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Abstract— HVAC commissioning is one of the most efficient processes to minimize energy waste and reducing performance gap by verifying and documenting ...
Analysis of Energy Reduction through HVAC Commissioning A Case Study of a LEED Certified New Building

Young Ki Kim

Hasim Altan

Architectural Engineering Department, College of Engineering, University of Sharjah Sharjah, UAE [email protected]

Architectural Engineering Department, College of Engineering, University of Sharjah Sharjah, UAE [email protected]

Abstract— HVAC commissioning is one of the most efficient processes to minimize energy waste and reducing performance gap by verifying and documenting building’s entire systems. It is reported that building energy consumption can be reduced up to 20-40% and most building system deficiencies can be addressed through HVAC commissioning. Despite these benefits, it is often challenging to analyze and quantify building’s energy savings of new building project through commissioning due to it is not easy to compare and analyze the actual energy use data and designed/calculated energy consumption. In this study, a case study of new building’s HVAC commissioning was carried out the part of LEED Certification proceeding, and the commissioning results were compared and analyzed against designed/calculated energy consumption. The comparison data were used for evaluating dynamic simulation model and energy reduction achievement by HVAC commissioning. Through this paper, it shows that HAVC commissioning is possible to propose the energy reduction with reducing performance gap. Within this paper, the case study building’s energy saving was achieved by 5.3% through HVAC commissioning. Keywords—Building Automation & Controls, Commissioning and Energy Management, Dynamic Building Simulation, LEED Certification, Building Performance Gap

I. INTRODUCTION A. Introduction Commissioning is a quality-focused process for enhancing the delivery of a project. The process focuses on verifying and documenting that a building’s heating, ventilation, and air conditioning (HVAC) and lighting systems perform correctly and efficiently and according to the design intent and owner’s project requirements (OPR) [1]. The building commissioning investigates, analyzes, and optimizes the performance of building systems by identifying and implementing measures to improve their performance. Building without having any commissioning would cost 8 to 20 percent more to operate than one that is commissioned, the payback of commissioning is relatively short, and on average, the cost of performing commissioning is payback in less than 5 years from energy savings alone [2]. A study of six new construction projects found that the total construction cost by 4 to 9 percent can be

reduced by commissioning [3]. According to Visiter’s study, it is also indicated that 20 – 40% of building energy use and most building defects can be reduced/solved through HVAC commissioning [4]. There is significant evidence to suggest that buildings do not perform as well as anticipated at design stage. Findings from the PROBE studies (Post Occupancy Review of Buildings and their Engineering) demonstrated that actual energy consumption in buildings will usually be twice as much as predicted [5]. Low Carbon Buildings Programme and Carbon Trust’s Low Building Accelerator have demonstrated that in-use energy consumption can be 5 times higher that compliance calculations [6]. Without commissioning, system and equipment problems can result in higher than necessary utility bills and unexpected and costly equipment repairs. There are many benefits associated with commissioning for building, including: -

Verifying equipment and controls function correctly

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Identifying and correcting sub-optimal operating conditions

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Identifying associated opportunities for energy savings

These noticeable benefits are the reason why commissioning is a requirement for buildings pursuing the LEED certification, and why building codes are gradually adapting commissioning activities into code. In this research, a newly constructed office building in South Korea was used to analyze the effectiveness of simulation and to implement the results into the HVAC commissioning to reduce energy consumption performance gap and also to achieve higher level in LEED certification. II. HVAC COMMISSIONING IN SOUTH KOREA A. HVAC Commissioning in Korea In order to secure quality of HVAC commissioning in Korea, Ministry of Land, Infrastructure and Transport (MOLIT) has implemented commissioning process for objective verification methods for mechanical systems

performance and their energy efficiency on standard specification by Korea Construction Standards Centre. However, commissioning remains challenging, as there are no specific standards established on the technical side yet. HVAC commissioning is considered merely as an additional work for attaining sustainable certificates rather than to minimize real operational deficiencies and energy use domestically and the commissioning is not mandatory. These are the reasons why commissioning is hardly conducted in Korea. Most of common problems of HVAC could be fixed after hand over the building to the Facility Manager shortly where the commissioning is planned to solving the problems. For new office constructions in Korea, however, are only able to analyze their actual energy use after minimum 2 years of completion. Therefore, there is no place to cut energy reduction through HVAC commissioning an after-design verification measure due to national policy and technical situations in Korea [7].

