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S. Claudet (CERN, Geneva) LHC Cryogenics OPeration team leader
LHC Cryogenics design and operation: optimization and reduction of the
energy consumption
LHC Cryogenics, optimisation of energy consumption 2/38
Outline Introduction to CERN and LHC Cryogenics
Power input for refrigeration, design & implementation
The Carnot factor
The heat loads (final user + distribution)
The refrigerators
Operation results, availability and power consumption
Indentified alternatives for further optimisation
Summary
LHC Cryogenics, optimisation of energy consumption 3/38
CERN in brief European Organization for Nuclear Research
Founded in 1954 20 Member States + Associates
Geneva, Switzerland
24 km of superconducting magnets @1.8 K, 8.33 T
p-p collisions 1034 cm-2.s-1 14 TeV
500 MJ beam energy
LHC Cryogenics, optimisation of energy consumption 4/38
Main reasons to superconducting
Compactness through higher fields Ebeam B . r Ebeam E . L [Gev] [T] [m] [Gev] [MV/m] [m]
For accelerators in high energy physics
Saving operating energy Electromagnets: Acceleration cavities Resistive: Pinput beam Pinput E2/w Superconducting: Pinput Rs BCS + Ro RBCS -BTc/T)
LHC Cryogenics, optimisation of energy consumption 5/38
Pt 3
Pt 4
Pt 5
Pt 6
Pt 7
Pt 8
Pt 1
Pt 2
Pt 1. 8
Cryoplant DistributionPresent Version
C r yogeni c pl ant
Magnets
Distribution
Layout of LHC cryogenics
8 x 18kW @ 4.5 K
24 km & 20 kW @ 1.8 K
130 t He inventory
LHC cryogenics is the largest, the longest and the most complex cryogenic system worldwide
LHC Cryogenics, optimisation of energy consumption 6/38
Magnet cooling scheme
1
10
100
1000
10000
1 10T [K]
P [k
Pa]
SOLID
HeII HeI
CRITICAL POINT
GAS
line
Saturated He II
Pressurized He II
1
10
100
1000
10000
1 10T [K]
P [k
Pa]
SOLID
HeII HeI
CRITICAL POINT
GAS
line
Saturated He II
Pressurized He II
0
500
1000
1500
2000
2500
3000
6 8 10 12 14B [T]
Jc [A
/mm
2]Nb-Ti @ 4.5 KNb-Ti @ 2 KNb3Sn @ 4.5 K
Jc [A
/mm2
] Superconductivity served by superfluidity !
sc conductors
Two-phase He @ 1.8 K Pressurised He @ 1.9K
Beam screen @ 4.6-20 K
Radiation screen @ 50-65 K
LHC Cryogenics, optimisation of energy consumption 7/38
How does it compare ?
020406080
100120140160180
1960 1970 1980 1990 2000Year
kW @
4.5
K
OMEGA,BEBC,
ISR Low-Beta
ALEPH,DELPHI,
LEP Low-Beta
LEP2
LHC, ATLAS, CMS
LEP2+
LHC:
144
kW
LHC
Tevatron, RHIC, Jlab,
ITER
Before LHC: existing experience for design, safety,
We did not start from scratch!
LHC Cryogenics, optimisation of energy consumption 8/38
Outline Introduction to CERN and LHC Cryogenics
Power input for refrigeration, design & implementation
The Carnot factor
The heat loads (final user + distribution)
The refrigerators
Operation results, availability and power consumption
Indentified alternatives for further optimisation
Summary
LHC Cryogenics, optimisation of energy consumption 9/38
Power input for refrigeration
8 such plants installed for LHC + specific units for the 1.8K process
40 MW installed electrical power
An obvious incentive to optimise each of the above contributing factors !
An idea of yearly operating costs (Power only) 11 months (320GWh) @ 60 CHF/MWh => 19.3 MCHF Already 1% is about 0.2 MCHF !!!
