One of the many issues facing cities, towns and campuses throughout. Making Connections in Miami: Cover Story

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1 Cover Story Making Connections in Miami: County improves plants, integrates cooling loops One of the many issues facing cities, towns and campuses throughout North America is the challenge of replacing old, inefficient infrastructure with new assets. In the case of district energy systems, wise investments in modern boilers, controls, thermal energy storage and combined heat and power technology can yield considerable savings in annual operating costs for decades to come. They can also enhance reliability and reduce greenhouse gas emissions. However, even when it can be demonstrated that the long-term savings will far exceed the cost of the improvements, plans for replacement often remain on the shelf for lack of financing. In 2008, Miami-Dade County, Fla., was faced with such a situation. County officials recognized the long-term potential that would result from critical investments in Miami-Dade s central cooling infrastructure. But rather than attempting to finance the improvements with county appropriations or bonding, officials turned to performance contracting, an option that recently had become more viable thanks to changes in Florida enabling statutes. The experience turned out to be advantageous for the county and commercial property owners as well. Background Miami-Dade is the eighth-largest county in the United States and home to 2.4 million residents. With 1,946 sq miles of land area, bordered by the Atlantic Ocean to the east and south, the Everglades to the west and Broward County to the north, Miami-Dade County provides infrastructure support to its 35 city government partners. County government provides many critical services including police, fire and rescue, water and sewer, Miami International Airport, library system, corrections, seaport, public housing, transportation and parks. It also owns a district cooling system or, to be more precise, two district cooling systems. The original Miami-Dade chiller plant was built in 1984 to provide chilled water to the county s downtown facilities. 12 District Energy / Second Quarter 2013

2 Center, right: A crane lowers coils into the new storage vault at the North Loop plant. Far left: New piping connects the two cooling loops. All photos courtesy ConEdison Solutions. Known as the Central Support Loop, the system serves 2.5 million sq ft of space in nine county-owned buildings. Until a recent upgrade, the plant produced 6,000 tons of chiller capacity from three 1,500-ton electrical centrifugal chillers (installed when the plant was built) and a newer 1,500-ton electrical centrifugal chiller. The site is physically constrained, effectively ruling out the addition of thermal energy storage or other plant expansions. Miami-Dade s other chiller plant, known as the North Loop, was acquired by the county from a private owner in It had been built in 1999 to operate as a commercial district chiller plant, initially serving the American Airlines Arena (home of the Miami Heat basketball team) and the Terremark Worldwide Technology Center, which essentially houses the main Internet switch for Central and South America. In its original configuration the plant produced 3,600 tons of chilled-water capacity; 1,200 tons of ice production capacity; and 17,280 ton-hr of ice storage capacity. Unlike the older plant, this facility had been designed to accommodate future expansion on both the water side and ice storage side. Miami-Dade s situation was far from optimal, yet the potential was significant. Miami-Dade s situation was far from optimal, yet the potential was significant. It owned two cooling plants: one that was old and inefficient with no room for expansion and another that was new, efficient and underutilized. By 2008, the county was facing multiple challenges with its district cooling systems: The county had approved the construction of two new buildings that would need district cooling service: the Children s Courthouse (designed to house juvenile courts and judges chambers) and Overtown Transit Village II. These additions would push the connected load of the Central Support Loop to 7,520 tons, far exceeding the system s 6,000-ton capacity. The Children s Courthouse was scheduled for LEED (Leadership in Energy and Environmental Design) Platinum or Silver certification, but LEED guidelines would prevent it from taking chilled water from a plant with R11 refrigerant chillers, the type used in the Central Support Loop. The two networks were not connected, prohibiting the North Loop plant from absorbing the added load created by the new county buildings. Miami-Dade wanted to solve all of these issues and begin realizing the potential of the North Loop plant. To help develop and implement a comprehensive plan, the county turned to ConEdison Solutions, which already had an established consulting relationship with the county and had also been the operator of the North Loop under its previous owners. The logical solution was to connect the two systems, modernize both plants and seek opportunities to add more private customers to the system through the retail sale of chilled water. A 20-year performance contract was developed in 2008 that would enable the county to build a District Energy / Second Quarter

