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 Quick. PEP® 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 properation? 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 (k. W, 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. 5 x 11) (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: k. W, k. Wh, Fuel charges, taxes, PPCA, etc. Page 15
Billing Analysis (cont. ) Page 16
Client* Billing Analysis (cont. ) What's going on here? *Confidential Page 17
Client Billing Analysis (cont. ) Page 18
Billing Analysis (cont. ) Page 19
Billing Analysis (cont. ) • • • Know the definitions and relationships of k. W and k. Wh. 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 (k. W). § Odd characteristics such as power factor. § Issues such as power quality. Page 21
Electrical Demand Control • Partially because demand (k. W) 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 (k. W) and consumption (k. Wh) 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 k. Wh 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 (k. W). • At some agreed-upon k. W 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 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 k. VA is needed to get the same k. W. Yet, we are paying for k. W. (? ? ? ) – 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 k. W/k. VA. See power triangle next page. o Correction is (usually) made by adding capacitor banks 32
Power Factor § Power triangle (k. V) x (I) x (√ 3) k. VAR k. W Motor load example: (k. VA) x (PF) or (HP load) x (. 746 k. W/HP) x (1/η) 33
Power Factor Example § A plant has 2, 000 k. W demand a power factor of 80%. How much capacitance is needed to correct this to 95%? (Why did I use 95%? ) Δk. VAR = 2000 (. 421) = 842 k. VAR 2500 k. VA Table Next Page 2000/. 8 = 2500 k. VA 2000 k. W 34 Δ k. VAR
Power Factor Table 35
THE GENERAL VIEW • Quick. PEP® • http: //www 1. eere. energy. gov/industry/quickpep/( wu 24 wh 55 es 44 h 1550 shxdjby)/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
Quick. PEP Screens and Sample Case (“TCC-1”) Page 37
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We will talk about where this data comes from in a bit… Must use blended k. Wh & k. W Cost Page 39
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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 $/k. Wh, uses about $11, 000 worth of electricity per year. – Over half of electrical energy consumed in the US is used by electrical motors. Sources: DOE – Best practices @ http: //www. oit. doe. gov/bestpractices/ Page 57
Electric Motor Management Energy Efficient Motors (Induction) • What is an Energy Efficient motor? – More copper and iron – less resistance losses – (I 2 R) or HEAT. – Better fans and bearings more carefully lubricated – therefore less friction. – Larger and heavier (typically). Page 58
Electric Motor Management Energy Efficient Motors (Induction) Source: Energy Management Handbook, 4 th Ed. , Turner, W. C. , 2001, The Fairmont Press, GA, p. 272, 273 Page 59
Electric Motor Management Energy Efficient Motors (Induction) • Energy efficient motor characteristics – – – – Higher inrush (LRA). More efficient and higher power factor. Save energy and reduce demand. Reduce load on cables, transformers, etc. (note higher efficiency and PF). Speed is slightly higher (this can be critical). Significantly larger inrush (LRA). Less vibration. Longer manufacturer’s warranties. Sources: Energy Management Handbook, 4 th Ed. , Turner, W. C. , 2001, The Fairmont Press, GA, p. 286 http: //www. wapa. gov/es/pubs/techbrf/eemotors. htm Page 60
Energy Efficient Motors To be considered energy-efficient, a motor’s performance must equal or exceed the nominal full-load efficiency values provided by NEMA in their publication MG-1. Page 61
Energy Efficient Motors Calculating Savings • • Power and energy savings depends on efficiency of standard vs. energy efficient motor. Calculation from replacing w/ EE, assuming same hp and % load: 1) Energy Savings ($) = hp x 0. 746 x L x C x N x (100/E std – 100/EEE) where: L = % Load * C = Energy Cost ($/k. Wh) 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, 4 th Ed. , Turner, W. C. , 2001, The Fairmont Press, GA, p. 286 Page 62
Energy Efficient Motors Calculating Savings (cont. ) 2) k. W Savings (Simplified Estimate) k. W = k. Wstd – k. WEE = (hp) (0. 746 k. W/hp) (100/Estd – 100/EEE) $Dem. Savings = [(k. W)std – (k. W)EE] ($/k. W. 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, 4 th 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/k. W each month. Electrical energy costs $. 05/k. Whr. • What are the operating savings for purchasing the energy efficient motor? Page 64
Energy Efficient Motors Example (cont. ) • Demand energy savings both occur – Demand savings = (50 hp) (0. 746 k. W/hp) (100/90. 7 – 100/94. 5) ($7/k. W. momth) (12 month/yr) = $138. 9 /yr – Energy savings = (50 hp) (0. 746 k. W/hp) ($0. 05/k. Wh) (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) • CFM 2 = CFM 1(RPM 2/RPM 1) 1 st law • SP 2 = SP 1(RPM 2 /RPM 1)2 2 nd law • HP 2 = HP 1 (RPM 2/RPM 1)3 3 rd law Source: Energy Management Handbook, 4 th 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: HP 2/HP 1 = (RPM 2/RPM 1)3 = [ (RPM 1 x 0. 80) / RPM 1 ]3 = 0. 51 HP 2 ~ 51% of HP 1 - A drop of 49% !! 72
