WO2000017568A1 - Dispensing device and method for filling a gas tank with a working gas, notably natural gas - Google Patents

Abstract

The invention relates to a dispensing device for filling a gas tank with a working gas, notably natural gas, comprising a source (1, 2) of working gas, for example in the form of a gas supply network or one or more mobile, exchangeable gas tanks; a storage tank (3) for the working gas; a distribution device (6) for transferring the working gas into a gas tank (7); and a device (4) which during distribution of the working gas from the dynamic gas storage tank (3) keeps the pressure in the dynamic gas storage tank (3) substantially constant by modifying the gas volume (3g) in said storage tank (3).

Description

description

Dispensing system and method for filling a gas tank with a working gas, in particular natural gas

The present invention relates to a dispensing system for filling a gas tank with a working gas, in particular with natural gas, according to the preamble of claim 1, and a method for filling a gas tank with a working gas, in particular with natural gas, according to claim 9.

Vehicles that run on natural gas as fuel are characterized by comparatively low pollutant emissions, which is particularly advantageous for buses in inner-city traffic. Natural gas as a fuel is available almost all over the natural gas distribution network. Other gases such as hydrogen or processed biogas can also be used as fuel.

Special gas filling stations are required to refuel vehicles. Since the specific calorific value of gases, such as natural gas, is comparatively low, the gas from gas filling stations has to be compressed and transferred in non-liquefied form to gas tanks or pressure vessels of motor vehicles. To ensure a maximum vehicle range, the vehicle gas tank should be filled to the maximum permissible operating pressure. Usually, maximum operating pressures of approximately 200 bar are currently assumed for motor vehicles.

6 shows three different concepts for refueling vehicles with compressed gas, as are known from the prior art. Fig. 6a shows schematically the so-called slow fill method, in which the natural gas is taken from the natural gas network 1 with a pressure of typically 0.2 to 50 bar or a gas container, compressed in a compressor 2 to the filling or operating pressure in the gas tank 7 and is transferred into the gas tank 7 via a gas pump 6. The slow fill method is usually used for the slow refueling of vehicles over a period of several hours, for example overnight. Costly high-performance compressors would be required to shorten the refueling time, but would remain unused between refueling processes.

In order to be able to implement gas filling stations of the type of petrol filling stations - i.e. with correspondingly short filling times - gas storage is used in the fast-fill method shown in FIGS. 6b and 6c, in which the compressed gas supplied by the compressor is temporarily stored between the individual refueling processes becomes. The size of the gas storage depends on the number and the chronological sequence of the vehicles to be refueled. In the method according to FIG. 6b, the gas is transferred from the gas storage 18 to the gas tank due to a pressure difference between the gas storage 18 and the gas tank 7. The removal of gas from the gas storage associated with such tank operations according to the overflow principle leads to a reduction in the gas pressure in the gas storage, with the result that, on the one hand, the tanking times become longer and, on the other hand, the gas flow between the gas storage and gas tank comes to a standstill when at a filling process the pressure in the gas tank rises so far that the pressure in the gas storage is reached.

Both such an unreasonable increase in the tanking time and falling below the maximum pressure in the gas tank limit the degree of utilization of the gas storage device, that is to say the ratio of possible gas extraction and maximum gas storage. To make matters worse, when buses are refueled quickly, they are refueled with 10% -15% above the permissible operating pressure of the gas tank, i.e. with 220-230 bar, in order to compensate for the temperature rise that arises and thus the gas expansion in the gas tank.

In order to increase the degree of utilization of the gas storage and to lower it - e.g. for economic reasons - to a lower maximum pressure, e.g. of 250 bar, it was proposed to design the gas storage 18 as a so-called three-bank system, in which the gas storage device 3 comprises individual gas storage devices with which the gas tank 7 is filled in sequence. For refueling, the gas tank is first connected to the first gas reservoir until a pressure of, for example, 130 bar is reached in the gas tank. Then switch to the second gas storage unit until a pressure of 170 bar is reached in the gas tank. The system then switches to the third gas storage unit until the desired final pressure of, for example, 200 bar has been reached in the gas tank. The construction and control of this 3-bank system is comparatively complex. With such a 3-bank system, the degree of utilization of the gas storage can be increased to 35-40% in practice.

