Patent Application
20090241558
This disclosure relates to cooling systems and, more particularly, to cryogenic cooling systems for high temperature superconductor (“HTS”) devices, in particular HTS fault current limiters (“FCL”).
High temperature superconductors may be used to construct superconducting FCLs, which control or limit fault currents within electric power distribution systems. Cryogenic cooling systems (e.g., conduction cooling systems, saturated nitrogen cooling systems, and subcooled nitrogen cooling systems with helium gas) are often used to maintain the HTS windings within the FCL at cryogenic temperatures required for the HTS to operate in a superconducting state even during periods of impulsive heating generated by fault currents in the system and experienced by the fault current limiter.
Unfortunately, while conduction cooling system have flexible operating temperatures, they suffer from slower recovery times. Further, while saturated nitrogen cooling systems have faster recovery times, they suffer from fixed operating temperatures. Additionally, while subcooled nitrogen cooling systems (with helium gas) have faster recovery times and flexible operating temperatures, liquid nitrogen is typically vented during a fault.
In a first implementation, a component cooling system includes a component tank configured to receive a heat-generating device. The component tank is at least partially filled with a subcooled liquid at a first pressure and at a first temperature. A cryogenic system maintains the component tank at essentially the first temperature. The cryogenic system includes a heat exchange system thermally coupled with at least a portion of the component tank. The heat exchange system is at least partially filled with a second saturated liquid at a second pressure and at essentially the first temperature. A cryostat tank is fluidly-coupled with the heat exchange system and allows for pumpless displacement of the second saturated liquid between the heat exchange system and the cryostat tank.
One or more of the following features may be included. A buffer tank may be configured to be at least partially filled with a first saturated liquid at a second temperature. The buffer tank may be fluidly-coupled with the component tank for allowing for pumpless liquid displacement between the component tank and the buffer tank.
A heating system may be configured to heat the first saturated liquid within the buffer tank to maintain the first pressure within the component tank. The first saturated liquid and the second saturated liquid may be saturated liquid nitrogen.
The heat exchange system may include a heat exchanger device positioned within the component tank. The heat exchanger device may include one or more tubing assemblies through which the second saturated liquid passes. The heat exchanger device may include a thermally conductive mass through which the one or more tubing assemblies pass.
The heat exchange system may include a heat exchanger device positioned external to the component tank. The heat exchanger device may be a cooling tank encapsulating at least a portion of the component tank.
The cryogenic system may include a cryostat positioned within the cryostat tank and configured to maintain the second saturated liquid at essentially the first temperature. The heat-generating device may be a fault current limiter device. The subcooled liquid may be subcooled liquid nitrogen. The second temperature may be greater than the first temperature. The second pressure may be less than the first pressure.
In another implementation, a component cooling system includes a component tank configured to receive a fault current limiter device. The component tank is configured to be at least partially filled with a subcooled liquid at a first pressure and at a first temperature. A buffer tank is configured to be at least partially filled with a first saturated liquid at a second temperature. The buffer tank is fluidly-coupled with the component tank for allowing for pumpless liquid displacement between the component tank and the buffer tank. A cryogenic system maintains the component tank at essentially the first temperature. The cryogenic system includes a heat exchange system thermally coupled with at least a portion of the component tank. The heat exchange system is at least partially filled with a second saturated liquid at a second pressure and at essentially the first temperature. A cryostat tank is fluidly-coupled with the heat exchange system for allowing for pumpless displacement of the second saturated liquid between the heat exchange system and the cryostat tank. A heating system is configured to heat the first saturated liquid within the buffer tank to maintain the first pressure within the component tank.
One or more of the following features may be included. The heat exchange system may be a heat exchanger device positioned within the component tank. The heat exchange system may be a heat exchanger device encapsulating at least a portion of the component tank. The cryogenic system may include a cryostat positioned within the cryostat tank and configured to maintain the second saturated liquid at essentially the first temperature. The subcooled liquid, the first saturated liquid, and the second saturated liquid may be liquid nitrogen.
