# CNG station gas storage scale and gas storage volume

The gas storage scale of a CNG station refers to its total gas storage capacity, which is expressed here by the volume (m3) in the base state. Gas storage volume refers to the internal volume of the equipment under working pressure and working temperature, expressed in nominal volume (m3). At present, the general steps for determining the gas storage scale are: first, calculate the gas storage capacity according to the process balance relationship, then determine the effective profit coefficient of the gas storage equipment volume based on the gas extraction type, etc., calculate the gas storage scale, and then calculate the gas storage capacity according to the nominal gas storage equipment The gas storage volume is obtained by rounding the volume series values, and then the final total gas storage capacity is calculated as the gas storage scale.

For different CNG stations, their production and supply are very different. We conduct specific analyses on different supply objects.

#### 1. CNG transport truck

When CNG transport vehicles have no requirements for refueling time, direct charging is generally used. That is, the compressor directly pressurizes the supply. The premise of this model is that the gas supply pipeline network can supply gas to the CNG station in real-time, so gas storage facilities are not required.

When it is necessary to increase the gas supply based on the maximum hourly production capacity of the compressor, gas storage facilities need to be installed. The capacity of gas storage facilities can be determined based on the difference between the supply volume during peak hours and the design hourly production volume of the CNG station, and a time of 1-2 hours can be selected to determine the gas storage volume.

When CNG stations need to quickly charge vehicles, gas storage facilities can also be set up. The required fast charging capacity at this time is the gas storage capacity of the gas storage facility.

Due to the large transportation capacity of CNG transport vehicles, unless a very large gas storage facility is installed, it is generally impossible to fully charge the CNG transport vehicle with fast charging.

In the end, a compressor is required for direct charging, so the fast charging capacity is only the carrying capacity of the CNG transport vehicle. a part of.

We can take a proportional value based on the total volume of CNG transport vehicles that need to be quickly recharged during the same period. The larger the proportional value, the shorter the gas filling time,

but the lower the effective utilization rate of the gas storage facilities, so it is necessary to Comprehensive analysis to determine this ratio.

#### 2. CNG peak shaving station

When a CNG station is used for city gas peak shaving, the gas storage capacity of the CNG station is the peak shaving gas storage capacity. The gas storage capacity at this time needs to be determined based on the needs of the city gas system.

#### 3. CNG filling station

The typical operating cycle of a CNG filling station should be based on the working hours of the maximum supply day. Due to the imbalance of gas supply and production in gas filling stations, rational selection of compressors and production arrangements to make the hourly production volume adapt to the hourly gas supply volume are important means to reduce the capacity of CNG gas storage facilities and increase economy.

For example, a gas filling station is equipped with a 1000m3/h compressor.

##### The gas filling volume and production volume in each period are shown in the following table:
 working hours Air volume (m³) Production volume (m³) Gas filling peak coefficient production peak factor Balance quantity (m³) Cumulative balance volume (m³) 5:00-6:00 30 0 0.05 0.00 -30 -30 6:00-7:00 100 0 0.18 0.00 -100 -130 7:00-8:00 200 300 0.36 0.54 100 -30 8：00-9:00 300 500 0.54 0.90 200 170 9:00-10:00 1000 1000 1.80 1.80 0 170 10:00-11:00 1700 1000 3.06 1.80 -700 -530 11:00-12:00 600 1000 1.08 1.80 400 -130 12:00-13:00 400 700 0.72 1.26 300 170 13:00-14:00 800 500 1.44 0.9 -300 -130 14:00-15:00 1200 1000 2.16 1.8 -200 -330 15:00-16:00 370 500 0.67 0.9 130 -200 16:00-17:00 600 500 1.08 0.9 -100 -300 17:00-18:00 500 500 0.90 0.9 0 -300 18:00-19:00 300 500 0.54 0.9 200 -100 19:00-20：00 200 500 0.36 0.9 300 200 20:00-21:00 400 500 0.72 0.9 100 300 21:00-22:00 1000 1000 1.80 1.8 0 300 22:00-23:00 300 0 0.54 0 -300 0 合计 10000 10000 18 18 0 0

Note: The peak coefficient refers to the ratio of the gas filling volume/production volume in this period to the average gas filling volume/production volume in each period throughout the day.

From the data in the table, it can be seen that the cumulative minimum value of gas filling volume and production volume under normal conditions is -530m3 and the cumulative maximum value is 300m3. Therefore, the gas storage capacity required for this station is 830m3 (baseline state).

CNG filling stations whose gas source is pipeline gas are limited by the gas supply pipeline network and cannot produce during peak civilian periods or gas outage periods. In order to ensure gas filling, the production system needs to be adjusted to the gas storage capacity required after the restriction.

##### As shown in the following table:
 working hours Air volume (m³) Production volume (m³) Gas filling peak coefficient production peak factor Balance quantity (m³) Cumulative balance volume (m³) 5:00-6:00 30 0 0.05 0.00 -30 -30 6:00-7:00 100 0 0.18 0.00 -100 -130 7:00-8:00 200 500 0.36 0.54 300 170 8：00-9:00 300 1000 0.54 0.90 700 870 9:00-10:00 1000 1000 1.80 1.80 0 870 10:00-11:00 1700 1000 3.06 1.80 -700 170 11:00-12:00 600 300 1.08 1.80 -300 -130 12:00-13:00 400 0 0.72 0 -400 -530 13:00-14:00 800 1000 1.44 0.9 200 -330 14:00-15:00 1200 1000 2.16 1.8 -200 -530 15:00-16:00 370 1000 0.67 0.9 630 100 16:00-17:00 600 500 1.08 0.9 -100 0 17:00-18:00 500 0 0.90 0 -500 -500 18:00-19:00 300 0 0.54 0 -300 -800 19:00-20：00 200 500 0.36 0.9 300 -500 20:00-21:00 400 1000 0.72 0.9 600 100 21:00-22:00 1000 1000 1.80 1.8 0 100 22:00-23:00 300 200 0.54 0 -100 0 合计 10000 10000 18 18 0 0

It can be seen from the table that under the same supply system, the cumulative minimum value of the difference between the gas filling volume and the production volume of the adjusted production system is -800m3 and the cumulative maximum value is 870m3. Therefore, the station’s output after the production is limited The required calculated gas storage capacity is 1670m3 (baseline state).

It can be seen that the required calculated gas storage volume is greatly increased due to production constraints due to gas supply.

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