LHC Cryogenics, optimisation of energy consumption 10/38
The Carnot Factor (1/3) The Carnot Factor is a direct consequence of the
combination of first and second thermodynamic laws
Heat / Work entering the system +
Heat / Work leaving the system -
This is THE governing effect for cryogenics
FirstLaw : Ý Q w Ý Q c W 0
SecondLaw :Ý Q wTw
Ý Q cTc
0
PowerInput : W Ý Q cTwTc
1
Carnotfactor: TwTc
1
ww TQ ,
cc TQ ,
W
LHC Cryogenics, optimisation of energy consumption 11/38
The Carnot Factor (2/3)
0
50
100
150
200
250
1 100Cold Temperature [K]
Carnot factor [-
He II 1.8K - 166
He 4.5K - 65.7
H2 20K - 14 N2
77K - 2.9
Graph for Twarm = 300 K For low temperatures:
TwTc
1 TwTc
- Use of low temperatures if no alternative
- Better intercept heat at higher temperatures
300 10 5 2
LHC Cryogenics, optimisation of energy consumption 12/38
The Carnot Factor (3/3)
Thermal shields 50-65 K
Beam screen as seen by the
beam
Cold Bore (2K)
(no convection)
LHC Cryogenics, optimisation of energy consumption 13/38
Minimising heat loads (1/4)
RnD: Large design & optimisation efforts for the cryostat and its sub-components
Heat loads management: Very detailed and methodic accounting of the various contributions, centralised contingency factors, periodic follow-up
Non-metallic composite support post for magnets, with heat intercepts
Multi-layer insulation
Power@cold x Carnot / %w.r.tCarnot
LHC Cryogenics, optimisation of energy consumption 14/38
Other RnD examples
LHe
20K
supply 50K
Max. for HTS
High Temperature Superconducting leads
Stainless Steel Plate heat exchangers
Below 2K specific components
Cold Compressors
LHC Cryogenics, optimisation of energy consumption 15/38
Exergy, Introduction Large scale (capacity) superconducting applications require distributing cooling power over long distances (high flow rates) with minimised temperature gradients for high thermodynamic efficiency
Exergy analysis (applied in the past for refrigeration plants) has been proposed as a way to quantify distribution losses, with the potential to help technical arbitration amongst competing solutions
Application
Refrigerator
?!? For losses !
LHC Cryogenics, optimisation of energy consumption 16/38
LHC Distribution, Exergy Flow Diagram
Thermal shielduseful (122 kW)
Pressure drop (22.9 kW)
JT valves (1.5 kW)
Standalonemagnet
useful (19.0 kW)
P & T current leads (58.9 kW)
Current leaduseful (63.0 kW)
P capillaries & control valves (65.4 kW)
Beam screenuseful (205 kW)
JT valves (44.7 kW)Subcooling HX (39.6 kW)
Return line (37.5 kW)HX tube (17.5 kW)
Main magnetuseful (364 kW)
Mixing Pt 23 (19.7 kW)
(107
9 kW
)
4.5
K re
frige
rato
r (11
03 k
W)
1.8 K refrigerator(34.1 kW)
Pit (8.0 kW)Subcooling (23.9 kW)
Mixing (25.8 kW)
LHC sectorFrom surface cryoplant
to underground
1.8 K Units (2400 W)
4.5 K Refrigerator
(18 kW)
30 % of Carnot
Refrigerator
1.8 K Main Magnets (Arcs)
Beam Screen Shielding
Current Leads Cooling
4.5 K Magnets (Straight sections)
Thermal Shield
73 %
76 %
52 %
47 %
84 % 95 % 72 %
68 %
LHC Cryogenics, optimisation of energy consumption 17/38
Helium refrigerators
CERN LHC
Capacity [Watts]
30%
The efficiency w.r.t Carnot does not depend on the temperature, but rather on the size
The largest possible the best !
