Best practices for engineering government buildings: Electrical and power systems

Participants:

• Michelle Blake, PEng, Vice President, Industrial Buildings, Stantec, Vancouver, B.C.
• Jeremy Cooan, PE, LEED AP BD+C, Senior Electrical Engineer, Stanley Consultants, Minneapolis
• Michael J. Rossini, PE, Associate, Senior Electrical Engineer, Bala Consulting Engineers, Boston
• Ciarán Smyth, PE, CEng, PMP, Vice President, WSP, New York City
• John Gregory Williams, PE, CEng, Vice President, Harris, Oakland
• Matthew Williamson, PE, Associate Principal, Arup, San Francisco

---

Are there any issues unique to designing electrical systems for these types of facilities?

Michael J. Rossini: Massport’s Logan Airport is an international air travel resource, which serves millions of flyers each year. As such, the infrastructure that serves and supports the airlines has evolved to be mission critical facilities. Events, occurrences and natural disasters that could impact the flow of goods, services and people have major financial impacts. As such, many electrical systems have become the focus of operational resiliency programs designed to mitigate potential operational disturbances. Elevated unit substations, redundant radial primary feeders and redundant secondary substations have become the norm, replacing single ended unit substations, single primary fed services and outdoor distribution equipment installed at grade, which could be subject to stormwater flooding.

Ciarán Smyth: There are specialized systems and equipment that comprise an airline terminal. Some of these are the baggage handling system (BHS) equipment, the security screening checkpoint equipment and equipment that serves the aircraft when they are not operating using jet fuel. Careful coordination of the requirements of this specialized equipment is required to assure that they are supplied with the power they require.

Additionally, some equipment requires power that is backed-up by uninterruptable power supply systems, some is supported by diesel generator power and some by “normal” utility company power. Resiliency and redundancy are of paramount importance for an active and vital airline terminal.

All of the above considerations are taken into account when designing the electrical distribution system for an airline terminal. Double-ended substations are typically provided for the distribution of utility company power. Sufficient generator power capacity is furnished to provide the level of terminal operation required during an extended utility company power outage. Electrical distribution equipment is arranged and located so that the panel boards are located on either the “land side” of the terminal and or on the “air side” (or secure side) of the terminal, depending upon where the equipment they serve is located to minimize jurisdictional issues that may arise when maintenance personnel must access the equipment.

Matthew Williamson: The Sacramento Valley Station masterplan project bus station has been designed to allow the charging of electric buses as well as of electric cars (either privately owned or car share system vehicles) as the lower level of the facility is a parking structure for the adjacent rail station. The bus charging systems required taking a new approach to the electrical design and involved working with the local utility company to address the electrical load that was significantly higher than similar structures. We also wanted to make sure that the facility was designed for a future where all vehicles were electric and required charging.

Michelle Blake: Most of these facilities require redundant power supply from the utility company and, depending upon the facility, quite a large power supply. This requires extensive discussions with the utility provider to determine how the site can be serviced and how long it will take to get this service. Backup power is a consideration as well. How much needs to be powered by the UPS and for how long? What needs to be powered by a generator and for how long? Will alternate energy sources be used, such as photovoltaic systems or cogeneration plants? The distribution of the power supply throughout the facility needs to be consider fixed and mobile equipment and “shore power” for electric vehicles. Electrification requires a completely separate power supply and distribution system but it must work with the low power system.

Jeremy Cooan: Power source reliability is an important issue to address when incorporating fleet electric vehicle charging infrastructure into a facility. This is especially important when relying on electric vehicles for revenue generation, such as with a transit organization or delivery service, as the loss of electrical service to the facility can result in the loss of vehicles for operations activities. Incorporation of redundant electrical services, alternate power sources, battery storage systems and microgrid technology within a facility used for fleet vehicle charging can help to increase system reliability.

What types of unusual standby, emergency or backup power systems have you specified for such facilities? 

Michelle Blake: Standard standby, emergency or backup systems include UPS and diesel or CNG generators. Generators can be permanent or mobile with a plug-in connection. We designed a natural gas cogeneration plant for the Whitby Rail Maintenance Facility. The plant supplies the majority of the building electrical loads with the waste heat captured and used for building heat needs. The combination of on-site backup diesel generation, the co-gen and locomotive generation electrical connections allow the restoration of power in the event of an extended power outage.