Electric Motor Management Fan Laws – Strange Example • Fan system 32, 000 CFM. Existing standard efficiency motor of 20 HP 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, 4 th 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, 4 th 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, 4 th Ed. , Turner, W. C. , 2001, The Fairmont Press, GA 77
Ex. : VFD Application - Cooling Water System For 50% load row: (100 hp)(0. 746 k. W/hp) (1. 1 -0. 2) (0. 23)(8, 760) = 135, 273 k. Wh/yr (135, 273 k. Wh/yr) ($ 0. 0287 /k. Wh) = $ 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 Issues u u u u 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
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Lamp 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/sclp 2/technicalguide/about/color. Rendering. Index. 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 4200 K 85 Deluxe cool white fluorescent 86 Low pressure sodium 0 -18 High pressure sodium 25 100 -Watt incandescent 100 Page 91
Color Temperature A measure of the “warmth” or “coolness” of a light source: < 3200 K = “warm” or red side of spectrum > 4000 K = “cool” or blue side of spectrum http: //www. fullspectrumsolutions. com/cri_explained. htm Page 92
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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 / ft 2 Lux = lumens / m 2 – Consensus standards for light levels are set by the Illuminating Engineering Society of North America (IESNA. org). Page 94
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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 / d 2 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, F 40 T 12 - 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+12 watts/ballast with 2 ballasts/fixture) = 184 Watts/fixture • Energy Cost: $0. 08/k. Wh , Demand Cost: $9. 00/k. W Cost Savings: k. Wh = (184 Watts/fixture) x (100/2 fixtures) x (16 hours/day) x (250 days/year) x (1 k. Wh/1, 000 Watt-hour) x ($0. 08/k. Wh) = $2, 944/year k. W = (184 Watts/fixture) x (100/2 fixtures) x (1 k. Wh/1, 000 Watt-hour) x ($9/k. W-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, F 40 T 12 - 40 watt lamps, per fixture (old) • 100 fixtures with four, F 32 T 8 - 32 watt lamps, per fixture (new) • Look up wattage of lamps and ballasts in Grainger etc. F 40 T 12 - (160 watts/fixture +12 watts/ballast with 2 ballasts/fixture) F 32 T 8 – (114 watts/fixture) Energy Cost: $0. 08/k. Wh , Demand Cost: $9. 00/k. W Cost Savings: k. Wh = (160 - 114 Watts/fixture) x (100 fixtures) x (16 hours/day) x (250 days/year) x (1 k. Wh/1, 000 Watt-hour) x ($0. 08/k. Wh) = $1, 472/year k. W = (160 - 114 Watts/fixture) x (100 fixtures) x (1 k. Wh/1, 000 Watt-hour) x ($9/k. W-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 u Widely used throughout industry, present in almost any industrial plant. u Source of energy for tools and machines. u Control medium. u Material handling. u Cleaning. u Relatively expensive to operate -- typical saving opportunities, 2050% - Folks, this is huge! u Management required on both supply and demand side. u 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, 4 th Ed. , Turner, W. C. , 2001, The Fairmont Press, GA Page 103
Compressed Air Systems (cont. ) u Supply Side u Air intake and filter. u Air compressor. u Dryer. u Storage tank. u Pressure / flow controllers. u Distribution lines. u Demand side u 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 u Rotary Screw u Most popular, range 30 - 200 hp. u Compact, low initial cost, fairly efficient. u Easy maintenance. Air or water cooled. u Reciprocating u Driven by an “automotive-type” piston. u Available in sizes from less than 1 hp up to above 600 hp. u Large, higher initial cost, very efficient. u 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 u Centrifugal u Kinetic energy developed by centrifugal impeller(s) (typically at 50, 000 rpm or more). u Usually large, typically above 150 hp. u Flow capacity decreases as the system pressure increases (head/capacity curve). Efficient modulation (surge point), VFD-suitable. u Good maintenance critical (shaft vibration). u 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 u 100 hp rotary screw compressor u First cost $50, 000 u 8, 640 operating hours per year u 75% load u Demand cost: $7/k. W-month ($84/k. W-year) u Energy cost: $0. 08/k. Wh u Average life: Maybe 10 years Annual op. cost = (100 hp)(0. 746 k. W/hp)(0. 75) x {($84/k. W. yr)+ ($0. 08/k. Wh)(8, 640 hr/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 u Intake air u As cool as possible, for every 5. 5ºF reduction approx. 1% of increase in the mass of intake air. (we will see this again…) u Intake filter, maintain in top condition. Size properly to minimize pressure drop. u Drivers u Electric motors, most common. u Diesel or Gas engines. u Steam engine or turbine. u Compressor cooling Source: “Compressed Air”, Royo, E. C. , 1991, Ed. Paraninfo, Madrid, Spain Page 110
Compressed Air Systems (cont. ) Support Systems u After-cooling and drying u Remove moisture (100% RH at compressor outlet). u In general, 20ºF of temperature drop reduces moisture content by about 50%. u Dryer: refrigerant (most common), regenerative-desiccant, deliquescent. u Air receivers (Often Missing…) u Smooth compressor cycling, reduce demand fluctuation. u 2 to 4 gallons per CFM. u Distributed throughout facility. Page 111
