Patent Application
20070079891
This invention relates to a system and method for transferring compressed gas from high-pressure storage vessels to a receiving vessel and more particularly to a system and method of controlling the temperature of compressed gas being transferred from one or more high-pressure storage vessels to a receiving vessel.
Cascade filling processes that employ multiple high-pressure storage vessels to charge a lower pressure-receiving vessel are known in the prior art, as exemplified in Borck U.S. Pat. No. 6,779,568. The '568 patent discloses that, for a constant filling time, the peak temperature of the gas in the receiving tank will be lower when a lower pressure storage vessel is used first during the cascade filling process. Thus, the '568 patent teaches controlling the order in which the storage vessels are utilized based on the difference in pressure within those storage banks.
The prior art also teaches that the temperature rise in a receiving tank can be limited by adjusting the filling rate from the high-pressure storage vessels, especially at the start of the filling process when the rate of temperature increases the greatest, as exemplified in Hwang, et al. U.S. Pat. No. 5,901,748 and Togasawa, et al. U.S. Pat. No. 6,598,624.
A further prior art approach for limiting or controlling the temperature rise in a receiving tank is to utilize additional hardware, such as a heat exchanger to cool the flowing gas stream from the high-pressure storage vessels, upstream of the receiving tank. The use of such additional hardware is disclosed in Sugano, et al. U.S. Pat. No. 6,360,793 and Cohen, et al. U.S. Pat. No. 6,619,336.
Although the above prior art disclosures focus on the impact that the filling process has on the receiving tank; none of those disclosures takes into account, or even recognizes the need to take into account, the impact of ambient temperature on the compressed gas within and leaving the compressed gas storage system during the process of filling a receiving tank. For example, at low ambient temperatures (e.g.,0° F.) the impact of isentropic expansion cooling due to the reduction in pressure within the storage system can be significant, as temperature within the gas storage and delivery system can approach the minimum safe operating limit (typically −40° F.).
Based on the limitations of the prior art approaches for storing and transferring compressed gas from high-pressure storage vessels to a lower pressure-receiving vessel a need is believed to exist for an improved system for controlling (e.g., increasing or decreasing) the amount of cooling of the compressed gas to be transferred to a receiving vessel based on ambient temperature conditions. It is to such a system and method that the present invention relates.
In accordance with the system and process of this invention, the operation of a compressed gas storage and delivery system is adjusted based on changes in ambient temperature conditions in order to minimize the impact of isentropic expansion cooling on the storage and delivery system. In particular, this invention has its greatest applicability in a system where compressed gas is being transferred from a series of high-pressure vessels into one or more low-pressure vessels and there is a desire to cool or warm the gas being transferred. More specifically, the invention has its most preferred applicability in the fueling of compressed gas vehicles, such as hydrogen or natural gas vehicles, where it is desirable to supply the vehicles with gas within a certain range of ambient temperature, such as above −20° F. and below 60° F.
A system for controlling the temperature of compressed gas being transferred from one or more high-pressure storage vessels to a receiving vessel in accordance with this invention includes a plurality of high-pressure storage vessels with compressed gas therein and a conduit for receiving the compressed gas from one or more of the plurality of high -pressure storage vessels and being adapted to communicate with a receiving vessel for transferring the compressed gas from said one or more of the plurality of high-pressure storage vessels to said receiving vessel. A plurality of flow-control devices is included in the system for controlling the flow of compressed gas from one or more of the storage vessels to the receiving vessel. A temperature-measuring device is employed for measuring the ambient temperature and a controller regulates the flow-control devices based on the measured ambient temperature to thereby control the storage vessel volume communicating with the receiving vessel from the one or more storage vessels, to thereby control the temperature of the compressed gas being transferred to the receiving vessel.
In the preferred embodiment of this invention a controller regulates the flow -control devices based on the measured ambient temperature by comparing the measured ambient temperature with a preset temperature to thereby control the storage vessel volume communicating with the receiving vessel from one or more high-pressure storage vessels.
In accordance with this invention the parameter being controlled directly in response to the ambient temperature is the storage vessel volume that is placed in flow communication with the receiving vessel to be filled; not the mass or pressure of the gas. However, the mass and pressure of gas transferred to the receiving vessel is effected by the storage volume placed in communication with the receiving vessel during the transfer or filling operation.
In accordance with the broadest aspects of this invention, different arrangements of storage vessels can be employed to establish the desired storage volume in flow communication with the receiving vessel at any given time during the filling operation. For example, a plurality of storage vessels having substantially the same volume can be employed to store the compressed gas, and different numbers of storage vessels can be grouped together under the control of an individual flow-control device. Thus, when it is desired to employ the smallest storage volume to fill the receiving vessel, the flow-control device communicating with the smallest number of storage vessels will be operated. When it is desired to communicate a larger storage volume with a receiving vessel, then the flow -control device that communicates a greater number of the high-pressure storage vessels will be opened to increase the storage vessel volume in communication with the receiving vessel to be filled.
