Basic Industrial and
Commercial Electrical Energy
Audit Training for Utility
Personnel
Draft
Robert Scott Frazier, Ph.D., CEM.
Assistant Professor,
Renewable Energy Extension Engineer
Biosystems & Agricultural Engineering
Oklahoma State University
(405) 612-3641
Page 1
What We Will Cover Today
•
•
•
•
•
•
•
Utility Background Data
QuickPEP® Software
Motors
Lighting
Compressed Air
HVAC
Process Heat
What You Should Come Away With
1. Ability to produce general recommendations
for the facility
2. Ability to generate a nice cover report with
graphics for the customer regarding energy
use
3. Ability to spot some of the more common
energy areas for opportunity
ENERGY AUDIT WORKSHOP
Before we begin …
There are two ways to look at a facility's
energy conservation (savings) potential:
(1) A general view – without much effort – how much
might we save and in what general areas?
(2) A detailed view – with more effort – at what specific
points in the plant can we place improvement
efforts and how much can we expect to gain from
these efforts?
Page 4
Eight (Typical) Key Energy Issues in Auditing
Facilities
1.
2.
3.
4.
5.
6.
7.
8.
Current situation -- getting a grip.
Process heating and cooling.
Steam and steam delivery.
Compressed air and air delivery.
Building and HVAC.
Lighting.
Electrical motors and systems.
System x system interactions (not specifically
discussed, but very important in overall
assessment).
Page 5
Eight Key Questions for Commercial and
Industrial Systems
1.
2.
3.
4.
5.
6.
7.
8.
What function(s) does this system serve?
How does this system serve its function?
What is the energy consumption of this system?
What are the indications that this system is properly
functioning?
If system is not working properly, how can it be
restored to proper operation?
How can the energy cost of this system be
reduced?
How should this system be maintained?
Who has direct responsibility for maintaining and
improving the operation and energy efficiency of
this system?
Page 6
What Equipment is Needed for Basic
Energy Auditing?
•
•
•
•
•
•
•
•
Inexpensive IR Thermometer
Digital Camera
Data Loggers (Onset, etc.)
Steel toe boots/shoes
Side shields for glasses (get your own)
Ear plugs (get your own)
Good notebook and multiple pens
Business cards
What Else Should You Know?
•
•
•
•
What Federal Incentives are there?
What State Incentives?
Visit http://www.dsireusa.org
Stay on top of it – it constantly changes with
the whims of Washington and state
government
Current Situation – Getting a Grip
•
•
•
•
•
•
Facility Background
Personalities
Rate Schedule
Billing Analysis
Energy Profiles – As a whole
Energy Profiles – By
systems/processes (if you can)
Page 9
Start a File (Hard and Softcopy)
• Everything goes in…
– “Google®” company
– Photos
– Hand notes
– Emails (Print if important)
– Correspondence
– Newspaper articles
– Napkins with notes
– Anything at all that has to do with this customer
Pre-Visit Phone Information I
•
•
•
•
•
•
•
•
•
•
•
Primary Contact Name:
Street Address of the plant we will be visiting:
Principal products Produced:
# of Employees:
Annual Sales ($):
Annual Energy Expenses ($):
# of Building we will be looking at:
Plant Area (square feet):
Production/yr (lbs, pcs…../yr):
Number of Shifts per day per week (and hours):
Primary Energy Users:
Boilers ….How Many, approx capacity (MMBtu, lbs steam, etc.)…Fuel type
Chillers….How Many, approx capacity………Size
Furnaces…How Many
Air Compressors…..How Many……What HP?
•
•
•
•
Type Of HVAC in Plant/Offices:
Type of Lighting in “
“:
Other Energy Users of Interest (Blow Molders, etc.) ……..Energy Size (kW, Btu, etc.):
Other: (Things you would like us to look at)
Do we need to bring safety Equipment? Don’t show up in open toe shoes or 3-piece suit. Leave jewelry at home.
Pre-Visit Phone Information II
You may need to get copies of originals bills. You are
the utility so you may have this in-house…
•
•
•
•
•
Energy bills (gas also possibly) for the past 12 consecutive months.
Water and sewer bills for the past 12 consecutive months.
Simple plant layout (8.5x11) (if they have it)
Process flow chart (if they have one)
List of primary energy consumers (e.g. motor list with horse
powers's, etc. if they have it)
** Part of this is to show the client – this is stuff they should have and
be aware of!
Personalities
•
•
•
•
•
•
Who is your main contact?
How important are they?
Are they threatened by this visit?
Plant manager knows the plant…
CEO can make sure projects get implemented…
Closing meeting – who is responsible for any
possible recommendations?
• Implementation and progress calls (let’em know
you will be calling)
Rate Schedule
• You are the utility person
• If you know nothing else, you should be able to explain
their rate schedule and bills
• Make sure you know if they are on a “special” internal
schedule
• If it’s a big customer, ask (internally) if there is anything
special you should know about these folks
• Ask engineering if there is something unusual about
their service or metering before you go out to the plant
(look like the company speaks as one)
Billing Analysis
•
•
•
•
One of our most important tools.
Get data for all meters at general
location.
Assemble data into spreadsheet (next
slide).
Break into columns showing: kW, kWh,
Fuel charges, taxes, PPCA, etc.
Page 15
Billing Analysis (cont.)
Page 16
Client* Billing Analysis (cont.)
Client Demand (kW) Data
What's going on here?
*Confidential
Billed vs. Actual Demand
900
Billed kW
850
800
Actual kW
750
700
650
1
2
3
4
5
6
7
Months
Page 17
8
9
10
11
12
Client Billing Analysis (cont.)
Page 18
Billing Analysis (cont.)
Page 19
Billing Analysis (cont.)
•
•
•
Know the definitions and relationships of kW and
kWh.
Understand what tariff the customer is on and
determine if it is the correct one (they will ask).
Understand the “fine print” items on the tariff and
how they work (e.g. power factor adjustment,
ratchet clauses, etc.)
Page 20
Electrical Energy Management
• Electrical energy management
is unique due to the nature of
electrical power.
 Almost impossible to store significant quantities of
this energy source (Maybe hydrogen in the near
future).
 Must have sufficient capacity to meet instantaneous
demands (kW).
 Odd characteristics such as power factor.
 Issues such as power quality.
Page 21
Electrical Demand Control
• Partially because demand (kW) is a
separate portion of the bill, we can
look at specific methods toward
reducing this charge (and impact on
electrical system).
• Try to keep in mind however that
demand (kW) and consumption (kWh)
are closely related.
Page 22
Electrical Demand
• The thing to keep in mind is that demand is a kind of
“snap-shot” of the maximum electrical draw – at any
particular time of the month from your facility.
• Recall also that this snap shot is not really
instantaneous but usually averaged over some
interval like 15 minutes
• That’s good for the customer – shorter intervals are
worse. Try to imagine why that is….
• Still, “Demand” is a reflection of how much electrical
equipment was on at a particular time in the facility.
Page 23
Electrical Demand & Load Factor
• There is a “Load Factor” column in the billing
analysis spreadsheet
• Load Factor = Total Month’s kWh divided by 720 x
measured monthly max demand
• If load factor is <<0.30 for a one shift operation or
<<0.6 for a three shift operation, there may be
demand control opportunities
• Load factor indicates how even/uneven the
electrical usage is during the billing period
(demand peaks), LF=1 is a perfectly consistent
load
Demand Control (cont.)
• Many demand reduction strategies will be
aimed at moving some of the load to different
times of the day so we don’t get a coincident
peak.
• Other strategies might include going to
different types of equipment.
• Lets look at some of these demand control
methods.
Page 25
Demand Control (cont.)
• Demand Shedding: In simplified form, the facility
operator will identify the high electrical draw pieces of
equipment that can have their operations
rescheduled to other times of the day.
• The operator (or software) will be monitoring the
facility or sub-area total demand (kW).
• At some agreed-upon kW point, the operator, or
software, will reschedule the previously identified
equipment to avoid a demand peak.
• Various automated systems available (web search for
“electrical demand control”)
Page 26
Demand Shedding (cont.)
• In a simpler scenario, schedules of the
equipment, or processes, are adjusted
so that the peaks are avoided ahead of
time.
• The problem is: Get it wrong once
during the month and a high demand
charge may be set.
Page 27
Demand Shedding (cont.)
• Examples of equipment that can
be Demand-Shed:







