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Facility managers are likely familiar with the cloud of black smoke that emergency back-up generator sets of a certain age produce. While newer gensets have been getting progressively cleaner since 2003 and no longer have this environmental and image problem, thousands of earlier gensets still smoke at startup and emit some major pollutants, according to Michael Pope, 2012 president of the Electrical Generating Systems Association (EGSA) and current past president. "That black smoke at startup and when the genset takes an electrical load is from unburned fuel and unburned oil," Pope explains.
The emissions from older emergency back-up gensets contain nitrogen oxides, carbon monoxide, hydrocarbons, particulate matter and even HCHO-formaldehyde, which contributes to smog and is a known carcinogen. When a genset is upwind of the HVAC system, the HVAC intake air pulls in the exhaust.
"One facility manager told me he could totally evacuate the building by starting up the emergency generators," says Pope, marketing manager and senior sales engineer at Clariant Corp. Within minutes, coughing building occupants would be leaving with watery eyes from the smoke.
Particulate matter, visible in the smoke emitted, is a problem being targeted by the U.S. Environmental Protection Agency (EPA), the California Air Resources Board (CARB) and other local and state agencies. Particulate matter is one-eighth the diameter of a human hair and is visible only because it is concentrated in the smoke. That incredible smallness allows particulate matter to be inhaled deeply into the lung. Medical studies have linked particulate matter to lung damage, premature death and aggravated respiratory conditions, such as asthma and bronchitis. Particulate matter also may be a cause of some cancers.
Because of diesel particulates, California and a growing number of other areas are requiring emergency gensets for health care and schools to control emissions.
Since 2003, when the EPA introduced its Tier I standard, technologies have brought significant reductions in exhaust emissions. Among the more significant, according to Pope, are electronic engine management systems and electronic injectors.
These improvements mean that today's gensets have engines with thermal efficiencies of 40 percent or more. "Today, engine manufacturers are exceeding 45 percent thermal efficiencies in their labs and 50 percent is very likely achievable," says Pope.
Older gensets, however, still emit clouds of unburned fuel and oil at startup. One reason they do is that National Fire Protection Association's Standard 110 requires emergency gensets to be online in 10 seconds. Two decades ago that was often achieved by injecting additional fuel while the engine was ramping up. That fuel is not efficiently burned, so it results in black smoke and over time even wet stacking, where unburned fuel and lube oil condense in the cool exhaust system and the resulting black "goo" leaks out from the exhaust manifold and connections.
The Electrical Generating Systems Association is comprised of more than 850 companies throughout the U.S. and around the world that make, sell, distribute and use on-site power generation technology and equipment. EGSA encourages the exchange of ideas and information for the mutual benefit of its members, the industry, and end-users, and serves as a source of information, education and training. EGSA is also the leading authority on recommended practices and the monitoring of performance standards for the on-site power industry.
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