Another approach to regulating the storage vessel volume in communication with a receiving vessel during any desired portion of the filling cycle is to actually employ storage vessels of different volumes and then communicate a desired storage vessel with a receiving vessel through actuation of a corresponding flow-control device, depending upon the storage vessel volume that is to be communicated with the receiving vessel.
Yet another approach permitting the communication of either the same or different storage vessel volumes in communication with a receiving vessel at any desired time during the filling cycle is to provide a plurality of high-pressure storage vessels, each having substantially the same volume, and placing each of those storage vessels in communication with a separate flow-control device upstream of a single, common conduit in flow communication with a receiving vessel to be filled. Thus, when a single flow-control device is opened only one of the high-pressure storage vessels will be in communication with the receiving vessel through the common conduit; when two flow-control devices are opened, two of such high-pressure vessels will be in flow communication with the receiving vessel thereby doubling the storage vessel volume in flow communication with the receiving vessel, etc. This latter arrangement provides substantial versatility in the storage and delivery system by permitting the storage vessel volumes in communication with a receiving vessel to be varied over a wide range during the filling of the receiving vessel. In particular, by selectively maintaining only one high-pressure storage vessel in communication with the receiving vessel at any given time during the filling cycle, the same storage vessel volume will always be communicating with the receiving vessel throughout the entire filling cycle. Alternatively, during different phases of the filling cycle two or more flow-control devices can be opened to thereby communicate two or more of the high-pressure storage vessels with the receiving vessel at any given time, thereby providing a greater storage vessel volume in communication with the receiving vessel at any desired time in the filling cycle.
A method for controlling the temperature of compressed gas being transferred from one or more high-pressure storage vessels to a receiving vessel includes the steps of providing a plurality of high-pressure storage vessels including compressed gas therein; connecting the plurality of high-pressure storage vessels to a receiving vessel so that the compressed gas in one or more of the high-pressure storage vessels can be transferred to the receiving vessel; measuring the ambient temperature and controlling the storage vessel volume in flow communication with the receiving vessel in response to the ambient temperature to thereby control the temperature of the compressed gas being transferred to the receiving vessel.
In a preferred method of this invention the step of controlling the storage vessel volume in flow communication with the receiving vessel in response to the ambient temperature is provided by a controller responsive to the difference between the ambient temperature and a preset temperature.
In one preferred method of this invention the step of controlling the volume of gas being transferred to the receiving vessel is carried out by controlling the number of storage vessels in communication with the receiving vessel as gas is being transferred from the storage vessels to said receiving vessels.
In accordance with another aspect of this invention, the step of controlling the volume of gas being transferred to the receiving vessel during a filling cycle includes the step of changing the number of storage vessels in communication with the receiving vessel during the step of transferring gas to the receiving vessel, whereby different gas storage volumes are in flow communication with the receiving vessel during different portions of the gas transferring operation.
In accordance with another aspect of this invention the step of controlling the volume of gas being transferred to the receiving vessel is carried out by communicating only one storage vessel at a time with the receiving vessel during the entire filling operation.
The invention will be described by way of example with reference to the accompanying drawings, in which:
Referring to
As can be seen in
Still referring to
It should be understood that when each of the banks 28, 30 and 32 of storage vessels is placed in flow communication with receiving vessel 40, the pressure in the storage vessels communicating with the receiving vessel drops as gas flows into the receiving vessel until the pressure in the storage vessels communicating with the receiving vessel equalize with the internal pressure of the receiving vessel. At that point in time the gas flow from the bank(s) of storage vessels communicating with the receiving vessel ends.
As can be seen in
Still referring to
Assuming that the ambient temperature measured by the device 42 is greater than, or higher than the preset temperature in the programmable logic controller (i.e., 10° F.), thereby establishing that the cooling of the gas should be maximized as it is being transferred to the receiving vessel 40, the programmable controller 44 will first open valve 36 to only communicate the storage volume of storage vessel 24 with the receiving vessel 40.
The pressure in the storage vessel 24, by virtue of this vessel constituting the smallest storage volume for delivering compressed gas to the receiving vessel 40, drops to the greatest degree possible in equalizing with the pressure in the receiving vessel, thereby delivering the coldest gas possible by taking maximum advantage of the heat of expansion cooling. Next, the programmable logic controller 44 will open the valve 34 to communicate storage vessels 20, 22 of bank 28 with the receiving vessel 40, and thereafter will open control valve 32 for communicating the three storage vessels 14,16 and 18 of bank 26 with the receiving vessel 40, thereby delivering a lower proportion of the compressed gas to the storage vessel 40 at warmer temperatures.
Alternatively, when the ambient temperature is less than the set point of the programmable logic controller (when it is generally cold), cooling of the gas during the transfer operation is not desirable. Under these conditions, the programmable logic controller 44 is programmed to first open valve 32 to communicate supply vessels 14,16 and 18 of bank 26 with the receiving tank 40. Since the pressure in these latter three cylinders 14,16 and 18 does not drop as much as the pressure did in storage vessel 24 on a warmer day (when the ambient temperature was greater than the preset temperature of the programmable logic controller) to equalize the pressure with that in the receiving vessel, the cooling of the compressed gas due to heat of expansion is minimized.