Chillers.
Air handlers.
Large pumps.
Large Grinders.
Recharging Stations (fork trucks, etc.).
Large unnecessarily illuminated areas.
Any large electrical load is a candidate…
Page 28
Demand Control (cont.)
• Duty Cycling
shedding)
(different than demand
 Long uninterrupted equipment run times lead to a
higher probability that coincident loads will produce a
“peak” demand.
 Imagine what types of equipment this sounds like
(hint – Air Handling Units)
 Duty cycling uses a signal (time, temperature or other
controlled parameter) for the on/off operation.
Page 29
Demand Control (cont.)
• Other demand and energy
control methods







Optimum start/stop.
Night setback.
Hot water reset.
Chilled water reset.
Boiler and chiller optimization.
Chiller demand limiting controls.
Free cooling.
Page 30
Power Factor Improvement
• This is an area that you (as a utility
person) need to be somewhat familiar
with.
• The reason is that your customers may be
billed for Power Factor and you are the
utility rep, therefore …
• You will still defer most technical problems
to engineering but lets be able to “talk-thetalk” a bit
Page 31
Power Factor
 Basics:
o Induction loads (big electric motors)
cause current to lag behind voltage so
more kVA is needed to get the same
kW. Yet, we are paying for kW. (???) –
Bottom line…Power Factor – BAD!
o Charge is applied when PF exceeds the
minimum level usually around 80 or
90% (95% for you folks!).
o Power factor is kW/kVA. See power
triangle next page.
o Correction is (usually) made by adding
capacitor banks
32
Power Factor
 Power triangle
(kV) x (I) x (√3)
kVA
kVAR
kW
Motor load example: (kVA) x (PF) or (HP load) x (.746 kW/HP) x (1/η)
33
Power Factor Example
 A plant has 2,000 kW demand and a power
factor of 80%. How much capacitance is
needed to correct this to 95%? (Why did I use 95%?)
ΔkVAR = 2000 (.421) = 842 kVAR
Δ kVAR
2500 kVA
Table Next Page
2000/.8 = 2500 kVA
2000 kW
34
Power Factor Table
35
THE GENERAL VIEW
• QuickPEP®
• http://www1.eere.energy.gov/industry/quickpep/(
wu24wh55es44h1550shxdjby)/default.aspx
• Plant Energy Profiler
• Quick “Expert System” that gives:
–
–
–
–
Estimated Breakdown of Energy Use
Estimated Savings Potential
Suggested Areas for Improvement
Graphics in a report type template
Page 36
QuickPEP Screens and Sample Case
(“TCC-1”)
Page 37
Page 38
We will talk about where this data comes from in a bit…
Must use blended kWh & kW Cost
Page 39
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Page 47
Page 48
Page 49
Page 50
Page 51
Page 53
Motors
• This is the beginning of the more “detailed”
energy audit
• Don’t panic though – all we want is a talking
knowledge of these systems
• You are not expected to be the expert on this
stuff – however, you can still provide some
insight and value for the customer…
Electric Motor Systems
• Electric Motors Power Many Machines
–
–
–
–
–
–
–
Pumps
HVAC
Fans (a type of pump actually)
Air compressor (again, a pump)
Conveyors
Any type of rotary motion…
Motors often the largest (electrical) energy user in a
facility
Electric Motors
• Savings in Electric Motor
Management We Will Look At:
– Energy efficient motors.
– Savings calculations from
improved efficiency.
– Motor rewinds.
– Motor drives.
Page 56
Electric Motor Management
Energy Efficient Motors (Induction)
• Why Energy Efficient?
– Motor efficiency: percentage of input power
actually converted to mechanical work.
– A small 20-HP motor continuously running, even at
a modest energy rate of 0.08 $/kWh, uses about
$11,000 worth of electricity per year.
– Over half of electrical energy consumed in the US
is used by electrical motors.
Sources: DOE – Best practices @ http://www.oit.doe.gov/bestpractices/
Page 57
Electric Motor Management
Energy Efficient Motors (Induction)
• What is an Energy Efficient
motor?
More copper and iron – less resistance losses –
(I2R) or HEAT.
– Better fans and bearings more carefully lubricated
– therefore less friction.
– Larger and heavier (typically).
–
Page 58
Electric Motor Management
Energy Efficient Motors (Induction)
Source: Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA, p.272,273
Page 59
Electric Motor Management
Energy Efficient Motors (Induction)
• Energy efficient motor
characteristics
–
–
–
–
–
–
–
–
Higher inrush (LRA).
More efficient and higher power factor.
Save energy and reduce demand.
Reduce load on cables, transformers, etc. (note
higher efficiency and PF).
Speed is slightly higher (this can be critical).
Significantly larger inrush (LRA).
Less vibration.
Longer manufacturer’s warranties.
Sources:
Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA, p.286
http://www.wapa.gov/es/pubs/techbrf/eemotors.htm
Page 60
Energy Efficient Motors
NEMA Threshold Full-Load Nominal Efficiency Values for EE motors (NEMA MG1 Table 12-10) 1
OPEN MOTORS
To be considered
energy-efficient, a
motor’s performance
must equal or exceed
the nominal full-load
efficiency values
provided by NEMA in
their publication MG-1.
ENCLOSED MOTORS
hp
3600
1800
1200
900
hp
3600
1800
1
82.5
80
74
1
72.5
82.5
1.5
82.5
84
84
75.5
1.5
82.5
84
2
84
84
85.5
85.5
2
84
84
3
84
86.5
86.5
86.5
3
85.5
87.5
5
85.5
87.5
87.5
87.5
5
87.5
87.5
7.5
87.5
88.5
88.5
88.5
7.5
88.5
89.5
10
88.5
89.5
90.2
89.5
10
89.5
89.5
15
89.5
91
90.2
89.5
15
90.2
91
20
90.2
91
91
90.2
20
90.2
91
25
91
91.7
91.7
90.2
25
91
92.4
30
91
92.4
92.4
91
30
91
92.4
40
91.7
93
93
91
40
91.7
93
50
92.4
93
93
91.7
50
92.4
93
60
93
93.6
93.6
92.4
60
93
93.6
75
93
94.1
93.6
93.6
75
93
94.1
100
93
94.1
94.1
93.6
100
93.6
94.5
125
93.6
94.5
94.1
93.6
125
94.5
94.5
150
93.6
95
94.5
93.6
150
94.5
95
200
94.5
95
94.5
93.6
200
95
95
250
94.5
95.4
95.4
94.5
250
95.4
95
300
95
95.4
95.4
300
95.4
95.4
350
95
95.4
95.4
350
95.4
95.4
400
95.4
95.4
-400
95.4
95.4
-450
95.8
95.8
-450
95.4
95.4
-500
95.8
95.8
-500
95.4
95.8
-Shaded area indicates motor classes covered by efficiency standards contained within EPACT 1992
Page 61
1200
80
85.5
86.5
87.5
87.5
89.5
89.5
90.2
90.2
91.7
91.7
91.7
93
93
93.6
93.6
94.1
94.1
95
95
95
95
900
74
77
82.5
84
85.5
85.5
88.5
88.5
89.5
89.5
91
91
91.7
91.7
93
93
93.6
93.6
94.1
94.5
-
Energy Efficient Motors
Calculating Savings
•
•
Power and energy savings depends on efficiency of standard vs. energy
efficient motor.
Calculation from replacing w/ EE, assuming same hp and % load:
1) Energy Savings ($) = hp x 0.746 x L x C x N x (100/Estd – 100/EEE)
where:
L = % Load *
C = Energy Cost ($/kWh)
N = annual operating hours
Estd = Efficiency Std motor
EEE = Efficiency energy eff. motor
* If “Load %” is measured or estimated as less than 60%, the motor is grossly under loaded and
the efficiency will be very low for either Std or EE – resize motor in this case.
Source: Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA, p.286
Page 62
Energy Efficient Motors
Calculating Savings (cont.)
2) kW Savings (Simplified Estimate)
kW = kWstd – kWEE = (hp) (0.746 kW/hp) (100/Estd – 100/EEE)
$Dem. Savings = [(kW)std – (kW)EE] ($/kW.month) (12 month/yr)
3)
Decision
Payback = $Motor Cost / [$Savings (Energy + Demand)]
Decision: Choose EE motor if D Payback < maximum desired Payback
Period!
Source: Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA, p.286
Page 63
Energy Efficient Motors
Example
• Premium efficiency 50 HP motor
available at 94.5% eff. to replace a std.
50 HP motor at 90.7% eff. Motor runs
8760 hrs/yr. Electricity demand costs
$7.00/kW each month. Electrical energy
costs $.05/kWhr.
• What are the operating savings for
purchasing the energy efficient motor?
Page 64
Energy Efficient Motors
Example (cont.)
• Demand and energy savings both
occur
– Demand savings = (50 hp) (0.746 kW/hp)
(100/90.7 – 100/94.5) ($7/kW.momth) (12
month/yr) = $138.9 /yr
– Energy savings = (50hp) (0.746 kW/hp)
($0.05/kWh) (8,760 h/yr) (100/90.7 – 100/94.5)
= $724.3 /yr
– Total savings = $ 863.2 /yr
Page 65
Motor Basics
Motor Rewinds
• Most rewind motors over 10 (40?) HP.
• Typical rewinds cost 60+% of a new motor.
• New motor could be an energy efficient
motor.
• Motor efficiency often suffers during rewind
average drop about 1% according to one
study and sometimes significantly more.
• If efficiency drops, losses increases, motor
runs hotter and won’t last as long.
Page 66
Electric Motor Summary
• Reduce un-needed run-time (ex.: automatic shutoff sensors).
• Reduce peak electrical demand (ex.: scheduling
production for off-peak hours).
• Improve plant power factor: PF decreases for
under-loaded motors. Don’t just put in PF
capacitors first.
• Improve the efficiency of motor power trains:
Cogged V-belts last longer and improve system
efficiency by 2% to 4% over regular V-belts, while
reducing maintenance and replacement costs.
• Replace the oversized motors: motor efficiency
and power factor degrades quickly when motors
are dramatically under-loaded.
• Work up an effective motor management program
(e.g., replacing failed motors with Energy
Efficient motors vs. rewinding when cost
justified).
Page 67
Motor Drives - Introduction
Recall the graphs of motor load and power factor?
• Many motor applications are inefficient
because…
– Motor is oversized for application
(therefore underloaded)
– Load varies from little to near full rated
load during process operation
– Fan or Pumps are being driven too fast for
actual application need
68
Motor Drives - Introduction
• Variable Torque Load
– increase with speed and torque are usually
associated with centrifugal fan and pump loads,
where (in theory) the HP requirement varies with
the cube of the speed change. When driving
positive displacement pumps, the HP
requirement varies as the square of the speed
change
69
Electric Motor Management
“Drives”
• Motors operate at fixed speeds, running between No Load RPM
and Full Load RPM
• Processes (pump, fan, etc.) often require other speeds on the
driven end. Load on the motor is affected.
• Various methods to vary speed: variable pitch pulley drives,
inlet-outlet dampers, inlet guide vanes, magnetic clutches,
variable frequency drives (VFD)
• A VFD varies frequency and voltage of the motor supply line to
match the load
• In constant torque applications VFDs can improve process
control and reduce maintenance costs (e.g. Conveyor)
• Variable torque applications, such as centrifugal devices (pumps,
blowers, fans), are desired applications for varying CFM or GPM
because of the “fan laws” by using VFD’s
70
Electric Motor Management
Fan Laws (Centrifugal Devices ONLY)
• CFM2 = CFM1(RPM2/RPM1) 1st law
• SP2 = SP1(RPM2 /RPM1)2
2nd law
• HP2 = HP1 (RPM2/RPM1)3
3rd law
Source: Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA, p.286
71
Electric Motor Management
“Fan Laws” Example
• Opportunities for considerable savings in
centrifugal devices by adjusting rotational speed
• Ex.: If the RPM of a fan can be reduced by 20%, its