In order to ensure a maximum operating pressure in the gas tank in each case, regardless of the form in the gas storage 18, the generic system according to FIG. 6c was proposed in DE 196 50 999 Cl. The gas storage 18, which can also be designed as a one-bank system, is followed by a compressor 11, which compresses the gas to the operating pressure. However, the pressure set of a compressor depends linearly on its upstream pressure. Thus, the throughput of the compressor 11 and thus also the tank time in this system vary depending on the degree of filling or admission pressure of the gas reservoir 18, that is to say in accordance with the vehicles already refueled in a tank cycle. Here too, a comparatively high residual pressure in the gas storage is required to ensure acceptable fueling times. The degree of utilization of the gas store 18 can be increased to approximately 50% to a maximum of 60% in this system. In summary, it can be said that in the fast fill process for refueling vehicles with compressed gas, the gas pressure in the gas storage plays a decisive and limiting role; in terms of tank time, reaching the maximum filling pressure in the gas tank and in relation to the degree of utilization of the gas storage.

The object of the present invention is to develop a generic device or such a method. In particular, the device and the method should enable shorter and calculable tank times, comparable to refueling with liquid fuels, as well as being able to ensure the filling pressure required in the gas tank.

This object is achieved by a dispensing system according to the characterizing part of patent claim 1 and by a method according to patent claim 9. Advantageous further developments are the subject of the subclaims.

Basically, the present invention is based on the idea of using a so-called dynamic gas store for the intermediate storage of gas as the gas store. The gas volume or the volume of a dynamic gas storage that can be used for storing gas can be varied and is changed during the refueling of the gas tank according to the invention so that the pressure of the gas in the gas volume of the dynamic gas storage is kept essentially constant. This measure ensures that essentially a constant amount of compressed gas can be transferred into the gas tank per unit of time. This measure also ensures that, owing to the essentially constant pressure in the gas volume, essentially 100% of the gas volume can be used, irrespective of the size of the gas volume and the amount of gas discharged into the gas tank. Overall, the refueling process is comparable to refueling with a liquid fuel with a constant pumping power. According to the invention, the dispensing system, which optionally includes a gas source for the working gas, a gas storage for the working gas and a delivery device for delivering the working gas to the gas tank, has a device that detects a change in the working gas during the delivery of the dynamic gas storage Volume of gas in the dynamic gas storage essentially keeps the pressure in the dynamic gas storage constant.

No further compressor needs to be arranged after the dynamic gas storage. In this case, the gas in the gas volume of the gas storage device is kept essentially at the operating pressure to be achieved in the gas tank during the delivery of the working gas or fuel gas. If, for example, a change in temperature when transferring the gas to the gas tank is to be compensated for, the pressure in the gas storage device can also be suitably higher. However, a compressor or a compressor unit can also be arranged downstream of the dynamic gas storage in order to suitably compress the gas to the operating pressure in the gas tank. Because of the constant upstream pressure, the throughput of the compressor will be essentially constant according to the invention.

The dynamic gas storage device preferably comprises a pressure fluid volume for receiving a pressure fluid in order to apply a predetermined pressure to the gas in the gas volume, which pressure is selected appropriately. Furthermore, a device is provided in order to supply a suitable amount of pressure fluid to the pressure fluid volume, in particular when the working gas is emitted from the gas volume, or to take it up again, particularly when filling the gas volume with working gas. By suitably changing the pressure fluid volume, gas can be transferred into a gas tank at a constant pressure in a simple manner.

The dynamic accumulator is preferably a hydraulic accumulator. A hydraulic accumulator consists of a container which is subdivided into two chambers by a bladder, a membrane, a freely movable, uncontrolled piston or the like, one chamber having an incompressible pressure fluid and the other is filled with gas. Hydraulic accumulators are used in the prior art for energy storage and energy transmission in hydraulic systems, the hydraulic energy being stored by compressing the gas enclosed in the gas chamber. According to the invention, however, a known hydraulic accumulator is used in reverse; by changing the pressure fluid volume, the gas pressure is kept essentially constant by correspondingly changing the gas volume of the gas reservoir.

The sum of the gas volume and the pressure fluid volume of the dynamic gas storage device is preferably constant or essentially constant. Thus, the amount of the hydraulic fluid supplied or discharged corresponds essentially to the amount of gas at the predetermined pressure, which is removed from the gas volume or supplied for refilling the gas storage device. A variation in the amount of gas supplied to the gas tank per unit of time can thus be achieved in a simple manner via the performance of the device, for example a hydraulic pump. It is advantageous that a relatively short refueling time is achieved in a simple and inexpensive manner by suitable design of the device.

It is advantageous that due to the essentially constant gas pressure in the system behind the dynamic gas storage, the refueling time is independent of the filling level of the gas storage. Rather, it depends on the power with which the device can supply hydraulic fluid to the hydraulic fluid volume.

