variable speed pumping in condensing boiler systems get the savings you paid for! october 9, 2012
TRANSCRIPT
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Brian Hammarsten, CEM – Trade Relations Manager at Xcel Energy
Peter Vinck – Senior Energy Efficiency Engineer at Xcel Energy
Russ Landry PE, LEED® AP - Senior Mechanical Engineer at the Center for Energy and Environment
Presenters
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Life Cycle Cost of Hot Water Systems Demand Side System Opportunities Transmission System Opportunities Supply Side System Opportunities Next Steps
Overview
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Condensing Boiler 1 MMBTU boiler purchase = approx $20,000 Lifetime cost for the gas to operate boiler = $112,800 Of the total cost of ownership, only 17% goes to the
purchase price of that boiler
Circulator Pump 5 hp pump costs = approx $2,000 Lifetime cost for the energy to operate pump = $26,750 Of the total cost of ownership, only 7.5% goes to the
purchase price of the pump
Component Life Cycle Cost
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System LCC* – Condensing Boiler, 2-way valve to heat exchangers, vfd on pump Total Equipment = $53,000
1 MMBTU condensing boiler purchase = $20,000 Valves & Piping modifications = $8,000 Pump and Drive package = $5,000 Labor and misc materials = $20,000
Total Energy Costs = $202,650 Lifetime cost for gas= $112,800 Lifetime cost for pump = $26,750 Lifetime cost for fans = $63,100
Of the total cost of ownership, only 15% to 30% goes to the purchase price of the initial equipment purchase
* This is a theoretical example
System LCC
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Demand Space heating Domestic water Process
Transmission (Piping, Pumps & Valves) Pumps Piping Coils
Supply Side Condensing boiler Combustion air fan Feed water pump Controls
Hot Water Systems
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Demand side opportunity investigation Temp set points? In your process do you really need 190
degree water or will 175 work? Outside air temperature supply water reset temperature Domestic Hot Water heating in off season
Demand Side Opportunity
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Outside air temp. vs supply water tempTemperature resets can be a great opportunity you might be missing during the higher outside air temperatures. Giving you lower losses due to over heating as well as lower return water helping a condensing boiler.
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Boilers are left in operation to support domestic hot water heat during summer. Consider separating the systems in order to increase
efficiency of domestic hot water year round. This would save on equipment life, energy costs,
redundancy, etc.
Demand Side (cont.) – Domestic Hot Water heating in off season
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If you have anything in this list, you may have some opportunity to reduce cost. Throttle valve-control system Bypass (recirculation) line normally open Multiple parallel pump system with same number of
pumps always operating Constant Pump operation in a batch environment or
frequent cycle batch operation in a continuous process Cavitations noise (at pump or elsewhere in the system) High system maintenance Systems that have undergone change in function
Reducing Pumping Costs
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Reduced transmission (pump) energy
Improved efficiency of condensing boiler
Reduced maintenance cost
Reduced System Flow Benefits
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Big Savings Potential Unique “green” investment opportunity when
replacing boiler or building new building >15% ROI for some projects
But… Savings Depend Heavily on Operating Conditions New construction optimal design very different
from typical boiler system Retrofit situations must be carefully evaluated
Supply Side Opportunity Applying Condensing Boilers
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Water Vapor Generated by Burning Natural Gas is Condensed Water vapor is natural product of burning natural gas About 12% of flue gas is water vapor, but…. Condensing Energy ≈ 2,000°F of Vapor Temperature Drop
Condensation Only Occurs at Low Water Temperatures Flue gas dewpoint ~130°F Efficiency keeps improving as temperature drops
How Condensing Boilers get that Efficiency “Boost”
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Chart for Showing Moisture in Air Issues
Curve at Top Shows When “Air” Can’t Hold Any More Moisture(aka dewpoint or saturated)
Once at the Top, Cooling More Condenses Moisture Out of Air
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75%
80%
85%
90%
95%
100%
60°F 80°F 100°F 120°F 140°F 160°F 180°F 200°F
Entering Water/Air Temperature
Eff
icie
nc
y
Applying Condensing Boilers vs Furnaces
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Applying Condensing Boilers vs Furnaces
75%
80%
85%
90%
95%
100%
60°F 110°F 160°F
Eff
icie
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y
Entering Water/Air Temperature
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Applying Condensing Boilers vs Furnaces
75%
80%
85%
90%
95%
100%
60°F 80°F 100°F 120°F 140°F 160°F 180°F 200°F
Entering Water/Air Temperature
Eff
icie
nc
y
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Three Rules for “Energy Value” of Condensing Boiler System
1) Return Water Temperature!2) Return Water Temperature!3) Return Water Temperature!
