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Building Energy Efficiency Analysis for a High Rise Condominium Building | LG

Building Energy Efficiency Analysis for a High Rise Condominium Building | LG

LG Electronics U.S.A. Commercial Air-Conditioning (LG CAC) conducted an energy efficiency option analysis for a proposed multi-family residential building design. To provide a concrete basis for analysis, the building would be built in Department of Energy (DOE) climate zones, 1A, 2A, 3A, 3B, 4A, and 5A. The study explored the energy usage and resulting cost savings of operating an LG Multi V™ Variable Refrigerant Flow (VRF) System as compared to other types of typical HVAC systems described in the Leadership in Energy and Environmental Design (LEED® for New Construction & Major Renovations™) baseline building. LG CAC created several computer simulations of proposed and baseline designs, all of which used the same floor plans, occupancy schedules, lighting power density, ventilation, and envelope types. Only the mechanical system types and associated efficiencies differed for each simulation. The simulations demonstrated that the proposed designs using LG Multi V VRF systems provided significant annual utility bill savings when compared to all LEED baseline and ASHRAE minimum efficiency building systems.

table 1 summary of LG milti v HVAC System Energy cost savings

Overview

This case study explores the implementation of a LG Multi V VRF system in a new construction apartment building. Specifically, it compares energy savings between the LG Multi V VRF system and a baseline building as the United States Green Building Council (USGBC®) LEED1. The study was conducted using a building model with the same physical properties and based on the exact same plans in seven different climates, six cities—Miami, FL (1A), Houston, TX (2A), Atlanta, GA (3A), Los Angeles, CA (3B), New York, NY (4A), and Chicago, IL (5A).
The building consists of 20-stories with a total area of conditioned space at 196,217 ft². The building includes 235 residential units of approximately 139,441ft², and 12,713ft²of retail on the ground level. The types of conditioned space included varying sizes and miscellaneous spaces such as lobbies and mechanical/electrical rooms (See Table 2). The building is expected to be open 24/7 with traditional residential occupancy schedules. The building’s envelope consisted of a mass wall with friction-fit insulation and roof with insulation entirely above a deck.

Space TypesSize (ft²)
Space Types139,441
Corridor / Stairs / Lobby43,106
Retail12,713
Office684
Mechanical273
Total196,217

 

Modeling Approach


Overview

To model the baseline and proposed design, LG CAC used the Quick Energy Simulation Tool (eQUEST) version 3.65. eQUEST is a 3-D building simulation program that was developed under funding from the U.S. Department of Energy (Developer: James J. Hirsch & Associates, http://www.doe2.com/). eQUEST performed energy and thermal calculations on an hour-by-hour basis for a typical one-year period, resulting in energy consumption models for baseline and proposed designs discussed in this case study.
LG CAC gathered the following building information from the building’s owner and design team:

  • Envelope properties
  • Floor plan and geometry
  • HVAC components
  • Lighting design
  • Occupancy schedules

To determine savings, the energy consumption was compared to a building meeting—but not exceeding—LEED 2009 building baseline requirements.

Sketch of a building energy model

 

Baseline Buildings

Three different baselines were developed consisting of multiple heating, ventilating, and air-conditioning (HVAC) systems. The conditioned areas were served by

  • ASHRAE Standard Baseline System 1, Packaged Terminal Air Conditioner (PTAC): a self-contained heating and air conditioning system commonly found in hotels, motels, senior housing facilities, hospitals, condominiums, apartment buildings, add-on rooms and sunrooms. A factory provided wall sleeve and separate unencased combination of heating and cooling components, assemblies, or sections was included. In this modeling assumption, it includes heating capability by hot water.
  • ASHRAE Standard Baseline System 2, Packaged Terminal Heat Pump (PTHP): a PTAC capable of using the refrigerating system in a reverse cycle or heat pump mode to provide heat.
  • Because water-source heat pump (WSHP) systems have recently become a popular choice to replace outdated HVAC systems, A WSHP with ASHRAE Standard 90.1-2007 minimum efficient cooling tower and boiler was considered as a reference baseline system.
  • In addition, because four-pipe chiller/boiler systems are typical HVAC systems used in many high-rise buildings, a four-pipe fan coil system with ASHRAE Standard 90.1-2007 minimum efficient chiller and boiler was also considered as a reference system.

This multi-family residential building is assumed to be fully heated and cooled. (See Table 4 for details about the specification of the baseline and proposed HVAC systems, respectively.)

Proposed Buildings

The proposed building models used Multi V air-source and water source VRF air-conditioning
systems, which are designed for medium to large-scale facilities such as commercial offices,
hotels, hospitals, schools, and residential buildings.

  • Multi V IV systems feature superior energy efficiency and longer piping capabilities and is ARHI 1230 certified. Boosted by LG’s high-side shell compressor, the system provided an increased inverter range for a better response to load matching. Multi V VRF system’s advanced rapid start feature enables the compressors to come on faster to meet startup load.