achievement is studied through energy simulation and actual building energy consumption monitoring. A. A Case study Building in Korea A case study building is a mixed-use building of office and retail, and is located in Seoul (Fig. 1). It was planned for various purpose such as to fulfill occupant’s needs, improve working environment, mitigate climate change and depletion of fossil fuels, reduce energy consumption and heat island effect, city environmental load, and increase aspects of sustainability. In order to achieve these, assessment categories in LEED were used for quantitative sustainable architectural design and planning. From design stage to construction stage, planning was done carefully in consideration of economic and environmental feasibility to achieve LEED Gold.

B. Energy Performance Gap in HVAC System Several studies indicated that buildings do not perform as designed and a study of 60 commercial buildings findings are below and top 13 faults in commercial buildings (Table. I) [8]: -

Over 50% suffered from control problems

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40% had problems with HVAC equipment

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33% had sensors that were not operating properly

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15% of the buildings studied were actually missing specified equipment TABLE I.

COMMON FAULTS IN COMMERCIAL BUILDINGS Top 13 Faults in Commercial Buildings

Fig. 1. Exterior view of the case study building

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Duct leakage

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HVAC system operates continuously during unoccupied period

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Lighting system illuminating space during unoccupied period

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HVAC system improperly balanced

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Improper refrigerant charge

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Economizer dampers operating incorrectly

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Insufficient evaporator airflow

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Improper controls setup/commissioning

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Control component failure or degradation

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Software programming errors

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Improper controls hardware installation

Gross floor area : 47.296 m²

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Air-cooled condenser fouling

Cooling : Screw chiller (360 RT), Turbo chiller (400RT) with Ice storage system

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Valve leakage

Table II below shows that building’s overview of architecture, mechanical equipment, and electrical equipment installation to improve energy efficiency and helping to achieve LEED Gold certification for this building. This project also implicated several advanced energy technologies such as building automation control, photovoltaic and Ice storage system using midnight power. TABLE II.

A CASE STUDY BUILDING OVERVIEW

Site area : 8,267m² Architecture

Mechanical

Building area : 3,506 m²

Heating : Boiler 7,000 kg/h Retail : Package Terminal Heat Pump 328,800 Kcal/h Control : IAQ Monitoring, CO2 sensor (DCV control)

III. RESEARCH METHODOLOGY Commissioning is categorized into fundamental commissioning and enhanced commissioning depending on methods use and the enhanced commissioning was carried out this study. The enhanced commissioning’s energy reduction

Lighting : LED 100% and Lighting Control Electric

Receptacle Load : Stand by power shut-off switch Renewable : Photovoltaic (68 kW)

B. Dynamic Simulation Energy reduction achieved from correcting the deficiencies during HVAC commissioning and it was analyzed and summarized quantitatively using energy simulation. To carry out the dynamic simulation study and satisfy the ASHRAE 90.1 and LEED Energy simulation requirements, Trace 700 Version 6.2 was used for building energy modeling and energy use analysis, respectively (Fig. 2).

Fig. 3. Secondary chilled water pump operation trends

Similar problems were indicated in primary chilled pumps, condenser water pump, and fan control was repeated. Such problems were corrected by specifying the sequence of operations and VSD control through TAB (Fig. 4).

