Mechanical Systems

Existing Thermal Energy Plant (TEP-1)

Buildings on the main campus receive chilled water and steam for heating and domestic hot water from the existing thermal plant, TEP-1, located in the northwest portion of the campus. TEP-1 has five chillers with a total capacity of 9500 tons and firm capacity of 6500 tons. The plant has two steam boilers, each constructed to provide 60,000 pounds of steam per hour. One of the boilers has been modified to reduce its capacity to 30,000 pounds per hour. As a result, TEP-1 has a total heating capacity of 90,000 pounds per hour and a firm capacity of 30,000 pounds per hour.

Chilled water and steam are distributed throughout the campus via a piping network located in utility tunnels, building crawlspaces, and utility trenches. There are a number of bottlenecks in the distribution system that prevent TEP-1 from providing additional chilled water and steam to the southern part of the campus even if capacity were to be added to the existing thermal plant.

Existing Thermal Loads

The campus peak cooling load is approximately 4000 tons, and the peak heating load is approximately 30,000 pounds of steam per hour. The main campus buildings connected to TEP-1 when the maximum heating and cooling loads were measured were the Recreation and Wellness Center, the PE Building, the Convocation Center, the University Center, the Humanities and Social Sciences Building, the Multi-Disciplinary Studies Building, the Business Building, the John Peace Library, the Science Building, the Arts Building, the Bioscience Building, the Engineering Building, and the Physical Plant.

Future Thermal Load Projections

For planning purposes, the load projections have been divided into two time periods. The first covers buildings that are either under construction or that have been funded and will be completed within the next five years; the second covers buildings that are anticipated by the master plan to be built after 2009.

Buildings projected to be added to the main campus thermal utility loops by 2009 include BSE 1, BSE 2, the University Center Expansion, the Main Building, and the Recreation/Wellness Center Expansion.

These buildings will add approximately 6500 tons of chilled water load and approximately 51,000 pounds of steam per hour (or the hot water equivalent) of heating load. This will bring the total campus load to 10,500 tons of cooling and 81,200 steam pounds per hour of heating. Refer to the figures at the end of this section for load projection calculations.

Buildings that will be added to the main campus thermal utility loops from 2009 to its eventual build-out include two new academic buildings, the Convocation Center Expansion, the Performing Arts Center, the PE Building Expansion, and the Special Events Center.

These buildings will add approximately 5050 tons of chilled water load and approximately 40,700 pounds of steam per hour (or the hot water equivalent) of heating load. This will bring the total campus load to 15,550 tons of cooling and 121,900 steam pounds per hour of heating. Refer to the figures at the end of this section for load projection calculations. Per request by UTSA, BSE 3 is included in the load projections for the main campus even though the master plan shows it located in the new area of campus to the east of UTSA Creek. This will provide flexibility for UTSA in the event that future needs dictate a main campus location.

Note that the Special Events Center is shown but is assumed to have loads that are not coincident with the other buildings. As a result, capacity for the Special Events Center is assumed to come from diversity in the other building loads. This will be reviewed at the time of design for the Special Events Center and small supplemental systems can be added on site if necessary.

Providing Additional Thermal Utility Capacity and Distribution

Additional heating and cooling capacity will be added in two ways. First, TEP-1 will be modified and renovated to increase heating capacity and to improve the reliability of its cooling and heating capacity. Second, a new thermal energy plant (TEP-2) will be constructed in the south portion of the campus to provide chilled water and heating hot water to buildings on the southern portion of campus. Existing and new central plant locations are indicated on the first figure.

TEP-1 Modifications and Renovations

There are three basic types of modifications that need to be made to the existing central plant: replacement and repair of existing equipment, distribution improvements, and capacity improvements.

Replacement and Repair of Existing Equipment

Much of the existing original equipment is nearing the end of its service life and is in need of replacement or repair. In addition, some upgrades to TEP-1 must be performed in order to address existing operational deficiencies.

• The three original wood cooling cells are in need of immediate replacement. The structure of the tower and its fill are deteriorating rapidly and are near failure. These towers will be replaced with cells of equal capacity that are constructed of extruded fiberglass. These towers will also be equipped with fire protection to bring the building into compliance with current codes. The construction of the cells will be staged to prevent shutdown of the plant.
• The concrete floor near the water softener is failing due to corrosion of the reinforcing steel from exposure to brine spills. This section of floor will be replaced. Several concrete columns above the roof are spalling due to corrosion of reinforcing steel. These columns will be repaired and treated to prevent further deterioration.
• The refrigerant monitoring, ventilation, and purge control sequences will be changed to correct problems with refrigerant detection and excessive air flow in the plant.
• The boiler stack transition for one boiler will be replaced.
• An additional pipe support will be added on the plant roof to reduce the load on an existing column that supports the main condenser water header.
• Automatic operators will be installed on the cooling tower basin isolation valves to allow the building automation system to automatically start and stop chillers, condenser water pumps and chillers.
• Chiller #2 (2000 tons) will be replaced.
• The engine coolant pump for the generator will be replaced.

