lhc cryogenics design and operation: optimization …...130 t he inventory...

$: LHC Cryogenics design and operation: optimization …...130 t He inventory LHC!cryogenicsisthelargest,!the longestand!themostcomplex cryogenicsystemworldwide !:RUNVKRS (QHUJ\ IRU VXVWDLQDEOH$
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


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


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)


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


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


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!




The Carnot factor


The refrigerators



Summary


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 !!!


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


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


The Carnot Factor (3/3)

Thermal shields 50-65 K

Beam screen as seen by the

beam

Cold Bore (2K)

(no convection)


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


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


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 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 %


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


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


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)


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




The Carnot factor


The refrigerators



Summary


From LHC Magnet String test

Tuning one of 8 LHC sectors

x 27!

500 PID loops


Cryo operator in Cern Central Control room Shift 24/7


Operation, indicators

Powering Alarms

Global availability


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


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


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



ColdCompressor

box

UpperCold Box

Interconnection Box

Cold Box

WarmCompressor

Station

LowerCold Box



ColdCompressor

box

Sha

ftS

urfa

ceC

aver

nTu

nnel


1.8 KRefrigeration

Unit

New4.5 K

Refrigerator

Existing4.5 K

Refrigerator

1.8 KRefrigeration

UnitWarm

CompressorStation

WarmCompressor

Station

WarmCompressor

Station

ColdCompressor

box



UpperCold Box

Interconnection Box

Cold Box

WarmCompressor

Station

LowerCold Box



ColdCompressor

box

UpperCold Box

Cold Box

WarmCompressor

Station

LowerCold Box


ColdCompressor

box

Sha

ftS

urfa

ceC

aver

nTu

nnel


1.8 KRefrigeration

Unit

New4.5 K

Refrigerator

Existing4.5 K

Refrigerator

1.8 KRefrigeration

UnitWarm

CompressorStation

WarmCompressor

Station

WarmCompressor

Station

ColdCompressor

box



UpperCold Box

Interconnection Box

Cold Box

WarmCompressor

Station

LowerCold Box



ColdCompressor

box

Surface

Shaft

Underground

1 Cryoplant could keep the helium inventory in place, and allow the

operation of LHC at low

level


Efficient operation at low load Typical LHC even point

UpperCold Box

Interconnection Box

Cold Box

WarmCompressor

Station

LowerCold Box



ColdCompressor

box

Sha

ftS

urfa

ceC

aver

nTu

nnel


1.8 KRefrigeration

Unit

New4.5 K

Refrigerator

Existing4.5 K

Refrigerator

1.8 KRefrigeration

UnitWarm

CompressorStation

WarmCompressor

Station

WarmCompressor

Station

ColdCompressor

box



UpperCold Box

Interconnection Box

Cold Box

WarmCompressor

Station

LowerCold Box



ColdCompressor

box

UpperCold Box

Interconnection Box

Cold Box

WarmCompressor

Station

LowerCold Box



ColdCompressor

box

Sha

ftS

urfa

ceC

aver

nTu

nnel


1.8 KRefrigeration

Unit

New4.5 K

Refrigerator

Existing4.5 K

Refrigerator

1.8 KRefrigeration

UnitWarm

CompressorStation

WarmCompressor

Station

WarmCompressor

Station

ColdCompressor

box



UpperCold Box

Interconnection Box

Cold Box

WarmCompressor

Station

LowerCold Box



ColdCompressor

box

UpperCold Box

Cold Box

WarmCompressor

Station

LowerCold Box


ColdCompressor

box

Sha

ftS

urfa

ceC

aver

nTu

nnel


1.8 KRefrigeration

Unit

New4.5 K

Refrigerator

Existing4.5 K

Refrigerator

1.8 KRefrigeration

UnitWarm

CompressorStation

WarmCompressor

Station

WarmCompressor

Station

ColdCompressor

box



UpperCold Box

Interconnection Box

Cold Box

WarmCompressor

Station

LowerCold Box



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)


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




The Carnot factor


The refrigerators



Summary


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]


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!


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 !!!


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)


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


View of a compressor station

Motors Oil Coolers Helium Coolers

4.2MW input power


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 ?


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!

lhc cryogenics design and operation: optimization …...130 t he inventory...

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