Opportunities for Achieving Significant
Energy Reduction in Existing University Buildings:
Developing efficient HVAC operations Michael Gevelber, Robert Choate, Kevin Sheehan, Thomas Vitolo,
Elijah Ercolino, Leah Ricci, Liz Lacy, Matt McHale, et. al.
Outline
• Overview of BU energy use
• How is energy used in buildings?
• Major opportunities for energy savings:
focus on HVAC
- Unoccupied mode
- Air changes
• Energy Benchmarks: When does gross
EUI mislead
- Implications for campus and building
comparisons
Acknowledgments:
Aandy Ly, Energy Manager
Dennis Carlberg,
Sustainability Manager
Summary of Findings from GE 520/MN 500: “Energy
Audit/Conservation Analysis of BU’s Charles River Campus”
2008
2009
2010
Michael Gevelber, Associate Professor Mechanical Engineering,
Co-chair BU Energy Working Group, Member of BU Sustainability Comm,
& Clean Energy and Environmental Sustainability Initiative (CEESI)
Results of 2007 Energy Audit
Total Energy Use
Energy Intensity (Per Sq Foot)
1.6E+12
1.4E+12
160
68% Growth in Energy Use
18% Increase in Energy Intensity
150
Natural gas
Btu
1.0E+12
8.0E+11
Electricity
6.0E+11
4.0E+11
Light oil
Btu/sq. foot (1000)
1.2E+12
140
130
120
110
2.0E+11
Heavy oil
0.0E+00
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
100
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
• What are the reasons for these trends?
• What can be done to reverse these trends?
Cleveland, C. (2007, Oct 24). Energy and Emissions Footprint: Boston University Charles River Campus. Presentation to the BU
Energy Club.
Extended Team
Michael Field, Former Asst. Provost Colleen McGinty, Director Construction Don DeRosa, Asst. Prof., SED
Shaun Finn, LEED Certified AP
Doug Zook, Assoc. Prof., SED
Gary Nicksa, VP Operations
SED Green Committee
Eric Gauthier, IT
Tom Daley, Assoc. VP Facilities
William Steward, IT
Bill Walter, Asst. VP Facilities
Larry Valles, Lab Manager, Biology
Chuck Von Lichtenberg, IT
Domenic D’Alleva, HVAC
Tim O’Connor, Electrical
Tom Parker, Automation
Building Managers:
Paul Arsenault, HVAC
Carlos Vazquez
Tyrone Lawless
Mark Harney, Asst. VP Facilities
Aandy Ly, Asst. Dir., Energy
Zhonghong Peng, Assoc. Dir.
Roger Seale
Dennis Batista
Fernando Sousa
Paul Rinaldi, Space Management
Karen Zaharee, Analyst
Outside Experts:
Domenic Armano, Manager, Johnson Controls
Mike Penn, OEHS
Ray Thompson, Sales Manager, Andover
Peter Harris, Director Operations, B&V Testing
Stephen Drummey, Drummey Mechanical
Building Energy Use by Fuel
Charles River Campus
Energy Supply
106 kBtu
2005‐2007
Energy Expenses/GHG
BU Energy Use Index: kbtu/ft2, by building type
LSEB (468)
Energy Cost
CRC
9.3 M ft2
79%
1.2 M ft2
21%
10.5 M ft2
100%
(1)
Total
Average BUMC Energy Density 335
361
300
kBTU/Ft^2
Net Area
BUMC
400
350
FY2007
Photonics (336)
SMG (220)
250
248
226
200
140 BSR (140)
150
Average CRC Energy Density 117
100
50
109
106
72
125
114
141
92
89
72
CRC
‐ Focus on high energy density buildings
NOTES:
(1) BUMC Net Area does not include NEIDL and rental properties
(2) Data sources from BU energy audit class (M. Gevelber) & Facilities (P. Zhong & A. Ly)
BUMC
BUMC Admin
BUMC Education
BUMC Research
Offices
Classrooms
Labs
Brownstone Offices
Dorms
Apartments
Brownstone Residences
Activity
Retail
0
Seven Building Analysis
‐Sargent ‐SMG ‐15 St Mary’s ‐PRB ‐44 Cummington ‐LSEB ‐Photonics
Energy Cost Density by Building
450
$14.00
400
$12.00
350
$10.00
250
Energy Densit
y
200
$8.00
Energy Cost Density
$6.00
150
$4.00
100
Gas
Gas
50
Elec.
$2.00
Elec.
-
$Sargent
•
•
SMG 15 St. Marys PRB
44
Photonics
Cummington
LSEB
What drives energy performance? What are opportunities for improvement?
$/sq.ft.
Kbtu/sq.ft.