3 much larger district cooling system by modernizing the Central Support plant, completing the buildout of the North Loop plant and interconnecting the two distribution networks. The performance contract would effectively allow the county to use future operating savings to pay for the capital expansion. RMF Engineering was selected to provide consulting services working in collaboration with ConEdison Solutions engineering team for the plant upgrades and network interconnection. The performance contract would effectively allow the county to use future operating savings to pay for the capital expansion. A Comprehensive Solution Between 2010 and 2012, a series of major improvements was implemented. At the Central Support plant, one of the old 1,500-ton electric chillers was replaced and another 1,500-ton chiller was added, bringing the capacity up to 7,500 tons. Related controls and infrastructure were also upgraded and added to accommodate the new chillers and improve operating efficiency. Over at the North Loop plant, contractors added another 2,500-ton electrical centrifugal chiller, bringing the capacity up to 8,500 tons. A new two-cell cooling tower was installed to match the two existing 4,000-ton units. Another thermal storage vault was added, bringing the total to three. The additional ice storage capacity would enable the plant to increase its electric demand shift and take advantage of millions of dollars in rebates from Florida Power and Light, the local utility. In fact, when the total potential load shift of up to 8,500 tons is factored in, the rebate potential is $4.1 million. Completing the upgrade was an electric distribution motor control center expansion, the replacement of many of the facility s pumps, the addition of new variable-speed drives and the expansion of the facility s direct digital control system. The final component that would unlock the full potential of the upgraded North Loop plant was the interconnection of the two distribution networks (fig. 1). This proved to be quite a challenge. The loops were separated by a distance of 1,100 ft; the connection would need to be made through the high-density downtown area; and the work would need to be completed quickly, with minimal disruption to traffic and existing infrastructure. In order to minimize the impact on the particularly busy NW 8th Street, North Miami Avenue and NW 1st Avenue intersections, engineers employed microtunneling to create two 40-inch tunnels that would accommodate two 24-inch chilledwater lines. The 180- and 250-ft tunnels were bored 25 ft below the surface over a three-month period with the NW 8th Street- North Miami Avenue intersection completed first. The extreme depth was necessary in order to avoid other underground utilities. Extensive geotechnical survey work was undertaken to determine the correct depth of 25 ft. A jack-and-bore method was also considered for installation of this piping; however, geotechnical testing of the substrate resulted in the need to deploy the microtunneling method instead. The interconnection was completed in October 2012, and the combined plants are now functioning as one integrated system. One of the challenges of the project was to provide the flexibility to connect future customers anywhere along the two loops. There is a physical separation of the two loops through isolation butterfly valves installed at various locations along the underground piping loops, explains André LeBlanc, director of operations for ConEdison Solutions. Basically, the Central Support Loop and the North Loop are interoperable through the opening and closing of these isolation butterfly valves. This allows for flexible shifting of chilled-water load from one loop to the other in a very straightforward manner. While the combined system has only been operating for a few months, LeBlanc estimates that it will reduce the county s cost of producing chilled water by approximately 27 percent, even with the load that it has today. The county also has the capacity to sell chilled water for cooling service to private customers at a rate that is better than they could produce themselves due to the North Loop s physical capacity and the overall operating efficiency of the plant. They will also benefit from the reliability of the district cooling service. In the case of the System Snapshot: Miami-Dade County, Fla. Startup Year Number of Buildings Served Total Square Footage Served Total Capacity Total Number of Chillers Fuel Types Distribution Network Length Piping Type Piping Diameter Range System Pressure System Temperatures System Water Volume Source: ConEdison Solutions. Chilled-Water System 1984 Central Support Loop system starts up 1999 North Loop system begins operation 2012 Two loops integrated 14 5 million sq ft 16,000 tons 52,000 ton-hr thermal energy storage 10 water chillers; 4 glycol chillers Electric 3.5 miles Preinsulated ductile iron 12 to 24 inches 90 psig 36 F supply/54 F return 1.2 million gal 14 District Energy / Second Quarter 2013

4 Figure 1. Miami-Dade County Chilled-Water Interconnect Project. American Airlines Arena Terremark Worldwide Technology Center Source: ConEdison Solutions. District Energy / Second Quarter

