Philipp Arnold Section Leader Cryogenics wwweuropeanspallationsourcese Proton Driver Efficiency Workshop March 02 2016 Outline Introduction Cryogenic Design Choices Some theory Cooling ID: 930224
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Slide1
Energy efficiency considerations in cryogenics
Philipp ArnoldSection Leader Cryogenics
www.europeanspallationsource.se
Proton Driver Efficiency Workshop
March 02, 2016
Slide2Outline
IntroductionCryogenic Design ChoicesSome theoryCooling below 4.5KThermal shield Part-load operation Staging
LN2 pre-
cooling
Heat RecoveryHelium Inventory ManagementSummary
2
Slide3(1.1) View of the Southwest in 2025
3
Max IV
– a national research
facility, under construction, opens
up in 2015
Science City – a new part of
town
Lund
(113 500)
Malmö
(309 000)
Copenhagen
(1 200 000)
MAX IV
ESS
Slide4(1.2) ESS Cryogenic System
Pure Helium
Gas Storage 1
20 m
3
LHe
Tank
Standalone Helium Purifier
Helium Recovery System
Pure Helium
Gas Storage 2
Accelerator
Cryoplant
T
est & Instrument Cryoplant
5 m
3
LHe
Tank
Target Moderator
Cryoplant
LHe
Mobile
Dewars
Test Stand Distribution System
Instruments & Experiments
LN2 Storage Tanks
LN2 Mobile
Dewars
Cryogenic Distribution System
Cryomodules
Cryomodule
Test Stand
Target Distribution System
Hydrogen Circulation Box
Hydrogen Moderator
Slide5(1.3) ESS Energy high level goals
5
Slide6Outline
IntroductionCryogenic Design ChoicesSome theoryCooling below 4.5KThermal shield Part-load operation Staging
LN2 pre-
cooling
Heat RecoveryHelium Inventory ManagementSummary
6
Slide7(2.1) Power consumption -
TheoryRemember Carnot(theoretical efficiency):
7
Desired cooling temperature
Ambient temperature
Heat load
Electrical input power
Actual consumption:
Efficiency of Carnot: depending on Q and T
Normalising
all heat loads to 4.5K load: ACCP ~ 250 W/W
P/Q = 66 W/W @ 4.5K
Slide8(2.1) Refrigeration vs. liquefaction
8Figures from CERN Divisional Report
CRYOGENICS FOR PARTICLE ACCELERATORS AND DETECTORS
(2002), U. Wagner, Ph. Lebrun, L. Tavian et. al. 4.5K isothermal refrigeration
Liquefaction
Slide9(2.2) Cooling
below 4.5KCooling below 4.5K means sub-atmospheric pressures need to be createdVacuum pumps (rotary vane + roots) for smaller capacitiesCold turbo compressors for bigger capacities
Impact on system reliability and operability
Helium purity must be ensured (purification, helium guards)
Serial rotating equipmentSpares
9
Slide10(2.2) Cryomodule cooling at 2K
10
Production of 2 K helium
in
2-4 K heat exchanger and a sub-sequent
JT
valve in
each of
the cryomodule–valve box
assemblies
Heat
load on CDS only on 4.5K, not 2K level
Slide11(2.3) Thermal shield
Thermal shield pressures and temperatures depend not on ideal COP w.r.t. Carnot but on entire cryogenic systemTemperature level where appropriate expansion stage is
Shield
Pressure = HP of cryoplant
Temperature spread = expansion turbine temperature step 11
Type
Temp
Max. load
Exergy
CMs and CDS
2 – 4 K
3060 W
79%
Thermal shields
33 – 53 K
11 380 W
11%
Coupler cooling
4.5 – 300 K
9.0 g/s
10%
300 K
115 K
70 K
53 K
33 K
24 K
9 K
6 K
4.5 K
Slide12(2.4) Part load operation
12
Slide13(2.5) Cryoplant staging
13
Two
sets of flow parts for
cold rotating equipmentturbine expanders
cold
turbo
compressors
Variable frequency drives for SP and LP compressors
Slide14(2.6) LN2 pre-cooling
TICPWITH LN2 PRE-COOLING CM testing: “constant level liquefaction w/o internal freeze-out purification”
Liquefaction for
LHe
consumers: “rising level liquefaction w/ internal purification” Turbo-expanders can be optimized to perform efficiently in both operation modes
Much
better plant fit
with
easy adapting when higher rate needed (switch pre-cooling on)
14
ACCP
WITHOUT LN2 PRE-COOLING
~80% of the load is at 2K
with cold compression translated to 4-20K refrigeration
~20 tons of cold mass max do not impose tough cool-down requirements
No substantial CAPEX impact
Downsides of LN2 usage like dependency on regular supply and increased traffic at ESS more severe
Slide15Outline
IntroductionCryogenic Design ChoicesSome theoryCooling below 4.5KThermal shield Part-load operation Staging
LN2 pre-
cooling
Heat RecoveryHelium Inventory ManagementSummary
15
Slide16(3.1) Oil flooded screw compressors
Adiabatic compression16
ESS high pressure stage:
Suction pressure: 4 bar(a)
Discharge pressure: 20.5 bar(a)
NOT FEASIBLE!
