Good News, I’m happy to announce that our Existing Building Commissioning (EBCX) projects are now officially completed and we implemented the majority of the EBCx measures that were identified in the investigation phase. You can read my previous posts about these projects here and here. On behalf of the UHN Energy and Environment Department, I would like to extend a special thanks to Natural Resources of Canada (NRCan) for rolling out this program and financial support of these EBCx studies.
We believe showcasing the success stories of our projects is a valuable tool in raising awareness of the importance of EBCx in reducing energy usage and the carbon footprint of the facilities. It also provides information about the challenges and lessons learned during this process, so other organizations can proactively address them in their plans.
In this post, you can read the EBCx case study of Toronto General Hospital. The case study for Toronto Western Hospital will be published in the next post.
Building Name/Type: Toronto General Hospital
Location: Toronto, Ontario
Project: Retro-commissioning of Toronto General Hospital
HVAC Retro-Commissioning and District Energy Retro-Commissioning at Toronto General Hospital. The work started in late 2019 and the investigation phase was completed by March 2021. Finn Projects was retained by UHN as the consultant and collaborated with in-house staff for performing the study.
Size of Commissioned Area: Toronto General Hospital is a major research and teaching hospital. TGH has 6 buildings with a total area of 2.0 million square feet.
Total Commissioning Investment: $127,700
Energy Cost Savings: $200,000 per year (1.79% of total annual energy cost)
Simple Payback: 0.6 year
Energy Savings: 14,385 GJ per year (3.3%)
GHG Emission Reductions: 576 tonnes per year (3.95%)
Quantified annual non-energy benefits: Improving health, safety and comfort of the hospital patients and staff by complying with design and codes requirements. Enhancing the controllability of the HAVC system components such as fan speed, the status of the VAV box, damper positions, etc. which results in operational cost-saving, more accurate fault detection and faster troubleshooting.
PROJECT OVERVIEW AND BACKGROUND
Toronto General Hospital is a major research and teaching hospital with 471 beds and 56,000 visits to the emergency department annually. TGH has 6 buildings with a total area of 2 million square feet. The oldest wing of Toronto General Hospital was constructed in 1957. Toronto General Hospital has undergone additional construction and renovations since then with the Munk hospital wing being the newest addition in 2003. The Toronto General Hospital uses over 47 GWh of electricity and 180 million pounds of district steam annually.
In 2018, the campus connected to the Enwave district deep lake cooling system for building cooling and process loads in lieu of producing chilled water locally. This project yielded 2.7MW peak demand savings, over 7MWh annual electricity savings, 65,000 cubic meters of water savings, and about $250,000 annual cost savings for the site. Part of being a district energy customer means abiding by certain rules of the supplier. In order to ensure flow availability to all customers and maintain the reliability of the system, the supplier requires to return chilled water above a certain temperature. Chilled water flow to the campus is modulated by the district supplier to maintain the return water temperature at the setpoint. This arrangement can be problematic for buildings with low delta T syndrome and it will eventually lead to high chilled water supply temperatures and reduced ability to cool spaces. Anticipating this issue, when redesigning our central plant to be supplied by Enwave, the hospital installed a “polishing” chiller (CH-3) as a heat pump to heat up the return water and sub-cool the supply water to meet both building cooling demand and Enwave return water temperature requirement. This process allowed the hospital to gain the benefits of connecting to district cooling, but is inefficient from an energy efficiency standpoint.
With the above in mind, one of the goals of this project is to improve delta-T to reduce the operation of the polishing chiller, thereby conserving electricity. Moreover, Enwave’s cooling plant operates at higher efficiency with warmer return water, so there is a benefit to both the hospital and the district system if retro-commissioning can improve our delta-T.
Supporting the goal of improving the operation of the central chilled water plant, a secondary focus of the project was to improve the operation of our aging stock of air handling units (AHUs). Many AHUs serving the campus are of 1980s vintage and older, featuring pneumatic controls. Although well maintained, these are prime targets for efficiency gains.
In order to accomplish the goals of improving delta T and overall mechanical system performance, UHN hired an external consultant to perform a recommissioning of the central chilled water plant and a selection of AHUs. The work included investigation of chilled water plant operation, review of trend data, AHUs zone identification, performance review of selected AHUs, and terminal unit control review. The goal was to achieve a more efficient system with minimum investment.
The final component of this case study is a review of existing steam traps on site. The average steam trap fails at about 7 years of age, and with almost 500 steam traps on-site at TGH, it is important to keep them operating smoothly. Another contractor specializing in steam trap audit and repair was hired to complete this portion of the recommissioning project.
The primary objective of this RCx project was to reduce the energy usage and carbon footprint of the hospitals through optimizing the energy use of the existing mechanical systems. The secondary objective was to demonstrate the value of existing building commissioning (EBCx) in healthcare facilities for the University Health Network’s senior management and encourage them to consider (EBCx) projects for other UHN facilities. The other objectives and benefits of the project included:
- Increase comfort level for building occupants and tenants.