energy consumption will be:
HP2/HP1 = (RPM2/RPM1)3
= [ (RPM1 x 0.80) / RPM1 ]3
= 0.51
HP2 ~ 51% of HP1 - A drop of 49% !!
72
Electric Motor Management
Fan Laws – Strange Example
• Fan system 32,000 CFM. Existing standard
efficiency motor of 20HP and 1750 RPM.
Considering replacing with a new 20-HP, EE motor
(1790 RPM).
• What is the impact on energy consumption?
New CFM = 1790/1750 x 32,000 CFM = 32,731
New HP requirement = (1790/1750)3 x 20 = 21.4 HP
7% increase !
Source: Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA, p.287
73
Typical Power Consumption of
Various Motor Control Systems
Sv
Svfd
Sv = Savings at 60% load
when going from
“constant volume” to
“variable inlet vane”
Svfd = Savings at 40% load
when going from
“constant volume” to
“variable frequency drive”
Source: Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA, p.296
74
Electric Motor Management
Selection of Best Option
• Outlet vane control (“potato in exhaust”)
– Simple and effective (watch for cavitation or surging)
– Not efficient, infrequently used
– Great candidate for conversion to others
• Inlet vane control (“potato in carburetor”)
– Simple and effective (watch for cavitation)
– More efficient than outlet but significantly less than other
options, fairly frequently used
– Great candidate for conversion to others
75
Electric Motor Management
Selection of Best Option
• Variable Frequency Drive (VFD)
–
–
–
–
–
Probably most efficient
Competitive cost
Harmonic concerns (input and output)
Remote (clean area) installation
Multiple motors may be connected to one drive providing higher
savings, but sizing is critical
– Motors and load must be agreeable to VFDs (may need cooling)
• Magnetic clutches (permanent magnet or eddy current)
– Bulky and heavy on motor shaft (seen on older applications)
– No harmonics
– Close to same savings but less
76
VFD Application – Typical Loading
Profile
Source: Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA
77
Ex.: VFD Application - Cooling Water System
Total Hp
Load Factor
Operation (hrs/yr)
Consumption Charge ($/kWh)
Conversion Factor: 1 Hp =
Percent Load Cycle Fraction
20%
0
30%
0.05
40%
0.16
50%
0.23
60%
0.23
70%
0.20
80%
0.09
90%
0.03
100%
0.01
TOTAL
1
100
1
8,760
0.0287
0.746
hrs/yr
0
438
1401.6
2014.8
2014.8
1752
788.4
262.8
87.6
8760
Power i/p Ratio[1]
Present VFD
kWh Savings $ savings
1.1
0.09
0.00
0.00
1.1
0.11
32348.05
928.39
1.1
0.14
100376.99
2880.82
1.1
0.2
135273.67
3882.35
1.1
0.29
121746.30
3494.12
1.1
0.43
87568.46
2513.21
1.1
0.62
28231.03
810.23
1.1
0.85
4901.22
140.67
1.1
1.16
-392.10
-11.25
510,053.63 $14,638.54
For 50% load row: (100 hp)(0.746 kW/hp) (1.1-0.2) (0.23)(8,760) = 135,273 kWh/yr
(135,273 kWh/yr) ($ 0.0287 /kWh) = $ 3,882.35/yr
Total annual savings: S Savingsi = $14,638.54 , Simple Payback ~ 1.2 years
Source: Oklahoma Industry Assessment Center, Report OK#0703
78
$$$$ - Summary
• Choose the technology that the facility staff
understands and likes to use
• You probably don’t want to mix technologies in a
given facility
• Most efficient is VFD followed closely by magnetic
clutching followed (way back) by inlet and outlet
vane controls
79
$$$$ - Summary
• For cooling towers work on air side as opposed to
water side
– Larger motors
– Doesn’t affect operation as much (freeze protection,
biological control, etc.)
• Concentrate on centrifugal devices not axial or
reciprocating
– Chilled water pumps, cooling water pumps, etc.
– Blowers on cooling towers or VAV HVAC units
80
$$$$
Variable Speed Drive Applications
•
•
•
•
•
Chilled water pumps for large campus
Cooling tower water pumps
VAVs using inlet vane
Forced draft (blower) cooling towers
Any large centrifugal blower or pump that runs a
lot!
– Constant volume? Convert to variable volume
– Variable volume with inlet or outlet control
81
$$$$ - Summary
Opportunities for Pumps and Fans
•
•
•
Reduce/Vary Flow Rate. In pump and fan applications, the work required by the
pump or fan is the product of the volume flow rate and the pressure drop
through the distribution system. The pressure drop through the distribution
system is proportional to the square of the volume flow rate. Thus, pump/fan
work is proportional to the cube for volume flow rate. Because of this, small
reductions in fluid flow rate can mean large reductions in motor power (“fan
laws”)
Reduce System Pressure Drop. Reducing pressure drop through piping and
ducts can reduce pump/fan energy consumption. In new applications, specify
large diameter pipes/ducts, low pressure-drop fittings and minimize corners
where possible. Then select an appropriately-sized pump or fan for the
calculated pressure drop.
In retrofit applications, open partially closed valves and remove unnecessary
fittings. Next, resize the pump impeller or slow the pump/fan to take
advantage of the reduced pressure drop. Depending on the individual
pump/fan curve, reducing pressure drop without modifying the pump/fan may
actually increase the volume flow rate and pump/fan energy consumption.
82
Electric Motor Management
Axial and Reciprocating
Pumping/Fans
• Centrifugal laws do not apply (power and flow
relationships are more linear due to positive displacement
characteristics)
• More difficult to predict savings
• We use linear so no real savings if “on/off” presently used
• Obviously, savings if converting from constant volume to
variable volume
83
Lighting
Lighting
• In an industrial facility lighting may be less
than 10% of the electrical load
• In a commercial facility, lighting will probably
be between 25-45% of the electrical energy
load
• Here in Texas, lighting will tend to be a lower
percentage because the A/C loads are so high
in the summer
Lighting
Lighting Issues
 Required light level (foot candles).
 Fixture efficacy (Lumens/Watt).
 Lumen output of lamps and fixtures.
 Color Rendering Index (CRI).
 Color temperature (Kelvins).
 Types of light sources.
 Light quality.
Page 86
Principles of Efficient Lighting Design
• Light levels meet requirements.
• Light sources are efficiently produced
and delivered.
• Qualities meet the application
– Balance efficiency (“efficacy”) with architecture, light quality, and
visual comfort.
• Automatically control lighting operation.
Page 87
Types of Light Sources
•
•
•
•
•
•
•
•
Incandescent.
Fluorescent .
Tungsten Halogen.
Mercury Vapor.
Metal Halide.
High Pressure Sodium.
Low Pressure Sodium.
Others.
Page 88
Efficiency
Better
Page 89
Lamp Color
Color Rendering Index (CRI)
Indicates the effect of a light source on the
color appearance of objects:
75 – 100 CRI = Excellent color rendition
65 – 75 CRI = Good color rendition
55 – 65 CRI = Fair color rendition
0 – 55 CRI = Poor color rendition
http://www.nyserda.org/sclp2/technicalguide/about/colorRenderingIndex.asp?section=1.1.4
Page 90
Typical CRI Values
Light Source
CRI
White deluxe mercury
45
Cool white fluorescent tube
65
Daylight fluorescent
79
Metal halide 4200K
85
Deluxe cool white fluorescent
86
Low pressure sodium
0-18
High pressure sodium
25
100-Watt incandescent
100
Page 91
Color Temperature
Color Temperature
A measure of the “warmth” or “coolness” of a
light source:
< 3200K = “warm” or red side of spectrum
> 4000K = “cool” or blue side of spectrum
http://www.fullspectrumsolutions.com/cri_explained.htm
Page 92
Page 93
Amount of Light Required
For Specific Applications
• We often use more light than is
needed for many applications and
tasks.
– Light levels are measured in footcandles (or lux, in SI
units) using an illuminance meter.
FC = lumens / ft2
Lux = lumens / m2
– Consensus standards for light levels are set by the
Illuminating Engineering Society of North America
(IESNA.org).
Page 94
Page 95
Some typical light levels needed are:
Parking lot
Hallways
Factory floor
Offices
Inspection
Operating room
2 Footcandles
10 Footcandles
30 Footcandles
50 Footcandles
100 Footcandles
1,000 Footcandles
Page 96
Fundamental Law of Illumination or
Inverse Square Law
E = I / d2
where
E = Illuminance in *footcandles (desired or needed)
I = Luminous intensity in lumens (from lamp specs)
d = Distance from light source to surface area of interest
(this you can vary depending on ceiling)
*One footcandle is equal to one lumen per square foot
Page 97
Example
In a high-bay facility, the lights are mounted on the ceiling
which is 30 feet above the floor. The lighting level on the
floor is 50 footcandles. No use is made of the space
between 20 feet and 30 feet above the floor.
In a theoretical sense – that is, using the fundamental
law of illuminance – what would be the light level in
footcandles directly below a lamp if the lights were
dropped to 20 feet?
FC = 50(302/202) = 112.5 footcandles (shortcut calc)
98
What to Look for in Lighting Audit
• Inventory of lighting equipment (what's
there)
• Determine lighting loads (total wattages).
• How are lights controlled? (panels, hardwired?)
• Light levels at work tops and useable
spaces (use inexpensive light meter)
• Hours in use (tricky – survey or log)
• Lighting circuit voltage (if you’re an
electrician)
Lighting Calculations
Energy Savings from delamping or turning off unneeded lamps
• 100 fixtures with four, F40T12 - 40 watt lamps, per fixture
• Facility runs 2-shifts for 250 days a year
• Light levels on warehouse floor = 110 footcandles
• Delamp or turn off half the lamps (after doing inverse sq law calc)
• Look up wattage of lamps and ballasts in Grainger etc. (160 watts/fixture+12watts/ballast
with 2 ballasts/fixture) = 184 Watts/fixture
• Energy Cost: $0.08/kWh , Demand Cost: $9.00/kW
Cost Savings:
kWh = (184 Watts/fixture) x (100/2 fixtures) x (16 hours/day) x (250 days/year) x (1
kWh/1,000 Watt-hour) x ($0.08/kWh) = $2,944/year
kW = (184 Watts/fixture) x (100/2 fixtures) x (1 kWh/1,000 Watt-hour) x ($9/kW-month) x 12
(months/year) = $994/year
Total yearly savings = $3,988/year
Lighting Calculations
Energy Savings from switching to more efficient lamps
• 100 fixtures with four, F40T12 - 40 watt lamps, per fixture (old)
• 100 fixtures with four, F32T8 - 32 watt lamps, per fixture (new)
• Look up wattage of lamps and ballasts in Grainger etc. F40T12 - (160 watts/fixture
+12watts/ballast with 2 ballasts/fixture)
F32T8 – (114 watts/fixture)
Energy Cost: $0.08/kWh , Demand Cost: $9.00/kW
Cost Savings:
kWh = (160 - 114 Watts/fixture) x (100 fixtures) x (16 hours/day) x (250 days/year) x (1 kWh/1,000
Watt-hour) x ($0.08/kWh) = $1,472/year
kW = (160 - 114 Watts/fixture) x (100 fixtures) x (1 kWh/1,000 Watt-hour) x ($9/kW-month) x 12
(months/year) = $173/year
Total yearly savings = $1,645/year –
Sounds Good Right?
Wait a minute … Installed Cost = Over $30,000
Payback = 18 years (if installed all at once)
Compressed
Air
Compressed Air Systems
 Widely used throughout industry, present in almost any industrial
plant.