A gas network connection can be considered as a gas source for supplying the system, provided the gas network provides suitably pre-compressed gas, for example at 50 bar. Mobile and / or interchangeable gas pressure containers, which are connected to the dispensing system, are also suitable as gas sources, particularly for remote gas filling stations without their own gas network connection. However, if the tap system is connected to a gas pipeline network with a relatively low gas pressure, the gas is removed from the The gas network is preferably suitably pre-compressed, the gas pressure after the compression being able to be well above the filling pressure of the gas tank, for example in order to reduce the total volume of the dynamic gas storage.

The device is preferably a hydraulic pump with conventional control in order to add a suitable amount of hydraulic fluid to the hydraulic fluid volume, e.g. B. hydraulic oil, supply or discharge from this.

In a first embodiment, the dispensing system comprises one or more dynamic gas stores, which are either filled with gas directly from a gas source, as mentioned above, or which are connected downstream of a compressor for compressing the gas removed from the gas source. The compressor can be operated continuously or intermittently. During the filling of the gas volume, a connection to a hydraulic fluid or hydraulic reservoir is preferably released, so that the gas volume of the dynamic gas reservoir can increase while displacing hydraulic fluid. To fill the gas tank, the dispensing device or the dispenser releases a connection between the gas volume and the gas tank. Furthermore, the connection between the hydraulic fluid reservoir and the hydraulic fluid volume is preferably blocked and a hydraulic pump for conveying hydraulic fluid or hydraulic fluid into the hydraulic fluid volume is switched on. The hydraulic pump is controlled so that the gas pressure in the gas volume remains essentially constant. Additional hydraulic fluid thus leads to a corresponding increase in the hydraulic fluid volume and a decrease in the gas volume of the dynamic gas storage

The pressure in the gas volume preferably corresponds to the filling pressure of the gas tank. However, if appropriate, the dynamic gas storage can also be designed for a lower gas pressure than is required for the operating pressure of the gas tank. In these cases, the dynamic gas storage is followed by a compressor, which compresses the gas to the filling pressure. This compressor is used according to the invention a constant admission pressure is applied so that the throughput of gas is essentially constant. Thus, according to the invention, a constant gas flow rate per unit of time is guaranteed.

The gas volume of a dispensing system is designed according to the number of vehicles to be refueled in a certain time interval (e.g. peak load / peak hour), the size of their respective gas tanks and the performance of the compressor. For this purpose, several dynamic gas storage devices can be connected in parallel to form a cascade or a bundle, which is considered as a unit by the control of the system, that is to say is simultaneously filled with gas or is used to refuel vehicles. Furthermore, several cascades or bundles can be connected in series in order to refuel via a cascade or a bundle and at the same time fill another cascade or another bundle with compressed gas.

In a further embodiment according to the invention, the dispensing system comprises both dynamic and passive gas stores, that is to say gas stores with an essentially constant gas volume, as are used in single-bank or multi-bank systems. For example, the passive gas storage is connected upstream of the dynamic gas storage. The passive gas storage device can be a one-bank system or a multi-bank system. In this embodiment, the gas from the gas source is continuously or intermittently first transferred to the passive gas storage device and temporarily stored there. At the beginning of a cycle, the gas is then transferred from the passive to the dynamic gas storage. For this purpose, the passive and dynamic gas storage devices are preferably connected to one another via a shut-off valve. The shut-off valve is preferably closed during the delivery of gas from the dynamic gas store into the gas tank, so that the gas is temporarily stored in the passive gas store for the next tank cycle. When the delivery of gas to the gas tank is complete, gas is transferred from the passive gas storage via the then opened shut-off valve into the gas volume of the dynamic gas storage in order to replenish the gas volume of the dynamic gas storage. With this Refilling the gas volume of the dynamic gas storage is drained of pressure fluid in the manner mentioned above and the gas volume of the dynamic gas storage is increased. Before refueling again, the shut-off valve is closed again and the gas in the gas volume of the dynamic gas storage is compressed, if necessary, to the operating pressure of the gas tank or, if appropriate, to a pre-pressure which is matched to a downstream compressor.

The control of the dispensing system can alternatively or alternatively also be carried out in such a way that the upstream gas storage is always filled when this allows the utilization of the dispensing system or the capacity of the compressor, for example even when no gas is being transferred from the dynamic gas storage to the gas tank becomes.

In this embodiment, too, the individual dynamic gas stores of the dispensing system can be bundled into cascades and these can be connected in series in order to enable parallel refueling and refilling from the passive gas store.

In this embodiment, the degree of utilization of the gas storage of the dispensing system depends on the ratio of the geometric volume of passive and dynamic storage and varies between 40% and 100%.

