Update Dedicated Heat Recovery Chiller Technology. Don Frye. Gulf South

Transcription

1 3/5/2018 1

2 Update Dedicated Heat Recovery Chiller Technology Don Frye Gulf South

3 Good design is an intentional act Begin with the end in mind Basic Bldg Tenants IAQ (low VOC & CO 2 ) Controlled Temp & RH Building Type Simplicity vs Complexity Allotted Space Sound Economic Reasoning Life cycle cost energy consumption Serviceability Maintenance / Parts / Service - Cost

4 DEDICATED HEAT RECOVERY CHILLERS

5 Chiller Heat Recovery

6 Goals for Today History of Heat Recovery Why Use Heat Recovery Define Heat Recovery How does it work Types of Heat Recovery Types of Chillers Leaving Water Temperatures? Compressor Type / Refrigerant Water flow arrangements New Technology 3/5/2018 6

7 Historical Perspective Energy crisis Oil embargo Much interest in heat/energy recovery Numerous publications Small Scale Introduction of DHRC Chillers Building boom Energy crisis forgotten Waning interest in energy recovery Environmental issues Renewed interest in energy recovery Less engineering experience

8 Goals for Today History of Heat Recovery Why Use Heat Recovery Define Heat Recovery How does it work Types of Heat Recovery Types of Chillers Leaving Water Temperatures? Compressor Type / Refrigerant Water flow arrangements New Technology 3/5/2018 8

9 Dedicated Heat Recovery Lots of Reasons to Utilize Heat Recovery 3/5/2018 9

10 Heat Recovery Reasoning Saves Energy (Btu s/ft2) (Simultaneous Heating/Cooling Loads) High system COP s achievable Works well with condensing boilers Per ASHRAE Journal Article March 2007 Reducing Energy Cost w/ condensing boilers & heat recovery chillers Required by code - ASHRAE 90.1 Good for Indoor Air Quality Good for the environment Reduce emissions & carbon footprint 3/5/

11 Energy Savings 3/5/2018 Per Gulf Power 11

12 Energy Savings 3/5/2018 Per CG-PRB014-EN 12

13 Symbiotic Relationship 3/5/

14 ASHRAE Waterside Energy Recovery IF THEN Facility operates 24 hours per day Heat rejection exceeds 6 million Btu/hr (~ 450 tons) Design service water heating load exceeds 1 million Btu/hr Required energy recovery is (smaller of): 60% of design heat rejection Preheating water to 85 F Unlimited reheat if 75% of reheat energy is site-recovered or site-solar - exemption

15 Why - Heat Recovery Chillers Applications Laundry Water Heating Swimming Pool Heating Process Heating Domestic Hot Water Typical Buildings Building Heat Dehumidification Reheat Ice Hockey Rink VAV Reheat Large Hotels Resorts Recreational Facilities Schools Hospitals Process Cooling & Heating Data Centers

16 Assessing Feasibility Heat Recovery Recovered heat vs. additional chiller energy/cost System load profile Hours with simultaneous loads Part-load chiller operation Internal and solar loads Avoid equal full-load hours/bin analysis

17 Simultaneous Heating & Cooling Load 3/5/

18 assessing feasibility Heat Recovery Calculate coincident cooling/heating loads Account for various fuels Model various utility rates Accurately model chiller heat-recovery conditions and energy use Model system configurations Show emission reductions (optional)

19 Goals for Today History of Heat Recovery Why Use Heat Recovery Define Heat Recovery How does it work Types of Heat Recovery Types of Chillers Leaving Water Temperatures? Compressor Type / Refrigerant Water flow arrangements New Technology 3/5/

20 Chiller Heat Recovery Terminology

21 Definitions Thermodynamics The first law, also known as Law of Conservation of Energy, states that energy cannot be created or destroyed in an isolated system. 3/5/

22 Definitions - Heat recovery, heater, or heat pump? Heat Recovery - the primary function of a chiller is to provide cooling, and a portion of its rejected heat is used to satisfy heating loads. Heater the primary function of the chiller is used to provide heat from its condenser. The chiller can be thought of as a water to water heat pump also know as dedicated heat recovery. Heat pump is defined as a chiller with the capability for the evaporator and condenser to change roles.

23 Definitions Full or Partial Heat Recovery? Heat Balance - the heat of evaporation plus the heat of compression equals the condensing heat energy available. Full Heat Recovery the entire condensing heat energy is utilized. Desuperheater cycle plus the condensing cycle. Partial Heat Recovery utilizes the desuperheating cycle to recover sensible heat between the compressor discharge and the start of condensing.