Source of energy for tools and machines.

Control medium.

Material handling.

Cleaning.
 Relatively expensive to operate -- typical saving opportunities, 2050% - Folks, this is huge!
 Management required on both supply and demand side.
 Air power is 3 times more expensive than electrical power!
Sources: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
“Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA
Page 103
Compressed Air Systems (cont.)
 Supply Side

Air intake and filter.

Air compressor.

Dryer.

Storage tank.

Pressure / flow controllers.

Distribution lines.
 Demand side

Users.
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 104
Compressed Air Systems (cont.)
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 105
Compressed Air Systems (cont.)
Air Compressor types
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 106
Compressed Air Systems (cont.)
Air Compressor types
 Rotary Screw

Most popular, range 30 - 200hp.

Compact, low initial cost, fairly efficient.

Easy maintenance. Air or water cooled.
 Reciprocating

Driven by an “automotive-type” piston.

Available in sizes from less than 1hp up to above 600hp.

Large, higher initial cost, very efficient.

Usually multi-stage with intercooling.
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 107
Compressed Air Systems (cont.)
Air Compressor types
 Centrifugal

Kinetic energy developed by centrifugal impeller(s) (typically at 50,000
rpm or more).

Usually large, typically above 150hp.

Flow capacity decreases as the system pressure increases (head/capacity
curve). Efficient modulation (surge point), VFD-suitable.

Good maintenance critical (shaft vibration).
 Other types less used
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 108
Compressed Air Systems (cont.)
Example: Operation cost vs. Initial cost

100hp rotary screw compressor

First cost $50,000

8,640 operating hours per year

75% load

Demand cost: $7/kW-month ($84/kW-year)

Energy cost: $0.08/kWh

Average life: Maybe 10 years
Annual op. cost = (100hp)(0.746kW/hp)(0.75) x {($84/kW.yr)+
($0.08/kWh)(8,640hr/yr)} = $43,372/yr
During the compressor’s life, it will use almost half a million dollars in electrical energy!!
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 109
Compressed Air Systems (cont.)
Support Systems
 Intake air

As cool as possible, for every 5.5ºF reduction approx. 1% of increase in
the mass of intake air. (we will see this again…)

Intake filter, maintain in top condition. Size properly to minimize
pressure drop.
 Drivers

Electric motors, most common.

Diesel or Gas engines.

Steam engine or turbine.
 Compressor cooling
Source: “Compressed Air”, Royo, E.C., 1991, Ed. Paraninfo, Madrid, Spain
Page 110
Compressed Air Systems (cont.)
Support Systems
 After-cooling and drying

Remove moisture (100% RH at compressor outlet).

In general, 20ºF of temperature drop reduces moisture content by about 50%.

Dryer: refrigerant (most common), regenerative-desiccant, deliquescent.
 Air receivers (Often Missing…)

Smooth compressor cycling, reduce demand fluctuation.

2 to 4 gallons per CFM.

Distributed throughout facility.
Page 111
Compressed Air Systems (cont.)
Support Systems
 Distribution

Looping (more is better).

Size length and diameter to minimize pressure loss (bigger is better).

Slopes.
 Traps and draining points

Allow removal of condensate from lines.

However…may be source of air leaks if poor maintenance.
 Separators
Page 112
Compressed Air Systems (cont.)
 Demand side - Users

Some inappropriate uses of compressed air

Open blowing (use brushes, electric fans, blowers, etc).

Aspiration/bubbling (use low-pressure blowers).


Sparging – aerating or oxygenating liquid with compressed air (use low-pressure
blowers or mixers).

Venturis (use vacuum systems).

Unregulated hand-held blowing guns.

Cabinets cooling (use air conditioners or fans).
Air Quality (which do they have?)

Plant air (needs to be fairly dry)

Instrument air (needs to be clean and dry)

Process air (squeaky clean, completely oil-free?)
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 113
Compressed Air Systems (cont.)
 Demand side - Users

Pressure at the point of use






Supply pressure recommended by manufacturer.
Insufficient pressure translates to productivity losses (therefore,
crank pressure up – right?)
Pressure drop in distribution <= 10% (i.e., if 90 psig at receiver, then
not less than 80 psig at point of use) – crank it up some more!
Pressure drops caused by undersized piping and/or accessories,
leaks, improper filters, regulators, lubricators – more!
Monitor between compressor and storage tank.
Approximately 1% additional energy required for each 2 psig
increase in air pressure (see where this is headed?)
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 114
Compressed Air Systems (cont.)
Pressure Drops
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 115
Compressed Air Systems (cont.)
 Demand management

Quantity (Cubic Feet per Minute - CFM)

Sum of average needs.