%w.r.tCarnot
LHC Cryogenics, optimisation of energy consumption 18/38
Pinput : 4.2 MW
0
100
200
300
400
500
TORESUPRA
RHIC TRISTAN CEBAF HERA LEP LHC
C.O
.P. [
W/W
@ 4
.5K
]
Carnot Limit
18 kW @ 4.5 K Refrigerators 33 kW @ 50 K to 75 K - 23 kW @ 4.6 K to 20 K - 41 g/s liquefaction
TORE SUPRA RHIC TRISTAN HERA LEP LHC CEBAF
400
200
0
Carnot
COP 230W/W
LHC Cryogenics, optimisation of energy consumption 19/38
Contracting refrigerators
Adjudication : LOWEST
CAPITAL Cost + OPERATING cost over 10 years Similar amounts !
1/3 Low load
2/3 Max load
Operating cost: Garanteed power consumption x hours x 60 CHF/MWh Real performance measured for acceptance, with bonus/malus correction
LEP/LHC 4.5K Refrigerators performance test
100150200250300350400450500
0 20 40 60 80 100Cooling Capacity [%]
COP [W/W]
Values provided in quotations by bidders
(6600 hr/yr)
LHC Cryogenics, optimisation of energy consumption 20/38
Testing the cryogenic sub-systems
Point 8 Storage
Sector 7-8 Sector 8-1
Surface
Cavern
QSCA QSCB
QSRB
QURC
QUIC
QURA
Shaft
QSCC QSCC
Tunnel
QURC
QSRA
Performance assessment of all sub-system (at least a type test) before being connected to the next one
A coherent approach with the contracting approach;; a way to get familiar with process optimisation and tuning for availability
LHC Cryogenics, optimisation of energy consumption 21/38
Outline Introduction to CERN and LHC Cryogenics
Power input for refrigeration, design & implementation
The Carnot factor
The heat loads (final user + distribution)
The refrigerators
Operation results, availability and power consumption
Indentified alternatives for further optimisation
Summary
LHC Cryogenics, optimisation of energy consumption 22/38
From LHC Magnet String test
Tuning one of 8 LHC sectors
x 27!
500 PID loops
LHC Cryogenics, optimisation of energy consumption 23/38
Cryo operator in Cern Central Control room Shift 24/7
LHC Cryogenics, optimisation of energy consumption 24/38
Operation, indicators
Powering Alarms
Global availability
LHC Cryogenics, optimisation of energy consumption 25/38
0
10
20
30
40
50
60
70
80
90
100
25-Jan 22-Feb 22-Mar 19-Apr 17-May 14-Jun 12-Jul 9-Aug 6-Sep 4-Oct 1-Nov 29-Nov
Availability [%]
weekly AVG Monthly AVG Scheduled Stops
LHC Cryo global availability 2010
Powering tests
Based on LHC_Global_CryoMaintain signal per unit of time
Nice learning curve for such a large & complex system
LHC Cryogenics, optimisation of energy consumption 26/38
0
10
20
30
40
50
60
70
80
90
100
24-Jan 21-Feb 21-Mar 18-Apr 16-May 13-Jun 11-Jul 8-Aug 5-Sep 3-Oct 31-Oct 28-Nov
Availability
Between TS 2010 Scheduled Stops Daily 2011 Weekly 2011 Between TS 2011
Legend: : PLC P8_QSCB
: Single Event
LHC Cryo global availability 2011
PLC US85
CCs COM US25
PLC P8
Crate 81
Oil filters
P8
Crates
PLC US85
PLC US45 Induced
CCs P8/P4
PLC US45
400V
Degradation of availability correlated with LHC ramp-up in luminosity
Mitigation measures: - Some in place since end of August - More complex ones for Xmas break
LHC Cryogenics, optimisation of energy consumption 27/38