In a further embodiment of the invention, the total number of installed gas stores is divided into two groups, one group being operated as a dynamic gas store and the other group as a passive gas store in normal operation. If a compressor fails, be it an upstream compressor, e.g. to compress the gas from the gas network and pump over into the gas storage, or be it a downstream compressor between the gas storage and gas tank, the other group is also operated as a dynamic gas storage.

If the gas storage group, which is passive in normal operation, precedes the dynamic gas storage group, the operation of the gas storage is as normal in normal operation described in the previous embodiment. If the compressor between the gas line and gas storage fails, the previously passive gas storage group takes over its function. For this purpose, a connecting line between the gas line and this gas storage is activated. The gas then flowing into the gas volume of this gas storage group is compressed to the pressure by the hydraulic device, as required in the downstream dynamic gas storage group, and then over-pumped into it. Whether the performance of the failed compressor can be fully or partially compensated for by the compressor performance of the upstream gas storage group depends on a number of factors, e.g. the percentage of the failed compressor in the total compressor performance, the admission pressure in the gas network, and the Size of the gas volume of the upstream gas storage group and the performance of the hydraulic system.

If the gas storage group, which is passive in normal operation, should be able to replace a downstream compressor in the event of a failure, it is arranged behind this compressor for this purpose. In normal operation, this gas storage group is refilled between two tank processes by the downstream compressor to the filling pressure of the gas tank. During the subsequent refueling process, gas flows from this passive gas storage group into the gas tank until the pressure difference between this gas storage and the gas tank becomes too small. The gas tank is completely filled with gas from the dynamic gas storage via the compressor. If the downstream compressor fails, the previous passive gas storage unit is operated as a dynamic gas storage unit and is therefore coupled to the dynamic gas storage unit group, for example as a further cascade (s) or bundle. This dynamic storage, which has been enlarged in this way, then works in two cycles: after filling by the upstream compressor, the gas in the gas volume is first compressed again from the gas pressure generated by the upstream compressor to the filling pressure of the gas tank which is now required. The vehicles can then be refueled in the second cycle. Here too, the pressure increase to the full filling pressure of the gas tank required in the first cycle only applies if the subsequent switched compressor consists of only one unit. However, if this is a group of compressors in which the failure of a unit is to be secured, the pressure in the gas volume should only be increased to such an extent in the first cycle that the upstream pressure is sufficient so that the remaining compressors can ensure the required cycle time. Another advantage of this arrangement of a gas storage group behind a downstream compressor is that the compressor capacity to be installed can be designed to be lower due to the time span of the compressor work to be performed.

All of the previously described embodiments can be viewed as modules. As such, these modules can be combined as desired with other or the same modules or with individual elements, such as passive or dynamic gas stores, compressors, etc. In particular, all of the above-mentioned embodiments can be combined with a downstream compressor or with one or more downstream gas stores, in particular dynamic gas stores.

In all of the embodiments, the control of the gas storage is carried out in a suitable manner, for example by means of an electronic, programmable control which has the necessary access to the elements of the system.

This control also ensures communication with the control of the dispenser and that of the upstream compressor. The downstream compressor is preferably controlled via the control of the dispenser or a central control unit.

When the volume of pressure fluid is reduced, the pressure fluid contained therein is preferably emptied into a corresponding container and thereby relaxes to the atmospheric pressure. To increase the volume of hydraulic fluid, hydraulic fluid is removed from the container and from the device brought to the pressure level in the dynamic gas storage when pumping into the hydraulic fluid volume. In order to also utilize the energy contained in the hydraulic fluid, a dynamic gas accumulator can be combined with a conventional hydraulic accumulator, as is known from the prior art, in all embodiments.

For this purpose, the hydraulic fluid released by the hydraulic fluid volume of the dynamic gas accumulator when the gas volume is refilled is directed into the hydraulic fluid volume of the hydraulic accumulator with simultaneous compression of a gas volume of the hydraulic accumulator. Conversely, the compressed gas in the hydraulic accumulator is used as an energy source to convey hydraulic fluid from the hydraulic fluid volume of the hydraulic accumulator into the hydraulic fluid volume of the dynamic accumulator when the gas tank is being refueled, so that the gas volume of the dynamic gas accumulator is reduced.

The invention will now be described by way of example and with reference to the accompanying drawings, in which:

1 shows a first embodiment of the invention without (FIG. 1A) and with (FIG.