Use secondary storage tanks.

Use local pressure regulators (reduce artificial demand).
 System controls (just be aware there are out there…)

Individual compressor control

Start/stop – reciprocating or rotary screw.

Load/unload - motor runs with open valve – unload, 40%.

Modulating inlet – rotary and centrifugal.
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 116
Compressed Air Systems (cont.)
 System controls (cont.)

Multiple compressor control: orchestrate compressor operation and air
delivery.

Cascading set points: need higher set points to maintain system pressure
above minimum.

Sequencers: match supply/demand by taking compressors on/off. Lower
set points achieved. Highly cost effective.
 Flow controllers
 Bottom line: If client has multiple, large (100 HP +) compressors running,
they should have a fairly sophisticated control mechanism like sequencers.
Ask to talk to air compressor contractor if client is unaware.
 Often clients simply keep adding compressors without addressing control and
leakage problems…
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 117
Compressed Air Systems (cont.)
 Air Leaks – Easiest Recommendation You Will Ever Make…No Brainer

Expensive..really expensive!

Good System - 10% Leakage, typical 20-30% (recall the expense to run
slide…)

When on/off control: Leakage(%)=(Tx100)/(T+t)
T=On-load time (min)
t=Off-load time (min)

If other control strategies:
Leakage (CFM)=Vx(P1-P2)/(Tx14.7)x12.5
P1=normal operating pressure, in psig
P2=50% P1
V=total system volume, in CFM
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 118
Compressed Air Systems (cont.)
 Air Leaks (cont.)

Ultrasonic acoustic detector.

Soapy water in suspected areas.

Off-production schedule.

Look at


Connections and fittings.

Hoses.

Filters and regulators.

Valves.