Cryogenic architecture Typical LHC even point
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
Sha
ftS
urfa
ceC
aver
nTu
nnel
LHC Sector (3.3 km) LHC Sector (3.3 km)
1.8 KRefrigeration
Unit
New4.5 K
Refrigerator
Existing4.5 K
Refrigerator
1.8 KRefrigeration
UnitWarm
CompressorStation
WarmCompressor
Station
WarmCompressor
Station
ColdCompressor
box
Even pointOdd point Odd point
MP StorageMP Storage MP Storage
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
Sha
ftS
urfa
ceC
aver
nTu
nnel
LHC Sector (3.3 km) LHC Sector (3.3 km)
1.8 KRefrigeration
Unit
New4.5 K
Refrigerator
Existing4.5 K
Refrigerator
1.8 KRefrigeration
UnitWarm
CompressorStation
WarmCompressor
Station
WarmCompressor
Station
ColdCompressor
box
Even pointOdd point Odd point
MP StorageMP Storage MP Storage
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
UpperCold Box
Cold Box
WarmCompressor
Station
LowerCold Box
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
Sha
ftS
urfa
ceC
aver
nTu
nnel
LHC Sector (3.3 km) LHC Sector (3.3 km)
1.8 KRefrigeration
Unit
New4.5 K
Refrigerator
Existing4.5 K
Refrigerator
1.8 KRefrigeration
UnitWarm
CompressorStation
WarmCompressor
Station
WarmCompressor
Station
ColdCompressor
box
Even pointOdd point Odd point
MP StorageMP Storage MP Storage
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
Surface
Shaft
Underground
1 Cryoplant could keep the helium inventory in place, and allow the
operation of LHC at low
level
LHC Cryogenics, optimisation of energy consumption 28/38
Efficient operation at low load Typical LHC even point
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
Sha
ftS
urfa
ceC
aver
nTu
nnel
LHC Sector (3.3 km) LHC Sector (3.3 km)
1.8 KRefrigeration
Unit
New4.5 K
Refrigerator
Existing4.5 K
Refrigerator
1.8 KRefrigeration
UnitWarm
CompressorStation
WarmCompressor
Station
WarmCompressor
Station
ColdCompressor
box
Even pointOdd point Odd point
MP StorageMP Storage MP Storage
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
Sha
ftS
urfa
ceC
aver
nTu
nnel
LHC Sector (3.3 km) LHC Sector (3.3 km)
1.8 KRefrigeration
Unit
New4.5 K
Refrigerator
Existing4.5 K
Refrigerator
1.8 KRefrigeration
UnitWarm
CompressorStation
WarmCompressor
Station
WarmCompressor
Station
ColdCompressor
box
Even pointOdd point Odd point
MP StorageMP Storage MP Storage
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
UpperCold Box
Cold Box
WarmCompressor
Station
LowerCold Box
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
Sha
ftS
urfa
ceC
aver
nTu
nnel
LHC Sector (3.3 km) LHC Sector (3.3 km)
1.8 KRefrigeration
Unit
New4.5 K
Refrigerator
Existing4.5 K
Refrigerator
1.8 KRefrigeration
UnitWarm
CompressorStation
WarmCompressor
Station
WarmCompressor
Station
ColdCompressor
box
Even pointOdd point Odd point
MP StorageMP Storage MP Storage
UpperCold Box
Interconnection Box
Cold Box
WarmCompressor
Station
LowerCold Box
Distribution Line Distribution Line
Magnet Cryostats, DFB, ACS Magnet Cryostats, DFB, ACS
ColdCompressor
box
Surface
Shaft
Underground
Done for 50% of LHC !
