Massachusetts Energy Efficiency Partnership. 5. High Efficiency Systems for Large Boilers

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1 5. High Efficiency Systems for Large Boilers

2 Terminology >Economizer Captures exhaust heat to warm feedwater >Heat Recovery Heat Exchanger Heat exchanger in the flue gas to warm some other load entirely >Possible loads Domestic hot water Hydronic (hot water) space heating Separate in floor space heating Even outdoor sidewalk ice melting 198

3 Efficiency Improvement >Economizer Improvement for low temperature water boilers only 2-4% Improvement potential rises for higher pressure steam boilers Function of the return condensate temperature and the boiling point >Flue Gas Condenser Efficiency improvement depends on finding and isolating a lower temperature load 199

4 Economizers >Additional heat exchanger added onto larger boilers to enhance efficiency >Newer technology for intermediate sized steam boilers Pressures to 250 Psig (or so) MMBH Most commonly fire-tube 200

5 Economizer 201 Picture Courtesy of Spirex Sarco and Cleaver Brooks

6 Generic Economizer >Used to preheat feedwater before it enters boiler >Adds efficiency to the extent feedwater requires pre-heating >May allow condensation or not 202 Picture Courtesy of Spirex Sarco

7 Economizers >Market development PAST: economizers for smaller boilers were produced by secondary equipment supplier NOW : large boiler manufacturers are now producing their own economizers SHOWN: Cleaver Brooks Economizer on CB Boiler 203 Picture Courtesy of Cleaver Brooks

8 Gases Must Be Hotter than Boiling Water in All Locations Including at the Exit Exhaust Issue Hot Gases are Passing Heat to Boil Water Flue Gas is Typically F Hotter than Water s Boiling Point 204

9 Economizer Flue Gases will Leave Somewhat Above Condensate Return Temp Flue Gases Pre-Heat Returning Condensate 205

10 Economizer Operation 206 Picture Courtesy of DOE

11 Economizer DA Conflict De-aerator Must Preheat Water before Economizer 207

12 An Overall System Complete Layout Best Left to an Expert 208

13 Economizers Non-Condensing >This economizer will not handle condensation 209 Picture Courtesy of Cleaver Brooks

14 Economizers How the ByPass Damper Works 210 Picture Courtesy of Cain

15 Economizer Mounting for Smaller Units >Economizer supported by boiler >Limitation on the weight boiler can support 211 Picture Courtesy of Cleaver Brooks

16 Economizer Mounting for Larger Units >Weight of larger economizers will require supports and rigging >Both horizontal and vertical mounting is possible 212 Picture Courtesy of Cleaver Brooks

17 Economizer Efficiency with High Make-Up Water Levels 213 Picture Courtesy of Cleaver Brooks

18 Economizer Efficiency with Non-Condensing Economizer 214 Picture Courtesy of Cleaver Brooks

19 Third-Party Economizers 215 Picture Courtesy of Cain

20 Economizer Condensing >This CB factory built economizer WILL handle condensation 216 Picture Courtesy of Cleaver Brooks

21 Condensing Economizers Condensing Temperatures 217 Picture Courtesy of DOE

22 Economizer Condensing >TWO Water Passes 218 Picture Courtesy of Cleaver Brooks

23 Economizer Condensing >TWO Water Passes 219 Picture Courtesy of Cleaver Brooks

24 The System Condensing Steam Boiler 220

25 The System Alternative Layout Make-Up Water Temp. Usually ~50 0 F 221

26 New Concepts in Industrial Steam Boiler Systems 222

27 New Internal Economizer 223 Picture Courtesy of Hurst Boiler

28 Direct Contact Economizers 224 Picture Courtesy of DOE

29 For Larger Boilers >Very large boilers, high pressure boilers, and boilers built for power generation will come equipped with economizers as standard equipment 225

30 Large Boiler Economizer - Watertube Boiler Components >Uses left over heat in the exhaust gases to pre-heat feedwater 226 Picture Courtesy of W Ryan

31 Large Boiler Economizer 227 Picture Courtesy of Babcock and Wilcox

32 III. Industrial Scale High Eff. Water Heating

33 Learning Objective >Understand new options for improving the efficiency of large scale commercial and industrial water heating 229