24 Heat Recovery Equations Heat available for recovery = 12,000 + (kw/ton 3,412) Btu/ton hr Chilled Water Flow, in gpm: F 1 Condenser Water Flow, in gpm: F 2 Chilled water supply Temperature: t 1, F Chilled water return Temperature: t 2, F Condenser entrance Temperature: t 3, F Condenser Leaving Temperature: t 4, F Assumptions Specific Heat of H 2 0 = 1.0 Density of H 2 0 = 8.333lb/gal Heat Recovered = 500 F 2 (t 4 t 3 ) Btu/h Cooling = 500 F 1 (t 2 t 1 ) Btu/h Cooling (Long Equation) = F 1 gal 60min 1 Btu min hr 1 lb F 8.33 lb 1 gal (t 2 F t 1 F )

25 Heat Recovery Equations COP = Cooling Effect+Heat Recovered Work 1 x 3412 = 500 [ F 1 t 2 t 1 +F t 2 4 t 3 ] Work 1 x 3412 COP = kw/ton EER = 12 kw/ton

26 Goals for Today History of Heat Recovery Why Use Heat Recovery Define Heat Recovery How does it work Types of Heat Recovery Types of Chillers Leaving Water Temperatures? Compressor Type / Refrigerant Water flow arrangements New Technology 3/5/

27 Standard heating and cooling Heat Disposal System Heat Generation System

28 Heat Recovery Thermodynamics Potential Heat Recovery 3/5/

29 Shifting Load with Dedicated Heat Recovery Heat Removal Heat Disposal System Heat Recovery Heat Generation

30 No Heat Recovery

31 Partial Heat Recovery

32 Full Heat Recovery

33 Goals for Today History of Heat Recovery Why Use Heat Recovery Define Heat Recovery How does it work Types of Heat Recovery Types of Chillers Leaving Water Temperatures? Compressor Type / Refrigerant Water flow arrangements New Technology 3/5/

34 Chiller Heat Recovery

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36 Water Cooled Chiller Summary

37 Air Cooled Chiller Summary

38 Chillers - Monolithic

39 Chillers - Modular

40 waterside heat recovery Effect on Chillers Compressor work is proportional to lift Lift is pressure Δ evaporator & condenser Warmer condenser water (for heat recovery) raises condenser pressure Changes in lift affect different compressors differently Positive displacement Scroll & Rotary Screw Fixed Speed or Variable Speed Handle Well Centrifugal (full load vs. part load) Single Stage or Multi-Stage Caution

41 pressure positive-displacement water chiller Refrigeration Cycle heat recovery 5 expansion device condenser 4 3 liquid/vapor separator 2 compressor 7 6 evaporator 1 enthalpy

42 chiller capacity, % positive-displacement water chiller Capacity compressor type: scroll screw leaving-condenser water temperature

43 power increase, % kw/ton positive-displacement water chiller Efficiency compressor type: scroll screw (S) screw (M) screw (L) leaving-condenser water temperature

44 pressure 2-Stage Centrifugal Refrigeration Cycle P hr P c P 1 heat recovery 6 condenser 4 expansion 5 devices economizer 2-stage compressor P e evaporator 9 1 enthalpy

45 power increase, % kw/ton centrifugal chiller performance Power Increase 40 Heat recovery Chiller F power increase compressor change impeller diameter impeller diameter, inches condenser water temperature, F

46 pressure difference chiller control Condensing Temperature C A 90 B vane position refrigerant flow rate

47 % maximum pressure differential heat-recovery chiller control Condensing Temperature unloading with constant leaving hot-water temperature C A B unloading with constant entering hot-water temperature % load

48 centrifugal compressor Impeller Dynamics R V r refrigerant flow rate V t rotational speed diameter refrigerant flow rate diameter rotational speed

49 centrifugal compressor Surge R V r < static pressure V t

50 heat-recovery chiller control Condensing Temperature Compressor type Positive displacement Acceptable basis of control Entering-condenser water temperature Leaving-condenser water temperature Provides less capacity Uses more power Centrifugal Entering-condenser water temperature Reduces likelihood of surge

51 Heat-Recovery Chillers Positive Displacement Compression Positive Displacement Chiller condenser options Characteristic Partial HR Heater DRHC Configuration Second No extra smaller condenser condenser Application Preheating Large baseloads heating loads or continuous operation Leaving water Warm/Hot Hot Capacity control? Yes Yes Chiller efficiency Increases Decreases Lvg Ht Wtr Control Yes Yes

52 Heat-Recovery Chillers Dynamic Compression Centrifugal Chiller condenser options Characteristic Dual Auxiliary DRHC Configuration Second, Second, No extra full-size smaller condenser condenser condenser Application Large Preheating Large baseheating loads heating loads loads or continuous operation Leaving water Hot Warm Hot Capacity control? Yes No Yes - Caution Chiller efficiency Decreases Increases Decreases Lvg Ht Wtr Control Limited n/a Limited