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Getting Heat Into a Space in a Building:“Typical” Central System
-20°F
0°F
20°F
40°F
60°F
80°F
100°F
120°F
140°F
160°F
180°F
Gas, Coal or Oil3,500 – 4,000F
Avg Boiler Water 170FBoiler
Radi
ator
s
Air H
andl
er/V
AV
Mixed or Cooled Air
Mi x
~350 to 400F
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Central System Designed for Condensing Boiler
-20°F
0°F
20°F
40°F
60°F
80°F
100°F
120°F
140°F
160°F
180°F
Gas at 3,500F
Boiler Water 160F Average
BoilerRa
diat
ors
Heated Air
Mixed or Cooled Air
M ix
Radi
ant
Fl
oor
+
Air
Han
dler
/VAV
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Heat Carried by Water or Air Depends on temperature change (TD or T) Depends on water or air flow rate
Carrying Heat from One Place to Another
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75%
80%
85%
90%
95%
100%
80°F 100°F 120°F 140°F 160°F 180°F
Entering Water Temperature
Bo
ile
r E
ffic
ien
cy
System Piping: Driving Return Water Temperature Down
Typical Flow
Low Flow
Avoid 3-way/4-way Valves on Main Line Reduced Flow Brings Down Return Temperature If Mixed Boilers – Cold Water & Max Load to Condensing
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Lower Flow (e.g. Pump VSD & 2-way Valves) Pump Energy Savings Low Return Water Temperature = Condensing Boiler
Efficiency Improvement If low delta, may be good opportunity in any system
Outdoor Reset Control Reduces Load from Overheating & Pipe Heat Loss Lower Return Water Temperature = Condensing Boiler
Efficiency Improvement If high temperatures in mild weather, may be good
opportunity in any system
System & Load Affects on Condensing Boiler Efficiency “Boost”
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Outdoor Reset Lowers Water Temperature
As the heating load goes down, less temperature difference is needed to drive the heat flow.
-20°F
0°F
20°F
40°F
60°F
80°F
100°F
120°F
140°F
160°F
180°F
Boiler Water 150F Average
Space 75F
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Traditional Coil-In Tank Requires High Boiler Temperatures Efficiency > Traditional Water Heaters Efficiency Sacrificed with Condensing Equipment
Service Hot Water: Driving Return Water Temperature Down
130°F
Boiler
>130°F
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Product-Specific Issues Small water passages in old cast iron system Pressure drop compatibility with system Flow rate compatibility (short-cycling) Control coordination Dual temperature inlets
General Load & System Issues Ability to provide adequate heat w/low return
temperatures Ability to reduce flow rate w/out branch balance problems 2-way valves on loads to replace 3-way valves
Key Design & Application Considerations: Preventing Problems
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Venting Considerations Design & Installation Details to Deal with Condensate Sidewall Venting Can Cause Moisture Problems With
Large Boilers Orphaned Water Heater Vent Cost Key Factor @Bottom of Hi-Rise
Key Design & Application Considerations: Preventing Problems (cont.)
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Space Heating Elements System Piping System Control—Pump System Control—Temperature Service Hot Water
Key for Condensing Boiler Efficiency: Driving Return Water Temperature Down
75%
80%
85%
90%
95%
100%
80°F 100°F 120°F 140°F 160°F 180°F
Entering Water Temperature
Bo
iler
Eff
icie
nc
y
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Condensing Boilers Can Be a Great, Green Investment Success Depends on Different Approach by All
Minimize return water temperature! Minimize return water temperature! Minimize return water temperature!
High Efficiency Boiler Information Air-Conditioning, Heating, and Refrigeration
Institute (www.ahrinet.org) EnergyStar.gov California Energy Commission web site Consortium for Energy Efficiency
www.cee1.org/gas/gs-blrs/gs-blrs-main.php3www.cee1.org/gas/gs-blrs/Boiler_assess.pdf
In Conclusion....
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Utilities offer rebates to customers to help pay for the
identification, energy savings quantification, and for the
changes once implemented. Check with your electric and gas utility to see what rebates the offer
There are several here today Programs to look for:
Study (investigation process) – Heating System Optimization, C/I Turn
Key, Audits Tune ups – Boiler Tune ups, Steam Trap Leak Study, Recommissioning Prescriptive Measures – O2, Stack Dampers, pipe insulation, new
boilers, VFDs, Motors Custom – Insulation of valves, rebates for industrial process heating
systems, most demand side measures, piping modifications, adjust
temp set points.
Utility “Key”
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The following slides are bonus material that was cut from the final, live presentation due to time constraints.
Bonus Slides
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Controlling Excess Air Even More Important Excess air reduces concentration of water vapor Dewpoint decreases
Condensing Boiler Sensitivity to Excess Air