1B) downstream compressor;

2A shows a further embodiment with a passive and a dynamic

Represents gas storage;

2B shows a further embodiment with a passive and a dynamic

Represents gas storage, wherein the passive gas storage can also be operated as a dynamic gas storage;

3A illustrates another embodiment of the invention in a normal mode of operation with dynamic and passive gas storage; 3B shows the embodiment according to FIG. 3A in a further operating mode, the passive gas reservoir being changed to a dynamic one;

Fig. 4 shows the parallel connection of several dynamic gas stores to one

Represents cascade or an aggregate;

5 shows the series connection of several such cascades according to FIG.

4 represents;

6 shows three examples of gas dispensing systems from the prior art; and

Fig. 7 shows the combination of a dynamic gas storage and a hydraulic

Gas storage device according to the invention for storing the energy of the pressure fluid.

In the figures, the same reference symbols designate the same or equivalent parts or elements. It should be noted that the figures are only schematic drawings in which only the most important valves and elements are drawn.

Figure 1A shows a first embodiment of the invention. The gas is taken from the gas source 1, for example a gas line or a mobile gas container, compressed by the compressor 2 and transferred into the gas volume 3g of the dynamic gas storage 3. In addition to the gas volume 3g, the dynamic gas storage also comprises a pressure fluid volume 3o which is separated from the gas volume 3g by a piston, a membrane or the like. By moving the piston or deforming the membrane, the gas volume 3g and the pressure fluid volume 3ö can be changed continuously. The sum of the two volumes is constant. For filling, hydraulic fluid flows in a first cycle via the shut-off valve 9 in a pressure fluid reservoir 4. The gas volume 3g thus reaches its maximum size. In a second cycle, the shut-off valve 9 is then closed and the gas volume 3g is filled with gas via the compressor 2 until the maximum operating pressure in the dynamic gas reservoir 3 is reached.

To refuel the gas tank, for example a vehicle, the valve 5 or a valve of the dispensing device or dispenser 6 is opened and the connection between the gas volume 3g and the gas tank 7 is released. Then compressed gas flows into the gas tank 7 via the delivery device 6. Via the hydraulic pump 4, hydraulic fluid or hydraulic oil is simultaneously pumped into the hydraulic fluid volume 3ö of the dynamic gas accumulator 3. The output of the hydraulic pump 4 is controlled so that the pressure in the gas volume 3g remains essentially constant. Thus, the volume of hydraulic fluid that is supplied to the hydraulic fluid volume 3ö corresponds to the volume of the gas delivered to the gas tank at the predetermined pressure.

The gas volume 3g can be emptied to a minimum value in order to fill the gas tank 7 of a vehicle. After reaching the minimum value, the control unit interrupts the connection to the gas tank 7. The valve 9 is opened again, so that the hydraulic fluid due to a residual compressed gas in the gas volume 3g or due to the gas flowing in from the compressor 2 from the pressure fluid volume 3ö Gas storage is pressed out. After reaching the maximum gas volume, the dynamic gas storage 3 is available for a new refueling process. If the compressor 2 does not compress the gas to the operating pressure to be achieved in the gas tank 7, the gas in the gas volume 3g is compressed to the operating pressure by increasing the pressure fluid volume 3o before the refueling process.

FIG. 1B shows a further embodiment, in which a further compressor 11 is connected downstream of the dynamic gas storage 3 in order to convert the gas from the gas volume 3g to the compress the operating pressure to be achieved in the gas tank. Because the gas admission pressure of the compressor 11 is kept constant due to the hydraulic pump 4, the amount of gas delivered by the compressor 11 per unit time is essentially constant. The pressure in the dynamic gas storage is correspondingly lower than the operating pressure in the gas tank.

Fig. 2A shows a further embodiment of the invention which comprises a passive gas storage 17, i.e. a gas storage with constant gas volume, and comprises a dynamic gas storage 3. The passive gas storage is a 1-bank gas storage or multi-bank gas storage. The discharge of compressed gas from the gas volume 3g of the dynamic gas storage 3 takes place in the manner as in the embodiments according to FIG. 1.

The interaction between the passive gas store 17 and the dynamic gas store 3 takes place as follows: as long as the gas pressure in the gas store 17 is greater than or equal to the gas pressure required for filling the gas tank 7 in the gas volume 3g of the gas store 3, the valve becomes the valve for filling the gas volume 3g 12 open. When the volume 3g has reached the desired value with regard to the gas quantity and / or pressure, the valve 12 is closed. The gas tank 7 can then be refueled by vehicles from the gas volume 3g in the manner described above. The operating pressure is regulated via the power of the hydraulic pump 4.