Fig. 2. Energy simulation model

C. Actual Data Gathering After conducting HVAC commissioning from January to December in 2014, deficiencies found from Testing and Balancing (TAB) and functional testing was corrected, and actual annual energy consumption of the building was monitored and these data were used for dynamic simulation’s verification and analysis. IV. RESEARCH FININGS The HVAC commissioning and the dynamic simulation was conducted for one year in 2014. It found the deficiencies of energy performance gap in HVAC system of the case study building. It also studied for calculating energy reduction by HVAC commissioning in the case study building. A. Energy Performance Gap in the Case study Building Through several stages of commissioning, four major deficiencies were found. One was that during HVAC functionality and performance check. Where the number of AHU operation increases, design flow rate should also increase as it works as VRF system. However, it was shown in Fig. 3 chilled water pump was always operated maximum flow rate where the cooling is demanded (in blue bars chart). After HVAC commissioning, it was corrected by implementing variable speed drive (VSD) control as it planned (in red bars chart).

Fig. 4. AHU Fan control

B. Dynamic Simulation Varification

Fig. 5. Simulation result compared to actual enregy consumption

V. CONCLUSION After carrying out the HVAC commissioning for one year, the actual annual energy consumption of the building was recorded, analyzed, and compared against the simulation results for verification. Before reviewing actual building situations, such as vacancy rate of the leased office, operating hours of ice storage cooling systems, there were not within the acceptable value for validating the simulation model (Fig. 5). After reflecting the actual building situations, the simulation’s energy consumption was close to actual energy consumption (Fig. 6).

As commissioning process in Korea, it is not established as standardized methodologies yet and there are many challenges in terms of its application such as technical, economic and political issues. Despite these issues, this research took place to verify building performance through HVAC commissioning with the involvement of developers, contractors, architects, commissioning agents, sustainability consultants, and all stakeholders from the initial design stage to hand-over stage. This research provides two measures that could be more usable for domestic application with a real case study. The first measure is to predict energy consumption through energy modeling with the application of optimization technologies. Precision level of predicting energy performance is important. Verifying reduction goal achievement with actual energy use after occupancy especially is significant. Lastly, together with reasonable control and management of the building through HVAC commissioning, quantitative feedback process on energy reduction during planning is very important to applying implemented predictions. It needs to emphasize HVAC commissioning and M&V that can lead to a quantitative understanding of energy reduction and successful energy performance planning and verifications during the architectural design stage.

Fig. 6. Simulation result compared to actual enregy consumption

C. Energy reduction by HVAC Commissioing

ACKNOWLEDGMENT This research was partially supported by EAN technology which provided expertise that greatly assisted the research, although they may not agree with all of the interpretations provided in this paper.

REFERENCES [1] [2]

[3] Fig. 7. Energy saviing after HVAC commissioning

After finding performance gap in HVAC system in a case study building and corrected these findings, it was simulated with dynamic simulation software tool. The energy consumption was reduced by 2.1% for fan control, 1.4% for condenser water pumper, 0.4% for primary chilled water pumps, and 1.4% for the secondary chilled water pump. Therefore, the energy reduction of the case study building by HVAC commissioning was 5.3% of total energy consumption (Fig. 7).

[4]

[5] [6]

[7]

[8]

ASHARE Guideline 0-2013, “The Commissioning Process”, PNNL21003 Washington State University Extension Energy Program with support from Northwest Energy Efficiency Alliance, “Building Commissioning for New Buildings; 2005. Energy Efficiency Fact sheet. EnergyIdeas Clearinghouse.”, WSUEEP98-018 California Commissioning Collaborative. California Commissioning Guide for New Buildings; 2006, http://www.cacx.org/resources/documents/CA_Commissioning_Guide_ New.pdf Visier, J. C., et al., “Commissioning tools for improved energy performance, Results of IEA ECBCS Annex 40”, 2005, IEA Published the report PROBE studies archive http://www.usablebuildings.co.uk/Pages/UBProbePublications1.html Carbon Trust’s Closing the Gap Publication http://www.carbontrust.co.uk/publications/pages/publicationdetail.aspx? id=ctg047 Jong-Wooa, Choi., “Design of Ongoing Commissioning System using Energy Facility Working Database”, Proceedings of Architectural Institute of Korea, 09. 2013 U.S. Department of Energy. Building Commissioning, The Key to Quality Assurance; http://www.peci.org/documents/PECI_BldgCxQA1_0500.pdf