Energy Performance of Low Charge NH3 Systems in Practice. Stefan S. Jensen

Transcription

1 Energy Performance of Low Charge NH3 Systems in Practice Stefan S. Jensen

2 Introduction Central type, dual compression stage, ammonia vapour compression systems. Main Design Features: Reciprocating Compressors (One Screw Plant) VFD s on Everything Combination of Superheat and Quality Control (DX) Evaporative Condensers (No Receiver) Hot Gas Defrost

3 Global Events and Their Significance for NH3 Why Are COP 21 (Paris) and The Montreal Protocol Amendment (Kigali) Important for the Global NH 3 Industry? They Are Potentially Very Good For Business: NH 3 Has No Direct Global Warming Effect Used Correctly NH 3 Can Minimize Indirect Emissions NH 3 is in the 2L Flammability Category Like R32 and a Range of Synthetic Low GWP Refrigerants NH 3 is Cheap and Technically/Environmentally Mature

4 The Refrigeration Plants Locations Perth Tamworth Lismore Melbourne Townsville Refrigerated vol., m³ Cool room, 16 C Cool room, 4 C Freezer, -25 C 43,000 10,000 10,000 43,000 31,000 Yes No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

5 The Refrigeration Plants Locations Perth Tamworth Lismore Melbourne Townsville Annex, 4-8 C No. of comp. stages No. of 1 st stage comps. No. of 2 nd stage comps. Yes Yes Yes Yes Yes N/A 2 2 Comp. type Recip. Recip. Screw Recip. Recip.

6 The Refrigeration Plants Locations Perth Tamworth Lismore Melbourne Townsville VFD s (all) Yes Yes No Yes Yes Evap. Cond. Yes Yes Yes Yes Yes Cond. fan VFD s Evaporator enhancement Evaporator fan VFD s Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes NH 3 feed DX DX Flooded DX DX

7 The Refrigeration Plants Locations Perth Tamworth Lismore Melbourne Townsville Injection Control SH SH Level SH/X SH/X Defrost Hot Gas Hot Gas Hot Gas Hot Gas Hot Gas Pipe Material Fe Fe Fe 304SS 304SS Legend: DX: Dry Expansion SH: Superheat SH/X: Superheat + Quality Fe: Carbon Steel

8 Energy Consumption Locations Perth Tamworth Lismore Melbourne Townsville SEC, kwh/m³*a SEC = Specific Energy Consumption Excepting Townsville SEC is for entire facility Auxiliaries (IT, Light & Power, split A/C systems, fork lift charging etc.) ~20% Feasibility of office A/C with NH 3 and chilled water/glycol in lieu of HFC? The Lismore problem? More about that later

9 Energy Consumption Townsville

10 PV Panel Contribution Perth Location Total Annual Energy Consumption, MWh Perth ( )/9*12 =1,226 Record Period Refrigerated Volume, m³ SEC, kwh/m³*a 43, MWh supplied by PV panels from to MWh supplied by the grid from to Allowance of ~20% for auxiliaries SEC = 22.7 kwh/m³*a

11 PV Panel Contribution

12 The Lismore Problem Locations Perth Tamworth Lismore Melbourne Townsville SEC, kwh/m³*a Floating head pressure reduced SEC to kwh/m³*a This remains almost twice as high as Tamworth. Why? - Single Stage Compression - No Compressor Speed Control - Poor Compressor Part Load Efficiency - Poor Compressor Combination

13 Energy consumption [kwh/month] The Lismore Problem Monthly Energy Consumption Comparison Month

14 The Lismore Problem Compressor Combination Combination #1: Single Stage Screw Compressor Combination #2: Single Stage Screw Compressor with Economizer (e) Combination #3: Single Stage Screw and Dual Stage Reciprocating Compressor Combination #4: Single Stage Screw (e) and Dual Stage Reciprocating Compressor Combination #5: Dual Stage Screw Compressor Combination #6: Dual Stage Screw and Dual Stage Reciprocating Compressor Combination #7: Dual Stage Reciprocating Compressors Pattern I: Combination of Plates and Freezer Stores, Load Variation % Pattern II: Combination of Blasts and Freezer Stores, Load Variation %