34 Overview >Understanding efficiency in water heating systems >Tankless water heaters >Condensing water heaters >Savings potential >High efficiency pool heaters >Industrial Scale Water Heating 230

35 Understanding Efficiency in Water Heating Systems 231

36 Understanding Efficiency Measurements Review from Fundamentals of Gas Technology Course >Steady State Efficiency >Recovery Rating >First Hour Rating >EF-Energy Factor 232

37 Efficiency Measurements are Based on Conventional Water Heaters >Residential ~40,000 Btu/h >Commercial <250,000 Btu/h >Storage tank, gas burner, combustion gases vent through middle of tank Picture Courtesy of Natural Resources Canada 233

38 Recovery Rate >Steady State Efficiency = Efficiency at which a water heater will heat a continuous flow of water >Recovery Rate = Rate (in gallons/hr.) at which a certain size burner will generate hot water on a continuous basis >If the water draw is less than or equal to the Recovery Rate the water heater will never run out of hot water 234

39 Recovery Rate >Recovery Rate indicates the amount of water in gallons that can be heated in 1 hour >Recovery Rate (gallons per hour) = Gas Input x Steady State Efficiency (Temperature Rise x 8.34) >Efficiency for a Gas Water Heater ~0.75 (75%) Do NOT use the Energy Factor on the rating label >Typical temperature rise is 80 F (40 F in 120 F out) 235

40 Recovery Rate Calculation in Units Btu Gas Input X Steady State Efficiency hr Recovery Rate lb 1Btu (Temperature Rise) 8.34 gal 0 lb F For a 40,000 Btu/Hr Burner Btu 40, Hr Gallons Recovery Rate lb 1Btu Hr 120 F 40 F 8.34 gal lb >This means that the water heater could produce 45 gallons per hour of 120 F water FOREVER 0 F 236

41 Water Heater Efficiency Measurements >Steady State Efficiency (more exact) Efficiency of the water heater when heating an infinitely prolonged water stream running at the water heaters recovery rate >Energy Factor A residential efficiency measurement Efficiency of water heating when the water heater is producing 64 gallons of heated water per 24 hour period 237

42 Maximum Output Based on Recovery Rate For a 40,000 Btu/Hr Burner : Gallons Recovery Rate 45 1,080 Hr Gallons Day >Water heater could produce 1,080 gallons / day to meet a steady 45 gallon / hour load that occurs all 24 hours of the day >Unlikely to ever happen in a real application 238

43 Storage Efficiency >Effect of stacking >Only a portion of the water is at a useful temperature >Upon draw water is consistently hot until usable water runs out >Then promptly cold 239

44 First Hour Rating >Most customers do not want to produce hot water forever. They want to know how much hot water they can draw at one time before the heater runs out. The First Hour Rating is useful: First Hour Rating Recovery Rate (1hr) (0.7)(Tank Volume) 240

45 First Hour Rating First Hour Rating Recovery Rate (1hr) (0.7 x Tank Volume) > If for the example, the tank was 40 gallons First Hour Rating First Hour Rating gallons 45 (1hr) hr 73 Gallons 0.7 x 40 gallons Indicates that the water heater can produce 73 gallons over the first hour 241

46 Why is This Important? >First hour rating depends on power input and tank size >Gas water heaters have much higher power input than electric water heaters >Therefore, a smaller gas heater can have a HIGHER first hour rating and usually do This means the customer can take more showers, wash more clothes, and so on with a smaller gas water heater than a larger electric heater >MORE convenience while using LESS space 242

47 Right from the State Water Heater Catalog 243 Picture Courtesy of State Industries

48 Efficiency Based on Recovery Rate Reversing the Recovery Rate Calculation Efficiency Recovery Rate gal hr (Temperature Rise Btu Gas Input hr lb 1Btu F) 0 gal lb F 244

49 Efficiency Based on Recovery Rate For a 52,500 Btu/Hr Burner : Recovery Rate First Hour Rating 0.7(Capacity) gal Recovery Rate (40) 56 hr Efficiency gal lb 1Btu 56 (80 F) 0 hr gal lb F Btu 52,500 hr Efficiency in Constant Recovery 71.17% 245

