HyPerformance Upgrade in a Research institute, Taiwan
The chilled water system at the IT Research Institute (ITRI) in Taiwan was experiencing the common problem of Low Delta T Syndrome in traditional ON-OFF-controlled variable flow systems, leading to over-flow, discomfort, and noise. To address this issue, the ITRI partnered with the IMI Hydronic Engineering team in Taiwan to improve system performance and efficiency achieving energy savings of up to 60%.
This is a summary of the project, for further details on how the assessment was carried out and the data analyzed to reach such conclusions please download the full report here
The Industrial Technology Research Institute (ITRI) is a research and development organization located in Taiwan that is focused on promoting industrial development and technological innovation. As part of their efforts to reduce energy consumption and promote sustainability, the ITRI wanted to assess its HVAC system to identify energy savings and improve indoor comfort.
The system in question was used to condition the air in two mixed-use buildings (office and research laboratory), with a chilled water plant supplying chilled water to both buildings, with a 500RT centrifugal chiller and a 400RT magnetic bearing centrifugal chiller working in tandem to provide cooling capacity.
The primary/secondary chilled water system used constant flow control on the primary side, while the secondary side was divided into three zone pumps with variable speed control. The system also featured fan coil units as terminal units, with an ON-OFF-controlled two-way valve in variable flow system as the control valve for the fan coil unit.
However, the system suffered from the Low Delta T Syndrome, which led to over-flow of the chilled water flow rate in part load condition, even if the system was in design condition. This problem caused the chillers to operate at lower efficiency, resulting in wasted energy consumption and increased energy consumption for the entire HVAC system.
The Hydronic Challenge
In Taiwan, the typical design for HVAC systems in commercial buildings includes fan coil units as terminal units and the control valve for the fan coil unit is an ON-OFF-controlled two-way valve in a variable flow system.
However, traditional ON-OFF-controlled variable flow systems face many technical issues, mainly related to inadequate TAB on-site, leading to Low Delta T Syndrome - over-flow of the chilled water flow rate in part load condition. Inadequate TAB on site is a key reason why most existing chilled water systems suffer from this syndrome, leading to discomfort and noise generation.
Moreover, the energy cost of the whole HVAC system increases as the variable speed pumps in the variable flow system cannot reduce frequency due to improper operation of control valves in the hydronic system.
The ITRI aimed to optimize the hydronic system to improve energy efficiency and human comfort while delivering stable room temperature without oscillations.
With the government’s policy of energy saving and carbon dioxide reduction in recent years, the equipment of air conditioning system in the ITRI had been replaced in recent years. From the early plan for replacement of the magnetic bearing centrifugal chiller to improve the chiller’s operation efficiency, to install variable frequency control to the chilled water pumps, and replace the old fan coil unit with new ones, etc. However, optimising the control of the hydronic system is not solely dependent on having highly efficient equipment, but rather on how effectively it can be operated in an energy-efficient manner.
The strategy of optimisation of the hydronic system for the air conditioning system from IMI Hydronic Engineering was to:
- Install differential pressure controllers on the branches of the hydronic system and redoing TAB (Testing, Adjusting, and Balancing) for the whole chilled water hydronic system on-site
- Adjust the differential pressure of each differential pressure controllers on branches
- Optimised the setting of the operating frequency of variable zone pump
As the chilled water flow could be precisely controlled at any working conditions, the hydronic system could maintain the temperature difference between supply and return chilled water temperature as high as possible without chilled water over-flow. The variable-flow chilled water plants could be operated in a higher efficiency condition, as the variable frequency chilled water pumps and chillers could be reduced the energy consumption during part load conditions.
Based on the implementation of the proposed solution, the research institute was able to achieve significant energy savings. They performed an analysis of energy consumption of the 400RT high-efficiency magnetic bearing centrifugal chiller before and after the optimization project and they were able to measure a reduction on energy consumption of at least 20%, and even up to about 60% in winter. In addition, the energy consumption of variable chilled water zone pumps could be reduced as high as 42%, and even up to 60% in some seasons, with an estimated payback period of just three years.
Additionally, the implementation of the intelligent valve controller allowed for better control of the chilled water flow rate, resulting in improved indoor comfort and reduced noise generation
The technical expertise provided by IMI Hydronic Engineering team was critical to the success of this project. Highly efficient equipment is not enough to guarantee an optimized hydronic system control and by expertly identifying the issues with the existing system (inadequate TAB on-site, the use of traditional ON-OFF-controlled variable flow systems) they were able to propose an upgrade solution that addressed the issues at their core to deliver on all the project’s objectives: significant energy savings, improved indoor comfort, and reduced noise levels.