Since its establishment in 1918, Fort Bragg has become one of the US Army's largest and most critical facilities. Unfortunately, by the 1990s, years of financial neglect had crippled the fort's energy infrastructure. But the situation was an opportunity for Honeywell Building Solutions—a chance to implement a distributed energy and power management program—if the company was willing to make a multi-million dollar bet on new technology and engineering designs.

Starting in 1997, Honeywell installed a wide array of improvements and cost-saving measures (see sidebar), the latest, and certainly the most innovative, being the completion of a prototype cooling, heating, and power (CHP) generation system. The goals for the CHP system were far-reaching and required the creation of a team that included Encorp (network technology and infrastructure management), Broad Air Conditioning Co. Ltd., (absorption chillers) I.C. Thomasson Associates Inc. (engineering services), and Chelsea Group Ltd. (indoor environmental building services). Under Honeywell's guidance, the team set out to develop an economically superior CHP system: one that could serve, with online optimization, as a reference design for simplified installation and supervisory control systems.

The results have reduced energy consumption costs by $1.8 million per year. But the accomplishment required a new type of financing, a new design in absorption chillers, a new automation system, and a modular approach to construction.

When Honeywell began, it found a staggering backlog of work. The fort has gone through a number of construction upgrades, the last in 1950, and the Army still hasn't replaced much of the technology from 50s. Among the worst problems: fourteen aging central energy plants producing either steam or chilled water.

Most were limping along on their last legs, according to Gregory Bean, director of the fort's department of public works. “Our engineers have one of the most difficult challenges around, because there's a new problem every day,” says Bean. “Things have been under-maintained and over-utilized, and we have very demanding customers.” The fort hosts the 18th Airborne Corps, the 82nd Airborne Division, command units for Special Forces, and 44,000 soldiers plus their families. Bean estimates another 10 years of significant construction and $3 billion worth of upgrades just to return to acceptable operating standards.

Rising energy costs helped to create the unacceptable situation, yet they also created the urgency for action, since the Army is under an executive order to reduce energy usage throughout its facilities. Bean says there was barely enough money to keep the doors open and to respond to safety issues, so the Army had to implement a program that somehow leveraged other people's money.

The other people's money happened to be Honeywell's. The company is working under an Army Corps of Engineers multi-state Super Energy Savings Performance Contract (ESPC). The ESPC runs for 24 years and Honeywell assumes all risks and startup costs. The savings gained from energy efficiency projects are reinvested in the installation's infrastructure, with savings from the investment split between the fort and Honeywell. A maximum of 10% goes to the installation and 90% to Honeywell for the repayment of capital investments. Honeywell has agreed to achieve a 35% energy reduction by 2010, using the fort's 1985 energy baseline as the benchmark.

So far, Fort Bragg has seen a 25% drop in energy costs over the last seven years, resulting in a savings of $57 million. Savings have accelerated with the newest addition to the fort's energy arsenal: the $11 million prototype CHP system. For the overall design of the system, Honeywell contracted with the engineering firm of I.C. Thomasson Associates Inc.

“First, we built it on paper by doing an electric and thermal model of Fort Bragg's heating plant,” explains John Wimberly, Thomasson's president. “Just understanding the annual thermal cycle and connected load was an important part of the equation.” Thomasson's engineers evaluated the barracks' annual thermal cycle down to a monthly and hourly basis. They chose the generator, heat recovery and chiller components that could be constructed and connected using a modular approach, rather than extensive custom installation. The studies and engineering design took roughly eight months, followed by 13 months of construction and one month of startup and commissioning. Thomasson worked under a “design-procure-construct” contract. Ultimately, the firm was responsible for all phases of design and construction for a turnkey system that would be owned by Honeywell.

Thomasson's design starts with a Solar 5.5-MW gas combustion turbine. Dual fuel capability allows switching, on the fly, from natural gas to No. 2 fuel oil. The turbine exhaust fires both a Broad 1,000-ton absorption chiller and, concurrently, a heat-recovery steam generator producing up to 80,000 pounds of steam per hour.

According to Honeywell engineer and project director Jim Peedin, the only significant problem was backpressure for the chiller. “We wound up adding induction fans to the absorption chiller so the flow was properly split between the steam and the chiller,” Peedin explains. “In this case the path of least resistance for the gas coming from the turbine was more toward the heat-recovery steam generator, so we had to add some extra boost to make sure the absorption chiller got its fair share of gas.”

The turbine's electricity output typically feeds into the base's power network, but in an emergency it can be reconfigured to serve in a microgrid application. The steam generator provides heating and hot water at the barracks accommodating the troops plus families, and the chiller cools the same facilities.

The ultra-efficient design of the prototype and its chiller are great news for future projects, according to Ron Fiskum, technical manager for DOE's Office of Distributed Energy. “The chiller is a big breakthrough,” says Fiskum, “In the past, this wouldn't have been possible, and when I started our program at the DOE we gave workshops where 200 people came to participate and figure out how we could create a system like what we're seeing at Fort Bragg. And the beauty of it is that it's a modular design.”

Fiskum notes that a similar modular CHP system is now running in Austin, TX. For companies with smaller load demands, United Technologies Company Power has an example of a scaled-down modular CHP system installed at an A&P market in Mt. Kisko, NY.

Although CHP systems are inherently more efficient, Fort Bragg's system is further enhanced with Encorp's automated control system known as Energy Information System (EIS), a centralized computer terminal center. “With a dual fuel system and various operating modes, computerized automation is needed,” says Peedin. “Fuel switching is rather complicated when you have very high-priced gas plus high-priced electricity and thermal loads to consider.” Some of the key decision factors analyzed by EIS include: fuels and inlet cooling to get maximum throughput to the generator; fuel price economics versus system output; moderation of chilling load and chilling capacity to provide inlet cooling.

