Patent Application: US-201113180695-A

Abstract:
an energy efficient data center incorporating superconducting power transmission cables coupled with cryogenically cooled semiconductor inverters and converters , used to supply power to cryogenically operated or room - temperature computers and servers . other options and features include a lighting system whose performance is enhanced by the cold temperatures , fiber optic connections operated at cryogenic temperatures , integrated renewable energy power sources , advanced energy storage technologies , cryogenically operated computers , and a number of other cryogenic hardware . the operating temperature of the cryogenic components can be anywhere in the range between 0 k and 200 k , with other components operating above 200 k .

Description:
described is an energy efficient data center based on the technologies described above . the proposed cryogenic data center , shown in fig6 and 7 , integrates superconducting transmission lines ( hts , lts , or a combination of the two ), cryogenically cooled power conversion equipment ( cryogenic power inverters and converters ), and cryogenically cooled computers into a single structure . power is obtained either from the national power grid or from one or more other energy sources , including renewable and environmentally friendly energy systems such as those based on photovoltaic cells ( solar power ), wind power , biofuels , hydroelectric power , tidal power , fuel cells , clean natural gas , and others . excess power generated by these renewable and clean energy sources may be placed back onto the grid . the data center incorporates a common bus structure that integrates power from several power sources used in tandem . the data center may be built around cryogenically cooled computers ( e . g ., servers ), or these could be operated at conventional temperatures with only the power distribution and conversion system cooled . power conditioning is achieved using cryogenically cooled inverters and converters , which transform ac and dc power of given voltages and currents into ac or dc power of different voltage and current at higher efficiencies than are possible with conventional power conversion equipment . superconducting transmission lines within the data center carry either dc or ac power among cryogenic computers , cryogenic power conditioning equipment , and energy storage systems . the transmission line cables can also supply a cryogenic fluid or gas to the other components in the system ( i . e ., computers and power conversion equipment ). note that dc cables permit the transmission of twice the power for the same voltage ratings . of particular importance in this application is that only relatively short lengths of superconducting cables are required for the concept , and that these can carry dc rather than ac power . the energy storage means can comprise of a combination of several conventional energy storage technologies or advanced energy storage means , including superconducting magnetic energy storage ( smes ), flywheels , advanced batteries , super - capacitors , and so on . the energy storage systems may also include cryogenically cooled capacitors [ 16 ]. superconducting transmission lines can also be used to transmit data among computers and servers , as well as for high - performance interconnections among computer chips . the data center may also incorporate superconducting fault current limiters , superconducting transformers , superconducting inductors , superconducting coils , or superconducting generators . superconducting motors or cryogenically operated piezoelectric motors can be used for hard drives , robotics , or other purposes . devices based on superconducting josephson junctions can also be included , as can quantum computers . maintenance can be facilitated using detachable superconducting leads , which allow for sections of equipment to be disconnected from the cryogenic environment and warmed up independently . this would allow repair or replacement of components without disabling the entire cryogenic data center . such leads are currently being developed by the inventors at mtech labs . the cryogenically cooled computers and power conditioning equipment may also include cryogenically cooled fiber optic transmitters and receivers , as well as light - emitting diode - based displays . fiber optics can be used to transmit signals from cryogenic to room - temperature environments with reduced heat load . cryogenically cooled light emitting diodes can also be used for more efficient light generation , as shown in fig8 [ 17 ]. network switches and routers could also be operated at cryogenic temperatures for improved performance ( especially at the system level ), or simply for easier integration with other cryogenic components . few conventional devices work as - built at low temperatures , and most of these would have to be specially designed . for example , electrolytic capacitors would have to be replaced with ones containing polymer films , ceramics , or other cryogenically compatible dielectrics , and some transistors would have to be replaced with cryogenically qualified semiconductor technologies . packaging is also an important consideration , as many materials crack at cryogenic temperatures . cryogenic cooling equipment may comprise of cryo - coolers , or convection - or conduction - based cooling systems utilizing liquid nitrogen , liquid helium , or cold gaseous nitrogen or helium . any gaseous or liquid cryogen could be used . a centralized cooling system may be most efficient . a liquid nitrogen generation plant could be included on - site , and liquid nitrogen generation could be achieved mainly in off - peak hours in order to shed the power consumption load . the preferred embodiment of the cryogenic data center , shown in fig6 , consists of a network or superconducting power busses 1 , with dc current supplied to it from either a power generation source 4 or the national power grid 5 ( in which case it would include an additional transformer to isolate power in the cryogenic data center from said national grid ), wherein said power is converted , if necessary , from ac to dc or from dc of one voltage level to dc power of another voltage level through a plurality of cryogenically operated ac / dc inverters and / or dc / dc converters 2 as required to optimize efficiency