San Jose State University Chiller Plant Improvements

San Jose State University

Date Created: May 3, 2017
Date Posted: May 3, 2017
Sustainability Topics: Buildings, Energy
Content Type: Case Studies

Project Overview

The Chilled Water Plant underwent a major retrofit which was completed in 2012, which included the replacement of two electric chillers and the re-piping of the plant to allow the absorption chillers to be run in series with the electric chillers. Basic controls were installed as part of the retrofit.

After the retrofit, the plant consists of two high efficiency electric chillers with variable speed drives, two steam absorption chillers and an ice storage thermal energy storage system with a dedicated glycol chiller. As part of the retrofit, the electric and absorption chillers were repiped, to allow the electric and absorption chillers to be operated in series. This greatly improved the efficiency of the chiller plant, as it allows the electric and absorption chillers to operate in series-counter flow configuration, where they are most efficient. Additionally, the pumping on the primary chilled water side was converted to variable flow from constant flow. A new control system was installed at the chiller plant to control the equipment. A PLC system was chosen, which allowed for complex sequence of operations to be implemented and the system also includes robust trending (data collection) capabilities.

The MBCx project, completed in 2016, focused on implementing more advanced control sequences to maximize the efficiency of the plant and minimize energy usage. Detailed analysis was conducted utilizing trend data from the first year of operation of the plant, to characterize and develop accurate operating equipment curves for the individual pieces of equipment, and to determine optimal sequence of operations to minimize overall energy usage at the chiller plant. The optimized sequence of operations included cooling tower staging, condenser water temperature reset strategy, and evaporator pumping optimization.

Background

The San Jose State University Chiller Plant has been undergoing continual improvements to optimize the efficiency and minimize the energy use of the plant. The plant underwent a major retrofit, which was completed in 2012. As a follow-up project, to improve the operational efficiency of the plant, an MBCx project was performed at the plant, completed in 2016. Additional projects are planned to continue the optimization of the plant. This presentation will cover the history of the improvements at the San Jose State University Chiller Plant including the goals and results, and future planned improvements to the plant.

The original chiller plant retrofit project addressed the anticipated load growth on campus as well as increased the operational efficiency of the plant. The major measures that were implemented in this retrofit included:

  • Replacement of the constant speed electric centrifugal chillers with new variable speed chillers with larger capacity
  • Converting the primary chilled water pumping from constant flow to variable flow
  • Modifying the piping in the Chiller Plant to allow the centrifugal and absorption chillers to be operated in series-counter flow configuration on both the chilled water and condenser water sides of the chillers.

The expected cooling load at the Central Plant is expected to increase in the future building renovation projects as well as new buildings coming on line. Increasing the capacity of the Central Plant with the two chiller replacements addressed this issue. The retrofit also improves the efficiency of the plant, with the higher efficiency chillers, piping modifications, conversion of the primary pumping system to variable flow as well as new sequence of operations.

The next MBCx project was performed at the plant, completed in 2016, which focused on implementing more advanced control sequences to maximize the efficiency of the plant and minimize energy usage. Additional projects are planned to continue the optimization of the plant, including the installation of an adaptive-control system.

The improvements at the chiller plant are on-going, in a constant effort to optimize efficiency and minimize energy use, while meeting the campus demands on the system.

Goals

The chiller plant retrofit project addressed the anticipated load growth on campus as well as increased the operational efficiency of the plant. The major measures that were implemented in this retrofit included:

  • Replacement of the constant speed electric centrifugal chillers with new variable speed chillers with larger capacity
  • Converting the primary chilled water pumping from constant flow to variable flow
  • Modifying the piping in the Chiller Plant to allow the centrifugal and absorption chillers to be operated in series-counter flow configuration on both the chilled water and condenser water sides of the chillers.

The goals of the second phase of the project was to complete the MBCx on the chiller plant, which focused on implementing more advanced control sequences to maximize the efficiency of the plant and minimize energy usage.

Implementation

The confluence of EnerNOC working closely with campus staff from Facilities, Operations, and also with the controls contractor produced quality control throughout the project and maximized the needs of the campus while closely monitoring the efficiency aspects of the central plant’s performance design.

Finally, following the retrofit, EnerNOC worked directly with the campus to provide measurement and verification services to calculate the energy savings achieved from the project.

Timeline

The retrofit project design commenced in mid-2010 with design and construction was completed in 2012. The follow-up Monitoring-Based Commissioning project commenced in 2015 and was completed with verified savings in 2016. Major milestones in the MBCx project included initial data acquisition, pre-functional testing and data calibration, data analysis and SOO optimization, implementation, and measurement and verification.

Financing

Total project cost was $315,033. Funding was through the utilities capital planning fund.

Incentives received from PG&E totaled $133,399.

Results

The retrofit project, completed in 2012, yielded the following savings: Project Cost: $5,531,914 CSU/UC Retrofit Incentive: $532,670 Electric savings: 680,887 kWh/yr Natural Gas savings: 369,247 therms/year Annual Cost Savings: $319,080 Simple Payback (with incentive): 15.7 yrs CO2e savings: 2,094 metric tons CO2e/year

The MBCx project, completed in 2016, yielded the following savings: Project Cost: $315,033 CSU/UC Retrofit Incentive: $133,399 Electric savings: 190,248 kWh/yr Natural Gas savings: 87,740 therms/year Annual Cost Savings: $84,177 Simple Payback (with incentive): 2.15 yrs CO2e savings: 503 metric tons CO2e/year

Total Savings from Chiller Plant Improvement Projects: Project Cost: $5,846,947 CSU/UC Retrofit Incentive: $666,069 Electric savings: 871,135 kWh/yr Natural Gas savings: 456,987 therms/year Annual Cost Savings: $403,157 Simple Payback (with incentive): 12.85 yrs CO2e savings: 2,597 metric tons CO2e/year

Lessons Learned

Lessons learned throughout the two projects include:

  • Project must be a collaborative process to meet desired goals including the University, design engineer, contractors, and commissioning agent
  • The University and commissioning agent should work closely with controls contractor when implementing sequence of operations
  • Commissioning agent should work closely with plant operators and controls contractor during functional testing
  • Divide up complex projects into phases to get individual components working properly before integrating together, rather than trying to include everything at once.
  • Be cognizant of any incentive program requirements and deadlines.

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