15 Source: Lorentzen, Gustav, Energiøkonomisering i Kjøleteknikken, Scandinavian Refrigeration 4/1981 Compressor combination Screw [kw] Recip. [kw] Pattern I, [MWh/a] Pattern II, [MWh/a] The Lismore Problem Compressor Combination x500-1x500-1x452 1x48 1x452 1x48 1x500-1x452 1x48-3x150 1x50 1,845 1, ,890 1,825 1, ,250 1,150 1,075 No VFD s and No Medium Temperature Loads = Dual Stage Compression = Economizer

16 Low Charge NH3 vs. HFC Low Charge NH3 Heat Loads LT HT Flour Room, 16 C 11.1 Cool Room, 4 C 51.2 Freezer, -25 C Annex, 4 C Total, 43,000 m³ Monthly kwh Cost A$13,752 (04/2015) Monthly Supply (04/2015) 81.2 MWh Air Cooled HFC Heat Loads LT HT Freezer 1, -25 C 88.8 Freezer 2, -25 C 94.8 Cool Room 1, 4 C 46.0 Cooler Corridor, 4 C 6.0 Cool Room 2, 4 C 17.6 Dock, 4 C 41.1 Annex, 4 C 82.1 Total, 22,000 m³ Monthly kwh Cost A$ 42,000 (avg.) All Heat Loads in [kw]

17 Monthly Supply of ~80 MWh is not unusual Low Charge NH3 vs. HFC Monthly kwh Consumption

18 Is It the NH3 That Does It Or Are Other Factors Affecting Energy Performance? Item Energy Conservation Factor Percentage Impact, [%] 1 Selection of Compressor Type Evaporator Fan Speed Control Evaporator Design Compressor Capacity Control Compressor Turn-Down versus Load Variation Condenser Size, Fan Speed Control and Efficiency Liquid Injection Control into The Evaporators Elimination of Liquid within Suction Lines Low Friction Schedule SS in lieu of Carbon Steel Piping 1-2

19 Is It the NH3 That Does It Or Are Other Factors Affecting Energy Performance? Item Factor Reference 1 Compressors Practical comparison between two systems 2 Evaporator VFD Practical comparison between two systems 3 Evaporator Design Practical experience from several systems 4 Capacity Control Retrofitting of VFD s to dual stage screw system (Sydney) 5 Turn-Down See Tamworth and Gustav Lorentzen Table 6 Condenser See Tamworth example 7 Injection Practical measurements of differences 8 Dry Suction Theoretical estimate 9 304SS Measurement at Truganina

20 Plant Images Townsville Tamworth Lismore Perth Melbourne

21 Latest Jobs Not Discussed With Higher Mobility and Lower NH3 Charges ~0.7 kg/kw or ~5 lbs/tr Medium Temperature Secondary Refrigerant Loop and Horizontal Vessels

22 Latest Jobs Not Discussed With Higher Mobility and Lower NH3 Charges Ambient Air Defrost i.e. No Need to Accommodate Defrost Condensate ~1 kg/kw Capacity 197 kw Operating NH 3 Inventory ~2 kg

23 Discussion.or Why Bother With Synthetic Refrigerants? - The Energy Performance of Low Charge NH 3 is Up To 2/3 Better than HFC - NH 3 Belongs to the 2L Flammability Category Like R32 and Many HFO s - Additional Capital Cost of Central Low Charge NH 3 Usually Returned in 3 Years - Loss of NH 3 Charge in One of Three Freezer Coils Usually Yields <200 ppm NH 3 concentration in the refrigerated space - Use of Low Friction 304SS Piping Extends Plant Durability Significantly - Central Type Low Charge NH 3 Plants Are Extendable Like Liquid Overfeed Plants - Exceptionally Low Indirect Emissions IF DESIGNED & CONTROLLED CORRECTLY - No Direct Refrigerant Emissions - Completely Future Proof - High Degree of Operator Safety

24 Discussion Thank you for your time! Questions?