If the gas pressure in the passive gas storage 17 is lower than the pressure required to fill the gas tank 7 in the gas volume 3g, then after closing the valve 12, the gas pressure in the gas volume 3g has to be raised to the required pressure, ie to the filling pressure of the gas tank. This is done by pumping hydraulic fluid or hydraulic oil into the hydraulic fluid volume 3ö via the hydraulic pump 4 and thus increasing this volume until the gas pressure has been raised to the required pressure by the corresponding reduction in the gas volume. In the configuration according to FIG. 2A, this is the filling pressure of the gas tank 7. If, on the other hand, a further compressor is connected downstream of the dynamic gas storage unit 3, the required pressure can be selected to be lower, corresponding to a suitable pre-pressure of the compressor. Subsequently, the vehicle can be refueled.

FIG. 2B shows a further embodiment of the invention, in which a further gas store is connected upstream of the dynamic gas store 3. In normal operation, the mode of operation of the gas store 13 corresponds to the mode of operation of the passive gas store 17 in FIG. 2A. The function of the gas storage device 3 corresponds to the description of FIG. 1A.

If the compressor 2 fails, the gas store 13 is operated as a dynamic gas store in order to take over the function of the failed compressor 2 in whole or in part. For this purpose, it is checked in a first cycle whether the amount of gas contained in the gas volume 13g has the pressure that the compressor 2 normally delivers and that is expected from the gas storage device 3. If this is not the case, the hydraulic system is increased by pumping hydraulic fluid into the hydraulic fluid volume 13o and the required gas pressure is built up by correspondingly reducing the gas volume 13g. Once this has been done, the compressor cycle can begin.

Upon request by the gas reservoir 3, the valve 12 is opened and gas is pumped over from the gas volume 13g into the gas volume 3g with the aid of the hydraulic system 4. Then valve 12 is closed and the hydraulic fluid is emptied into the hydraulic fluid reservoir via the valve of the hydraulic system. When the gas volume has reached its maximum in this way, the valve of the hydraulic system 4 is closed and the valve 10 is opened. As a result, gas flows from the gas source into the gas volume 13g. As soon as the pressure equalization is reached here, the valve 10 is closed and via the Hydraulic system 4 compresses the gas in the gas volume 13 g to the required pressure. The next compressor cycle can then begin.

3 shows two modes of operation of a further embodiment of the invention. In the figures, dashed lines indicate elements or connections which are not active in the respective operating mode.

In the normal operating mode shown in FIG. 3A, the first gas storage 3 works as a dynamic gas storage, with a pressure of 160 bar, for example, and the second gas storage 13 as a passive gas storage, i.e. as gas storage with constant gas volume 13g. The gas volume 3g is filled in the manner described above until the maximum volume and a gas pressure of, for example, 160 bar is reached. In addition, in the breaks between two refueling processes, the gas volume 13 g is filled in accordance with the pressure carried by the compressor 16, for example to 200 bar. At the beginning of a refueling process, the gas volume 13g works as a 1-bank system and releases gas into the gas tank 7 via a connecting line which is then open due to the pressure drop between the two gas volumes. The gas tank 7 is filled to the maximum filling pressure in the manner described above by changing the volume of the gas volume 3 g at constant pressure and then recompressing with the aid of the compressor 16.

In the event that, for example, the compressor 16 fails or is switched off, the compressor 16 can be bridged via the connecting line 15, as shown in FIG. 3B. Here, the dispensing system changes to the failure mode of operation shown in FIG. 3B, in which the pressure fluid volume 13o is connected to the hydraulic reservoir via the hydraulic pump 4 and the direct connection, shown in broken lines, between the gas volume 13g and the gas tank 7 is interrupted.

The gas storage device 13 is thus coupled to the gas storage device 3 as a further cascade (s). The processes for this one dynamic gas storage are as follows: The compressor 2 fills the gas volume of the gas storage device from the gas source 1. When this filling process is complete, the hydraulic system 4 compresses the gas in the gas volume to the filling pressure of the gas tank 7. The gas tank 7 of vehicles can then be refueled via the gas pump 6.

FIG. 4 shows the possibility, instead of only a dynamic gas store - as previously shown as preferred in all embodiments - also suitably interconnecting several gas stores and optionally emptying them for filling the gas tank of vehicles.

For this purpose, for example in the basic configuration according to FIG. 1A, the one dynamic gas store 3 is replaced by the parallel connection of several dynamic gas stores 3a, 3b,... 3n shown in FIG. This bundle of dynamic gas accumulators thus formed is controlled as a unit: the compressor 2 fills it as a unit with compressed gas, and for refueling vehicles it is emptied as a unit via the hydraulic system 4 via the fuel dispenser 6.

