Real choices for remote site energy applications
Regulations may restrict the use of fossil fuels for backup power at remote telecommunications sites. Some high-efficiency alternative power sources are both environmentally friendly and operate at a reasonable cost.
Do you have a remote site-one fed by ac mains but with a backup power source? Or one with a diesel generator as the prime power source? Are you planning a new site or major upgrade to an existing site and your tenants demand a solid standby power source? New, updated and changed federal regulations may have an expensive impact on your plans if you choose to use a diesel generator. New and changed regulations may affect your use of motor fuels. Several new, high-efficiency power sources now exist, and upcoming technology could have a positive impact on your bottom line.
Unless you regularly work with environmental regulations, you may not be familiar with some of the new restrictions placed on above-ground fuel storage tanks (AST), waste oil handling, battery stacks and in certain cases, exhaust gases. For a more detailed look at these federal regulations, all of which are available on the Internet, see the list on page 48.
The listing shows the maze of regulations that kick in when you use a motor fuel generator set as a prime or reserve power source. This may explain the rise in popularity of solar systems.
An immediate cost and regulatory savings may occur if you switch your generator fuel to Compressed Natural Gas (CNG), propane, butane or other LPG or natural gas. Waste methane can be used as an energy source in some locations, and it may have tax incentives or tax breaks. If you have access to ac mains as a prime power source, you will still want a backup power source. A hybrid of a battery stack and ac charger/inverter (UPS) may work if your need for standby power is short-lived or limited. An additional shortcoming is the weight of the battery stack and potential for regulation under the “Community Right to Know” (SARA title II or III), section 101, 102 or 103. This rule deals with extremely hazardous materials (EHM)-battery acid in this case.
Further clouding the issue are remote RF sites in occupied buildings where the National Fire Code kicks in. Batteries generate explosive gases so they usually have their own rooms and the presence of large amounts of sulfuric acid tends to make landlords nervous. Many of these rules and regulations come out of tragic and unnecessary fires, explosions or loss of life caused by these regulated devices.
If you’re ready to throw in the towel, smile, things are getting better. New energy technology-some sponsored by the Department of Energy (DOE)-is making its way into the marketplace. The first of these “new” technologies is the fuel cell. Often associated with “outer space” or the movie, Apollo 13, fuel cells have come a long way. One of several types of fuel cells may be an economical source of power for your site-either as a primary or backup supply.
Types of fuel cells found on the current market are phosphoric acid, proton exchange membrane (solid polymer), molten carbonate, solid oxide, or alkaline. Phosphoric acid systems, especially those used in co-generation systems are often primary power sources for large computer systems, hospitals or isolated building complexes. Efficiencies as high as 85% are not uncommon. The Alaska National Guard, for example, has had such a system in use since 1997 without a hiccup-powering an office complex and the state disaster communications complex. See the photos at www.dodfuelcell.com/richardson.html. Fueled by natural gas, which is not burned, the ‘waste’ heat is used to heat the building complex and provide domestic hot water. These types of units, properly sized, make a prime choice for those urban sites where you want to replace a noisy generator, reduce waste oil and reduce exhaust emissions.
Another common fuel cell on the market is the proton exchange membrane (PEM). Most technical staffs are aware of these cells in the marketplace-the byproduct of the energy generation process is water, water you could drink. Using hydrogen and air as feedstocks, PEM cells offer high-power density and small size. Any ‘waste’ heat can be vented or used to regulate room/shelter temperatures. The DOE claims that you will soon see this type of fuel cell at home, in your car, as a battery supply for cellphones or even to run your camcorder. Other fuel cell types are still in development or are for large applications, not suited for a communications site.
If you have a remote site, a hybrid system of solar panels and a thermoelectric generator (TEG) in tandem to charge a battery stack/inverter combo is a solid economic choice for those sites where access is a problem for some part of the year. This type of system is in daily use by the U.S. Air Force at several remote Alaskan sites (www.nwvt.com/PB_Kollsman.html) to power a ground system. Fueled annually, when the ground is frozen solid, the TEG provides both power and heat. In the summer months, solar arrays and almost 24 hours of sunshine fill the energy needs of the system. TEG manufacturers, such as Global Thermoelectric (www.globalte.com/index.htm) offer a wide range of systems in different output (heat and electricty) ranges. Another TEG supplier, Hi-Z Technology (www.hi-z.com/) offers entire systems or TEG modules so you can construct your own system to recover waste heat. Both will use CNG, natural gas, propane or butane-allowing a wide choice of supply.
The final class of “new” technology energy sources are zinc-air and aluminum-air batteries. These types of batteries do not use an acid electrolyte-a brine solution in conjunction with high purity metal electrodes delivers the current for a backup power source or to supplement your charging system. While most cannot be recharged, the waste stream is easily handled. Known for their small size and high energy densities, these batteries may find their way into your automobile sometime soon; for communications applications they are now an “off-the-shelf” product available in different voltage and current ratings.
The communications site owner/operator, whether in the rural countryside or deep in a city high-rise, now has a choice for energy supplies without using internal combustion engines or heavy, acid-laden batteries. Green and clean products, ranging from TEG systems to esoteric metal-air battery systems, are available as proven off-the-shelf technology giving low-cost, high-density energy solutions.