53 heat-recovery chillers Dual Condenser heat-recovery leaving capacity chiller condenser water control? efficiency Full capacity hot yes decreases Partial capacity warm no increases heat-recovery condenser standard condenser evaporator water-cooled chiller with centrifugal compressor

54 chilled water system Configuration Options Primary secondary Preferential loading Sidestream Variable primary flow

55 system configuration Primary Secondary off 52.6 F 40 F 750 gpm 52.6 F 300 gpm 52.6 F 56 F 40 F heat-recovery chiller 40 F 225 gpm 40 F 825 gpm production (supply) distribution (demand)

56 system configuration Preferential Loading off 51.2 F 40 F 750 gpm 51.2 F 525 gpm 56.0 F 40 F 40 F 225 gpm production (supply) distribution (demand) 300 gpm 56 F heat-recovery chiller 40 F 825 gpm

57 system configurations Sidestream Loading off 50.2 F 40 F 900 gpm 50.2 F 51.2 F 40 F 75 gpm production (supply) distribution (demand) 56 F 42.7 F 300 gpm 56 F heat-recovery chiller 40 F 825 gpm

58 System Configurations: Sidestream Loading Control strategies: Satisfy heating requirements Maintain leaving-condenser water temperature (positive-displacement compressors)

59 system configurations Variable Primary Flow Piping heat-recovery chiller in sidestream position may simplify control bypass line VFD modulating control valve for minimum chiller flow heat-recovery chiller control valve

60 Heat Recovery Simultaneous heating and cooling needs all year Heat recovery captures and uses waste heat to reduce load. Lowers heating bills Reduce carbon footprint

61 Goals for Today History of Heat Recovery Why Use Heat Recovery Define Heat Recovery How does it work Types of Heat Recovery Types of Chillers Leaving Water Temperatures Compressor Type / Refrigerant Water flow arrangements New Technology 3/5/

62 Updated Compressor Type Simultaneous Heating and Cooling Good Ideas 3/5/

63 TTH / TGH High Lift Compressor Wide Operating Map Air Cooled Chiller Ability to operate up to 140F ambient temp with Evap LWT = 44F Air-Water Heat Pump Generate up to 122F hot water at 32F ambient Water Cooled Chiller Heat Recovery Generate up to operate up to 157F condenser LWT with Evap LWT = 44F Suction Connection Economizer Port Discharge Connection

64 Chiller Heat Recovery No Reversing Valve Improves reliability and efficiency Simultaneous Heating and Cooling Without using Geothermal water as a transfer buffer 30% Efficiency Gain for Simultaneous Loads 5-8% efficiency gain for normal loads Typically Reduces 1 Module Per Array Reduces footprint and electrical load Compressor Run Time Equalization

65 Good Idea TO WATER HEATER AND SYSTEM Dedicated Heat Recovery Chiller V 2 HX CIRCULATING PUMPS, P 2 TANK HEAT RECOVERY PUMPS, CHILLER COND. W 1 CHILLER EVAP. DOMESTIC WATER SUPPLY P 1 F 2 F 1 T 4 T 1 T 3 T 2 CHILLED WATER PUMPS, P 4 PARALLEL V 3 SERIES TO CHILLERS FROM CHILLERS TO CHILLED WATER PUMPS

66 Case Studies 70

67 Heat Recovery Science Museum of Minnesota Utilized Dedicated Heat Recovery Over 75% improvement in heating cost Savings of nearly $300,000/year 3Yr payback Moved facility toward carbon neutrality Transforms museum into living lab to carry out its mission. (CASE-SLX483-EN)

68 Summer Reheat Tri-North Middle School 100 ton Heat Recovery Chiller IPS Tri-North = $170,851 IPS Tri-North = $118,710 Savings = $52,141 per year Source - Multistack

69 Evansville State Hospital 1 mil BTU/H DHRC 40,000 Therms NG Annually $50,000 Annual Energy Savings 300 Metric Tons CO2 Equivalent of Saving 21,000 Gallons of Gasoline Annually And, Two New Gas Meters Runs Fully Loaded nearly Year Round Source - Multistack

70 Summary Action Items 1. Heat Recovery is not about making the hottest water. 2. It s about moving btu s that would normally go to the environment. 3. Heat Recovery works well with condensing boilers. 4. Don t push the limits just because you can. 5. Service & Support Are Critical to Success. 6. Consult your local manufacturer s rep to get the details on how their system works. 7. Think about the Log Mean Temp Difference. Chilled Water 72F space with 44F water. Why 180F hot water for 72F space? Doesn t make sense. 8. Conserve don t use more energy than you have to. 77

71 Dedicated Heat Recovery Don Frye Systems Account Manager Gulf South Trane