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. Current situation -- getting a grip.
2. Process heating and cooling.
3. Steam and steam delivery.
4. Compressed air and air delivery.
5. Building and HVAC.
6. Lighting.
7. Electrical motors and systems.
8. System x system interactions (not specifically
discussed, but very important in overall
assessment).
Page 5
Eight Key Questions for Commercial and
Industrial Systems
1. What function(s) does this system serve?
2. How does this system serve its function?
3. What is the energy consumption of this system?
4. What are the indications that this system is properly
functioning?
5. If system is not working properly, how can it be
restored to proper operation?
6. How can the energy cost of this system be
reduced?
7. How should this system be maintained?
8. 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
900
Billed kW
Billed vs. Actual Demand
850
What's going on here? 800
750 Actual kW
700
*Confidential 650
1 2 3 4 5 6 7 8 9 10 11 12
Months
Page 17
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 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 2 Footcandles
Hallways 10 Footcandles
Factory floor 30 Footcandles
Offices 50 Footcandles
Inspection 100 Footcandles
Operating room 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, hard-
wired?)
• 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, 20-
50% - 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
• 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
$$$
Hours per year for the wet bulb temperature ranges below 50ºF
WB Observation hour group (hrs) Total
Temp. (F) 01-08 09-16 17-24 observations (hrs)
45/50 220 178 200 598
40/45 194 165 195 554
35/40 210 172 196 578
30/35 416 277 353 1046
Fort Worth, T X Total 2,776
Source: Engineering Weather Data
Number of hours are approximate and may vary each year
156
Night Setback
$$$$
• Night setback: lower thermostat settings for
nighttime, weekend and holiday hours (winter).
Setup for summer.
• Savings can be huge. In Texas bin data proves
about 40% savings for a nightime/weekend set
back program. For thermally heavy buildings,
savings can be a larger percentage.
• Often this can be done by turning off AHUs
especially in core zones; but be very careful of
mold and IAQ in general.
– (That should generate some discussion)
157
Chiller Energy Savings
$$$$$
• Basically, very large HVAC units for cooling
entire buildings or processes
• Chillers usually rated in kW/Ton (cooling) –
lower is better
• They can be complex but you should be aware
of some opportunities to save energy
• Often oversized – not good
• Even if new, there is an opportunity to save 5-
20% in operating costs
Chiller Energy Savings
$$$$$
• 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
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Energy Saving Areas for Process Heating:
Heat Exchanger Condition
Thttp://www.energystar.gov/ia/business/industry/clnwtrsd.pdf#search=%22fire%20tube%20scale%22
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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.
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Process Cooling System Components
– Look Familiar?
• Cooling towers.
• Chillers.
• Delivery systems.
• Controls.
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Diagram of Typical Chiller
85°F Condenser Water 95°F
Condenser
Compressor
Expansion High Pressure Side
Valve Motor
Low Pressure Side
Evaporator
45°F 55°F
Chilled Water
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“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.
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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/
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