- Reduction in utility costs, allowing for funds to be spent toward other initiatives in the building portfolio/healthcare.
- Improve day-to-day operations; retro-commissioning results in a reduction in the number of service calls and requests brought about by underperforming and inefficient systems that requires high levels of reactive maintenance.
Environmental Stewardship, including the efficient use of energy, water and other resources, has been a central part of UHN operations for over 20 years. The Energy and Environment (E&E) department of UHN has taken a lead in the continuous improvement of mechanical systems from an energy efficiency standpoint. E&E manages: energy conservation projects, ongoing commissioning, BAS controls upgrades and scheduling, and Greenhouse Gas (GHG) emissions reductions. Performing retro-commissioning and BAS upgrade services are an ongoing mission of the E&E team of experienced internal building controls specialists; however, for large-scale, comprehensive EBCx projects, typically the E&E hires a third party consultant to work with the in-house team. For instance, in 2012, UHN retained Finn Projects to do the RCx investigation for the TGH building. Finn Projects was once again, retained for the current EBCx study. The E&E team led the work of this consultant and ensured collaboration between all the stakeholders during the project’s investigation phase.
The initial scope of the EBCx project was very broad. However, once we received a few quotes, we realized the original scope had to be limited to meet the allocated budget. Even after revising the scope, still the project cost became almost 25% higher than the expected price as a result of the challenges we encountered, the major one being the COVID 19 pandemic.
As mentioned earlier, retro-commissioning at UHN has been recognized as an ongoing task and inherent duty of the Energy and Environment department and operation team. Hence the outcome of the project will result in adjustments in the associated building operation processes and improve the energy performance of the hospital.
INVESTIGATION AND ISSUES IDENTIFIED
Chilled water system:
- Improper chilled water setpoints. For example, during periods of extreme heat, it was noted that the plant chilled water discharge setpoint was reduced and not returned to the original setpoint. At a lower CHW discharge temperature, the knock-on effect was also a lower return CHW temperature, which in turn forced the polishing chiller to work harder to meet the return water temperature requirements.
- Fluctuations in supply temperature from the district energy provider. We created an alarm in BAS and in case it happens frequently we inform Enwave about the issue and request an action plan
- Erratic chilled water valve trends
- Obsolete floor-level building automation
- Heating/cooling valve hunting or out of calibration
- Excessive supply of fresh air, fresh air damper position adjustment
- Convert variable inlet vanes (VIV)s to VFDs and/or remove inoperative VIVs left behind
Steam Trap Audit
- Several out of service or malfunctioned steam traps were identified in the mechanical rooms
IMPLEMENTATION AND RESULTS
Unfortunately, the ongoing COVID-19 pandemic has had a dramatic impact on the work feeding into this case study. As an acute care hospital, UHN’s priority during this time has been patient and staff safety. Site visits/reviews were delayed and, ultimately, the final recommendations were delivered beyond the 2021 cooling season. Consequently, the real-world results of the changes recommended to the cooling system have not yet been realized. This section will discuss the implementation and expected savings.
Chilled Water System Review
The EBCx exercise yielded several low-cost measures as well as several more capital-intensive projects. UHN has implemented the following low-cost recommendations related to the chilled water system and will continue to monitor related performance improvements in the coming cooling season:
- Ensure chilled water discharge temperature is maintained at the design level
- Ensure any fluctuations in district chilled water temperature are accounted for. We created an alarm in BAS and asked the BAS technician to continuously monitor it. In case it happens frequently we would inform Enwave about the issue and request an action plan
- Tuning of PID loop for chilled water valves on AHUs that were noted to be acting up
UHN also recognizes the potential value of the more capital-intensive recommendations from the EBCx exercise. For example, the report recommended replacing vintage pneumatic chilled water valves in order to improve delta T. UHN has developed design guidelines that call for upgraded chilled water valves during all AHU refurbishment projects. All future AHU upgrades will incorporate “energy valves,” which feature an integrated flow meter and supply/return temperature sensors. These valves enable the site to directly monitor and control delta T at the coil level, preventing costly chilled water overflow and optimizing chilled water usage. Furthermore, UHN is currently implementing a stand-alone project to install seven energy valves on key AHUs throughout the site. AHUs were selected based on valve size as well as proximity to the central plant (valves closer to the plant face higher pressures and are more likely to overflow chilled water).
Other larger-scale recommendations will have to wait for a more extensive overhaul of the HVAC systems at the site. These recommendations include installing dedicated cooling for dehumidification loads (given existing space limitations, this would represent a major overhaul of HVAC systems serving most of the operating rooms on site), eliminating decoupler pipe between primary/secondary system (given the current configuration, this would require a major shutdown of chilled water to entire hospital). Although UHN can’t implement these recommendations along with the timelines of this case study, the insights will help inform future design practices during major projects.