in the system . the dc current in the superconducting power bus network 1 is then converter again to the required voltage , current , and current type ( ac or dc ) via another set of cryogenically operated ac / dc or dc / dc converters 2 for delivery to the load , which may include a plurality of cryogenically operated computers and servers 3 , a lighting system 10 , and cryogenic network switches and routers 7 . these loads may also be operated at conventional temperatures , in which case cryogenic leads would be required to transition current from the cryogenic environment to the room - temperature environment . the data center may also include a network of superconducting data transmission lines 9 to interconnect said plurality of cryogenic computers and servers 3 . the cryogenic cooling system 6 may consist of a single , centralized cryo - cooler or tank of liquid nitrogen , or a plurality of distributed cryo - coolers of cryogenic storage tanks . cryogenic fluids and gases can be delivered to any cryogenic loads through the cable cryostats associated with the superconducting dc bus network 1 . energy storage can be achieved using cryogenically operated devices 11 , such as smes units , or room - temperature devices 8 such as flywheels , or preferably a combination of both . in a report generated for congress , the u . s . epa identified a number of ways in which the efficiencies of data centers could be greatly improved [ 1 ]. while superconducting cables were briefly touched upon , the cryogenic operation of computers and inverters was not suggested . others have proposed utilizing superconducting dc buses for use in data centers , including joseph minervini &# 39 ; s group at the mit plasma science and fusion center [ 2 ]. this group does advance the possibility of integration with renewable energy sources such as solar and wind , as well as integration with advanced energy storage technologies such as superconducting magnetic energy storage and flywheels . however , they do not propose operating the computers or computer chips at cryogenic temperatures , nor do they include cryogenic power conversion . this integration is the main innovation of the proposed concept . much work has also been done in the past in adapting and developing computers and computer chips to operate at cryogenic temperatures , especially 77 k [ 3 , 6 - 11 ]. however , most previous work focused on improvements in computer performance at low temperatures , and not on integration of these devices in large numbers with superconducting components and cryogenic power conversion equipment . also , because of the high cost of cooling an individual computer , most of this work has ceased . the proposed data center could use a common cryogenic platform to cool multiple components , including superconducting transmission lines , computers , power generation equipment , and lighting systems . fig1 shows the cost of powering and cooling servers is rapidly approaching that spent in purchasing and installing new servers [ 4 ]. fig2 shows the distribution of energy consumption in a typical data center , with the majority going to the servers , but with energy expended in cooling close behind . when the power conversion and distribution equipment is added to the cooling equipment , the energy consumed by hardware other than computers and servers is greater than 50 % of the total [ 2 ]. fig3 shows a conventional 460 vac data center power system [ 5 ]. fig4 shows the cryogenic performance of the cryocircuits mos - 03 mosfet , developed and tested by mtech . the on - state resistance of this device drops by a factor of 15 to 30 compared to 300k and 400k operation , respectively . fig5 : efficiency versus load for an energy star representative 75 - kva transformer model ; taken from a 1999 study by the cadmus group , inc . [ 15 , p . viii ; graph re - created ]. also included on the graph is the projected efficiency of mtech &# 39 ; s 75 - kw cryogenic inverter and a similar mtech inverter operating at room temperature . note that due to the lack of magnetization losses in the inverter , the device &# 39 ; s efficiency continues to increase at low powers . these preliminary efficiency calculations include refrigeration losses ( 10 w / w ) to keep the inverters cold . fig6 illustrates the cryogenic data center concept ( in one embodiment ). fig7 illustrates a possible implementation of the cryogenic data center concept . fig8 shows the decrease in forward diode current with decreasing temperature in a light emitting diode for a given light output . u . s . epa , “ report to congress on server and data center energy efficiency ,” aug . 2 , 2007 , available online at http :// www . energystar . gov / ia / partners / prod_development / downloads / epa_datacenter_report_congress_final1 . pdf j . v . minervini , l . bromberg , m . takayasu , c . miles and n . r . labounty , “ hts dc cables for power distribution in data centers ,” workshop on superconducting dc transmission and distribution , mit plasma science and fusion center , cambridge , mass ., feb . 25 , 2009 . s . wainner and r . richmond , the book of overclocking : tweak your pc to unleash its power , no starch press ( 2003 ). g . lawton , “ powering down the computing infrastructure ,” computer , ieee , 40 , issue 2 , p 16 - 19 , february 2007 . pratt , a ., p . kumar , and t . v . aldridge . evaluation of 400v dc distribution in telco and data centers to improve energy efficiency ,” 29 th ieee intelec 2007 , 2007 , rome , italy d . t . vader and v . c . vasile , “ high performance thermal interface for low temperature electronic modules ,” u . s . pat . no . 5 , 463 , 872 , issued nov . 7 , 1995 h . yamamoto , “ multichip module packaging for cryogenic computers ,” circuits and systems , 1991 ., ieee international symposium on , 11 - 14 jun . 1991 page ( s ): 2296 - 2299 vol . 4 s . novotny , “ performance evaluation of a gifford - mcmahon refrigerator for cryogenically cooled computer applications ,” thermal phenomena in electronic systems , 1990 . i - therm ii ., intersociety conference on , 23 - 25 may 1990 page ( s ): 97 - 100 the cadmus group , inc ., “ metered load factors for low - voltage , dry - type transformers in commercial , industrial , and public buildings ,” a study funded by the northeast energy efficiency partnerships , inc . 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