Staying Lean and Green

By Tom Wozniak, P.E., Senior Electrical Engineer, and Bill Newman, P.E., Senior Mechanical Engineer, Giffels, Southfield, Mich. September 1, 2005

When Henry Ford built his revolutionary manufacturing complex on the banks of the Rouge River in Dearborn, Mich., its vertically integrated approach became respected throughout the world as a model for industry.

And for several decades, the Ford Motor Company’s “Rouge” operated under the notion that America was blessed with an infinite supply of natural resources. But by the late 1990s, depletion of natural resources had become a common concern, lean manufacturing processes had replaced the methods of the past, and the facilities and infrastructure of the Rouge began to succumb to the ravages of time.

The company was determined to revitalize the Rouge by embarking upon a redevelopment plan that incorporated a number of lean manufacturing and environmental features, thus creating a “model of 21st century sustainable manufacturing.” The ensuing project included a 1.09 million-sq.-ft. assembly plant, a 907,000-sq.-ft. body shop, 250,000 sq. ft. for a historic assembly building and a 70,000-sq.-ft. historic Dearborn glass plant.

Electrically speaking

Getting down to specifics, the design of this LEED-certified facility’s electrical systems spanned a period of five years with design criteria established at the outset in a series of meetings between the design engineers and Ford engineers. The design scope included process fit-up in addition to general building systems design.

Primary power for the new facilities, which are now completed, is distributed at 13.8 kV. One of the biggest power challenges was finding a route for the main 13.8-kV feeders from the source at the 120/13.8-kV primary substation to the body shop, final assembly and chiller building. The previous primary substation had only been designed to replace old switchgear that fed various substations on the site through an old underground duct-bank system and did not take the new facilities into consideration.

Consequently, all of the 15-kV feeder cables leaving the new substation were routed through two 68-ft. by 14-ft. cable vaults on the west end of the primary substation. From these vaults, cables were routed in short runs of new duct banks to existing manholes and then through the existing duct banks where they replaced the old cables. Fortunately, there were enough spare 15-kV breakers in the primary substation to support project requirements.

The underground duct-bank system was filled to capacity, and the congestion of other underground utilities, plus building interferences, precluded the construction of new duct banks. However, the only way to wire the cables above grade to the new facilities was to route them through the cable vaults and then transition them overhead. The cable vaults were a spider web of 15-kV cables, but with the aid of an electrician hired by the construction manager, the engineers were able to snake the new cables through. At the wall at the end of one of the vaults there was just enough room to box out a new duct bank for the cables. Cables from the other vault were installed to this vault via an existing short duct bank connecting the two vaults. The new duct bank was extended from the vault wall by about 20 ft. and then raised up to a new trestle that had been constructed specifically for the new cables. With much difficulty, 10 three-conductor, 500-kcmil, 15-kV cables were routed from the switchgear through the cable vaults and up to the trestle. This trestle ultimately hooked up with the main trestle supporting the mechanical utilities.

Thus, the 15-kV teck-type interlocked armor cables convey power from the primary substation to primary switchgear at the assembly building, body shop and chiller building. Two 15-kV feeders supply each of these facilities, as the primary switchgear in each facility is double-ended with two normally closed main breakers and a normally open tie breaker. Each primary feeder has ample capacity to supply the entire load in case the other feeder is out of service and all 13.8-kV circuit breakers are the vacuum-breaker type.

Teck cable was chosen for its superior ability to protect the current-carrying conductors in outdoor installations. The overall jacket on conventional interlocked armor cables can deteriorate over time when installed outdoors, where moisture can enter the cable. Teck cable has jackets over and under the armor, with the inner jacket providing an added degree of protection against moisture ingress.

Substations to suit

The primary switchgear in the body shop supplies seven 480Y/277-volt building power substations and five 480-volt welding power substations. Each substation consists of two primary switches, two 2,500-kVA silicone fluid-filled transformers and draw-out power-air circuit breakers in a secondary selective arrangement, with two normally closed main breakers and a normally open tie breaker. Each primary switch is fed from a different bus in the primary switchgear. Finally, 1,600-amp busways fed from the substation feeder breakers complete the 480-volt distribution scheme. The final assembly distribution scheme is similar except there are only four 480Y/277-volt substations in that building.