Ciarán Smyth: The Port Authority of New York and New Jersey establish the requirements for the battery run time for the UPSs that serve main information technology rooms and intermediate distribution frame rooms for the Terminal B redevelopment project at LaGuardia Airport. Some UPSs require as much as eight hours of run time. The automatic transfer switches that route utility power to certain terminal building loads and diesel generator power to those loads when there is an outage of utility company power have been segregated into those that serve code-mandated life-safety loads and those that serve loads that the terminal operator requires to be energized for smoother operational and business considerations.

Michael J. Rossini: While most of the backup standby systems are not wholly unusual or unique, how they are employed is of special interest. Each location is studied against specific sea level elevations and empirical stormwater levels. The selected equipment, such as standby generators, are then installed at elevated heights to safeguard operational readiness and stormwater mitigation.

What are some of the challenges when designing electrical, power and lighting for utilities, public works or transportation projects?

Jeremy Cooan: One challenge is the sheer scale of electrical service required for a large fleet electric vehicle charging operation. Using public transit buses as an example, a single 150-kilowatt charger might be specified for every four to eight buses within a facility. If a bus depot is expected to service and charge 100 buses, the vehicle charging infrastructure could add 3-4 megawatt of additional electrical load on the facility. This has a large effect on the sizing of the electrical services required, distribution equipment and overall electrical design of the facility. Incorporating this type of infrastructure into an existing building has the additional challenge of likely needing to provide additional electrical services to the building.

Michael J. Rossini: Challenges associated with large transportation projects include operational integrity, temporary services and complex phasing of the scope of work. Engineers must be proactive and responsive and design strategically, so that facilities like Logan Airport can remain fully operational. Temporary services that are implemented while selective scope is completed are not disposable systems but rather part of the complete project solution.

Ciarán Smyth: The challenges are not unlike those of most projects, except that the requirements for utilities, public works and transportation projects may exceed those of the local and national codes. Familiarity from the outset of a project with the requirements and standards of local authorities having jurisdiction will make for a more smoothly and efficient project design and construction. Communication in the early stages of the project and throughout the project is essential in making sure that the special standards and functionality requirements of the public agencies are satisfied.

How are such projects designed to ensure that the infrastructure can handle new, high-density equipment now and in the future?

Ciarán Smyth: Typically, the electrical infrastructure capacity is determined by studying actual data from other similar projects. Flexibility is ensured by providing an agreed-upon additional percentage of spare capacity. Similarly, an agreed-upon spare capacity of spaces in distribution equipment is also provided.

Certain trends in equipment types are also considered when determining infrastructure capacity, such as the provision of charging stations for electric powered tugs in airport terminals, as opposed to the still prevalent gas-powered tugs.

Of great importance is the allocation of spare pathways and floor space in electrical rooms (when possible) for future distribution equipment and feeders. For future security checkpoint scanning equipment, for example, that was known to be coming but that were not yet part of the Transportation Security Administration standard, circuit conductors were upsized to accommodate the new equipment power requirements while the overcurrent protection devices were selected to suit the present equipment, making the switch over, when it occurs, minimally disruptive to the day-to-day activities of the active terminal.

Michelle Blake: Low power supply and distribution systems are typically design with 25% to 50% spare electrical capacity to accommodate future unknowns. Future electric vehicle power or charging requirements are assessed based on fleet growth and technology assumptions and spare capacity is designed accordingly.

Michael J. Rossini: Project power system design typically includes the aggregation of power density calculations for the following types of loads: facility and ground support equipment loads, airline tenant loads, commercial/retail tenant loads, technology/UPS loads and TSA/security loads. In general, the system design must accommodate load growth to varying degrees, within each of the types, while remaining within physical and spatial constraints.

What are some key differences in electrical, lighting and power systems you might incorporate in this kind of facility, compared to other projects?

Michelle Blake: These facilities often have high and low voltage power supply and distribution systems. Lighting systems in shop and storage spaces require careful consideration of light levels required for maintenance activities carried out under the vehicles, either on hoists or over pits and on maintenance platforms at roof levels. Power supply for mobile maintenance equipment must be thoughtfully located to prevent cables run over the floor, creating tripping hazards.

How does your team work with the architect, municipality, owner’s rep and other project team members so the electrical/power systems are flexible and sustainable?

