Westfield owns and manages Southcenter Mall, a 1,400,000 SF 3 story shopping center with over 240 stores in Tukwila, WA. The mall consists of an older section which was originally constructed in the late 1960s and a new section which was added in 2008 that significantly increased the mall’s size (and energy consumption). The new section had never been properly commissioned and building systems in the older section had suffered from degradation over time.
Abraxas Energy Consulting completed an energy audit and retro-commissioning (RCx) study in late 2009. The project was similar to the retro-commissioning scope for the Energy Services proposed at TRACEN Petaluma. The building systems were thoroughly investigated and recommendations for low cost measures as well as some important capital improvements were made.
Abraxas Energy approached stakeholders of Westfield Mall with a proposal to complete a retro-commissioning study on the older section of the mall and a commissioning study on the newer section. The study was paid for in part by the Puget Sound Energy retro-commissioning program. Puget Sound Energy’s program is based on BCA best practices. The approach was similar for both sections of the mall. It involved a detailed investigation of heating, ventilating, and air conditioning (HVAC) and lighting equipment and controls at the mall.
This investigation included several site visits by a team of three engineers and technicians. The on-site engineers made observations of the operating characteristics of the systems and inventoried the equipment to be investigated. Technicians performed diagnostic testing on all HVAC equipment. Data logging and trend logging per industry standard procedures was also undertaken.
An evaluation of operations and maintenance (O&M) procedures and tasks was also carried out. The on-site engineers determined if there were any minor adjustments which could be made to O&M procedures which would result in energy savings or the extended life or improved operation of equipment.
In malls, air balance is extremely important. If stores are positive pressure relative to the common areas, the store HVAC will provide conditioning for the common areas. If the stores are negative pressure relative to the common areas, the mall will provide conditioning for the stores. Airflow tests on a sample of stores throughout the mall were conducted. A Hot Wire Anemometer (HWA) measured the air velocity at the doorway of each store. Multiplying the velocity by the area yielded the airflow into or out of the store. From this information, the customer was provided an indication of the air balance in the store, without having to pay for an expensive test and balance.
Utility bills were audited for errors, or to find whether there were better alternative rates. Utility incentives were identified which helped to pay for retro-commissioning measures identified, and an implementation plan was created.
In general, the investigation and testing process focused on discovering quick payback measures capable of improving energy efficiency, equipment performance, and maintenance effectiveness.
The RCx study identified resulted in twelve fully developed recommendations which together would save the mall $190,000, with a simple payback of 2 years. Low cost retro-commissioning measures included recharging the refrigerant in compressors, cleaning coils, rescheduling AHUs, supply air reset, and connecting the EMS system in the new section of the mall (which was not properly connected and never operational until that time). Energy auditing measures were also identified and developed in the report. These included lighting upgrades, escalator controls, variable frequency drives on supply fans, boiler replacement and new compressors.
In addition, small repairs were made to the EMS to make it functional. Faulty sensors and actuators were identified, as were lighting control and building envelope issues. It was determined that nearly all of the lighting controls in the older mall had been bypassed through either key lock switches, manual switches or hard wiring, and remained energized all hours. Some of these bypasses were resolved by our staff during the study.
The RCx study was approved by Puget Sound Energy and funds were released to customer to help pay for the study.
The recommendations provided a combined savings for Southcenter Mall of $197,000 with a simple payback of about 2 years. Additionally, many operational recommendations were made which were not fully evaluated but would certainly benefit the mall through improved operating efficiency, extended equipment life, and in some cases lower maintenance costs.