Compressed Air Systems (cont. ) Support Systems u Distribution u Looping (more is better). u Size length and diameter to minimize pressure loss (bigger is better). u Slopes. u Traps and draining points u Allow removal of condensate from lines. u However…may be source of air leaks if poor maintenance. u Separators Page 112
Compressed Air Systems (cont. ) u Demand side - Users u Some inappropriate uses of compressed air u Open blowing (use brushes, electric fans, blowers, etc). u Aspiration/bubbling (use low-pressure blowers). u Sparging – aerating or oxygenating liquid with compressed air (use low-pressure blowers or mixers). u u Unregulated hand-held blowing guns. u u Venturis (use vacuum systems). Cabinets cooling (use air conditioners or fans). Air Quality (which do they have? ) u Plant air (needs to be fairly dry) u Instrument air (needs to be clean and dry) u 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. ) u Demand side - Users u Pressure at the point of use u u u 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. ) u Demand management u Quantity (Cubic Feet per Minute - CFM) u Sum of average needs. u Use secondary storage tanks. u Use local pressure regulators (reduce artificial demand). u System controls (just be aware there are out there…) u Individual compressor control u Start/stop – reciprocating or rotary screw. u Load/unload - motor runs with open valve – unload, 40%. u 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. ) u System controls (cont. ) u Multiple compressor control: orchestrate compressor operation and air delivery. u Cascading set points: need higher set points to maintain system pressure above minimum. u Sequencers: match supply/demand by taking compressors on/off. Lower set points achieved. Highly cost effective. u Flow controllers u 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. u 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. ) u. Air Leaks – Easiest Recommendation You Will Ever Make…No Brainer u Expensive. . really expensive! u Good System - 10% Leakage, typical 20 -30% (recall the expense to run slide…) u When on/off control: Leakage(%)=(Tx 100)/(T+t) T=On-load time (min) t=Off-load time (min) u If other control strategies: Leakage (CFM)=Vx(P 1 -P 2)/(Tx 14. 7)x 12. 5 P 1=normal operating pressure, in psig P 2=50% P 1 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. ) u Air Leaks (cont. ) u Ultrasonic acoustic detector. u Soapy water in suspected areas. u Off-production schedule. u Example of annual cost of leaks for a typical installation Look at u u Hoses. u Filters and regulators. u Valves. u u Connections and fittings. Non-operating equipment. 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 100 hp 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 person or CO 2 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 Re. Heat 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 60 o. F 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
$$$ Number of hours are approximate and may vary each year 156
Night Setback $$$$ • Night setback: lower thermostat settings for nighttime, weekend and holiday hours (winter). Setup for summer. • Savings can be huge. In Texas bin data proves about 40% savings for a nightime/weekend set back program. For thermally heavy buildings, savings can be a larger percentage. • Often this can be done by turning off AHUs especially in core zones; but be very careful of mold and IAQ in general. – (That should generate some discussion) 157
Chiller Energy Savings $$$$$ • Basically, very large HVAC units for cooling entire buildings or processes • Chillers usually rated in k. W/Ton (cooling) – lower is better • They can be complex but you should be aware of some opportunities to save energy • Often oversized – not good • Even if new, there is an opportunity to save 520% in operating costs
Chiller Energy Savings $$$$$ • 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
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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 (O 2) and Carbon Monoxide CO or combustible in flue gases and "tune" the burners periodically to maintain low values for O 2 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 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 u. Energy in streams of air, exhaust gases, liquids leaving the boundaries of a plant or building. u. Quantity of waste heat: H [Btu/hr] = m [lb/hr] x Δh [Btu/lb] m = density [lb/ft 3] x volumetric flow [ft 3/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, 4 th Ed. , Turner, W. C. , 2001, The Fairmont Press, GA, p. 189 Page 176
Waste Heat Recovery (cont. ) u Other concerns u How close is location where heat is needed? u Is the waste heat available when needed? u Is the waste heat compatible with a heat exchangers? u 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, 4 th 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=%22 fire%20 tube%20 scale%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. Do. E) U. S. Do. E Bestpractices web site http: //www 1. eere. energy. gov/industry/bestpractices/ IAC web site http: //www 1. eere. energy. gov/industry/bestpractices/iacs. html Technical publications web site http: //www 1. eere. energy. gov/industry/bestpractices/technical. html http: //www. dsireusa. org/ Page 185
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