Michael J. Rossini: Teaming with Massport’s utility systems project manager allows the design team to get real time utility data. This invaluable demand load data is used as a benchmark against connected load calculations, aiding the design team in “right” sizing the equipment.

Michelle Blake: During the functional programming stage, our integrated team of architects, industrial engineers and building system engineers work with the end-users to understand their operational requirements. We design the facility to meet the operational requirements. We work with other stakeholders to identify and resolve and challenges with the electrical/power system requirements.

Ciarán Smyth: Communication and experience are the keys to every successful project. Sharing knowledge and information about present and future trends in requirements, as well as specific design concepts, are realized in regularly scheduled meetings and in the establishment of agreed-upon project design criteria via the review of written narratives and design drawing reviews.

For example, if a municipality or authority mandates the use of photovoltaic panels or if their use is suggested by the design team, the space required, the aesthetics, the technical considerations and the cost are clarified, vetted and ultimately approved by the key team members mentioned above. Additionally, an electrical utility and generator power distribution system was devised to allow for the building to operate in a close to “business-as-usual” mode during an extended utility power outage that automatically provides sufficient power to code-mandated life-safety loads should a life-safety emergency arise during an extended power outage.

What kind of lighting designs have you incorporated into such a project, either for energy efficiency or to increase the occupant’s experience?

Michael J. Rossini: As anyone would expect, LED luminaires are the new standard when designing projects at facilities like Logan International Airport. However, the use of RGBW DMX based lighting has made its presence in high profile spaces in recent major projects. It’s all about the customer experience at the airport, the look and feel of the lighting, the colored accents and the color changing feature lighting. Massport has gone beyond utilitarian functionality in its approach to lighting for all projects. They want travelers to enjoy coming to the airport, understanding that gate terminals are a memorable source of first and last impressions for travelers.

Michelle Blake: For energy considerations and maintenance considerations, LED lighting is used throughout the facility. To increase the occupant’s experience, attention is given to task, ambient and occupant-controlled lighting.

Ciarán Smyth: All of the lighting fixtures used for the LaGuardia Airport Terminal B Redevelopment project use LED technology for its energy efficiency, long life and reduced maintenance.

When designing lighting systems for these types of structures, what design factors are being requested? Are there any particular technical advantages that are or need to be considered?

Michelle Blake: The most common design factor being requested is adequate lighting levels in the workshop areas.

Are you seeing more smart- or microgrid aspects on such projects? If so, how have you served these needs?

Ciarán Smyth: The current increasing trend toward smart and microgrid aspects could provide flexibility and resiliency to airline terminal projects. However, the LaGuardia Airport Terminal B Redevelopment project did not include this technology.

Matthew Williamson: Yes, we are seeing more transit-oriented developments that aim to better integrate the public transit structures into the community. The Sacramento Valley Station bus station project has a large canopy which is ideal for solar PV with microgrid systems which can aid transit-oriented development and adjacent properties target net zero energy goals.

Jeremy Cooan: The incorporation of smart- or microgrid technologies into these types of facilities to manage electric vehicle charging equipment and local generation resources will be a trend in the future. As more facilities add electric vehicle charging infrastructure, the need for managing this electrical load on the overall electric grid will be greater. Using local renewable energy sources and energy storage systems to provide an off-grid energy source for vehicle charging will allow for greater flexibility in the operation of these systems.

When designing lighting systems for these types of structures, what design factors are being requested? Are there any particular technical advantages that are or need to be considered?

Ciarán Smyth: Branch circuit panel boards that are both programmable and remotely-controllable, which are dedicated to lighting loads and have onboard dimming capability, have been provided for the energization and control of all lighting fixtures on the project. These dedicated panel boards have been circuited to either life safety power ATSs or standby power ATSs. Thus, every lighting fixture is connected to generator power.

This arrangement is a means by which the terminal operator’s request to maintain flexibility regarding lighting issues was realized. The operator’s desire was to have the capability to easily control lighting zones automatically or manually from virtually any location and to be able to easily energize certain lighting zones in a flexible fashion during extended power outages when the building was running on diesel generator power to maintain a great degree of “business-as-usual” under these conditions. Occupancy and vacancy sensors were also employed on the project as well as daylighting which included automatic control of shades.

Do you have experience and expertise with the topics mentioned in this content? You should consider contributing to our CFE Media editorial team and getting the recognition you and your company deserve. Click here to start this process.