sector for dynamic loads, after specific adjustments made
8MW (2x4MW)
Competitive for recovery after stops (<10hrs for CC, <24hrs after power failure for 2 sectors)
LHC Cryogenics, optimisation of energy consumption 29/38
Power Consumption
0
5
10
15
20
25
30
35
40
45
03-Jul-2009
02-Oct-2009
01-Jan-2010
02-Apr-2010
02-Jul-2010
01-Oct-2010
31-Dec-2010
01-Apr-2011
01-Jul-2011
30-Sep-2011
Power input
Installed power
Nominal operation
Cryo optimised power
Stop
Cryoplant
Tests
LHC physics LHC physics
Cool down
Powe
r [MW
]
HWC
LHC Cryogenics, optimisation of energy consumption 30/38
Outline Introduction to CERN and LHC Cryogenics
Power input for refrigeration, design & implementation
The Carnot factor
The heat loads (final user + distribution)
The refrigerators
Operation results, availability and power consumption
Indentified alternatives for further optimisation
Summary
LHC Cryogenics, optimisation of energy consumption 31/38
What else could be done ? Further optimise the operation of the cryogenic system with the 2 remaining sites to be operated with 1 Refrigerator for 2 sectors [Cryo + LHC OP]
Evaluate the possibility,impact and effects of allowing reduced cooling water temperature to better match atmospheric conditions [Cryo + Cooling]
Evaluate the possibility, impact and effects of recovering heat at the compressor station [Cryo + Cooling + CERN]
If heat recovery would be interesting, evaluate the possibility, impact and effects of changing the LHC operation schedule (with steady operation in winter time to combine two above effects) [Cryo + Cooling + CERN]
LHC Cryogenics, optimisation of energy consumption 32/38
Reducing cryoplants in operation ?
Pt 3
Pt 4
Pt 5
Pt 6
Pt 7
Pt 8
Pt 1
Pt 2
Pt 1. 8
Cryoplant DistributionPresent Version
C r yogeni c pl ant
- P4: Very specific with Radio-frequency cavities, not foreseen to stop one plant - P18-P2: Tests done in 2010 not conclusive yet, impedance and heat loads at P2, to be understood => Not much to be expected, but worth trying to keep process and technical competencies, and identification of limits
In operation Ready but stopped
Process being
studied
Tests from P18 NotOK (Yet)
RF!
LHC Cryogenics, optimisation of energy consumption 33/38
Cooling water temperature (1/2) Cooling water supply - Present operating conditions
0
5
10
15
20
25
30
01-Jan-2010 02-Apr-2010 02-Jul-2010 01-Oct-2010 31-Dec-2010
Temperature [K]
P18
P2
P4
P6
P8
Specified (23 C +/- 1C)
Work with Cooling team to be as specified or lower
Specific cooling supply from SPS very large cooling loop, no load when SPS stopped
=> An advantage for the cryogenic process !!!
LHC Cryogenics, optimisation of energy consumption 34/38
Cooling water temperature (2/2) Point 8 - 2010
-10
-5
0
5
10
15
20
25
30
35
01-Jan-2010 02-Apr-2010 02-Jul-2010 01-Oct-2010 31-Dec-2010
Temperature [C] - Power
Water supply Inlet Cold BoxOutside air Power input
Condensation
Freezing
Some potential gain (15C as min)
LHC Cryogenics, optimisation of energy consumption 35/38
Compressor station flow scheme
Water:
Inlet & Outlet conditions
Up to 3.5MW/Ref.
Oil:
Inlet & Outlet conditions
Up to 3MW/Ref. Motors:
Few kw
Helium:
Some 100s kW
LHC Cryogenics, optimisation of energy consumption 36/38
View of a compressor station
Motors Oil Coolers Helium Coolers
4.2MW input power
LHC Cryogenics, optimisation of energy consumption 37/38
29C 150m3/h
29C 300m3/h
Heat recovery potential 20C
500m3/h 30C
500m3/h 22C
22C
22C
For Cryogenics:
- Only oil coolers concerned (fraction?)
- Only with existing technology and no serious operational risk !
85C
45C
From Cooling point of view: - Warmer temperatures / bacteria - Transients / other users
Helium Oil
Motors
Separate cooling water distribution for additional coolers
In parallel with existing coolers
In series
Not so straightforward, worth a study ?
LHC Cryogenics, optimisation of energy consumption 38/38
Summary LHC cryogenics is the largest, the longest and the most complex cryogenic system worldwide. From design to operation, availability and energetic efficiency have played key roles.
We could achieve a reasonable global availablity (around 95%) so far with beams while operating close to best reasonably possible efficiency of the cryogenic system (25MW for 40MW installed) and reducing helium losses during beams operation period
Potential improvements, but with impacts on others: (global optimum!) Lowering the cooling water temperature Moderate heat recovery (still in the MW range)
Future systems will have to evaluate such new features at design!
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