Calibrated Energy Simulations Of Potential Energy savings In Actual Retail Buildings

Open Access
Author:
Alhafi, Zuhaira
Graduate Program:
Architectural Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
October 31, 2014
Committee Members:
  • Pr Jelena Srebric, Dissertation Advisor
  • William P Bahnfleth, Committee Chair
  • Stephen James Treado, Committee Member
  • Qian Wang, Special Member
Keywords:
  • Ventilation rate
  • Indoor air quality
  • Energy savings
Abstract:
Retail stores are commercial buildings with high energy consumption due to their typically large volumes and long hours of operation. This dissertation assesses heating, ventilating and air conditioning saving strategies based on energy simulations with input parameters from actual retail buildings. The dissertation hypothesis is that “Retail store buildings will save a significant amount of energy by (1) modifying ventilation rates, and/or (2) resetting set point temperatures. These strategies have shown to be beneficial in previous studies. As presented in the literature review, potential energy savings ranged from 0.5% to 30% without compromising indoor thermal comfort and indoor air quality. The retail store buildings can be ventilated at rates significantly lower than rates called for in the ASHRAE Standard 62.1-2010 while maintaining acceptable indoor air quality. Therefore, two dissertation objectives are addressed: (1) Investigate opportunities to reduce ventilation rates that do not compromise indoor air quality in retail stores located in Central Pennsylvania, (2) Investigate opportunities to increase (in summer) and decrease (in winter) set point temperatures that do not compromise thermal comfort. This study conducted experimental measurements of ventilation rates required to maintain acceptable air quality and indoor environmental conditions requirements for two retail stores using ASHRAE Standard 62.1_2012. More specifically, among other parameters, occupancy density, indoor and outdoor pollutant concentrations, and indoor temperatures were measured continuously for one week interval. One of these retail stores were tested four times for a yearlong time period. Pollutants monitored were formaldehyde, carbon dioxide, particle size distributions and concentrations, as well as total volatile organic compounds. As a part of the base protocol, the number of occupants in each store was hourly counted during the test, and the results reveal that the occupant densities were approximately 20% to 30% of that called by ASHRAE 62.1. Formaldehyde was the most important contaminant of concern in retail stores investigated. Both stores exceeded the most conservative health guideline for formaldehyde (OEHHA TWA REL = 7.3 ppb). This study found that source removal and reducing the emission rate, as demonstrated in retail stores sampled in this study, is a viable strategy to meet the health guideline. Total volatile compound were present in retail stores at low concentrations well below health guidelines suggested by Molhve (1700µg /m²) and Bridges (1000 µg /m²). Based on these results and through mass–balance modeling, different ventilation rate reduction scenarios were proposed, and for these scenarios the differences in energy consumption were estimated. Findings of all phases of this desertion have contributed to understanding (a) the trade-offs between energy savings and ventilation rates that do not compromise indoor air quality, and (b) the trade-offs between energy savings and resets of indoor air temperature that do not compromise thermal comfort. Two models for retail stores were built and validated against actual utility bills. Energy simulation results indicated that by lowering the ventilation rates from measured and minimum references would reduce natural gas energy use by estimated values of 6% to 19%. Also, this study found that the electrical cooling energy consumption was not significantly sensitive to different ventilation rates.