300
HVAC Cost and Energy Implications
Building
Sargent
SMG
15 St. Marys
PRB
44 Cummington
Photonics
LSEB
% Energy HVAC % Cost HVAC
71%
53%
69%
57%
60%
53%
61%
50%
38%
18%
52%
28%
72%
64%
•HVAC accounts for 60‐70% ‐of energy use and 50‐65% of energy cost in a building.
How does a Building HVAC system work?
How much energy can be saved in a
building?
Outdoor Air Temp:
30 Degrees
Exhaust Air
Damper
Intake
Dampers
AHU
Heating
And/Or
Cooling
•Currently energy enriched air is being
exhausted around the clock—not based
on occupancy
•How can energy use be decreased
without affecting comfort?
•Setback/Increase of temperature in
winter/summer
Return Air
•Dehumidify only when necessary
•Reduce exhaust of conditioned air
during low occupancy
Building:
70 Degrees
40,000 CF
Building Circulation
Building Energy Use Average Daily Temp. 2007
Cooling season: May‐Late August
•Cool to 55, then heat to 70
Heating season: Sept – Mid April
Indoor Temperature
Energy Use Determined By:
Outdoor Conditions
• Temperature • Humidity
Indoor Air temp Settings
Percent of outside air needed fo
air quality
Outdoor Temperature
Heating
Cooling
$/CFM by Building
Fans
Cooling
Winter Heating
Summer Reheat
Average $/CFM Breakdown
Winter
Building Heating Reheat Cooling
19%
Average 24%
14%
Fans
43%
•$3-5/CFM
=> Reduce CFM
Set Back Analysis
15 St Mary’s St.
First Case Study
50,000 sq ft office/class building
Analysis of Summer Results (15 St Mary’s)
Before Unocc.
140
120
kWh
100
80
60
40
Average Summer kWh 2008
Weekday
User Demand
~40 kWh
Weekend
Unocc. Mode Savings
2009 Unocc. mode
180
Should change start up to
avoid spike
User
140
Demand
120
100
80
60
40
20
20
0
0
1:00 4:00 7:00 10:00 1:00 4:00 7:00 10:00
AM AM AM AM PM PM PM PM
Time
Weekday
Average Summer kWh 2009
160
kWh
180
160
With Unocc.
Weekend
Minimal Fan/AC
Why so high?
1:00 4:00 7:00 10:00 1:00 4:00 7:00 10:00
AM AM AM AM PM PM PM PM
Time
• Profound drop in demand (38%) during Unocc period
• 11 hour unoccupied
• Some implementation issues observed
Original Estimate Updated
Reduce Nighttime Exhaust (8 hrs)
Estimate of Potential Setback Savings
•Find energy used to condition a
unit volume of air
Cooling electricity savings •Find volume of air exhausted
Heating oil savings
•Add energy used to condition air
across all units of air exhausted
Estimated Savings
$12,522
21%
•11% of total oil ($7,400)
•7% of total electric. ($10,900)
13%
~$20k
Estimated Implementation Cost
$50k
<2
$17,500—about 1 year payback
$17.5k to Andover
The rest is Rebalance! Was it
needed?
Implementation Lessons
80
Need to spec out more thorough
implementation
– OA Damper Stuck open
– Winter AHU heating level 100%
– Spike when heat comes on
78
Temperature(F)
•
Room Temp
76
74
72
70
68
Setpoint
66
64
12:00
PM
6:00 PM
12:00
AM
6:00 AM
12:00
PM
•
•
Utility and AHU level analysis: check
to see what’s really happening. Need
to coordinate between HVAC staff,
automation, and energy.
What was really necessary
– Rebalancing?
Flow (cfm)
Time of Day
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
SAFlow
RAFlow
12:00 6:00 AM 12:00 6:00 PM 12:00
AM
PM
AM
Time of Day
Energy Savings: Solving for the Hidden Costs of HVAC
Achieving Energy Efficiency in Existing Commercial Buildings
Our Focus: HVAC is 50‐70% of ALL energy used in mid/large size buildings
Strategy: Reduce high air flow rates which were implemented when energy was cheap.
Our Solution
• Develop new tool to re-optimize HVAC control
• This is not addressed by current tools
• Based on real buildings, experience and data
Funded by MA Clean Energy Center
Professor Gevelber & Professor Wroblenski BU Mechanical Engineering
Basis for Opportunity/Value
•
•
•
•
Many buildings designed when energy was cheap so used high air flow to assure ventilation, humidity, and thermal needs were met. For existing buildings, hard to know “how low you can go”
Should base design on minimum air flow for ventilation & lab safety
Our system provides easy basis to re‐optimize
Overall Building ACH vs. Energy $/sq.ft.