Implementing all of the proposed chilled water measures, an estimated savings of 3,727,080kWh would be achieved, primarily by reducing the operation of CH-3. These kWh savings would represent a GHG emissions reduction of 121 tons CO2eq using the average emissions factor for the Ontario grid of 32.6 g/kWh (per the 2019 report titled “A Clearer View on Ontario’s Emissions” from The Atmospheric Fund). In reality, it may only be possible to achieve a fraction of those savings through recommissioning alone.
The recommissioning study of selected AHUs at Toronto General Hospital encountered similar COVID-related delays to the chilled water investigation although we were able to complete some tasks internally on a faster timeline. Measures uncovered by the recommissioning exercise include reinstatement of heat recovery systems and recalibration of sensors that are identified to be malfunctioning. We replaced three defective supply air humidity sensors and recalibrated/returned four temperature sensors as part of this project.
The investigation revealed several opportunities on AHUs for the replacement of inlet vanes with fan motor VFDs. Rather than throttling the fan inlet to maintain pressure setpoints, VFDs accomplish the same task by reducing the motor speed, yielding significant electricity savings. From an operations and control standpoint, the VFDs have enabled remote start/stop capability. Operators can react quickly to control fans from the central control room whereas in the past control was physically done at the MCC panel in the mechanical room. Additionally, electrical parameters of the motor such as current, power, etc. are monitored on the front end. The annual electricity savings of Fan-17 and Fan-22 respectively are 320,734 kWh ($32,073) and 344,116 kWh ($34,412).
After the RCx process identified obsolete space level controls, UHN implemented a replacement and recalibration of 70 VAV controllers. Additionally, VAV boxes were rebalanced to ensure design requirements were being met. At each controlled space, aging non-adjustable room temperature sensors have been replaced by modern adjustable thermostats. End-users can adjust room temperature setpoints and even override the VAV box to the occupied mode if it is an unoccupied period. As a result, temperature control and occupant comfort have improved. From the BAS front end, operators gained an enhanced ability to monitor and adjust the VAV boxes to accommodate the needs of the space users.
The upgraded controls enabled the hospital to create space-specific occupancy schedules to save energy on electricity, heating, and cooling. The resulting savings totaled 77,000 kWh/year of electricity ($7,700/year), 637,829 lbs of steam ($4,638/year), and 7,904 ton-hrs/year chilled water ($893/year).
The recommissioning process yielded additional highly capital-intensive recommendations that will be considered in our longer-term capital planning.
Steam Trap Audit
The Steam trap audit was completed April 2020. Out of 477 steam traps, the contractor found 89 traps out of service and 26 defective traps. Based on the audit results, 2.7 million pounds of steam can be saved annually through replacing or fixing the traps.
UHN Facilities operation team have already started replacing the defective steam traps. Defective high-pressure steam traps are at the highest priority as the amount of heat waste is higher. Medium and low-pressure traps are the next priority.
World Health Organization (WHO) has recognized climate change as one of the most urgent threats to human health in the 21st century. Energy management playing a key role in mitigating the causes and impacts of climate change. A majority of the identified measures in the EBCx study improve the performance of energy use within the hospital so will have a positive impact on global warming and the health of all Canadians.
Other benefits of this project included:
- Reduction in utility costs, allowing for funds to be spent toward other initiatives in the building portfolio/healthcare.
- Increased comfort level for building occupants and tenants.
- Improved day-to-day operations; retro-commissioning will result in a reduction in the number of service calls and requests brought about by underperforming and inefficient systems that requires high levels of reactive maintenance.
- Improve performance of chilled water system. Currently, some buildings at Toronto General Hospital have poor delta-T on chilled water. We must operate a chiller to boost temperatures to meet Enwave requirements. By implementing the identified measures in the chiller study, we can improve delta-T to reduce the operation of the chiller and save electricity. We may also be able to reduce overall cooling demand by reducing simultaneous heating and cooling.
The key takeaway from the project is that success is achieved by combining the fresh set of eyes of a third-party recommissioning professional with the detailed historical and operational knowledge of HVAC systems held by the building owner/operators. On one hand, the building owner may have long-standing biases and tunnel vision that can be a barrier to solving systemic issues. On the other hand, the recommissioning professional might not understand some of the idiosyncrasies of the site and the history that led to the current state. There is some magic in bringing these two parties together to gain new insights and develop strategies to improve performance.
In order to facilitate this dynamic, scope of work and obligations of each party need to be very clear, while also somewhat flexible. When it comes to existing building commissioning, there are huge numbers of variables and potential paths to explore. This ambiguity and open-endedness can lead to confusion related to scope creep, level of detail of the investigation, calculation methods, monitoring and verification, etc. It is crucial to have a clear strategy, metrics, and goals in mind when undertaking existing building recommissioning.
When the experiences of the building owner/operators and the recommissioning professional are properly balanced, many useful projects such as those described in this case study can result.
This EBCx is made possible by a financial contribution from Natural Resources Canada.