ILC Power and Water Use Review

SLAC B214 'FUJI' room (SLAC)

SLAC B214 'FUJI' room


Marc Ross (SLAC)
Goals of this meeting: Develop a power usage reduction strategy and plan related CFS (FNAL) engineering work for the next 8 weeks (up to the Valencia meeting). What sets the service tunnel temperature? What sets the beam tunnel temperature? Modelling to be done in 3 weeks by FNAL PPT mechanical (Wands). This isthe group who did the Nummi tunnel modelling. Osha limitations on the type of work people do in given environments. Is the service tunnel work'heavy' per their rules? Should our goal be to make the environment such that there are no work restrictions? Should we be concerned at this stage withthe installation phase of the project (no - this meeting is to address operating power requirements). Can zoning be used to limit the cost of tunnel air conditioning? (no - it seems that there should be circulation of some sort). Approximately 16 MW is used for dehumidifying the service tunnel input air. POwer requirements are also listed for the periodic (1/3 RF units) dehumidifiers in the beam tunnel. In the Vancouver model, the tunnel in the service tunnel is fed through one linac shaft and removed from the adjacent one(s). The beam tunnel is sealed, so all of the humidity is from equipment water leaks or ground water. The model does not include 'recirculation'. This is what is done in the HERA and PETRA tunnels. Friday Wilhelm will tell us the power requirements are (also those expected for XFEL) The single tunnel does not allow for simple recirculation schemes. We considered alternative schemes where the air passes first through the service tunnel and subsequently through the beam tunnel in a sort of single pass system. This may allow a reduction of the beam tunnel dehumidifiers. The total planned air velocity is 1 MpH (88 feet / minute ... 20000cubic feet / minute). There was a general consensus that the target humidity is between 30 and 40%. 40 % is achieved in HERA. This corresponds to a dew point of 50 degrees F. It is reported that higher levels of humidity cause concrete and infrastructure corrosion. All of the planned sites (except perhaps the proposed CERN site) would require dehumidfiers. Issues associated with closed-circuit air systems: radiation (in the form of radionuclides), fire (pressure difference between the 2 tunnels), and cryogenic safety (ODH).
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  • Thursday, 7 September
    • 08:30 12:00
      Thursday, AM
    • 08:30 10:15
      Tunnel Temp Issues 1h 45m
      Limitations, Requirements, Desireable Features, Design Strategies
      Speaker: Tom Lackowski (FNAL)
      Here are some notes from today's meeting: 1) the power required for the whole ILC - (a partial rollup presented at Vancouver in July ~ 358 MW) - is now 274 MW. We (mostly) limited our discussion to linac power systems today. The linac RF system power use is 93 MW (unchanged from Vancouver). An additional 69 MW is used for support systems (29 for cryo, 22 for support electrical - e.g. klystron magnets/filaments, electronics, 17 for water and 1 for magnets). Non linac systems use 102 MW and will be discussed Friday. 2) some of the total ILC use is 'climate dependent' and will be perhaps 10% less on cold dry days. 3) roughly 10% of the (total ILC) power consumed is for tunnel air 'conditioning' - the term refers both to thermal and humidity control. This can be reduced most effectively by reducing heat rejected to air and overall tunnel air flow. There are some savings by using recirculated air. This is done at DESY. 4) The overall figure of merit ratio 'watts required to remove one watt power dissipated' is about 0.18 for the ILC. This is not far from existing machines. 26% of the dissipated power is removed via chilled water / 74% is removed through 'process' (LCW) water. We think this should be 15 / 85 or better. Both the power consumed and the capital cost of the installed CFS mechanical equipment will be reduced. 5) The klystron collector delta T should be increased to 40 degrees F. This allows 28% reduction of the process water pump-related power. Initial discussion with CPI indicates this should be ok. Heavy insulation of the collector and surrounding piping will be needed. 6) The baseline modulator / charging supply system needs modification to provide >0.95 power factor. There are no fundamental cost drivers or technical challenges associated with achieving an appropriate power factor. Nevertheless, the impact of 0.95 power factor (added distributed cable plant infrastructure and transformer heat dissipation) has not been included in the baseline design. There is a recent DESY note on this topic. 7) We recommend changing the baseline design to one process water skid / two RF units, rather 1/1. This reduces equipment cost and consumed power. We will investigate reducing the number of skids further; and try to identify an optimum. 8) We recommend a re-evaluation of the linac electronic (relay-rack) loads.
    • 10:15 10:30
      break 15m
    • 10:30 12:00
    • 12:00 13:00
      Lunch 1h
    • 13:00 18:00
      Thursday, PM
    • 13:00 14:30
      Tunnel Cooling/ Linac Air Cooling and Dehumidifier Design 1h 30m
      Speaker: Lee Hammond (FNAL)
      Lee – taken Illinois summer max temps as a criteria of outside air and dehumid to 49 deg F dewpoint and putting into every other shaft and exh at other shafts. The air travels 5km . Total air volume is 20000 CFM. The 1mph is an historic number at FNAL. Comp to CERn. This sets the large dehumid on the surface. Don’t run this system for the beam tunnel when beam is on. No air in or out of beam tunnel during operation. Criteria are agreed upon for the dewpoint. Even for a CERN site. Reduce the cost by reducing the airflow requirement. Recirculate? How is this done with miles of tunnel? Use the beam tunnel? 3 things: radiation, cryo, escape. The tunnels were separated for these reasons. In a normal situation there would be a pressure difference. The service tunnel is not ODH zone. Will there be N2 used in the service tunnel? Skids makeup tank and waveguide pressurization. Where does the mile/hour come from . Osha 200 CFM/person 200CFM/brake horsepower diesel and another criteria for digging. One air change / 3 hours is pretty low compared to occupied buildings. Does sealing the beam tunnel result in dry enough air. There are scattered dehumid in the beam tunnel. There are 2 schemes discussed: one cycle with the beam/service tunnel and indefinite recycle. OSHA standard for the storage of flammable and combustible liquids – 6/hour. 10CFR1926.152.B4Vi . release of rock related gas. Separate water sources – spilled water and ground water. These are small compared to the water in the surface air. (one dehumidifier in the beam tunnel every 3 RFun its – present model).why not extend this to the length of the tunnel? This is a 3rd model – using only one central.
    • 14:30 14:45
      break 15m
    • 14:45 16:00
      Power Usage Summary 1h 15m
      Speaker: John Santic (FNAL)
    • 16:00 17:30
      Power Factor - w modulator experts 1h 30m
      Speakers: Chris Jensen (Fermi National Accelerator Laboatory) , Clay Corvin (SLAC)
      Requirements on power factor (Dick) not been looked at. How much variation is allowed on the line? DESY addressed this in a recent paper. They addressed this differently. They must keep the 5 10 Hz fluct .25 % what the utility sees. DESY analyzed what it takes to arrange this. Recommend a rectifier and a switcher on top of that. The switcher is only working on 20%. The rectifier works on the rest. The total harmonic distortion. Phase shifting transformers. There is a design impact for making the different kinds of phase shifting transformers. The ILC linac cost model should be modified to include these devices 1) DC rectifier, 2) and switcher supply, and 3) phase shifter transformers.
  • Friday, 8 September