Bifuel Technology Helps Generators Provide Power
July 2012 - Power & Communication
Emergency power engines typically run on diesel or natural gas. Some have bi-fuel capabilities; those designed with cogeneration in mind may use biogas, sewage gas or even methanol as fuel sources. Diesel is usually less expensive than natural gas, says Prosser. However, having a bi-fuel application means not as much diesel fuel needs to be stored onsite, and the genset can run for a longer time. "The generator starts off on diesel and then changes over to natural gas," says Bob Hafich.
Pope explains that a typical bi-fuel mixture is 70 percent gas with 30 percent diesel and requires no modification to the engine.
Interest is growing for cogeneration applications, but running diesel gensets for such applications remains costly today because of emissions control equipment required.
"However," Prosser says, "continuous gas engines can work well with combined heat and power applications. I think that area will continue to grow as demand for electricity outweighs supply, and natural gas prices remain low." Federal mandates and investments in alternative energy options also will encourage that growth, says Prosser.
Emissions controls for generating sets are based on horsepower and grouped into tiers, according to Joe Hafich, co-president of Emergency Systems Service Co. With the Environmental Protection Agency (EPA) classifying some areas of the country as out of compliance or on the cusp of new clean air requirements, the gensets' tier level becomes more important.
Tier 2 and Tier 3 units, which are for backup power only, are the standard for many places. Engine emissions controls currently can range up to Tier 4 for prime power and demand response applications, but such technology currently comes with a hefty price tag. "For standby generators, you are probably okay with Tier 2 or Tier 3 emissions controls," says Joe Hafich. "But if you plan on using the genset for energy savings, then a new set of emissions standards apply."
"It's not just federal mandates," says Prosser. "State, local and municipal mandates for clean air in most cases exceed EPA standards."
Switchgear and Controls
Today's backup power units feature sophisticated switchgear. For critical operations such as hospital operating rooms or research laboratory clean rooms, the switch from utility power to emergency power can be accomplished in seconds. For crucial but not critical applications, the switch may be delayed so that it comes on only when necessary.
Emergency power engines are smart, thanks to advanced microprocessor controllers. "The controllers allow for such things as fuel mapping and adaptations for other variables," says Prosser. "The protocols are usually on a common platform so they can communicate with the building management system, wirelessly or through Web technology. Through user-defined parameters, they can send a variety of alarms and even site conditions can be factored in for optimum operation of the genset."
Today's backup power units also have self-diagnostics. "If a fault condition is detected during one of these tests, a signal is sent to a defined location or device so facility managers know instantly there's a potential problem," says Habic. Through laptop or handheld devices, diagnostics also can be directed by the facility manager. "You can even run cylinder compression tests without touching the engine," says Pope.
Habic sums up the benefits of modern electric generator sets as requiring less travel, less fuel and less labor than earlier models. "You don't have to be on site to know what's happening," Habic says. "Through remote monitoring, you can see if the generation unit failed a cycle test or if there are any safety concerns."
Emergency power systems are designed to run many hours before major internal engine repairs may be needed. Preventive maintenance is crucial. The sophistication of today's backup power generation sets requires "savvy technicians," as Habic says.
"It's really important that the technician working on your emergency power system is qualified to do the work," says Pope. Transfer switches, engine controls, genset running and an annual load bank test are critical elements to making sure the gensets will operate when they are needed.
To that end, the Electrical Generating Systems Association (EGSA) developed an industry standard by developing the EGSA Technician Certification Program (not manufacturer-specific). "If the technician can pass our certification exam, he or she is really an important asset to your emergency power reliability," says Pope.