50 Effective Efficiency for a Standard Residential Heater >A 40 gallon gas water heater could produce a large amount of water (1080 gal/day) >Realistic residential load is much lower Standard load assumed at 64 gal/day The remainder of the time, the heater is keeping the tank warm Keep warm energy is lost to the home DOE rating procedure measures this 246

51 Effective Efficiency for a Standard Residential Heater Larger Commercial Load Anywhere on This Line 80% 75% Tank Loss Average Home Energy Factor Efficiency Steady State or Recovery Efficiency 70% 65% 60% 55% 50% 45% Effective Efficiency Hot Water Flow in Gallons per Day 40% 247

52 Tankless Water Heaters 248

53 Tankless Water Heaters >What are they? >Why would a standard tankless water heater be more efficient? 249

54 Tankless Gas-Fired Water Heaters >Residential input is 125,000 Btu/h >Commercial input <725,000 Btu/h >Best suited to constant HW demand >No storage >Higher capital cost >Compact Hot Water Out Cold Water In 250

55 Tankless Gas-Fired Water Heaters Picture Courtesy of Takagi 251

56 Why Would a Tankless Water Heater be More Efficient? Eliminated Tank Loss Tankless 80% 75% 70% Steady State or Recovery Efficiency 65% 60% 55% Effective Efficiency Energy Factor Efficiency Hot Water Flow in Gallons per Day 50% 45% 40% 252

57 Why Would a Tankless Water Heater be More Efficient? >Without the storage tank the tank loss is removed Tank Heat Loss 80% 75% Steady State or Recovery Efficiency 70% 65% 60% 55% Effective Efficiency Energy Factor Efficiency Hot Water Flow in Gallons per Day 50% 45% 40% 253

58 Normal Situation 80% 75% Tankless Typical Usage Range 70% 65% 60% 55% Effective Efficiency Tank Type Hot Water Flow in Gallons per Day % 45% 40% 254

59 Issues with Tankless Systems >Larger burner is required First hour and recovery rates are the same One shower will require a 125 MBH burner More sophisticated safety controls >Electric components Needs power connection >Overall more expensive Power burner More controls 255

60 Sizing Tankless Systems 256 Picture Courtesy of Takagi

61 Tankless Gas-Fired Water Heaters 257 Picture Courtesy of Takagi

62 Tankless Gas-Fired Water Heaters 258 Picture Courtesy of Bosch

63 Also Applied to In Floor Space Heating 259 Picture Courtesy of Robur

64 Also Applied to Warm Air Space Heating 260 Picture Courtesy of Rheem

65 Applied to Heating 261 Picture Courtesy of Rheem

66 Issues with Tankless Systems >Overall combustion process is no more efficient than a standard tank system Similar exhaust temperatures >Why not a condensing unit? 262

67 Condensing Water Heaters 263

68 Condensing Water Heaters >Substantial increase in efficiency and heater first cost >Condensing heat exchangers are elaborate and must be built of high grade stainless >Best applications are systems that require large quantities of hot water 264

69 New Technology in Water Heating Condensing Water Heater 265 Picture Courtesy of American Water Heater

70 Condensing Water Heater >Larger heat exchanger >Combustion blower >Requires electric connection 266 Picture Courtesy of American Water Heater

71 Condensing Water Heater >Alternative - Top Mounted Burner 267 Picture Elements Courtesy of A.O.Smith

72 Condensing Water Heater >Combustion blower can power a longer more elaborate exhaust >Typically sidewall exhausted 268 Picture Courtesy of A.O. Smith

73 Condensing Water Heater >Sealed combustion is typical 269 Picture Courtesy of A.O. Smith

74 Condensing Tankless System >Very high efficiencies due to cold entering water >In 98% range Both recovery efficiency and energy factor 270 Picture Courtesy of Navien