Weather conditions can bounce around almost as much as prices, and EIS monitors and responds to hot weather forecasts with options to pre-cool the base during off-peak hours, to avoid purchases of electricity at peak rates later in the day.

Moreover, EIS controls other systems beyond just the CHP. It's responsible for the management of various power sources that include 15 diesel generators (eight MW total output) and one five-kilowatt fuel cell. “The diesel generators were originally assigned to high-security facilities, but now they are more flexible,” says Peedin. “We've been working toward putting in dedicated circuits on the distribution system so that we can add and drop off all unrelated loads and tie particular facilities together.”

The dedicated circuits allow the diesels to contribute peak shaving load management power by using closed transfer systems and intelligent communication gateways. The original OEM engine controls and transfer switches are still in place, so emergency backup capabilities remain uncompromised. But during emergencies, the diesels are drafted into service as a microgrid, with their operations based on utility availability and load management requirements.

The automated system monitors utility consumption across the distribution network via data from more than 256 meters communicating on a fiber optic network. Along with the CHP system, it controls other central plant and facilities equipment, and launches the diesel generators for peak shaving based on demand, energy market prices, and weather conditions. The market price information is important because Fort Bragg purchases electricity on a time-of-use tariff from Carolina Power & Light. At 4 p.m. each day, the utility provides hourly electric prices for the next 24-hour period.

The diesel generators typically perform about 200 hours of peak shaving duties per year, but EIS squeezes maximum efficiency out of the generators in some very sophisticated ways. It determines the optimal sequence of operation for each of the 15 diesels based on the proximity of a generator to the load, emissions measurements, the age of its fuel, and its operating and maintenance history.

All told, the tasks accomplished by EIS encompass a full range of operations. It identifies facilities with high conservation potential and analyzes their load profiles to determine the most economical use of power and power purchases. When applicable, EIS identifies locations and opportunities for cogeneration applications and analyzes real-time pricing data from suppliers to optimize the balance between purchasing power and use of the on-base generation. And that includes the option of shutting down the CHP completely. During the moderate temperature seasons of spring and fall, the barracks don't require much heating or cooling, so Honeywell has found it more economical to shut the system down and rely on utility power.

The efficient design of the prototype and its chiller is great news for future projects.

Performance has more than met Honeywell's expectations, and Peedin notes that plans are already in the works to add more diesels for an additional 16 MW of peak shaving capacity.

Also in the works are other distributed energy applications.

First, a photovoltaic system for one of the larger roofs of the base exchange. Then Peedin and his team are looking at the use of alternative fuels. “We could use a gasification process that would produce what we would call synthetic natural gas,” Peedin explains. “With the price of gas rising, these biomass projects are becoming much more economically feasible.” One possible method would use an integrated gasification combined cycle. Synthetic natural gas could be used in heating or powering a turbine or internal combustion engine. Waste wood products are the most likely source of biomass at this point.

Rising gas prices also have opened the door to different chiller configurations. Peedin and his team are weighing the economics of the current heat recovery and steam generator-absorption chiller configuration against an alternative currently under testing by the DOE, Oak Ridge National Laboratory, and Austin Energy. The system uses a turbine exhausting directly into a chiller, but without the heat recovery steam generator. The full thermal output of a 4.5-MW natural-gas-powered Solar Turbines combustion turbine exhausts directly to a 2,500-ton Broad chiller. Testing has verified fuel efficiency of over 80%, using the higher heating value (HHV) of natural gas.

Another area for evaluation is the cost performance between absorption and centrifugal electric chillers. “Depending on your thermal load, it's almost more practical to go with a gas turbine so you're producing at peaking power, and then using a centrifugal electric chiller because they're so much more efficient,” says Peedin. “The electrical centrifugal chiller is really a very high-efficiency machine and takes about 0.5-kilowatts per ton of chiller capacity. So if you use it in conjunction with thermal storage, that's really the competition for an absorption killer.”

Thermal storage takes many different forms (such as making ice during off-peak hours), but for the fort's large central plants, Peedin anticipates cooling and storing water in tanks of 2 to 3 million gallons. Obviously, such tanks require a considerable patch of real estate. Although Fort Bragg has the space, Ron Fiskum sees a widespread demand for modular systems where large amounts of space aren't available.

“The military needs modular systems like this,” Fiskum explains. “I get calls from overseas embassies and ground forces where they have power outages every two or three hours. So systems like this give them control over their power, and that's critical. If something like their radar goes out, they're dead in the water.”

Beyond government sites, Jim Peedin predicts a strong future for the benefits of modular installations targeting industrial and institutional applications. “Colleges could take advantage of this and you see a number of industrial facilities that have plenty of use for onsite generation,” says Peedin. “And during a utility failure they could produce power for enough time to shut down or to continue operations. We're seeing the microgrid concept commanding a lot more interest, whether it's for the Department of Defense or college campuses—particularly with the impact of these killer hurricanes, and certainly we have a concern about terrorism and sabotage.”

The CHP projects at Fort Bragg, Austin, and Mt. Kisko received funding and research from the Department of Energy's Distributed Energy Program and Oak Ridge National Laboratory. The intent is to accelerate the development of integrated energy systems and packaged systems for commercial and institutional buildings. Information about the Department of Energy Distributed Energy Program and Oak Ridge National Laboratory integrated energy systems is available at: www.eere.energy.gov and www.ieswebcast.com.

Writer ED RITCHIE specializes in energy, transportation, and communication technologies.

DE - March/April 2006