Distribution Improvements

The current chilled water pumping system consists of constant speed pumps in TEP-1 with variable speed pumps located in each building. As building loads decrease, plant operators can control chilled water pressure by turning pumps off and on. This method of controlling flow results in imprecise pressure control, wasted energy, and flow problems in buildings at the beginning and ends of the chilled water loop.

To eliminate these problems, variable frequency drives will be installed on the plant chilled water pumps and the control system will be reprogrammed to modulate chilled water flow from the plant pumps to maintain necessary pressure differentials across building chilled water connections on the campus loop. Additional control system monitoring points and other control system modifications will be added to make the system fully functional.

Capacity Improvements

One of the two existing boilers was initially constructed to provide 60,000 pounds per hour of steam but was later modified to reduce its capacity to 30,000 pounds per hour of steam. This was done to provide better operation at low loads. The original equipment was retained to allow the boiler to be converted back to 60,000 pounds per hour capacity.

Given the anticipated increase in steam load, original equipment will be reinstalled to increase the boiler capacity to 60,000 pound per hour as soon as possible. At the same time, boiler controls will be updated to replace out-of-date and inefficient boiler firing and safety controls. This will increase the total heating capacity of TEP-1 to 120,000 pounds per hour and the firm capacity to 60,000 pounds per hour.

New Thermal Energy Plant (TEP-2)

The initial build-out for TEP-2 will include sufficient heating and chilling capacity to meet the requirements of all the main campus buildings scheduled for completion in the next five years. The building space and distribution infrastructure will be scalable so that the plant can be expanded to serve all new buildings shown in the campus master plan. This includes capacity for BSE 3 in the event that it is built on the main campus.

To meet the projected total cooling load growth over the next five years, the new plant will be equipped with a 1250-ton variable speed drive chiller and two 1630-ton constant speed drive chillers. A 1750-KW emergency generator will be installed and configured to allow operation of the variable speed drive chiller and related auxiliaries in the event of a failure of normal electric power. Space will be provided to allow three more chillers of the same size to be added in the future.

TEP-2 will connect to the campus chilled water loop through BSE 2 to the 16-inch line which is being extended as part of the BSE 1 building project. A new line will be extended to the Performing Arts Center. This line should be sized and located to also service BSE 3 if it is located south of BSE 2. The chilled water distribution system has been analyzed to confirm that the projected peak campus load can be met with one chiller out of service at either thermal plant.

In lieu of installing new steam boilers and connecting into the existing steam and steam condensate return systems, the new thermal plant will be equipped with hot water boilers. Hot water boilers will provide a system that is lower in maintenance and installed cost and does not require the continuous supervision which a steam system does. Two 800-hp hot water boilers will be installed initially in the new plant, one of which will be redundant. A third boiler will be added in the future when the load growth exceeds the capacity of a single boiler.

Chilled Water Distribution

Shah Smith & Associates prepared a network analysis to ensure that chilling capacity could be delivered to the buildings without excessive differential pressure in the between the supply and return lines. Excessive pressure will not only increase energy costs, but will also result in flow control problems in buildings closest to the plants.

The analysis indicates that the new central plan can be located in the proposed location and provide 100% of its capacity by connecting to the 16-inch chilled water line being extended to the proposed BSE 2 building. The result will be differential pressures at both plants of less than 25 psi and minimum differential pressure at each building of between 15 and 5 psi. This will provide good flow to each building on the loop with reasonable energy consumption. Refer to the figure for connection of the new central plant to the adjacent buildings and existing campus chilled water distribution loop.

Shah Smith & Associates also analyzed the distribution system to determine if TEP-1 and TEP-2 could meet the campus loads if a chiller failed at either plant. The proposed configuration provided sufficient flow and differential pressure at each building for stable operation at full cooling load. When the three academic buildings on the north side of campus are constructed, 16-inch chilled water supply and returns will be installed from the north side of the existing central plant east to the new buildings. This will reduce water velocities in the 24-inch main running south from TEP-1 as well as the required differential pressure at the plant necessary to maintain flow to all the buildings on the loop. The extension is shown in the figure. A more complete analysis is included in the UTSA Main Campus Chilled Water Distribution Study issued under a separate cover.

Steam Distribution

Shah Smith & Associates prepared a network analysis of the existing steam system to determine how the new buildings on the main campus could be served using the existing steam infrastructure in conjunction with a hot water system installed in TEP-2.