75 271 Picture Courtesy of Navien

76 Condensing Tankless System >Condensing efficiency, plastic venting 272 Picture Courtesy of Noritz

77 Savings Potential 273

78 Savings Potential in Residential Loads is Limited Economic Analysis of Water Heating Option 1 Option 2 Hot Water Consumption = 64 Gallons/Day 64 Gallons/Day Cold Supply Water Temperature = 42 Deg F 42 Deg F Hot Water Temperature Desired = 120 Deg F 120 Deg F Effective Efficiency = 55% 75% Water Heater Gas Consumption/Year MMBtu/Yr MMBtu/Yr Current Gas Cost= 8 $/MMBtu 8 $/MMBtu Total Water Heating Bill $ $/Yr $ $/Yr Operating Cost Difference = $58.94 $/Yr In this case the appropriate efficiency is the energy factor due to the low volume of water required per day 274

79 Savings Potential In Larger Commercial Loads Economic Analysis of Water Heating Option 1 Option 2 Hot Water Consumption = 2000 Gallons/Day 2000 Gallons/Day Cold Supply Water Temperature = 42 Deg F 42 Deg F Hot Water Temperature Desired = 120 Deg F 120 Deg F Effective Efficiency = 75% 95% Water Heater Gas Consumption/Year MMBtu/Yr MMBtu/Yr Current Gas Cost= 8 $/MMBtu 8 $/MMBtu Total Water Heating Bill $5, $/Yr $3, $/Yr Operating Cost Difference = $1, $/Yr In this case the appropriate efficiencies may be the steady state efficiency due to the much higher volume of water required per day 275

80 High Efficiency Pool Heaters 276

81 Pool Heaters >Related to boilers in construction >Generally a specialized industry >Need to handle pool water chemistry, high flows, and low delivery temperature Low delivery temperature should make condensing technology practical 277

82 Pool Heaters >Added first cost makes condensing operation more attractive to large loads with long operating seasons commercial or community pools 278 Picture Courtesy of Raypak

83 Condensing Pool Heaters 279 Picture Courtesy of Raypak

84 Condensing Pool Heaters 280 Picture Courtesy of Raypak

85 Pool Heaters 281 Picture Courtesy of Raypak

86 Smaller Condensing Pool Heaters 282 Picture Courtesy of Certiken British Manufacturer

87 Industrial Scale Water Heating 283

88 Common Hydronic Boiler-Fired Industrial Water Heating 284 Picture Courtesy of Natural Resources Canada

89 Common Steam-Fired Industrial Water Heating 285 Picture Courtesy of Natural Resources Canada

90 Indirect Boiler Heat Recovery Water Heating 286 Picture Courtesy of Natural Resources Canada

91 New Technology in Water Heating Commercial Direct Contact Water Heater 287 Picture Courtesy of Armstrong

92 Direct Contact Water Heaters >Drops of water are sprayed directly thru exhaust gases Droplet surface is the heat exchanger Spray of drops produces huge surface areas Large capacity in small packages >Pipeline quality gas has little tendency to contaminate water Minor sulfur content However, water should not be re-circulated 288

93 Direct Contact Water Heaters 289 Picture Courtesy of Custom Thermal

94 Direct Contact Water Heaters 290 Picture Courtesy of Dunlop Systems

95 Direct Contact Economizers 291 Picture Courtesy of Kemco

96 Direct Contact Economizers 292 Picture Courtesy of Thermal Engineering of Arizona

97 Summary >Understanding efficiency in water heating systems >Tankless water heaters >Condensing water heaters >Savings potential >Booster water heaters >Direct contact water heaters >High efficiency pool heaters 293

98 Summary >Savings from more expensive higher efficiency equipment depends on the size of the water load >Larger commercial loads make paybacks shorter >However, greater premium to green image in the residential market 294

99 IV. On-Site Generation and CHP

100 Learning Objectives >The electric generation and delivery industry is undergoing changes and significant strains >Only by understanding the current situation and future outlook can we understand drivers for gas fired on-site generation >Develop familiarity with new distributed generation equipment by understanding the technical advantages, limitations, and the marketable features 296

101 Overview >The current market conditions >The emergency generator market >What is distributed generation/cogeneration? >Cogeneration >Existing and emerging distributed generation equipment Microturbines Fuel cells 297

Existing and Emerging Energy Efficient Gas Technologies

Existing and Emerging Energy Efficient Gas Technologies Gas Technology Institute Copyright 2015 by Gas Technology Institute (GTI) No portion of this material may be reproduced without the expressed written