Quasi-isothermal compression by oil injection
T>300°C for ESS HP stage discharge
In fact: inlet ~40°C, outlet ~80°C
Slide17(3.2) Heat from screw compressors
17
ESS high pressure stage
:
Helium flow: 0.735 kg/sOil flow: 19.285 kg/s
Electrical consumption: 1.45 MW
Heat into oil cooler: 1.13 MW
Slide18(3.3) Heat Recovery
18No elevated oil or helium temperatures out of compressor suppliers specsDedicated cooling water circuit for cryoplant (quality constraints of available cooling water in the building)Slow temperature control on cooling water side, fast temperature control on oil side
Cooler design state of the art e.g. for
Kaeser
compressorsCooling function has priority over heat recovery return
Compr
. motor
Middle temperature Return
Middle temperature Supply
Oil vessel
Helium compressor
Helium cooler
Oil
cooler
He to fine oil removal
He from cold box
High temperature Return
Middle temperature Return
27°C
27°C
30°C
30°C
30°C
39°C
71°C
39°C
83°C
49°C
74°C
40°C
69°C
37°C
Slide19Outline
IntroductionCryogenic Design ChoicesSome theoryCooling below 4.5KThermal shield Part-load operation Staging
LN2 pre-
cooling
Heat RecoveryHelium Inventory ManagementSummary
19
Slide20(4) Helium Inventory Management
20
1
2
3
Helium inventory in CMs and CDS ~ 2 tons during normal operation
20
m
3
LHe
tank as second fill
Another 2 tons when 80% full
Facilitate helium management in transient modes
Battery of warm storage tanks
Try to
Never warm up the entire system
Leave as much helium liquid as possible
(less purification
)
Recover helium as much as possible
Guard sub-atmospheric systems (less purification
)
Slide21Outline
IntroductionCryogenic Design ChoicesSome theoryCooling below 4.5KThermal shield Part-load operation Staging
LN2 pre-
cooling
Heat RecoveryHelium Inventory ManagementSummary
21
Slide22(5.1) Summary
Conceptual phaseCryogenics is expensive and energy demandingSelect carefully the operation temperature by far the biggest impact
Keep in mind that a large load portion is static always substantial energy consumption regardless of beam
Talk early to cryoplant vendors to define best technology (cold compression, LN2, 2K heat exchanger position)
Consider heat recovery if clients are around22
Slide23(5.2) Summary
Purchasing the cryoplantConsider OPEX over several yearsConsider OPEX particularly for turn-down scenariosDefine
shield conditions
w.r.t
. overall efficiency Think about flexibility (VFDs, staging)Specify exactly LN2 and heat recovery set-up
C
onsumption measurement and
penalisation
Acceptance tests of turn-down automation
23
Slide24(5.3) Summary
Start up and operationsPlan long acceptance testing Focus on stable controls, otherwise turn-down will be controlled with heaters for stability reasonsSpend long time on initial drying and cleaning
Try to adapt the plant to actual loads as good as possible (look for pressure drops, bypass valves, temperature mixing)
Watch helium inventory closely (leaks)
24