Non-operating equipment.
Example of annual cost of
leaks for a typical installation
Establish a leak prevention program
Source: “Improving Compressed Air Performance, a sourcebook for industry”, http://www.oit.doe.gov/bestpractices/
compressed_air/pdfs/compressed_air_sourcebook.pdf
Page 119
Savings Example: Waste Heat Recovery
Winter
Summer
Dampers
Thermostat
Fan
Heat Exchanger
Hot Water
Cooling air
Heat available: approx.
250,000 BTU/hr per 100hp
Source: “Aire Comprimido”, Royo, E.C., 1991, Ed. Paraninfo, Madrid, Spain
Page 120
Compressed Air Summary
•
•
•
•
•
•
•
Compressed air is an expensive utility – people treat it
like it’s free!
Look for alternatives before deciding to use it for a
particular need.
Use appropriate multiple-compressor controls.
Properly size lines and storage tanks – don’t skimp
here.
Match demand supply pressure – Keep pressure at a
minimum.
Preventive maintenance to avoid air leaks and maintain
traps/drain working – pain in the rear and not sexy but
this is where the money can be really saved…
Recover waste heat – it’s free - they already paid for it
elsewhere…
Page 121
HVAC
HVAC(R)
•
•
•
•
•
Heating
Ventilation
Air Conditioning
Cooling
Refrigeration
HVAC
• Probably the largest electrical energy user for
many of your customers
• Systems can be complex but there are some
things to watch for even if you are not an
expert
• Lets go over a bit of background first…
HVAC System Components
• Controls (thermostat, computer)
• Energy Supply (electricity, natural gas)
• Heating or cooling unit (compressor,
evaporator, condenser, valves, burner)
• Distribution system
(Ductwork, dampers, etc.)
Functions of HVAC Systems
• Purpose: provide and maintain a comfortable
environment within a building for the occupants
or for the process being conducted.
• HVAC systems were often not designed with
energy efficiency as one of the design factors.
• Health and productivity of employees & clients
are the most important criteria.
126
HVAC Environmental Control Factors
HVAC systems function to provide an environment in
which these four factors are maintained within
desired ranges:
•
•
•
•
Temperature
Humidity
Air distribution
Air quality
127
HVAC Typical Design Conditions
•
•
•
•
70 degrees F temperature
50% relative humidity
30-50 FPM air movement
20 CFM outside air per person or CO2
less than 1000 ppm (ASHRAE 62-1999
Ventilation Standard)
• ASHRAE std. 55 (next slide)
128
ASHRAE Std. 55 (can be complex)
129
The three principle functions of HVAC
systems controls are:
1.
2.
3.
To maintain comfortable conditions in the space by
providing the desired cooling and heating outputs,
while factors which affect the cooling and heating
outputs vary.
To maintain comfortable conditions while using
least amount of energy (on old systems this is not
really a consideration)
To operate the HVAC system so as to provide
safety for the occupants and equipment.
130
HVAC Primary Equipment
• Chillers (Big)
• Direct expansion (DX) systems
(Rooftop, Pad Mount)
• Boilers (Gas - Steam)
• Furnaces (Typically Natural Gas)
131
HVAC Secondary Systems
•
•
•
•
•
•
Single duct, single zone system
Single duct, terminal reheat system
Multizone system
Dual duct system
Single duct, variable air volume system
Fan coil system
Examples on next pages from Bloomquist 1987
132
Secondary Systems
Single Zone
System
Multi- Zone
System
133
Secondary Systems
Dual Duct
System
Terminal
ReHeat
System
134
Secondary Systems
Variable Air Volume
(VAV) System
Fan Coil
Unit
135
4-Pipe Boiler/Chiller system
136
Power and Energy Terms Used in Air
Conditioning
• One ton of A/C = 12,000 Btu/hr
• A ton is a measure of A/C power, and is used
when sizing systems, or when determining
electrical demand
• One ton-hour of A/C = 12,000 Btu
• A ton-hour is a measure of A/C energy, and is
used when sizing storage tanks for thermal
energy storage (TES) systems, or when
determining electrical energy consumption.
138
HVAC System Performance
Measures
1.
Energy Efficiency Ratio (EER)
EER = Btu of cooling output
Wh of electric input
2.
Coefficient of Performance (COP)
COP = Energy or heat output (total)
Energy or heat input (external)
= EER/ (3412 Btu/Wh)
139
Principles for HVAC Management
1.
2.
3.
4.
Most buildings are “thermally heavy” when
occupied (produce much internal heat) and the
amount usually dwarfs weather demands (how
could you spot that bills?)
Cooling is much more expensive than heating when
occupied because of the above
Almost all heating for thermally heavy buildings
occurs at night and weekends (when not occupied)
and most of it occurs at night in even thermally
light structures (see an opportunity?)
You can’t do much to reduce the cooling/heating
load but you can dramatically impact “how you
satisfy that load” (Why is this?)
140
HVAC Guiding Principles cont.
5.
6.
7.
8.
A good place to save money is how you supply the
heating and cooling (Variable Air Volume, new
chillers, new boilers, chilled water reset, etc.)
It is difficult and expensive to significantly
change the building envelop (walls, windows, etc.)
in existing buildings
The winter sun hits your south wall (friendly) but
the summer sun hits your east wall (unfriendly)
and your west wall (most unfriendly). That’s a
tough one to change though…
Most energy that enters a building generates heat
in that building (225 Btu/person, electricity for
lights and motors, etc.)
141
Thermally Heavy Buildings
• See Guiding Principle One: Most TH buildings
produce much internal heat
– Outside conditions not very important
– Much more cooling and less heating required
(12 months per year of cooling not unusual)
– Economizers often can save much money but
can be difficult to maintain and control on DX
units (more later)
– Heating demand occurs at night, etc. when
building is not occupied.
142
$$$$
• Thermally Heavy Buildings
– Use economizers (or fix)
– Night set-back on heating (15 F to 55 F) will save
at least 40% of heating cost in most facilities
– Air Handling Units (AHUs) can be throttled down
(VFD) or turned off when building is not occupied –
put building “to sleep” at night. Outside air can be
throttled down or even off when building is not
occupied
– Above is especially true for buildings in temperate
areas (most of the US) and for core zones of
buildings
143
Thermally Light Buildings
• Different animal…
• These buildings produce little internal heat (but all
produce some) – examples: homes, lightly
constructed buildings, warehouses, maintenance
shops, storage units, etc.
• These buildings are very responsive to outside
conditions (cold, you heat; hot, you cool) – Can you
spot this on the utility bills?
• Heating and cooling cost close to being equal for
mid-Texas
144
$$$$
• Thermally light buildings
– Night set-back still saves about 40% of heating
cost for most areas if running at night
– Night set-up saves about 40% of cooling costs if
running at night
– “Core zone” management still possible
– Outside air management still possible
(economizers)
– AHU throttling still possible
145
Humidity Control
• Humidification
• Dehumidification
– “Controlling indoor air moisture to below 65
percent relative humidity will limit the
probability of supporting mold growth”
<http://www.wbaonline.org/everyone/hottopics.asp>
• HVAC systems typically over-cool the air to
remove water vapor, and then may have to heat
the air back up. This is called reheat, and
requires additional energy.
• Some contractors grossly oversize HVAC systems
– short cycling
146
$$$$
• Variable Air Volume (VAV) systems can dramatically
reduce energy distribution energy costs. (Cube Fan
Law)
• In some areas “bucking” (reheat) may be required
for humidity control, however be very careful of
simultaneous heating and cooling in other areas (e.g.
large exposed glass perimeter areas)
• Ask if building uses re-heat, ask if it has been
checked recently…
147
What to Look For with HVAC
• Controls:
– Are controls actually functional? (Some may be
disconnected etc.)
– Are thermostats calibrated?
– Are controls properly programmed?
– Are controls properly installed? (near heat
sources, on outside walls, etc.)
– If thermostats are air powered – are air lines clean
and dry?
– Are air handlers running 24/7? (no control)
What to Look For with HVAC
• Heating and Cooling Units
– Are heating and cooling coils clean?
– Is refrigeration system properly charged?
– Are temperature set-points set correctly? (chillers
are often set low for “insurance”)
– Carefully check temperatures of pipes, do gauges
show fluids moving, pressure?
– Look for evidence of bad housekeeping with HVAC
system (insulation falling off, leaks, mess…)
What to Look For with HVAC
• Distribution System
– Are grills clogged and dirty?
– Do dampers operate? Does anyone know?
– Is ductwork insulated? Are joints sealed?
– Are economizers operating? Does anyone know?
(described below)