Figure 2

  • Multi V Water IV systems use water as the heat exchange medium. Multi V Water IV systems have a compact footprint and feature long piping capabilities. As such, industry
    leading piping capabilities provide the ultimate in design flexibility and Multi V Water IV may reduce operational costs while providing reliable heat in colder regions. No need to place any units outdoor.

Figure 3

Component Comparison

  • Several components were considered and analyzed in the building model:
  • Modeled sizes and efficiencies (code minimum efficiencies)
  • Baseline building envelope
  • Lighting system
  • Mechanical system
  • Domestic hot-water system

Building Envelope

The model’s building envelope characteristics followed the baseline values stipulated by LEED, which adheres to ASHRAE Standard 90.1-2007:Table 3 Building Envelope Characteristics

Mechanical Systems: Air-Source VRF (Multi V IV)

  • Baseline mechanical systems included eighteen (18) packaged terminal heat pump units (PTHP) for each residential area, and electric unit heaters for stairs and common areas.
  • The baseline case was modeled so that the equipment efficiencies were based on minimum code requirements.

A PTHP system (ASHRAE Standard 90.1 Baseline System Type 2 Packaged Terminal Heat Pump) was the baseline as defined by ASHRAE Standard 90.1 2007 for the building size and type. Another choice for the building type and size was a 4-pipe fan coil system with ASHRAE Standard 90.1-2007 minimum efficient chillers and boilers. ASHRAE Standard 90.1-2007 minimum efficient WSHP systems have recently become a popular choice to replace outdated HVAC systems. Baseline and proposed HVAC systems were as follows:

Table 4 Air Handling Mechanical System

Mechanical Systems: Water-Source VRF (Multi V Water IV)

  • The baseline mechanical systems included eighteen (18) packaged terminal air conditioners (PTAC) for each residential area, and electric unit heaters for stairs and common areas.
  • The baseline case was modeled so that the equipment efficiencies were based on minimum code requirements.

A PTAC system (ASHRAE Standard. 90.1 Baseline System Type 1 Packaged Terminal Air Conditioner) was the baseline as defined by ASHRAE Standard 90.1 2007 for this building size and type. A PTAC system is a popular HVAC package used in many residential buildings. The proposed HVAC system was as follows:

Table 5

Domestic Hot Water

Baseline and proposed domestic hot-water systems were as follows:

Table 6: Domestic Hot-Water Characteristics.

BaselineProposed Notes
Gas-Fired Storage Water Heater (0.8 Energy Factor )SameASHRAE 90.1-2007 Table 7.8: Performance Requirements for Water Heating Equipment

Interior Lighting

Baseline and proposed interior lighting were as follows:

Table 7: Interior-Lighting Energy Characteristics.

 Baseline Proposed Notes
 Interior Lighting with a Lighting Power Density of 0.68 w/ft² (average) Same ASHRAE 90.1-2007 (Table 9.5.1: Lighting Power Densities Using the Building Area Method)

Receptacle Load

Baseline and proposed receptacle equipment were as follows:

Table 8: Interior-Lighting Energy Characteristics.

 Baseline Proposed Notes
Receptacle load, 0.67 w/ft² SameASHRAE 90.1-2007 ( TABLE G3.1 Modeling Requirements for Calculating Proposed and Baseline Building Performance )

Average Utility Rates Source

The study used the following sources for electrical and natural gas rates3:

Energy SourceMiami,
FL
(1A)
Houston,
TX
(2A)
Atlanta,
GA
(3A)
Los Angeles, CA
(3B)
New York,
NY
(4A)
Chicago,
IL
(5A
Electricity ($/kWh)0.11630.11640.10580.17040.19150.1195
Natural Gas ($/therm)1.6170.7481.2501.1300.9340.744

 

Results

Overview

We investigated the feasibility of reducing energy use in newly constructed high rise condominium buildings across the different climate locations in the United States relative to one built to comply with the minimum requirements of ASHRAE Standard 90.1-2007.

Results: Multi V IV (Air Source VRF System)

The building’s HVAC energy cost savings realized with the Multi V VRF system was 68% on average when compared to an ASHRAE Standard 90.1-2007 Baseline System Type 2 PTHP. When compared to a four-pipe FCU with ASHRAE minimum efficiency, the building’s HVAC energy cost savings realized with the Multi V VRF system were 66%. When compared to the energy cost of the WSHP system with ASHRAE minimum efficiency, the average building HVAC energy cost savings were 68%. Savings are detailed in the graphs below.

