PEM fuel cell systems: A reliable backup source for remote or extended-run power outages

PEM fuel cell systems: A reliable backup source for remote or extended-run power outages

Commercially available fuel cells with an integrated fuel reformer offer reliable, and cost-effective backup power for the telecom industry

BY KATHY FOSBERG
IdaTech, Bend, OR
www.idatech.com

In today’s 24/7/365 communications-on-demand world, businesses, individuals, emergency systems such as TETRA, 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 life-threatening 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 valve-regulated 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 1 to 4 hours of backup power, but battery functionality is negatively 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, they 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-turned-scientist 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.

Fig. 1: Diagram of fuel cell operation.

The type of fuel cell commercially available today and most appropriate for use with wireless telecommunications sites is the PEM (proton exchange membrane) fuel cell. These fuel cells are compact, durable, reliable, quiet, and operate at peak efficiency in a wide range of climates (—40° 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 elect ricity within seconds of activation.

The typical run time for one of today’s fuel cells operating on 6 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 hot-swapped 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 storage of additional bottles of hydrogen at a fuel cell installation and/or the remoteness of a fuel cell installation, which makes hot swapping unfeasible.

There is a new technology that has already been successfully deployed commercially and can extend fuel cell backup runtime not by hours, but by days. It is called a fuel processor.

A fuel processor uses a liquid fuel to make hydrogen on site and on demand. Fuel processing is the act of converting hydrogen rich fuels into pure hydrogen gas as needed, then feeding the pure hydrogen directly into a fuel cell stack. IdaTech of Bend, Oregon, has developed fuel processors for a variety of common fuels, including methanol, a liquid found in windshield washer fluid, and many other common products. Again, fuel cell systems with liquid fuel processors can provide backup power for days instead of a few hours by using energy dense liquid fuel.

IdaTech sells complete fuel cell systems with integrated fuel reformer and fuel tank. When the grid power fails at a wireless telecom site, a small battery string takes over the site’s load for a couple of minutes while the fuel reformer starts up, produces hydrogen, and then the fuel cell begins powering the site’s load.

The system is powered by HydroPlus liquid fuel, a mix of water and methanol (62% by weight methanol). The fuel reformer is highly efficient, recycling the waste heat from the fuel reforming process and directing it back to the reformer’s combustion chamber where the waste heat takes over as the heat supply to vaporize the liquid methanol/water fuel.

This system solves the problem of needed onsite on-demand electricity during power outages, and yields immediate savings in footprint, weight, regulatory setbacks (clear space requirements), simplified refueling and, most importantly, extended run times.

It takes one 59-gallon fuel tank of methanol/water fuel with a fuel reformer to produce 40 hours of 5-kW output power vs. 24 T-cylinders of hydrogen to produce the same amount of output power. The fuel tank and reformer create a 72% reduction in footprint and 67% reduction in weight over the amount of bottled hydrogen (and number of hot swaps needed) to produce the same 5-kW output power.

Fig. 2: Comparison of how much methanol fuel vs. hydrogen cylinders it takes to produce 40 hours of 5-kW output

The commercially available fuel cell with an integrated fuel reformer and supply of HydroPlus methanol/water fuel is an increasingly popular, highly reliable, and cost-effective backup power source for remote and/or extended run power outages for the telecom industry. ■