5 American Airlines Arena, the connection to the cooling loop system eliminated the need to invest in its own chillers and associated equipment, thus avoiding a major capital expenditure. The Two Plants Today The combined system now offers significant expansion capabilities and increased operating efficiencies. Between the two plants there is approximately 6,500 additional tons of chilled-water capacity available for future use. With the completion of the interconnection, 1,200 tons of the North Loop s capacity was shifted to facilities owned or controlled by Miami-Dade County. More of the load is gradually being shifted to the North Loop plant, with 3,000 tons of capacity still available to be shifted. As demand for the sale of chilled water increases, buildings shifted to the North Loop can be shifted back to the Central Support Loop, thus offering significant diversity and flexibility to Miami-Dade County and its private-sector customers. Today, the Central Support plant continues to be operated by county employees and has a capacity of 7,500 tons produced by five 1,500-ton electrical centrifugal chillers. The North Loop plant is operated by ConEdison Solutions personnel as part of its contract with Miami-Dade County. Total plant capacity is 8,500 tons provided by three electrical centrifugal chillers at 1,166 tons each and two at 2,500 tons each for chilled-water production at 36 degrees F; one electrically driven screw chiller rated at 800 tons for ice production at 24 F; one electrically driven screw chiller rated at 400 tons for ice production at 24 F; two electrically driven centrifugal chillers rated at 1,800 tons each for ice production at 24 F; six induced-draft cooling tower cells each rated at 2,000 tons of heat rejection; and three custom-built thermal energy storage tanks rated at 17,280 ton-hr each, for a total of 51,840 ton-hr. Even after the recent additions, the plant has the potential to add additional capacity if demand warrants in the future. Conclusion The completion of the Miami-Dade project has turned a series of problems into an opportunity that positions the county for success well into the future. In addition to providing added capacity and redundancy, the interconnection of the two plants has made it possible to implement a robust preventive and predictive maintenance program. This was made possible partially through the integration of the building automation system into the preventive maintenance program. A major factor in this outcome was the ability to utilize performance contracting, which allowed Miami-Dade County to borrow money to invest in more than $20 million of improvements and pay it back through the future savings it will realize by operating more efficiently. Today, Miami-Dade can operate the two plants more economically as one system than as two, while also achieving an anticipated reduction in greenhouse gas emissions of 327 metric tons annually. And it s all been accomplished at no cost to taxpayers. In this era of ever-increasing pressures on local government finances, that s a significant accomplishment. A History of Performance Contracting In 1994, the state of Florida promulgated performance contracting enabling statutes for public agencies (FS ) and a companion statute for public schools (FS ). While the statutes have been modified from time to time, they constitute the backbone of performance contracting in the state of Florida for public institutions. In June 1998, Miami-Dade County entered into what was to become a 10-year master agreement with four, and then three, energy service companies to fast-track project implementation, to simplify procurement of services from qualified providers and to manage the efforts through a programmatic approach. By the end of that 10-year period, Miami-Dade County had invested $58.7 million in energy conservation improvements at 142 sites under 36 project contracts. This program provided critical infrastructure improvements that have saved $7.4 million per year through the installation of energy-efficient technologies; this translates to an approximately 10 percent return on investment. The environment also benefited from this program that saved 73 million kwh/year; based on the U.S. Environmental Protection Agency s Greenhouse Gas Equivalencies Calculator ( com/3dmfdp) that reduced the county s carbon dioxide emissions by 56,753 metric tons annually, which is the equivalent of taking 10,395 passenger vehicles off the road. The program also saved 71 million gal of water, which is a critical commodity in South Florida. While the county was leveraging the benefits of a standardized performance contracting approach, the state of Florida took a similar program approach for its state agencies. In the beginning of 2008, Florida refreshed its state term contracting vehicle managed by the state s Department of Management Services with the inclusion of 10 state-qualified energy service contracts. The tie-in with Miami-Dade County is that while state agencies are required to use the state term contract, eligible users, including cities and counties, can use the state term contract and work with its 10 state-qualified energy service companies. The benefit to the county is that it can now leverage the resources of 10 recently qualified firms in a programmatic approach similar to the county s proven program approach. Editor s Note: District Energy would like to thank André LeBlanc, Michael Gibson and Christine Nevin of ConEdison Solutions for their contributions to this article. 16 District Energy / Fourth Second Quarter