Figure 4

Miami Results

Energy consumption by end use for Miami, FL (Climate Zone 1A) was as follows:

Figure 5

Figure 6 Figure 7 Figure 8

The following tables summarize the energy usage and cost savings for the different cases. The HVAC energy cost saving over the System 2, PTHP baseline for the Multi V IV VRF system is 66%. The HVAC energy cost savings over the Four-Pipe FCU and WSHP baseline systems for the Multi V IV VRF system were 63% and 70% respectively.

table 9 table 10

Houston Results

Energy consumption by end use for Houston, TX (Climate Zone 2A) was as follows:

Figure 9

Figure 10Figure 11   Figure 12

 

The HVAC energy cost saving over the baseline (Sys 2, PTHP) for the Multi V IV systems is 66%. The HVAC energy cost savings over the reference baseline systems (4-pipe FCU and WSHP) for the Multi V IV system are 64% and 68% respectively.

table 11 table 12

 

Atlanta Results

Energy consumption by end use for Atlanta, GA (Climate Zone 3A) was as follows:

Figure 13 Figure 14 Figure 15 Figure 16

 

The HVAC energy cost saving over the baseline (Sys 2, PTHP) for the Multi V IV systems is 67%. The HVAC energy cost savings over the reference baseline systems (4-pipe FCU and WSHP) for the Multi V IV system are 69% and 71% respectively.

table 13table 14

Los Angeles Results

Energy consumption by end use for Los Angeles, CA (Climate Zone 3B) was as follows:

Figure 17 Figure 18 Figure 19 Figure 20

The HVAC energy cost saving over the baseline (Sys 2, PTHP) for the Multi V IV systems is 73%. The HVAC energy cost savings over the reference baseline systems (4-pipe FCU and WSHP) for the Multi V IV system are 76% and 72% respectively.

table 15table 16

New York Results

Energy consumption by end use for New York, NY (Climate Zone 4A) was as follows:

Figure 21-23

Figure 24

 

The HVAC energy cost saving over the baseline (Sys 2, PTHP) for the Multi V IV systems is 66%. The HVAC energy cost savings over the reference baseline systems (4-pipe FCU and WSHP) for the Multi V IV system are 62% and 65% respectively.

Table 17-18

Chicago Results

Energy consumption by end use for Chicago, IL (Climate Zone 5A) was as follows:

 

Figure 25-28

 

Chicago Results

Energy consumption by end use for Chicago, IL (Climate Zone 5A) was as follows:

Table 19-20

 

Results: Multi V Water IV (Water Source VRF System)

The building’s HVAC energy cost savings realized with the Multi Water IV was 28% on average compared to an ASHRAE standard 90.1-2007 Baseline System 1 PTAC. When compared to 4-pipe FCU with ASHRAE minimum efficiency, the building HVAC energy cost savings realized with the Multi Water IV were 25% and when comparing HVAC energy cost of the WSHP system with ASHRAE minimum efficiency, the average building HVAC energy cost saving was 30%.

The savings are detailed in the graphs (See Figure 29~Figure 53) and are further detailed in tables in the Annual Building Energy Consumption Comparisons and Annual Energy Consumption by End Use Summaries (See Table 21~Table 32).

Figure 29

Miami Results

Energy consumption by end use for Miami, FL (Climate Zone 1A) was as follows:

Figure 30-33

The HVAC energy cost saving of the Multi V Water IV over the baseline (Sys 1, PTAC) is 29%. The HVAC energy cost savings over the reference baseline systems (4-pipe FCU and WSHP) for the Multi V Water IV are 22% and 35% respectively.

Table 21-22

Houston Results

Energy consumption by end use for Houston, TX (Climate Zone 2A) was as follows:

Figure 34-37

The HVAC energy cost saving over the baseline (Sys 1, PTAC) for the Multi V Water IV systems is 28%. The HVAC energy cost savings over the reference baseline systems (4-pipe FCU and WSHP) for the Multi V Water IV are 24% and 33% respectively.

Table 23-24

Atlanta Results

Energy consumption by end use for Atlanta, GA (Climate Zone 3A) was as follows:

Figure 38-41

The HVAC energy cost saving over the baseline (Sys 1, PTAC) for the Multi V Water IV systems is 25%. The HVAC energy cost savings over the reference baseline systems (4-pipe FCU and WSHP) for the Multi V Water IV are 20% and 25% respectively.

Table 25-26

Los Angeles Results

Energy consumption by end use for Los Angeles, CA (Climate Zone 3B) was as follows:

Figure 42-45

The HVAC energy cost saving over the baseline (Sys 1, PTAC) for the Multi V Water IV systems is 35%. The HVAC energy cost savings over the reference baseline systems (4-pipe FCU and WSHP) for the Multi V Water IV are 41% and 29% respectively.

Table 27-28

New York Results

Energy consumption by end use for New York, NY (Climate Zone 4A) was as follows:

Figure 46-49

The HVAC energy cost saving over the baseline (Sys 1, PTAC) for the Multi V Water IV systems is 27%. The HVAC energy cost savings over the reference baseline systems (4-pipe FCU and WSHP) for the Multi V Water IV are 22% and 29% respectively.

Table 29-30

Chicago Results

Energy consumption by end use for Chicago, IL (Climate Zone 5A) was as follows:

Figure 50-53

The HVAC energy cost saving over the baseline (Sys 1, PTAC) for the Multi V Water IV is 26%. The HVAC energy cost savings over the reference baseline systems (4-pipe FCU and WSHP) for the Multi V Water IV are 20% and 26% respectively.

Table 31-32

 

 

 

 

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