Re ECF Project: 2013-03

Project Title: Developing an energy saving design guideline for car park ventilation in response to decreasing emission inventory

Applicant: Dr. CHAN Ming-yin, Department of Building Services Engineering, The Hong Kong Polytechnic University

Total Approved Grant: $468,360 (ECF & WWGF: 50/50)

Duration: 1/8/2014 to 31/7/2017

Project Status/Remarks: Completed

The project aims to-

  • critically review the existing design guidelines for car park ventilation system design including fire protection requirement;
  • measure prevalent air quality in 30 car parks and establish a database for in-depth investigation;
  • critically review the vehicular emission inventory from 1990 to present status;
  • critically review the energy requirement of car park ventilation system; and
  • develop a new local design guideline for car park ventilation to cope with decreasing emission inventory.

Summary of the Findings/Outcomes:
Field measurement conducted in 30 mechanically ventilated car parks supported the reduction of ventilation rate. The main concern other than CO and NO2 is the heat stress. A Computational Fluid Dynamics (CFD) simulation was performed to study temperatures variation in the car park of The Hong Kong Polytechnic University (PolyU) with different ventilation rates. With the support of the mathematical models and measurement, it shows that the required ventilation rates for maintaining acceptable levels of pollutants and thermal environment in the PolyU car park (No. 19) are lower than the required (6 ACH-1), and it is possible to reduce the ventilation rate after a careful study. As recommended by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 62.1-2013, the latest suggested ventilation rate is 3.5 ACH-1 (Section 13.18) for car parks. The CFD simulation at PolyU car park took 3.8 ACH-1 and proved to be effective in controlling CO, NO2 and a temperature rise of one degree Celsius (outdoors/indoors). Research results suggest a ventilation rate in normal operation of 3.8 ACH-1, which tally with ASHRAE latest recommendation, and with an option of 6 ACH-1 at extremely congested conditions. A two-level ventilation strategy is proposed. Presentation was given in a seminar with over 300 participants from different sectors mainly from practicing engineers and HVAC (heating, ventilation and air conditioning) professionals.