In another implementation, a component cooling system includes a component tank configured to receive a heat-generating device. The component tank is configured to be at least partially filled with a subcooled liquid at a first pressure and at a first temperature. A buffer tank is configured to be at least partially filled with a first saturated liquid at a second temperature. The buffer tank is fluidly-coupled with the component tank to allow for pumpless liquid displacement between the component tank and the buffer tank. A cryogenic system maintains the component tank at essentially the first temperature. The cryogenic system includes a heat exchange system thermally coupled with at least a portion of the component tank. The heat exchange system is at least partially filled with a second saturated liquid at a second pressure and at essentially the first temperature. A cryostat tank is fluidly-coupled with the heat exchange system to allow for pumpless displacement of the second saturated liquid between the heat exchange system and the cryostat tank. A cryostat is positioned within the cryostat tank and is configured to maintain the second saturated liquid at essentially the first temperature.
The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will become apparent from the description, the drawings, and the claims.
Referring to
A fault current limiter may be constructed using superconductor tapes or wires. When designing a fault current limiter, the superconductor windings (such as those made from high-temperature or low-temperature superconductor material) may be configured such that the impedance of the fault current limiter is negligible when subjected to normal current loads. However, when exposed to fault current loads, the impedance of the superconducting windings may dramatically increase as the superconductor tape transitions from a superconducting state to a non-superconducting or “normal” state. When this transition occurs the tape's resistance goes from zero to a significant level of resistance and the fault current is therefore limited. Of course when this transition occurs, it results in the fault current limiter absorbing a substantial portion of the energy of the fault current. This energy absorption by the fault current limiter may result in the fault current limiter generating a large amount of thermal energy, which may be absorbed by component cooling system 10. The thermal energy must be absorbed without the liquid nitrogen forming gaseous bubbles as this could result in electrical breakdown in the system.
Examples of low-temperature superconducting materials includes: niobium-zirconium; niobium-titanium; and niobium-tin. Examples of high-temperature superconducting materials include: thallium-barium-calcium-copper-oxide; bismuth-strontium-calcium-copper-oxide; mercury-barium-calcium-copper-oxide; yttrium-barium-copper-oxide, or any of the MgB2 Magnesium diboride compounds
Component cooling system 10 may include a component tank 14 configured to receive heat-generating device 12 Component tank 14 may be configured to be at least partially filled with a subcooled liquid 16. Examples of subcooled liquid 16 may include, but are not limited to, subcooled liquid nitrogen.
Component cooling system 10 may include buffer tank 18, which may be configured to be at least partially filled with a saturated liquid 20. Examples of saturated liquid 20 may include, but are not limited to, saturated liquid nitrogen. Buffer tank 18 may be fluidly coupled with component tank 14, thus allowing for the pumpless displacement of liquids (e.g., subcooled liquid 16 and saturated liquid 20) between tanks 14, 18 during an event of fault or recovery time. For example, one or more pipe/tube assemblies (e.g., pipe/tube assembly 22) may couple component tank 14 and buffer tank 18. As used in this disclosure, pumpless displacement of liquids may be defined as the displacement of liquids without the use of any mechanical pump assembly.
As superconducting materials only achieve their superconducting characteristics when operating at low temperatures (e.g., <90 degrees Kelvin for YBCO superconductor), component cooling system 10 may include cryogenic system 24 for maintaining the temperature of component tank 14 (and, therefore, the liquid 16 within component tank 14) at a desired temperature (T1), which may vary based on the type and state of liquid included within tank 14. For example and as discussed above, component tank 14 may be configured to be at least partially filled with subcooled liquid 16. When subcooled liquid 16 is subcooled liquid nitrogen, temperature T1 may be in the range of 65-75 degrees Kelvin, preferably 67 degrees Kelvin. Accordingly, for a subcooled liquid nitrogen system, cryogenic system 24 may be configured to maintain the temperature of component tank 14 at essentially 67 degrees Kelvin.
Cryogenic system 24 may include a heat exchange system (e.g., cooling tank 26) that may be configured to be at least partially filled with saturated liquid 28. Examples of saturated liquid 28 may include, but are not limited to, saturated liquid nitrogen. When the above-described heat exchange system is configured as cooling tank 26, cooling tank 26 may encapsulate at least a portion of component tank 14.
