Clifford Power Systems sales manager.

"Batteries use rectifiers that use ac and convert it to dc power," Jewart said. "The problem with batteries is that they have short charge times from six hours to a minimum of just 30 minutes. Depending on traffic and clientele, power generation is always a key item to get the rectifiers running."

As companies grow, their capabilities increase along with the need for more powerful applications.

Heaven Sent
"When small companies are starting out, they generally do not use the generators right away," Jewart added. "These companies will eventually be swayed to the generator application in the long term. Small start-up companies have a good concept, but maintaining a service gets into an area that sometimes shows these companies are not up to speed. As revenues begin to roll in and the companies look to future expansion, they will begin to upgrade."

Manufacturers such as Generac and Kohler have introduced new generators in hopes of attracting new business.

Kohler's recently introduced COM-6 generator set is a permanent magnet generator powered by a command engine. This unit uses a variable-speed controller and power conditioner to provide precise dc voltage. This 6kW generator uses either natural gas or liquid propane.

Some service providers may be concerned about the generators' noise level. Many generator vendors offer the option of having the unit mounted in a sound-attenuated metal enclosure for quiet operation.

Kohler's new COM-6's electronic control monitors everything from fuel mixture to low oil pressure and permits the generator to operate at a specific speed to handle different load requirements.

In addition to their longer lifetimes, some generators allow service providers to remotely control the system, which sends a command to a unit via a transponder.

Kohler also has introduced the Series DLGK, which is designed for standby and prime power installations and is equipped with a master programmable logic controller, meters and safety shutdown circuits.

Dc generators offer wireless-service providers an economic alternative to battery reserve systems. Ac generators in gas-fueled configurations are able to meet the telecommunications requirement for uninterrupted power. These specific generators are available from 8.5kW to 2,000kW units and feature sound-attenuated housings, critical sound silencers, auto-transfer switches, weather housings and alarm systems.

Lucent Technologies recently introduced two new cell-site power systems. The GPS 2408 half-height equipment rack accommodates two shelves of four rectifiers for a maximum output current of 800A. This new application is designed for integration with a battery stand and provides power for low-capacity wireless applications in which cell-site space is limited. The GPS 2424 full-height rack supports three shelves and four rectifiers for a maximum output current of 1,200A and is designed for larger, higher capacity, 24V wireless applications.

Both units can convert ac input into the 24Vdc used to power wireless cell-site equipment.

Battery Proponents
"Batteries for wireless carriers seem to be the way to go," said Amanda Rogers, regional sales representative for Bell Atlantic Mobile. "Large companies may select the generators, but smaller companies are concerned with cost and reliability. When companies grow rapidly, so does the need for better services, increased quality, etc."

Like Lucent, Yuasa-Exide has introduced an updated version of its Dynacel DDH VRLA battery. The Dynacel offers a 125Ah plate and seal, which allows plates to grow as the battery ages.

Reltec supplies wireless and wireline applications. A single-point voltage adjustment can be made at the system's meter-control alarm module to set parameters for all power conversion units operating.

Many manufacturers of power supplies seek the proper system that gives service providers flexibility to deal with the unforeseen expansion of public networks.

Lucent's new Galaxy Power System can incrementally expand power capacity to meet the growth demands on public networks in switching and transmission, wireless switch centers and CATV applications.

"Higher Internet usage, optical networking and DSL deployment are just a few drivers that can create a bandwidth bottleneck for service providers in public networks," said Sayed Ali, Lucent product marketing manager.

"Whether or not service providers are able to accurately forecast their growth needs, the GPS 4848 gives them the most optimal building blocks in 200A increments to add power capacity when they need it," he continued. "The GPS 4848 is cost-effective because it allows for pay-as-you-go power, and its high efficiency can result in a lower life-cycle cost."

A battery's lifetime is often a critical factor in a wireless-service provider's decision-making process.

"High efficiency is our primary concern right now," said James Griffin, Pacific Bell Wireless senior sales representative. "Each company tries to stand apart from the rest. By introducing new batteries to the market and offering fewer battery replacements due to longer lifetimes and change-outs required during the end of a product's life cycle, companies are able to make their selections more easily."

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911 Shakedown

Keeping 911 up and running is essential in any city. However, in San Francisco, the city known for its devastating earthquakes, 911 takes on greater importance and larger proportions. The city just completed a new 911 facility, which is the emergency communications center for the city and fields all police, fire and medical emergency calls. Although the 911 facility currently is monitored and controlled on site, eventually it will be networked to the newly restored city hall and an 800MHz communications center. Both locations are backed up with Cummins Onan's PowerCommand generators with digital paralleling.

The 800MHz site is located on the city's Twin Peaks. Once during an electrical storm, the tower was struck by lightning, rendering the digital master control unusable. In addition, the facility experienced a major power outage. Because of the paralleling feature built in to the gen-set controls, the generators were able to start up and parallel to keep the facility running until the master control could be replaced.

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Touched by Regulations

The Environmental Protection Agency (EPA) requires generators of hazardous waste to certify on their hazardous-waste manifests that they have a waste-minimization program in place. Owners and operators of facilities must receive a permit for treatment, storage or disposal of hazardous waste on the premises where such waste was generated.

The Natural Gas Supply Association supports the EPA's plan to cap the amount of NOx emissions each state may allow generators to produce and then to grant the generators "credits" with which to comply with the limits. An output-based system also could allow low- or non-emitting generators, such as those using renewable energy, to benefit financially from the environmental contributions that many of them make.

"The EPA has been trying to control the NOx emissions, which is designed to add the migration of nitrous oxide and cap it," said Rhone Resch, director of environmental affairs for The Natural Gas Supply Association. "It has been a legal battle among different states. Some states are challenging it because they don't think they should be included or they don't believe they contribute to the air-pollution problems. We have intervened on behalf of the EPA to achieve lower emissions levels. It is better for the environment especially since the ozone is a major health problem in the United States."

Speed is a freelance writer based in Massachusetts.