CURTIS S.D. MASSEY is president of Massey Enterprises Inc., the world’s leading disaster planning firm. Massey Disaster/Pre-Fire Plans protect the vast majority of the tallest and highest-profile buildings in North America He also teaches an advanced course on High-Rise Fire Department Emergency Operations to major city fire departments throughout the U.S. and Canada. Massey also regularly writes articles regarding ‘new age’ technology that impacts firefighter safety. Special thanks to Capstone Turbine, ONSI Fuel Cells, Wikipedia, Bob Lasseter, Dennis Hughes, Ed Lewis, Bob Kistner, Joe Lechtanski, Steve Boos, Jim Haffey and Jim Jenkins
Part one of this series (August 2005) covered tenant redundant power supplies and how electricity comes into a building and is distributed to the tenants. Part two (June 2006) began this report on how an entire commercial building can meet some or even all of its power demand in the event it is removed from the local electrical grid. This issue must be understood by first responders, since it may impact their operations and their safety.
MICROTURBINES
Microturbines are an important emerging technology. They are an efficient, compact, ultra-low emission way to produce power and heat for combined heat and power applications. The microturbine engine is a combustion turbine that includes a compressor, turbine, generator and typically a recuperator.
Microturbines are usually fueled by high-pressure natural gas, which powers the turbine engine, although a wide range of approved fuels can be used. The engine has just one moving part, a shaft with a turbine wheel on one end, a permanent magnet generator on the other and an air compressor wheel in the middle. Air heated from the microturbine is injected along with natural gas into the combustion chamber. Pressure from the continuous combustion process generator exhaust turns the turbine, which generates electricity. Cooling fins outlet The 530-degree-Fahrenheit-heated, oxygen-rich, near-zero-pollutant exhaust passes into the heat exchanger system, where it heats water for domestic hot water and building heat. The electricity created from the microturbine is used to power virtually any demand for electricity. It produces dry, oxygen-rich exhaust with ultra-low emissions.
The system generates and uses high voltages as part of its function. An optional battery pack may exist. If so equipped, the typical battery pack is a lead-acid type, sealed and “maintenance free” (refer to part one to learn what this term means), with a battery isolation switch. The system’s gas plumbing is constructed of components that are designed and rated for the gas and pressures used. As part of the quality program, the system is pressure tested for leaks.
Microturbines can operate using a number of different fuels: landfill methane biogas from woody waste, wastewater treatment plants and animal farms, propane, natural gas, and such liquid fuels as kerosene or gasoline with electrical efficiencies in the 28%-to-30% range and up to 85% when including thermal efficiencies. They can run up to 16,000 hours (nearly two years of continuous use) between routine maintenance inspections. They also start rapidly (in less than one minute) and have excellent load-following characteristics that make them ideal for applications where electricity demand can fluctuate rapidly.
A microturbine can be compared to a miniature jet engine connected to an alternator and integrated into a unit that can be delivered complete with controls and ready to run (commonly referred to as a “plug-and-play” model). A 30-kilowatt microturbine is about as big as a large refrigerator. The unit can act as a stand-alone generator for standby, backup or remote off-grid power. Multiple systems can be combined and controlled as a single, larger power source called a “MultiPac.”
Microturbines may be configured into an array of up to as many as 100 units. Such an array will operate as a single power-generation source and can power an entire building, depending on size/load demands. Already, there are high-rise buildings in California, Oregon and Texas where MultiPacs power a significant portion of the building’s load demand separate from the city’s power grid.
FUEL CELLS
Fuel cell technology is moving to the forefront of the distributed-generation field and is increasingly being promoted as the driving force behind the coming hydrogen economy. Fuel cells offer higher efficiency than microturbines with low emissions, but are currently a much more expensive choice.
Although fairly new and still developing, fuel cells are the cleanest of all the potential cogeneration technologies. A fuel cell releases the energy in a hydrogen rich fuel source (such as natural gas) by allowing it to combine with oxygen in a catalytic reaction that produces no flame. The outputs of a fuel cell are limited to electricity in the form of a direct current (DC) voltage, water vapor and carbon or carbon dioxide.
In many ways, a fuel cell is like a large battery that will produce power and heat indefinitely as long as it is provided with a hydrogen-rich fuel source. Fuel cells are produced in a wide variety of types and sizes ranging from one to 250 kilowatts; MultiPacs can produce one megawatt and more. Commercial grade units run at extremely high temperatures (600-l,000F). This heat can be used for domestic hot- water needs, heating applications and air conditioning.
Without any flame and without moving masses such as turbine blades or reciprocating pistons, fuel cells convert the energy contained in the fuel directly into electricity. The electro-chemical processes employed enable not only high efficiencies, but they keep emissions at an exemplary low level. The exhaust air is free of noxious gases such as nitrous oxide and sulfur. Up to 30% more electrical power is created in comparison with conventional energy generation from local power plants. They are also quiet when compared to internal combustion engines, which can exceed 100 decibels, as they produce only around 60 decibels. Why so quiet? No combustion or moving parts.
While the high temperature heat output of Fuel cells makes them attractive for cogeneration applications (especially solid oxide fuel cells-SOFCs), earlier models have drawbacks. One is slow startup time. As a rule, the higher the operating temperature, the longer the startup time. Another issue is load-following capabilities. Microturbines and reciprocating engine generators can adapt to changes in electrical demand from 10% to 100% of rated load in seconds. Fuel cells are slower to react and have a much narrower throttling range. This is why a commercial application with both a relatively constant electrical demand and heat demand (i.e., a trading or banking data center, telecom facility) is an ideal application for fuel cells. Newer models of fuel cells have overcome these restrictive barriers and have virtually eliminated these two issues as obstacles. Some skyscrapers, such as the 48-story, 1.6 million-square-foot Durst building at 4 Times Square in New York City, employ fuel cell technology.