The 13.8-kV feeders to the chiller building supply a 13.8%%MDASSML%%4.16 kV double-ended substation for the chillers and a 13.8 kV-480Y/277-volt substation for the other loads. The secondary switchgear in the 4,160-volt substation consists of vacuum breakers. As in the assembly building and body shop, the secondary switchgear in both substations has a secondary selective arrangement. To minimize the size and cost of the chiller building, value engineering determined that outdoor switchgear would be the most economical scheme. System reliability was preserved by enclosing the switchgear in outdoor, walk-in type enclosures with all conduit entrances from the bottom. Transformers are the outdoor, cast-coil type, thereby eliminating the fluid containment issues associated with liquid-filled outdoor transformers.

Transformers at all substations are equipped with fan cooling. The increased kVA rating thus obtained assures that one transformer will be able to handle the entire substation load should the other feeder be out of service.

All main and feeder breakers at each substation are equipped with circuit monitors connected to the plant’s local area network, giving plant engineers remote computer access to real-time critical electrical data such as voltage, current, power and harmonic information using a standard web browser.

Power-factor of 450 kVAR correction has been provided at each half of every 480-volt unit substation in the final assembly building and every 480-volt building power substation in the body shop. The power-factor correction equipment is connected to a feeder circuit breaker at each substation. Since the process load connected to these substations consists of sensitive electronic loads such as programmable logic controllers, UPS and microprocessor-based controllers, a transient-free, harmonic-filtering, reactive-compensation system was selected. This system maintains a high overall power factor and absorbs up to 80% of the 5th harmonic current while eliminating voltage transients associated with traditional power-factor correction equipment.

An illuminating combination

The lighting design also reaps efficiencies. High-bay metal-halide light fixtures provide 30 footcandles (fc) of general plant illumination in manufacturing areas. T8 fluorescent lamps in industrial fixtures are used for task lighting where higher illumination levels are required. The metal-halide fixtures are provided with 400-watt pulse-start lamps and magnetic regulator ballasts. This combination maintains approximately 20% higher illumination levels than can be obtained with standard lamp-ballast combinations while also providing an estimated twice the rated lamp life.

Inside the final assembly building, thirty 12-ft. by 25-ft. skylights and ten 35-ft. by 100-ft. monitors on the roof emit sufficient sunlight on sunny days to permit alternate rows of high-bay fixtures to be turned off while still maintaining desired lighting levels. This is accomplished by using photocells in the monitors to control the lighting in the area surrounding each monitor.

Approximately 55 to 60 fc of general illumination for open office areas is provided using indirect lighting fixtures with 10% THD electronic ballasts and high-output T5 lamps. This achieves the dual purpose of minimizing veiling reflections on computer screens while maximizing lumen efficiency. Ultimately, a power density of 1.2 watts per sq. ft. has been realized. Also, the improved optics available with the T5 lamps permitted the fixtures to be mounted 18 in. below the 9-ft. ceilings and still achieve uniform lumen distribution across the ceiling. Meanwhile, task lighting at individual workstations supplements the general illumination to suit each employee’s needs, and 18-cell parabolic fixtures with T8 lamps are used in small offices with an occupancy sensor to turn the lighting off during periods of employee absence.

Similarly, both process and building lighting loads are controlled by a building automation system that shuts off the lights during non-occupancy periods.

Also, exit lighting fixtures are 277-volt LEDs with green lamps yielding an energy consumption of 1.7 watts per fixture.

One fc minimum of emergency lighting is provided throughout with the same type of fixtures used for general illumination. The emergency lighting and exit lighting fixtures are fed from online UPS located in the substation rooms. The UPS units eliminate the problems associated with emergency generators such as the brief period of total light loss and the restrike times of HID fixtures. Since the substation rooms in the body shop and final assembly building are in roof-mounted penthouses where summertime temperatures can easily exceed 100°F, battery cabinets were provided with thermostatically controlled air conditioners to maximize battery life.