It should be understood that the programmable logic controller 44 can be programmed to vary the number of valves that are opened at any given time, as well as the order in which those valves are opened, depending upon the desired amount of cooling of the compressed gas being transferred to the receiving tank 40. In particular, the storage and delivery system 10 is designed to be capable of delivering the coldest gas possible to the receiving vessel 40 when the ambient temperature measured by the device 42 is higher than a preset temperature in the programmable logic controller 44, and the cooling of the compressed gas transferred to the receiving tank 40 is desirably minimized when the ambient temperature measured by the device 42 is less than the preset temperature in the programmable logic controller 44.
In particular, the greater the pressure drop that takes place in the supply vessel to equalize with the pressure in the receiving vessel, the greater the cooling affect that is obtained. The greatest pressure drop is achieved by initially delivering compressed gas to the receiving vessel 40 from the smallest available volume storage vessel (i.e., 24) in the storage section 12 of the system.
Referring to
Still referring to
Each of the conduits in which the flow-control valves are included communicates downstream of those flow-control valves with a common feed line 116, and this latter feed line communicates with a supply line 118 for directing the flow of compressed gas from one or more of the storage vessels 104,106,108,110,112 and 114 to a receiving tank or vessel 120.
Still referring to
In accordance with the operation of the storage and delivery system 100, the ambient temperature measured by the temperature measuring device 122 is compared to the preset temperature in the programmable logic controller, and based upon that comparison, the programmable logic controller operates the various control valves 104A, 106A, 108A, 110A, 112A, and 114A in a programmed manner to aid in controlling the temperature of compressed gas being transferred from one or more of the high-pressure storage vessels, 104,106,108,110,112 and 114 to the receiving tank or vessel 120.
For example, assuming that the ambient temperature measured by the device 122 is more than or higher than a preset temperature in the programmed logic controller 124 (10° F for example), indicating that the ambient temperature is warm and that the compressed gas being transferred to the receiving tank or vessel 120 should be cool to its maximum extent, the programmable logic controller is programmed to selectively open each of the valves 104A, 106A, 108A, 110A, 112A and 114A, one valve at a time. In this manner, at any specific time in the gas transferring operation only one of the storage tanks 104,106,108, 110, 112 and 114 will be directing the flow of compressed gas into the receiving tank or vessel 120 to allow the pressure, in a single tank at a time, to equalize with the pressure in the receiving tank or vessel 120. In this mode of operation, the order in which the individual flow-control valves are opened is not important, but it is desirable that only one valve at a time be opened. This provides for the greatest degree of pressure drop in the storage vessels until pressure equalization takes place with the receiving vessel 120, thereby delivering the coldest gas possible by taking maximum advantage of heat of expansion cooling.
It should be understood that the programmable logic controller 124 can be programmed to override the above operating sequence (or any other sequence being carried out), as desired.
However, when the ambient temperature is colder than the set temperature, generally indicating that the ambient temperature is cold and that the compressed gas being transferred from the storage section 102 to the receiving tank or vessel 120 does not require significant cooling, the programmable logic controller 124 can be programmed to open more than one control valve at a time. For example, control valves 104A and 106A can be opened first when the temperature is less than 10° F. but more than 10° F. Another valve (for example, control valve 108A) could be opened if the temperature falls to 0° F. Ultimately, all of the valves can be opened at the same time to minimize heat of expansion cooling at the coldest temperature, e.g., −30° F., for example.
It should be understood that the above disclosed operation of the storage and delivery systems 10 and 100, including the sequence of their operation, can be varied within wide limits. The most important feature in this invention is that the system is designed to control the temperature of compressed gas being transferred from one or more high -pressure storage vessels to a receiving vessel based upon ambient temperature conditions.
A number of modifications can be made within the scope of this invention.
For example, the storage and delivery system 10, rather than employing three separate groups of storage vessels, with each storage vessel having essentially the same volume, can be designed so that each of the groups 26, 28 and 30 is replaced by a single storage vessel, with the storage volume of each vessel differing from the storage volume in every other vessel. For example, the bank 26 vessels 14,16 and 18 could be replaced by a single storage vessel having a storage volume corresponding to the total storage volume provided by the storage vessels 14,16 and 18. Likewise, the storage vessels 20 and 22, constituting the second bank 28 of storage vessels can be replaced by a single storage vessel having a storage volume equivalent to the total storage volume of the vessels 20 and 22. In this embodiment the storage vessel 24 will remain, presenting the desired storage vessel volume to be controlled by the supply valve 36.
The storage and delivery systems of this invention can be employed in a wide variety of applications. In one preferred application the systems can be employed in fueling of compressed gas vehicles such as hydrogen or natural gas vehicles, wherein it is desirable to supply the vehicles with gas within a certain temperature, such as above −20° F. and below 60° F.
Although illustrated and described herein with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention.