As shown in FIG. 5, the dispensing system can also comprise a plurality of gas storage cascades 3, 13, 23, ... connected in series, each consisting of a plurality of dynamic gas storage units 3a, 3b, ... 3n etc. connected in parallel.

This division of the gas reservoir into cascades makes it possible to perform the work cycles that normally take place one after the other - such as resting with compressed gas, refueling vehicles and the associated increase in the pressure fluid volume by filling in hydraulic fluid and finally emptying the hydraulic fluid into the hydraulic reservoir with a corresponding enlargement of the gas volume - now run in parallel. For example, the cascade 3 is used at a certain point in time for refueling vehicles, while at the same time the cascade 13 is filled with compressed gas by the compressor 2 and at the same time the cascade 23 is emptied of the pressure fluid. The gas storage cascades shown in FIGS. 4 and 5 can also be mobile units, for example for delivering compressed, processed biogas or hydrogen, which are delivered by a vehicle, for example a low loader, and connected to the dispensing system.

In order to make the best possible use of the energy contained in the hydraulic fluid, one or more dynamic gas accumulators can be combined with a conventional hydraulic accumulator for storing hydraulic fluid or hydraulic oil in all of the previously described embodiments, as shown in FIG. 7.

According to this embodiment, when the compressor 2 has brought the gas volume 3g back to the desired pressure, for example to 230 bar, the pressure in both the dynamic gas accumulator 3 and in the hydraulic accumulator 20 is identical to 230 bar, both in the gas volumes 3g and 20g as well as in the pressure fluid volumes 3ö and 20ö. As soon as the dynamic gas accumulator emits gas from the gas volume of 3 g for refueling, hydraulic fluid pumps 4 hydraulic fluid from 20o to 3o. As intended, the pressure in the dynamic gas reservoir remains constant or essentially constant 230 bar, while it decreases in the hydraulic reservoir 20 parallel to the delivery of gas from the gas volume 3 g. The power required by the hydraulic pump 4 for pumping over hydraulic oil from 20o to 3o at the start of gas delivery from 3g is very low and only reaches its maximum value when the gas volume 3g has reached its minimum. If the pressure in the hydraulic accumulator 20 is reduced to near atmospheric pressure at this point in time, the required pump output has only then reached the value that would be required for the entire removal of gas from the gas volume 3 g if the hydraulic oil was removed from an unpressurized hydraulic oil reservoir . When switching over to refilling the gas volume 3g by the compressor 2, the return valve of the hydraulic system is opened. The hydraulic oil stored in 3ö under a pressure of 230 bar and the refilling of the gas volume 3g also bring up the hydraulic accumulator again a pressure of 230 bar, so that the next tank cycle can begin after the return valve is closed. The gas stored in the gas volume 20g of the hydraulic accumulator can be any technical gas, for example nitrogen.

While the invention has been described above in connection with the refueling of a gas tank with compressed natural gas, it can be used in the same way for any other gases, for example for refueling with compressed, processed biogas, hydrogen and the like. The gas tank is preferably filled to a pressure of approximately 200 bar, with a gas tank capacity of, for example, 80 liters for cars and a few 100 liters for buses or trucks.