Keeping cool

A central chiller building serves the plant area, body shop and final assembly building via an innovative “big foot” air tempering system that maintains the temperature inside the buildings at 10°F below the outside ambient temperature.

The air in the building is replaced with fresh air every 30 minutes as the ductless system mixes warm air near the ceiling with cool air near the floor to create a more pleasant temperature at the work level. The building acts as one giant air duct, creating a slightly positive air pressure to keep out drafts when loading-dock doors are open.

The size of the new facility justified the use of an energy- and first-cost-savings system for cooling the plant spaces. Thus, chilled water is circulated to the air-handling units located on the roof of each plant. Ultimately, the system required approximately 10,000 tons of cooling, so to reduce first cost of the water chiller installation, a one-million-gallon thermal water-storage tank was employed. This tank enabled the chilled water system to be reduced in size, resulting in fewer chillers than a conventional system of the same capacity.

The storage tank is an open vessel that maintains approximately the same holding volume of water at all times. The water in the tank is stratified, with the cold water on the bottom of the tank and the warmer water on the top. Water is pushed into the bottom of the tank from the chillers to “charge” the tank, while at the same time warm water is drawn from the top of the tank and routed to the chillers. This occurs when the chillers are not fully loaded.

However, the lower first cost of providing fewer chillers is only one benefit of a chilled-water storage system. The other is the system’s operating cost. By base loading the chillers at full capacity, chilled water can be generated around the clock. When the system does not need the cooling capacity, it is diverted to the tank and stored for when the system calls for more cooling. Loading the chillers in this way allows for more efficient chiller operation and off-peak use. Furthermore, off-peak operation potentially reduces electrical demand charges and electrical usage charges depending on the local utility’s rate structure.

The HVAC units for the project were unusually large roof-mounted units that can be operated at up to 250,000 cfm each. Using larger units lowered first cost and centralized the maintenance locations. The HVAC units are used to maintain the plant areas at a positive pressure with respect to the outside atmosphere and are also an integral part of the smoke-control system in the building.

Typically, roof-mounted smoke-relief vents are installed in industrial buildings. These smoke vents add cost and contribute to roof maintenance problems. For this project, the solution was to use the large roof-mounted HVAC units with perimeter wall-mounted relief vents to contain and remove smoke from any portion of the building.

Looking back and forward

This extraordinary project demonstrates what can be accomplished when engineers, scientists, architects, executives, employees and members of the community work together to achieve a higher level of performance.

Just as the original River Rouge complex tested and proved Henry Ford’s theories about mass production and vertical integration, the revitalized Ford Rouge Center is becoming a living laboratory of advanced technical and environmental concepts developed to meet the demands of the 21st century.

Under One Green Roof

One of River Rouge’s most striking features is the world’s largest ecologically inspired green roof, which will dramatically enhance the Rouge area watershed by holding several inches of rainfall. When rain falls on the final assembly building’s 10.4—acre green roof, it is absorbed or filtered by sedum plants. Excess water then drains off the roof into stone storage basins located under the porous paved lot nearby. From there, it moves to swales and treatment wetlands where plants act as “nature’s filters” to prevent dirt from migrating into rivers and lakes.

The green roof also provides a protective layer over the more conventional waterproof roof and assists with the heating and cooling of the plant. This is achieved by the addition of an extra layer of insulating material. In the summer, the green roof will hold rainwater allowing for slow evaporation, which assists with the reduction of the building’s cooling load. The retention of the rainwater also creates less of a burden on the drainage system and will accomplish some minimal filtering of the water before it goes to the site’s storm water system.

Ford worked with Michigan State University to develop a customized lighter growth media at the same time the general building design was underway. The resulting new product was thin, light and flexible, but required that the green roof be irrigated until the plants were fully established. A temporary installation providing 21,000 gallons of water per day and the irrigation system were dismantled and removed when no longer required.