Cryogenic system 24 may further include a cryostat tank 30 fluidly coupled with cooling tank 26, thus allowing for pumpless displacement of saturated liquid 28 between cryostat tank 30 and cooling tank 26 by using gravity force. As discussed above, pumpless displacement of liquids may be defined as the displacement of liquids without the use of any mechanical pump assembly. For example, one or more pipe/tube assemblies (e.g., pipe/tube assemblies 32, 34) may couple cryostat tank 30 and cooling tank 26. As liquid 28 is a saturated liquid, if thermal energy is added to saturated liquid 28, a portion of saturated liquid 28 may transition (i.e., change state) to vapor 36. Cryogenic system 24 may further include cryostat 38 positioned within cryostat tank 30. Cryostat 38 may be configured to maintain saturated liquid 28 at essentially temperature T1 (e.g., 67 degrees Kelvin) and at its corresponding saturated pressure (P2). Cryostat 38 may include control circuitry (not shown) for monitoring the temperature and/or pressure of cryostat tank 30 and/or cooling tank 26 and for cooling (i.e., removing thermal energy from) cryostat tank 30 and/or cooling tank 26 whenever the temperature of cryostat tank 30 and/or cooling tank 26 is above the desired temperature (T1) and/or the pressure of cryostat tank 30 and/or cooling tank 26 is above the desired pressure (P2). For a saturated liquid nitrogen system, cryogenic system 24 may be configured to maintain the temperature of cooling tank 26 and cryostat tank 30 at a temperature (T1) of essentially 67 degrees Kelvin and a pressure (P2) of approximately 0.24 bar.
Component cooling system 10 may include a heating system 40 configured to heat saturated liquid 20 (within buffer tank 18) to a desired temperature (T2) and to maintain a desired pressure (P1). Accordingly, for a saturated liquid nitrogen system, heating system 40 may be configured to maintain the temperature (T2) of buffer tank 18 at essentially 105 degrees Kelvin. As component tank 14 and buffer tank 18 are fluidly coupled, pressure (P1) may be essentially the same in both tanks 14, 18. For a system that utilizes saturated and subcooled liquid nitrogen, heating system 40 may be configured to maintain the pressure (P1) of buffer tank 18 (and, therefore, component tank 14) at essentially 10 bar. Heating system 40 may include an electric resistive heating element (not shown) positioned to provide thermal energy to buffer tank 18. Additionally, heating system 40 may include control circuitry (not shown) for monitoring the temperature and/or pressure of buffer tank 18 and providing thermal energy to buffer tank 18 whenever the temperature of buffer tank 18 is below the desired temperature (T2) and/or the pressure of buffer tank 18 is below the desired pressure (P1).
Additionally, component cooling system 10 may include a second cryostat 42 (shown in phantom) configured to cool saturated liquid 20 (within buffer tank 18) to the desired temperature (T2) and to maintain the desired pressure (P1). Second cryostat 42 may include control circuitry (not shown) for monitoring the temperature and/or pressure of buffer tank 18 and for cooling (i.e., removing thermal energy from) buffer tank 18 whenever the temperature of buffer tank 18 is above the desired temperature (T2) and/or the pressure of buffer tank 18 is above the desired pressure (P1).
Component cooling system 10 may include a vacuum tank 44 for encapsulating various components of cooling system 10. For example, vacuum tank 44 may encapsulate cooling tank 26 (and, therefore, component tank 14), buffer tank 18, and cryostat tank 30. Due to the vacuum within vacuum tank 46, the various components of component cooling system 10 (e.g., cooling tank 26, buffer tank 18, and cryostat tank 30) may not be exposed to the thermal energy contained within the ambient air 46 surrounding vacuum tank 44.
As discussed above, heat-generating device 12 may be a fault current limiter. Accordingly, when exposed to a fault current (through e.g., conductors 48, 50), heat-generating device 12 may get hot, heat subcooled liquid 16 proximate heat-generating device 12, and add enough thermal energy to subcooled liquid 16 so that a portion of subcooled liquid 16 transitions from a liquid state to a gaseous state, thus creating gaseous bubble 52 (shown in phantom). As gaseous bubble 52 is larger in volume than the quantity of subcooled liquid 16 that changed state to form gaseous bubble 52, a portion of subcooled liquid 16 may be displaced (through pipe/tube assembly 22) into buffer tank 18. As discussed above, for subcooled and saturated liquid nitrogen systems, subcooled liquid 16 may be maintained at a temperature (T1) of 67 degrees Kelvin, saturated liquid 20 may be maintained at a temperature (T2) of 105 degrees Kelvin, both of which are at a pressure of 10 bar.