– If no one can answer – time to speak to client’s
HVAC contractor (try to get client to do this…)
– Is reheat on all the time?
System Improvement Options
$$$$
Big Ticket ($) Solutions
• Replace old chiller; possibly downsize oversized
chiller based on good load calculation
• Consider multiple chillers; consider installing a
small chiller for high cooling demand periods.
• Use VFDs on pumps, cooling towers (air side), and
chillers (not all) if applicable.
• Use heat recovery; use ozonation of cooling tower
water.
151
Economizer (Free cooling)
$$$$
• Use of outside air to provide air conditioning or to
ventilate a building when the enthalpy* of the
outside air is less than the enthalpy of internal air
and there is a desire to cool the building. In dry
climates, economizers can work well by measuring
dry-bulb temperature, however enthalpy based is
preferable, especially in humid climates.
• On smaller rooftop DX units, the economizers are not
maintained and are disconnected when they fail (be
careful)
* Heat and Humidity
152
Economizer
• Dry-Side economizer
Source: http://www.reznoronline.com/mpd/pub/reznor/products/maps/art/tpc_apguid_economizer.htm
153
$$$
Hours per year that the dry-bulb temperature ranges below 60oF
Dry Bulb Observation hour group (hrs)
Total
Temp. (F) 01-08
09-16
17-24 observations (hrs)
55/59
252
192
226
670
50/54
247
173
215
635
45/49
237
152
190
579
40/44
219
119
146
484
Fort Worth, T X
Total
2,368
Source: Engineering Weather Data
Number of hours are approximate and may vary each year
154
Economizer: Wet Side Economizer
Source: The ASHRAE Handbook: 2000 HVAC systems and Equipment
155
$$$
Hours per year for the wet bulb temperature ranges below 50ºF
WB
Observation hour group (hrs)
Total
Temp. (F) 01-08
09-16
17-24 observations (hrs)
45/50
220
178
200
598
40/45
194
165
195
554
35/40
210
172
196
578
30/35
416
277
353
1046
Fort Worth, T X
Total
2,776
Source: Engineering Weather Data
Number of hours are approximate and may vary each year
156
Night Setback
$$$$
• Night setback: lower thermostat settings for
nighttime, weekend and holiday hours (winter).
Setup for summer.
• Savings can be huge. In Texas bin data proves
about 40% savings for a nightime/weekend set
back program. For thermally heavy buildings,
savings can be a larger percentage.
• Often this can be done by turning off AHUs
especially in core zones; but be very careful of
mold and IAQ in general.
– (That should generate some discussion)
157
Chiller Energy Savings
$$$$$
• Basically, very large HVAC units for cooling
entire buildings or processes
• Chillers usually rated in kW/Ton (cooling) –
lower is better
• They can be complex but you should be aware
of some opportunities to save energy
• Often oversized – not good
• Even if new, there is an opportunity to save 520% in operating costs
Chiller Energy Savings
$$$$$
• Variable condenser water flow (VFD based on
Chiller demand)
• Condenser water temperature reset (VFD on
cooling tower fan based on basin temperatures –
tricky but big potential, about 1-2% savings per
degree lowered)
• Chilled water reset (Varies the temperature of
the chilled water in a loop such that the water
temperature is increased as the cooling
requirement for the building decreases)
• Saves about 1-2% for each degree increase in
chilled water temperature
• Mostly for simple systems and be careful of
humidity control
159
Air to Air Heat Recovery System
• Heat wheels:
– Transfer heat
– Transfer
humidity
Source: The ASHRAE Handbook: 2000 HVAC systems and Equipment and Airxchange Inc.
160
Cooling Towers
•
•
•
•
Natural draft (Large – power plants)
Force draft tower
Induced draft tower (Typical)
Remarkable devices that operate very efficiently
(COP 50 to 70 in some cases – dry weather)
• Maintenance intensive so many don’t use (this is
not “set & forget”)
• If you find cooling towers and they are well
maintained, they can save lots of energy
161
162
163
Cooling Tower Energy Savings
• Consider replacing old-dirty towers, newer
towers are up to 10 times the efficiency of >10
year old units
• Use towers to overcool chiller condenser
water for chiller energy savings
• Use VFDs on fans, basin water temperature is
signal to drive
• Use towers for “Free Cooling” in the right
conditions (use enthalpy control)
Process Heating and Cooling
• Process heating is vital to nearly all
manufacturing processes, supplying heat
needed to produce basic materials and
commodities. According to the U.S.
Department of Energy (DOE), heating
processes consume about 5.2 quadrillion Btu
of energy annually, which accounts for nearly
17 percent of all industrial energy use.
• Not the same as HVAC
(http://www.mntap.umn.edu/energy/heat.htm)
Page 165
Industrial
Processes
Process Heat Examples
•
•
•
•
•
•
•
Heat treat furnaces.
Food cooking.
Drying ovens.
Steam and heat exchanger systems.
Chemical and water heated baths.
Heated vessels of material.
Other…
Page 167
Energy Saving Areas for Process
Heating
• Reduce or eliminate openings in the furnaces
or ovens to reduce radiation heat losses
• Repair cracks and losses in the insulation of
furnace or oven walls, doors, etc.
• Use infrared heat thermometers or IR cameras
to detect heat loss
• Repair doors that don’t seal well on closing
Process Heating Survey
Conduct Process Heating Score Card:
• Have you conducted a detail energy assessment for your heating equipment using tools such
as Process Heating Survey and Assessment Tool (PHAST) to identify energy saving
opportunities?
• Do you measure oxygen (O2) and Carbon Monoxide CO or combustible in flue gases and
"tune" the burners periodically to maintain low values for O2 and combustibles in the
furnace flue gases?
• Have you sealed openings in furnaces and repaired cracks, and damaged insulation in furnace
walls, doors etc.?
• Do you regularly clean heat transfer surfaces to avoid build up of soot, scale or other
material?
• Do you have a program for calibration/adjustment of sensors (i.e. thermocouples),
controllers, valve operators etc.?
• Do you operate the furnace at or close to design load by proper furnace scheduling and
loading, and avoid delays, waits between production?
• Do you maintain proper (balanced or slightly positive) pressure in furnaces to avoid air
leakage in the furnace?
• Do you use any type of heat recovery system (i.e. recuperator, regenerator, water or heating
etc.) to recover heat form the furnaces flue gases?
Process Heating Survey
•
•
•
•
•
Please answer either a or b.
– a. Are you using a heat recovery method to use heat of flue gases from furnace
or air preheater to heat charge material, fixtures etc.?
– b. Are you using a heat recovery method to use heat of flue gases from furnace
or air preheater for lower temperature processes such as steam generation,
water heating or air heating for the plant or other application?.
Do you use design of fixtures, trays and other material handling system components
with minimum weight and proper material?
Do you use proper insulation for (or minimize use of) water or air cooled parts such
as rolls, load supports etc. used in furnaces?
Are you using the most cost effective source of heat for processes where it is
possible use alternate energy sources (i.e. steam vs. electricity vs. fuel firing) where
applicable?
Do your heating equipment and other heated parts use cost effective type and
thickness of insulation?
Energy Saving Areas for Process Heating:
Insulation Levels and Condition
Page 171
Energy Saving Areas for Process Heating:
Flue Gas Heat Recovery (Combustion Air Preheat)
Page 172
Energy Saving Areas for Process Heating:
Waste Heat “Cascading”
• Cascade waste heat. The heat from exhaust
gases can be used as a source of heat for
lower temperature process heating
equipment.
• For example, waste heat boilers can use the
thermal energy from flue gases to generate
hot water or steam. Waste heat from heat
treating furnaces can also be used in aging
or paint-drying ovens.
• To maximize benefits of the heat recovery,
the downstream heating equipment must be
in operation while the furnace (heat source)
is operating
Page 173
Energy Saving Areas for Process Heating:
Fuel Switching and Innovative Technologies
• Example:
Electrical
induction
heating
versus
large
natural
gas
furnace
for metal
treatment.
Page 174
Waste Heat Recovery
Energy in streams of air, exhaust gases, liquids
leaving the boundaries of a plant or building.
Quantity of waste heat:
H [Btu/hr] = m [lb/hr] x Δh [Btu/lb]
m = density [lb/ft3] x volumetric flow [ft3/h]
Page 175
Waste Heat Recovery
Quality of waste heat:
Temp. Range
T, ºC
Source
High
600 ≤ T ≤ 1,650
Exhausts from furnaces, kilns, and incinerators
Medium
200 ≤ T ≤ 600
Exhausts from engines, boilers, and furnaces
Low
25 ≤ T ≤ 200
Cooling water, process liquids
Source: Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA, p.189
Page 176
Waste Heat Recovery (cont.)
 Other concerns

