The power of change
Despite all of the advances in wireless technology — which have sparked blurry-fast evolutions of feature sets and devices, and spawned an alphabet-soup of acronyms for the latest protocols — power availability remains a simple, yet critical, factor.
With power, even the most arcane wireless systems can provide valuable, powerful communications across vast distances. Without power, the latest and greatest wireless infrastructure is nothing more than an expensive eyesore, and the niftiest devices transform into costly paperweights.
This fundamental reality often impacts the location of base-station sites. What an engineering map may identify as an ideal site — in terms of providing RF coverage in a remote area — may not be viable because the electrical power grid does not reach the location, and trying to extend commercial power to the prospective site would be cost-prohibitive.
For commercial wireless carriers, the good news is that consumers typically want to use their cell phones in areas where the power grid is readily accessible. But the first-response community does not always have that luxury, because emergencies often occur in areas where no power company could justify the cost of providing service.
“There are some interesting factors involved — whose land you're going over, whether the utility can be run overhead or underground,” said Jim Parcels, director of systems management for the Pennsylvania statewide radio system.
“Often, in state forest land and particularly state parks, they are loathe to allow overhead lines to be run,” he continued. “And, of course, the cost of running electricity underground is dramatically more expensive than running it overhead.”
Internal combustion-based generators are a traditional choice, but the need to refuel and maintain them in certain locations — particularly in mountainous areas — make them impractical, because the site may not be accessible for months in the winter.
In the past, such a scenario would require the state to pay the utility more than a hundred thousand dollars to extend electricity to a site or compromise its coverage in the area. But this spring, Pennsylvania plans to build a microcell site in Clinton County using renewable energy sources — solar and wind energy — and hydrogen fuel cells to power the site, in the process avoiding the capital costs associated with extending the power grid.
The notion of using alternative power sources for a communications site is not new. Less-developed parts of the world have harnessed alternative-energy sources out of necessity, because they lack a power grid in many locations. But the alternative-energy option typically has been deemed too expensive to be used regularly in the United States, where electrical service is almost ubiquitous.
Indeed, Pennsylvania seriously considered deploying fuel-cell solutions for some remote, high-profile tower sites for its statewide radio system eight years ago. The notion was dismissed at the time largely because the capital and operational costs associated with the solution were too expensive.
“In those days, when we looked at doing it, you were talking about a big trailer with a tank on it [to deliver hydrogen to the fuel cell at the tower site], so access was an issue and cost was an issue,” Parcels said. “It was just overwhelming.”
There also was a technical problem at the time, said John Struhar, Harris' director of Pennsylvania operations.
“They had problems because the discharge from a fuel cell is water,” Struhar said. “These things would freeze up because they were on mountaintops in the cold and the wind.”
Today, the alternative-energy option is more practical for several reasons. Heating elements have been integrated into the fuel-cell solutions, so freezing no longer is a problem, Struhar said. And Pennsylvania now is trying to power only single-channel microcell sites, which require about a tenth of the power of a full-fledged tower site that supports multiple channels and trunking features, Parcels said.
“With these microcells, the power demand is so much smaller that logistically, this all becomes so much more doable,” he said. “And, of course, in the intervening years, the technology has gotten so much more efficient than back in 2001, when we first looked at doing this.”
Indeed, the power design proposed by Harris for sites such as the one in Clinton County is a hybrid solution, with solar and/or wind energy being leveraged to the fullest extent. The hydrogen fuel-cell solution is used to recharge the large battery pack at the site when the renewable-energy sources do not produce enough energy — for instance, when several days of overcast weather results in the solar panels not generating much electricity.
The ability to combine the solar and wind systems with the hydrogen fuel cell component is giving Pennsylvania officials confidence that the microcell site will remain powered at all times.
“Since the solar ‘fuel’ — if you will — is free, and the wind fuel is free, you want to draw down on those sources to the greatest extent that you can and then allow the hydrogen portion of the solution to contribute when the other two aren't,” Parcels said. “[Solar and wind sources] may not eliminate the hydrogen cell, but [they] greatly increase your time span between having to refuel, which is really the critical element for us, because we have to assume that we can't get up there once per month during the winter to refuel the hydrogen.”
With a 16-cylinder hydrogen pack, a Pennsylvania microcell site should be able to operate off the fuel cell for at least a couple of weeks after the solar, wind and battery sources have been exhausted, according to officials. Buoyed by the typical amount of power generated from the renewable-energy sources, a microcell site may only need to have its hydrogen supply replenished every six to eight months, at a cost of about $2,200 per year for the hydrogen and for the cylinder rental, Parcels said.
Other advantages of the integrated Harris power solution are that it can be monitored and controlled remotely; that fuel cells are much quieter than internal-combustion generators; and that maintenance is much simpler than with a generator, Struhar said.
“You don't have to have a generator mechanic go out and work on it,” he said. “We can have one of our standard field techs who normally works on RF do it.”
Indeed, the fuel-cell solution is “very plug and play,” said Joe Blanchard, vice president of product management and business development for ReliOn, the fuel-cell subcontractor used by Harris. In addition, government data indicate that ReliOn's system provides greater reliability and availability than traditional generators, he said.
But fuel cells may not be the best choice for every scenario, Blanchard said.
“If you only want two hours of backup power for your site, batteries will almost always be the right solution,” he said. “When you get to six to eight hours and beyond, [fuel cells] compare favorably to batteries. If you're looking at higher cycle times or very long durations, then the [generators] sometimes will look better, but it depends on fuel logistics.”
Blanchard acknowledged that the fuel-cell industry still is maturing, so hydrogen suppliers are not nearly as numerous as their propane counterparts. However, with more than 2,500 outlets available nationwide, most industrial-grade users can be serviced without adding significant costs, he said.
One stigma the fuel-cell industry encounters is that hydrogen is inherently dangerous — a notion stemming primarily from the infamous images of the 1937 disaster when the hydrogen-filled dirigible Hindenburg exploded in a giant fire ball. Although hydrogen is a flammable gas, such fears are largely unfounded, Blanchard said.
“There are a lot of home tinkerers that have oxy-settling welders, and there are a lot of us who have propane barbecues, and both of those scenarios are far worse than a cylinder of hydrogen in terms of safety and potential hazard,” he said. “Most people don't think anything of checking for leaks when they change the propane tanks on their grills, and that could take their house down. If a cylinder of hydrogen [leaks], it looks like a blow torch — it's a concentrated heat, but it's basically fine and probably will blow itself out.”
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