The thermal energy of gaseous bubble 52 may be absorbed by subcooled liquid 16, resulting in gaseous bubble 52 reverting to a liquid state. During a typical fault current, the temperature (T1) of subcooled liquid 16 may increase from 67 degrees Kelvin to 70 degrees Kelvin. As discussed above, a portion of this 70 degree Kelvin subcooled liquid 16 may be displaced into buffer tank 18 (which is at least partially filled with 105 degree Kelvin saturated liquid 20). Accordingly, the temperature of saturated liquid 20 may drop to 94 degrees Kelvin and/or the pressure of saturated liquid 20 may drop to 5 bar. Accordingly, heater system 40 may be activated to heat saturated liquid 20 (within buffer tank 18) to desired temperature T2 (e.g., 105 degrees Kelvin) and/or to desired pressure P1 (e.g., 10 bar).
Further, as subcooled liquid 16 within component tank 14 is heated to 70 degrees Kelvin (during a fault condition), thermal energy from component tank 14 is conductively transferred to saturated liquid 28 within cooling tank 26. Sensing this increase in temperature, cryostat 38 may be activated to reduce the temperature of saturated liquid 28 (which is present in both cooling tank 26 and cryostat tank 30) from e.g., 70 degrees Kelvin to the desired temperature T1 (e.g., 67 degrees Kelvin). This recovery process may take hours depending on the excess available cooling power of cryostat 38.
Referring also to
Component cooling system 10′ may include a component tank 100 configured to receive heat-generating device 12 Component tank 100 may be configured to be at least partially filled with a subcooled liquid 102. Examples of subcooled liquid 102 may include, but are not limited to, subcooled liquid nitrogen.
Component cooling system 10′ may include buffer tank 104, which may be at least partially filled with a saturated liquid 106. Examples of saturated liquid 106 may include, but are not limited to, saturated liquid nitrogen. Buffer tank 104 may be fluidly coupled with component tank 100, thus allowing for the pumpless displacement of liquids (e.g., subcooled liquid 102 and saturated liquid 106) between tanks 100, 104. For example, one or more pipe/tube assemblies (e.g., pipe/tube assembly 108) may couple component tank 100 and buffer tank 104. As discussed above, pumpless displacement of liquids may be defined as the displacement of liquids without the use of any mechanical pump assembly.
Component cooling system 10′ may include cryogenic system 110 for maintaining the temperature of component tank 100 (and, therefore, the liquid 102 within component tank) at a desired temperature (T1), which may vary based on the type and state of liquid included within tank 100. For example and as discussed above, component tank 100 may be configured to be at least partially filled with subcooled liquid 102. When subcooled liquid 102 is subcooled liquid nitrogen, temperature T1 may be 67 degrees Kelvin. Accordingly, for a subcooled liquid nitrogen system, cryogenic system 110 may be configured to maintain the temperature of component tank 100 at essentially 67 degrees Kelvin.
Cryogenic system 110 may include a cooling tank 112 (i.e., a heat exchange system) that may be at least partially filled with saturated liquid 114. Cooling tank 112 may encapsulate at least a portion of component tank 100. Examples of saturated liquid 114 may include, but are not limited to, saturated liquid nitrogen.
Cryogenic system 110 may further include cryostat 116 positioned within cooling tank 112. Cryostat 116 may be configured to maintain saturated liquid 114 at essentially temperature T1 (e.g., 67 degrees Kelvin) and at a desired pressure (P2). Cryostat 116 may include control circuitry (not shown) for monitoring the temperature and/or pressure of cooling tank 112 and for cooling (i.e., removing thermal energy from) cooling tank 112 whenever the temperature of cooling tank 112 is above the desired temperature (T1) and/or the pressure of cooling tank 112 is above the desired pressure (P2). For a saturated liquid nitrogen system, cryogenic system 110 may be configured to maintain the temperature of cooling tank 112 at a temperature (T1) of essentially 67 degrees Kelvin and a pressure (P2) of approximately 0.24 bar.