Claims

claims 1. Dispensing system for filling a gas tank with a working gas, in particular natural gas, with a gas storage (3) for the working gas and a delivery device (6) to deliver the working gas to the gas tank (7), characterized in that the gas storage one dynamic gas storage (3), wherein a device (4) during the delivery of the working gas from the dynamic gas storage (3) via a change in the gas volume (3g) in the dynamic gas storage (3) the pressure in the dynamic gas storage (3) substantially constant holds. 2. Dispensing system according to claim 1, characterized in that the dynamic gas storage (3) comprises the gas volume (3g) and a pressure fluid volume (3ö), the device (4) when the working gas is released from the gas volume (3g) into the gas tank (7) the hydraulic fluid volume (3ö) of the dynamic gas storage (3) supplies hydraulic fluid to increase the hydraulic fluid volume (3ö) and to keep the working gas at constant pressure, the sum of the gas volume (3g) and the hydraulic fluid volume (3ö) in is essentially constant. 3. Dispensing system according to claim 2, characterized in that the gas source comprises a compressor (2) which is connected upstream of the gas reservoir (3) to compress the working gas to a first pressure in the gas reservoir (3), and / or that the gas reservoir (3) a second compressor (11) is connected downstream, the upstream pressure of which corresponds to the gas pressure in the gas store (3) and which compresses the working gas to the filling pressure in the gas tank (7). 4. Dispensing system according to one of claims 1 to 3, characterized by a passive gas storage (17) which is connected upstream of the gas storage (3) and which is connected to the dynamic gas storage (3g) for supplying working gas, preferably via a shut-off valve (12). 5. Dispensing system according to one of claims 1 to 4, characterized in that the dynamic gas storage (3) is preceded by a second gas storage (13) with a second gas volume (13g) and a second pressure fluid volume (13ö), the gas volumes (3g, 13g) are connected to one another, preferably via a shut-off valve (12), which second gas store (13) can be operated as a dynamic gas store, the second gas store (13) being initially filled with working gas and compressed to a predetermined pressure and then the working gas with the predetermined pressure in the gas volume (3g) of the dynamic gas storage (3) transferred. 6. dispensing system according to one of claims 1 to 4, characterized in that the dynamic gas storage (3) is followed by a second gas storage (13) which can be operated in a normal operating mode as a passive gas storage or in a further operating mode as a dynamic gas storage , In the normal operating mode, the gas tank (7) is filled by overflowing of working gas from the second gas storage (13) and by delivering working gas from the dynamic gas storage (3), which takes place essentially at constant pressure, and in which In another mode of operation, the working gas is alternately discharged or stored by the dynamic gas store (3) or the second gas store (13) or both gas stores (3, 13) are operated in synchronism. 7. Dispensing system according to one of the preceding claims, characterized in that the dynamic and / or the second gas store (3, 13) comprises a number of gas stores connected in parallel, such bundles of gas stores being cascaded in series. 8. Dispenser according to one of claims 2 to 7, characterized in that the device (4) with a hydraulic accumulator (20) is connected to pressurized fluid, which is released by the dynamic gas storage, to store or to provide pressure fluid to the dynamic gas storage. 9. A method for filling a gas tank with a working gas, in particular with natural gas, with the following steps: the working gas is taken from a gas source (1, 2); the working gas is stored in a dynamic gas storage (3); and the working gas is transferred into the gas tank via a delivery device (6), the gas volume of the dynamic gas storage (3) during the delivery of the Working gas from the dynamic gas storage (3) is changed so that the Pressure in the gas reservoir (3) is kept substantially constant. 10. The method according to claim 9, in which for transferring working gas into the gas tank a hydraulic fluid volume (3ö) of the dynamic gas storage (3) is supplied with hydraulic fluid, a device (4) supplying the hydraulic fluid volume (3ö) hydraulic fluid to the hydraulic fluid volume (3rd ) to increase and to keep the working gas essentially at constant pressure, the sum of the gas volume (3g) and the pressure fluid volume (3ö) being kept essentially constant. 11. The method according to claim 9 or 10, wherein the working gas with a compressor (2), which is connected upstream of the gas storage (3), is compressed to a first pressure when it is removed from the gas source (1), and / or at which the working gas for transfer into the gas tank (7) in a second compressor (11), which is connected downstream of the dynamic gas storage, is compressed to the filling pressure in the gas tank (7). 12. The method according to claim 9, in which a passive gas storage device (17), which is connected upstream of the dynamic gas storage device (3), is filled with compressed working gas and in which the compressed working gas is then fed into the dynamic gas storage device (3). is transferred. 13. The method according to claim 9, wherein the working gas is first filled in a second dynamic gas storage (13) which is upstream of the dynamic gas storage (3), then the working gas in the gas volume of the second gas storage (13) to a predetermined pressure compressed and transferred into the gas volume of the dynamic gas storage (3). 14. The method according to claim 9, in which in a normal mode of operation a second gas storage (13), which is connected downstream of the dynamic gas storage (3), is operated as a passive gas storage, in which method the gas tank (7) by overflow of working gas from the Gas volume (13g) of the second gas storage (13) and by delivering working gas from the gas volume of the dynamic gas storage (3), which takes place essentially at constant pressure, is filled and the second gas storage (13) is operated in a further mode of operation as a dynamic gas storage The working gas is alternately discharged or stored by the dynamic gas store (3) or the second gas store (13) or both gas stores (3, 13) are operated in synchronism. 15. The method according to any one of claims 9 to 14, wherein the working gas is stored in a number of parallel and dynamic or / and optionally dynamically or passively operable gas storage (3, 13). 16. The method according to any one of claims 10 to 15, in which hydraulic fluid that is released from the dynamic gas reservoir (3) is temporarily stored in the hydraulic fluid volume of a hydraulic reservoir (20) and in this way buffered hydraulic fluid the hydraulic fluid volume of the dynamic gas reservoir (3) again is supplied to transfer the working gas from the gas volume of the dynamic gas storage (3) into the gas tank (7).