To accommodate this approach, it will be necessary to design BSE 2 and the Performing Arts Center to utilize hot water from the new plant for heating purposes. Process steam loads in BSE 2 will use steam from the existing steam distribution system. If BSE 3 is located south of BSE 2, then it will also be subject to these requirements.

There is a bottleneck in the steam system in the 6-inch pipe that runs below the Science Building to the Bioscience and Engineering Building. Adding the process steam loads for BSE 2 and a future BSE 3 will require running hot water connections to the Science, Bioscience, and Engineering buildings to allow hot water from the new plant to offset steam usage in those buildings and to reduce the load on the bottleneck pipe. New buildings on the north and west part of the campus will use steam for heat to avoid the cost of installing a campus-wide hot water distribution system.

Converting the existing buildings from steam to hot water heat will be reasonably simple as the buildings currently use steam to hot water converters inside the buildings to generate heating hot water. Hot water piping from the new plant will simply need to be connected between the hot water converters and the building hot water pumps. The existing steam systems and connections will be left in place to provide further redundancy and to reduce the cost of the conversion.

New six-inch steam and four-inch condensate lines will need to be routed to the Recreation and Wellness Center expansion from the existing main under the Physical Education Building in order to receive heat from the central steam system. At the time of design, the costs of extending the line should be compared to the costs of installing a stand-alone system to determine which will be more cost effective.

A more complete analysis is included in the UTSA Main Campus Steam System Study issued under a separate cover.

Hot Water Distribution

Hot water will be distributed from the new central plant via direct-buried piping to the new BSE 2 building. This piping will be extended for future connections to the Performing Arts Center, the Special Events Center, and potentially BSE 3 at the initial buildout of the new central plant. If BSE 3 is constructed on the main campus, or the potential conversion of office space to lab space in BSE 1 occurs, hot water lines must be extended to the Science, Biosciences, and Engineering buildings. The hot water line expansion is shown in the figure.

East Campus

The drawing shows the East Campus site plan and the location of the East Campus thermal energy plant (TEP-3) that will be built in conjunction with BSE 3. This plant will be larger than TEP-2 (18,000 square ft) and will house chillers and steam boilers. To simplify operation and to reduce spare parts inventories, TEP-3 will be built using the same equipment types and sizes as TEP-2. The exception will be that TEP-3 will be equipped with steam boilers instead of hot water boilers due to the large steam loads required by the research buildings and the lack of another source of central steam. The food service buildings, housing and small stand-alone buildings will have independent heating and cooling systems.

Load Projections

For planning purposes, the load projections have been divided into two time periods: the first covers buildings will be completed by 2010, and the second covers buildings that will be constructed after 2010.

Academic 6 and BSE 3 will served by TEP-3 by the year 2010. These buildings will create approximately 2620 tons of chilled water load and approximately 24,500 pounds per hour of steam (or the hot water equivalent) of heating load (Refer to the figures at the end of this section for load projection calculations).

Academic 7, Academic 8, Academic 9, Research 4, Research 5, Research 6, and the three retail and student services buildings will be added after 2010. These buildings will add approximately 7170 tons of chilled water load and approximately 62,950 pounds per hour of steam (or the hot water equivalent) of heating load. This will bring the total East Campus load to 9800 tons of cooling and 87,500 pounds per hour of steam. (Refer to the figures at the end of this section for load projection calculations).

Thermal Energy Plant (TEP-3)

The initial build-out for TEP-3 will include sufficient heating and chilling capacity to meet the requirements of all of East Campus scheduled for completion by 2010. Due to distance and topography concerns, TEP-3 cannot be connected to the thermal utility loops serving the central campus. As a result, the plant must support not only the thermal loads, but must also have N+1 redundancy for all critical equipment. For the initial build-out, the plant will be equipped with a 1250-ton variable speed drive chiller and two 1630-ton constant speed drive chillers. A 1750-KW emergency generator will be installed and configured to allow operation of the variable speed drive chiller and related auxiliaries in event of a failure of normal electric power. Space will be provided to allow six more chillers of the same size to be added in the future.

Two 800 hp steam boilers will be installed initially in TEP-3, one of which will be redundant. Provisions will be made for the installation of two more 800-hp steam boilers as the east campus grows and loads require it.

Thermal Distribution

Figure 4 shows proposed routing for the chilled water, steam, and steam condensate lines on the east campus. Maximum use will be made of building crawlspaces, basements, and access areas under a future paseo to allow utility lines to be kept above grade. The section of piping between the plant and the first building will be installed in a utility tunnel to allow maintenance. No steam or condensate piping will be buried.