Component cooling system 10′ may include a heating system 118 configured to heat saturated liquid 106 (within buffer tank 104) to a desired temperature (T2) and to maintain a desired pressure (P1). Accordingly, for a saturated liquid nitrogen system, heating system 118 may be configured to maintain the temperature (T2) of buffer tank 104 at essentially 105 degrees Kelvin. As component tank 100 and buffer tank 104 are fluidly coupled, pressure (P1) is essentially the same is both tanks 100, 104. For a system that utilizes saturated and subcooled liquid nitrogen, heating system 118 may be configured to maintain the pressure (P1) of buffer tank 104 (and, therefore, component tank 100) at essentially 10 bar. Heating system 118 may include an electric resistive heating element (not shown) positioned to provide thermal energy to buffer tank 104. Additionally, heating system 118 may include control circuitry (not shown) for monitoring the temperature and/or pressure of buffer tank 104 and providing thermal energy to buffer tank 104 whenever the temperature of buffer tank 104 is below the desired temperature (T2) and/or the pressure of buffer tank 104 is below the desired pressure (P1).
Additionally, component cooling system 10′ may include a second cryostat 120 (shown in phantom) configured to cool saturated liquid 106 (within buffer tank 104) to the desired temperature (T2) and to maintain the desired pressure (P1). Second cryostat 120 may include control circuitry (not shown) for monitoring the temperature and/or pressure of buffer tank 104 and for cooling (i.e., removing thermal energy from) buffer tank 104 whenever the temperature of buffer tank 104 is above the desired temperature (T2) and/or the pressure of buffer tank 18 is above the desired pressure (P1).
Component cooling system 10′ may include a vacuum tank 122 for encapsulating various components of cooling system 10′. For example, vacuum tank 122 may encapsulate cooling tank 112 (and, therefore, component tank 100), and buffer tank 104. Due to the vacuum within vacuum tank 122, the various components of component cooling system 10′ (e.g., cooling tank 112, and buffer tank 104) may not be exposed to the thermal energy contained within the ambient air 124 surrounding vacuum tank 122.
When exposed to a fault current (through e.g., conductors 124, 126), heat-generating device 12 may get hot, heat subcooled liquid 102 proximate heat-generating device 12, and add enough thermal energy to subcooled liquid 102 so that a portion of subcooled liquid 102 transitions from a liquid state to a gaseous state, thus creating gaseous bubble 128 (shown in phantom). As gaseous bubble 128 is larger in volume than the quantity of subcooled liquid 102 that changed state to form gaseous bubble 128, a portion of subcooled liquid 102 may be displaced (through pipe/tube assembly 108) into buffer tank 104. As discussed above, for subcooled and saturated liquid nitrogen systems, subcooled liquid 102 may be maintained at a temperature (T1) of 67 degrees Kelvin, saturated liquid 106 may be maintained at a temperature (T2) of 105 degrees Kelvin, both of which are at a pressure of 10 bar.
The thermal energy of gaseous bubble 128 may be absorbed by subcooled liquid 102, resulting in gaseous bubble 128 reverting to a liquid state. During a typical fault current, the temperature (T1) of subcooled liquid 102 may increase from 67 degrees Kelvin to 70 degrees Kelvin. As discussed above, a portion of this 70 degree Kelvin subcooled liquid 102 may be displaced into buffer tank 104 (which is at least partially filled with 105 degree Kelvin saturated liquid 20). Accordingly, the temperature of saturated liquid 106 may drop to 94 degrees Kelvin and/or the pressure of saturated liquid 106 may drop to 5 bar. Accordingly, heater system 118 may be activated to heat saturated liquid 106 (within buffer tank 104) to desired temperature T2 (e.g., 105 degrees Kelvin) and/or to desired pressure P1 (e.g., 10 bar).
Further, as subcooled liquid 102 within component tank 100 may be heated to 70 degrees Kelvin (during a fault condition), thermal energy from component tank 100 may be conductively transferred to saturated liquid 114 within cooling tank 112. Sensing this increase in temperature, cryostat 116 may be activated to reduce the temperature of saturated liquid 114 from e.g., 70 degrees Kelvin to the desired temperature T1 (e.g., 67 degrees Kelvin). As discussed above, this recovery process may take hours depending on the excess available cooling power of cryostat 38.