The future: A highly likely scenario in the not-too-distant future will see small modular fuel cells situated every three to five floors of new high-rise buildings, providing electricity and heat for heating, cooling and hot water, meeting the full demands of tenants. If set up similar to the microturbine configuration described earlier and connected in a string or series, full-size fuel cells can provide power to run an entire building’s electrical demand from one location (a mechanical room). These units are much larger and generate greater electrical output than smaller modular fuel cell models, which are about the size of a mini-refrigerator.
The important thing to remember is that redundant power sources are clearly the way of the future. This, in turn, dictates a clear-cut understanding on the part of the fire service that disconnecting electricity to a given tenant space, floor and even an entire building will take time and assistance from various technical people. This may demand a “hold” approach to firefighting in areas where high-voltage equipment or cabling is located until all power is disconnected and verified as to so.
WHAT YOU NEED TO KNOW
Of primary concern to fire departments is that two or more independent power sources may have to be isolated during a major event, including fires involving electrical chaseways — the utility company feed(s) and the on-site DG (Distributed Generating) feed. Whether the source is emergency diesel or gas-fed reciprocating engine generators, microturbines or fuel cells, this electrical generating source must be located and isolated along with the incoming power feed(s). The time it takes to accomplish this will probably require some patience on the part of the incident commander, because this will not be a 15-minute operation. It will also require personnel from different companies to assist. Preplanning electrical cutoffs is prudent.
Hazards and risks of microturbines:
- Heavy concentrated floor loads. Unit weights vary between 900 and 3,000 pounds.
- The output voltage and residual capacitor voltage can injure or kill.
- Flammable fuel connection leaks are possible. Microturbine fuel is flammable and explosive. Without a customer- installed leak detector present and tied into an emergency stop device, there is a probability of a catastrophic event involving a fire and/or explosion should the gas leak and ignite.
- Relief valves for hot water and steam can fail. High internal temperatures can reach well over 800F.
- Keep all open flames and other ignition sources away from units.
- Units can store residual power for up to five minutes after disconnect with a battery pack, creating a shock hazard. Small amounts of sulfuric acid and hydrogen gas may be a potential threat.
- Exhaust must be vented to the outside. Dangerous emissions such as nitrogen dioxide and carbon monoxide can be produced by the fuel-combination process.
- Exhaust airflow and pipes are hot, up to 700F. Contacting a hot surface can result in severe burns. Reflex actions associated with such a contact could result in a secondary hazard such as an impact on a hard or sharp object. The exhaust is typically located on top of the system, which averages over six feet high and is not easily accessed.
- Electric shock may occur if equipment is not properly grounded or if fire personnel inadvertently contact hazardous voltage within the enclosure, which may result in severe burns or death.
- The electrical current created and used by the system may cause a fire if short- circuit protection and grounding measures have not been followed.
- Hazardous sound-pressure levels may exist when a unit is operating. Hearing protection is advised.
If on fire:
- Turn off the system
- Open and lock the electrical disconnect switch
- Unplug the batteries or activate the battery-isolation switch
- Verify that no voltage is present
- Dry chemical or C02 portable fire extinguishers can be used to suppress fires involving a unit (avoid using C02 extinguishers on battery fires)
In the event of a gas leak:
- Immediately cease operation of the equipment
- Close the fuel-isolation valve
- Ventilate the area
Most of the hazards noted above regarding microturbines apply to fuel cells as well, aside from the loud operating noise levels and dangerous emissions, since there is no combustion process involved with the operation of the unit. Also, most of the same hazards apply to reciprocating engine generators in regard to fuel leaks and possible ignition, shock hazards, exhaust issues, high noise levels, etc.
CONCLUSION
In summary the world is a constantly changing landscape. Advancements in technology dictate that the fire service stay on top of these new-age concepts and how they affect both the operation and functionality of modern commercial buildings, as well as their impact on firefighter safety.
This series of articles addresses many of these concerns and provides a broad perspective on issues that relate to the fire service and that can be drawn from and applied to a department’s training regimen. Standard operating procedures (SOPs) and standard operating guidelines (SOGs) should be reviewed annually and modified to reflect items relative to safety and the ability to quickly and effectively deal with incidents involving technologically advanced equipment.
Curtis S.D. Massey will present “The Dangers and Complexities of Modern High-Rise Commercial Buildings” at Firehouse Expo 2006, July 25-30 in Baltimore, MD.
Microturbines are an efficient, compact, ultra-low-emission way to produce power and heat for combined heat and power applications. The microturbine engine is a combustion turbine that includes a compressor, turbine, generator and typically a recuperator. Microturbines may be configured into an array of up to as many as 100 units. Multiple systems can be combined and controlled as a single, larger power source called a “MultiPac.”
The outputs of a fuel cell are limited to electricity in the form of a direct current (DC) voltage, water vapor and carbon or carbon dioxide. In many ways, a fuel cell is like a large battery that will produce power and heat indefinitely as long as it is provided with a hydrogen-rich fuel source.
Full-size fuel cells can provide power to run an entire building’s electrical demand from one location.