Office/
Class
Lab
ACH
14
Office/
Class
12
13.03
Lab
10
8.93
8
Vent for
100%Lab
6.18
6
4
2
4.75
Target
Target
3.2
3.2
Req. for Ventilation
0
Sargent
SMG
15 St. Marys
PRB
Photonics
LSEB
Our Core Concept
Room-by-room experiments
run through existing BAS
Chiller
VAV
Box
Determine actual
ACH for each room
(No plans needed)
Establish
minimum
ventilation needs
Reset ACH through existing BAS
software
Control
Air handling
unit
Building HVAC Schematic
Aggregation
enables
building-level
optimization
Enables
monitoring/
diagnostics &
commissioning
Which EUI should we use for analysis?
Energy Stars (based con CBECS data), and AASHE Stars
program are based on gross square feet
• Does using gross area hide or distort both campus and building
energy efficiencies?
• Key issues:
- buildings with larger parking lots &
- large interior spaces that are not conditioned
EUI Case Study: Medical Campus
• 19 buildings including 2 parking garages
Total Gross
Area (sq. ft)
Total Net
Area (sq. ft)
2,455,222
1,738,909
Gross Parking
(sq. ft)
Net Parking
(sq. ft)
969,998
620,491
Downtown Campus: Parking is 40% of Gross Area. Net is
71% of gross (but incl. parking since assignable) .
 How does considering net & parking affect
EUI Analysis (kbtu/sq ft)?
Analysis of Medical Campus EUI
What are the effects of parking?
Gross EUI*
Inc. Parking
Net EUI Inc.
Parking
136
190
Gross EUI
w/o Parking
Net EUI
w/o Parking
218
289
•Using Gross EUI, including parking, hides major energy use!
•212% difference between net w/o Parking and Gross EUI
Why does this happen? parking uses 10-20 kbtu/ft^2, BUT
need to consider net area includes parking since assignable!
*EUI = Energy Use Intensity in kBtu/sq. ft
Analysis of BU Charles River Campus
• 280 Buildings
• Gross Area: 11,690,000 sq. ft.
• Net Area: 9,362,500 sq. ft.
• (80% of gross)
• Building Parking: 701,400 ft2,
6% of area
Analysis of BU Charles River Campus
• While parking is only 6% area, its EUI is so low (10‐20 kBtu/sq. ft) that it distorts EUI calculation
Gross EUI
w/ Parking 124
w/o Parking 132
Net EUI
155
167
• 25% difference in EUI net to gross, but
35% difference in EUI for net and gross
area w/o parking
Analysis of Individual Buildings
Gross & Net Areas w/ Parking
Gross
Area
(sq.ft)
Net
Area
(sq.ft)
Parking
(sq.ft)
Gross
EUI
Net
EUI
Net EUI
w/o Parking
SMG classroom/offices
481,100
325,300
23,100
159
235
267
575 Comm: Dorm
87,600
79,000
33,000
82
90
160
808 Comm Art Space /
Office
266,000
244,400
38,000
71
77
99
• For individual buildings, taking account of net area &
parking yields significantly different results ( 68%-95%).
• Important for obtaining good building priority list
Summary
• What is the EUI of different buildings, org. by types:
provides roadmap
– Consider net area and w/o parking
• HVAC should be a major area of focus: 70% of energy
– require better coordination amongst facility groups, some special
experts and manpower, , but offer substantial cost reduction and
green benefits
• Implementing unoccupied modes
– Low cost: <1 yr payback & 10-15% Energy savings
• Deeper savings: focus on ACH
– Energy cost  ACH….and we are over-ventilating our buildings
– Mostly reprogramming, but rebalancing possibly required.
Average Electrical Use Breakdown
•Much of energy use is hidden both to occupants & building managers.
*HVAC elec is 58%
590 Comm Setback
• Unoccupied Hours:
– Offices
6pm – 7am
– Classrooms 11pm – 7am
• Affected area:
– 55,000 ft2 (50’% area)
– 222 terminal boxes
• Timeline:
– Proposal – Implementation • Project Managers:
– Colleen Mcginty
– Robbie Choate
Dec‐2009
Feb‐2010
Background/Overview
•
Existing commercial buildings offer significant energy savings opportunity 36% of US electricity
•
HVAC ~ 50‐70% of building energy use, but use is hidden. 20‐35% of electricity used to push air!
•
Key: reduce air flow. •
Our solution: Re‐optimize building HVAC system based on software approach.
• Works with existing Building Automation System (BAS)
•
Unique: Solves problem not addressed by current tools.
•
Nega‐watt: cheapest energy “source” by 4‐10x
Building Floor Area Profile
Charles River Campus
2007
Building Energy Use Profile
Electricity
Heating
Oil & Gas