Referring also to
Component cooling system 10″ may include a component tank 150 configured to receive heat-generating device 12. Component tank 150 may be configured to be at least partially filled with a subcooled liquid 152. Examples of subcooled liquid 152 may include, but are not limited to, subcooled liquid nitrogen.
Component cooling system 10″ may include buffer tank 154, which may be at least partially filled with a saturated liquid 156. Examples of saturated liquid 156 may include, but are not limited to, saturated liquid nitrogen. Buffer tank 154 may be fluidly coupled with component tank 150, thus allowing for the pumpless displacement of liquids (e.g., subcooled liquid 152 and saturated liquid 156) between tanks 150, 154. For example, one or more pipe/tube assemblies (e.g., pipe/tube assembly 158) may couple component tank 150 and buffer tank 154. As discussed above, pumpless displacement of liquids may be defined as the displacement of liquids without the use of any mechanical pump assembly.
Component cooling system 10″ may include cryogenic system 160 for maintaining the temperature of component tank 150 (and, therefore, the liquid 152 within component tank) at a desired temperature (T1), which may vary based on the type and state of liquid included within tank 150. For example and as discussed above, component tank 150 may be configured to be at least partially filled with subcooled liquid 152. When subcooled liquid 152 is subcooled liquid nitrogen, temperature T1 may be 67 degrees Kelvin. Accordingly, for a subcooled liquid nitrogen system, cryogenic system 160 may be configured to maintain the temperature of component tank 150 at essentially 67 degrees Kelvin.
Cryogenic system 160 may include heat exchange system 162 (e.g., a heat exchanger device) that may be at least partially filled with saturated liquid 164. Heat exchange system 162 may include one or more tubing portions (e.g., tubing portion 166) through which saturated liquid 164 may pass. Heat exchange system 162 may further include thermally conductive mass 168 configured to allow thermal energy (not shown) to pass between subcooled liquid 152 (contained within component tank 150) and saturated liquid 164 (passing through tubing portion 166.
Cryogenic system 160 may further include a cryostat tank 170 fluidly coupled with heat exchange system 162, thus allowing for pumpless displacement of saturated liquid 164 between cryostat tank 170 and heat exchange system 162 by using gravity force. As discussed above, pumpless displacement of liquids may be defined as the displacement of liquids without the use of any mechanical pump assembly. For example, one or more pipe/tube assemblies (e.g., pipe/tube assemblies 172, 174) may couple cryostat tank 170 and heat exchange system 162. As liquid 164 is a saturated liquid, if thermal energy is added to saturated liquid 164, a portion of saturated liquid 164 may transition (i.e., change state) to vapor 176. Cryogenic system 160 may further include cryostat 178 positioned within cryostat tank 170. Cryostat 178 may be configured to maintain saturated liquid 164 at essentially temperature T1 (e.g., 67 degrees Kelvin) and at its corresponding saturated pressure (P2). Cryostat 178 may include control circuitry (not shown) for monitoring the temperature and/or pressure of cryostat tank 170 and/or heat exchange system 162 and for cooling (i.e., removing thermal energy from) cryostat tank 30 and/or heat exchange system 162 whenever the temperature of cryostat tank 170 and/or heat exchange system 162 is above the desired temperature (T1) and/or the pressure of cryostat tank 170 and/or heat exchange system 162 is above the desired pressure (P2). For a saturated liquid nitrogen system, cryogenic system 160 may be configured to maintain the temperature of heat exchange system 162 and cryostat tank 170 at a temperature (T1) of essentially 67 degrees Kelvin and a pressure (P2) of approximately 0.24 bar.