How close is location where heat is needed?

Is the waste heat available when needed?

Is the waste heat compatible with a heat exchangers?
 Several applications
1. Heat pump
2. Recuperator
3. Economizers
4. Blowdown recovery
5. Desuperheat
6. Condensing heat recovery
7. Rotary wheel
Page 177
Waste Heat Recovery (cont.)
Heat Exchangers
Shell & Tube
Plate
Sources: Energy Management Handbook, 4th Ed., Turner, W.C., 2001, The Fairmont Press, GA, p. 205
Alfa Laval @ http://www.alfalaval.com
Page 178
Energy Saving Areas for Process Heating:
Heat Exchanger Condition
Thttp://www.energystar.gov/ia/business/industry/clnwtrsd.pdf#search=%22fire%20tube%20scale%22
Page 179
Process Cooling Systems
•
•
•
We sometimes find situations where the heated “product/process”
must be cooled to some point before the next process step can take
place (examples include injection molding, extrusion, …).
Other times we see “product” that requires a cooling process step
and then maybe a heating process step, and then maybe cooling
again (examples include food processes, …).
In these situations, the cooling cycle generally drives the cycle time
for production. Depending on mass and temperatures, we see a
variety of approaches. We may see small local cooling systems or
large centralized cooling systems.
Page 180
Process Cooling System Components
– Look Familiar?
•
•
•
•
Cooling towers.
Chillers.
Delivery systems.
Controls.
Page 181
Diagram of Typical Chiller
85°F
Condenser Water
95°F
Condenser
Compressor
High Pressure Side
Expansion
Valve
Motor
Low Pressure Side
Evaporator
45°F
Chilled Water
Page 182
55°F
“Free” Cooling and Rules of Thumb - Again
• Chillers demand about 1 Kw (input) for every
ton demand (output).
• Economizers -- Use of “outside air” to provide
cooling (when conditions permit, e.g. cool dry
air, relative to cooling demands).
• Controls that sense load (chilled water reset) -temperature of the chilled water in a loop such
that the water temperature is increased as the
cooling requirement for the process decreases.
• Saves about 1.5% for each degree increase in
chilled water temperature.
Page 183
End Day One
Web Sites (U.S. DoE)
U.S. DoE Bestpractices web site
http://www1.eere.energy.gov/industry/bestpractices/
IAC web site
http://www1.eere.energy.gov/industry/bestpractices/iacs.html
Technical publications web site
http://www1.eere.energy.gov/industry/bestpractices/technical.html
http://www.dsireusa.org/
Page 185