Component cooling system 10″ may include a heating system 180 configured to heat saturated liquid 156 (within buffer tank 154) to a desired temperature (T2) and to maintain a desired pressure (P1). Accordingly, for a saturated liquid nitrogen system, heating system 180 may be configured to maintain the temperature (T2) of buffer tank 154 at essentially 105 degrees Kelvin. As component tank 150 and buffer tank 154 are fluidly coupled, pressure (P1) may be essentially the same in both tanks 150, 154. For a system that utilizes saturated and subcooled liquid nitrogen, heating system 180 may be configured to maintain the pressure (P1) of buffer tank 154 (and, therefore, component tank 150) at essentially 10 bar. Heating system 180 may include an electric resistive heating element (not shown) positioned to provide thermal energy to buffer tank 154. Additionally, heating system 180 may include control circuitry (not shown) for monitoring the temperature and/or pressure of buffer tank 154 and providing thermal energy to buffer tank 154 whenever the temperature of buffer tank 154 is below the desired temperature (T2) and/or the pressure of buffer tank 154 is below the desired pressure (P1).
Additionally, component cooling system 10″ may include a second cryostat 182 (shown in phantom) configured to cool saturated liquid 156 (within buffer tank 154) to the desired temperature (T2) and to maintain the desired pressure (P1). Second cryostat 182 may include control circuitry (not shown) for monitoring the temperature and/or pressure of buffer tank 154 and for cooling (i.e., removing thermal energy from) buffer tank 154 whenever the temperature of buffer tank 154 is above the desired temperature (T2) and/or the pressure of buffer tank 154 is above the desired pressure (P1).
Component cooling system 10″ may include a vacuum tank 184 for encapsulating various components of cooling system 10″. For example, vacuum tank 184 may encapsulate component tank 150 (and therefore heat exchange system 162), buffer tank 154, and cryostat tank 170. Due to the vacuum within vacuum tank 184, the various components of component cooling system 10″ (e.g., component tank 150, buffer tank 154, and cryostat tank 170) may not be exposed to the thermal energy contained within the ambient air 186 surrounding vacuum tank 184.
As discussed above, heat-generating device 12 may be a fault current limiter. Accordingly, when exposed to a fault current (through e.g., conductors 188, 190), heat-generating device 12 may get hot, heat subcooled liquid 152 proximate heat-generating device 12, and add enough thermal energy to subcooled liquid 152 so that a portion of subcooled liquid 152 transitions from a liquid state to a gaseous state, thus creating gaseous bubble 192 (shown in phantom). As gaseous bubble 192 is larger in volume than the quantity of subcooled liquid 152 that changed state to form gaseous bubble 192, a portion of subcooled liquid 152 may be displaced (through pipe/tube assembly 158) into buffer tank 154. As discussed above, for subcooled and saturated liquid nitrogen systems, subcooled liquid 152 may be maintained at a temperature (T1) of 67 degrees Kelvin, saturated liquid 156 may be maintained at a temperature (T2) of 105 degrees Kelvin, both of which are at a pressure of 10 bar.
The thermal energy of gaseous bubble 192 may be absorbed by subcooled liquid 152, resulting in gaseous bubble 192 reverting to a liquid state. During a typical fault current, the temperature (T1) of subcooled liquid 152 may increase from 67 degrees Kelvin to 70 degrees Kelvin. As discussed above, a portion of this 70 degree Kelvin subcooled liquid 152 may be displaced into buffer tank 154 (which is at least partially filled with 105 degree Kelvin saturated liquid 152). Accordingly, the temperature of saturated liquid 156 may drop to 94 degrees Kelvin and/or the pressure of saturated liquid 156 may drop to 5 bar. Accordingly, heater system 180 may be activated to heat saturated liquid 156 (within buffer tank 154) to desired temperature T2 (e.g., 105 degrees Kelvin) and/or to desired pressure P1 (e.g., 10 bar).
Further, as subcooled liquid 152 within component tank 150 is heated to 70 degrees Kelvin (during a fault condition), thermal energy from component tank 150 is conductively transferred to saturated liquid 164 via heat exchange system 162 and pipe/tube assemblies 172, 174. Sensing this increase in temperature, cryostat 178 may be activated to reduce the temperature of saturated liquid 164 (which is present in both heat exchange system 162 and cryostat tank 170) from e.g., 70 degrees Kelvin to the desired temperature T1 (e.g., 67 degrees Kelvin). This recovery process may take hours depending on the excess available cooling power of cryostat 38.
While systems 10, 10′, 10″ are described above a using subcooled and saturated liquid nitrogen, other configurations are possible and are considered to be within the scope of this disclosure. For example, subcooled and saturated liquid helium may be used.
A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other implementations are within the scope of the following claims.
