Tube storage
Tube storage facilities are medium-sized natural gas storage facilities for balancing out fluctuations in demand: They are primarily used to cover daily consumption peaks, as they have high output and feed-in capacities. Due to their rather small volume (normally less than a million cubic meters), they are only suitable to a limited extent for compensating for seasonal fluctuations.
Natural gas tube storage facilities are classed as surface storage facilities, even though they are around two meters deep. They consist of steel or iron tubes with a diameter of up to 1.6 m, which are laid in a parallel meandering shape at a shallow depth and operated at pressures of 50 to 100 bar. Often they are built on the site of industrial plants.
Tube storage tanks are one option for large-scale storage in countries where - as in Switzerland - there are no geological structures suitable for deep underground storage. Compared to these, they are more complex, but have the advantage that the gas is available more quickly and fewer losses occur.
Temperature fluctuations and corrosion protection
The underground installation reduces large temperature fluctuations (day / night), which in the (humid) environment lead to heavy condensation on the iron surface of the pipe outside. Such temperature differences in the storage tank can also arise due to changes in the pressure of the gas - especially when filling (compression = heating) or emptying (with relaxation = cooling ). Since wet iron rusts and does not provide permanent protection for paintwork, the pipes are “cathodically” protected from corrosion on the outside. A “ sacrificial anode ” is buried next to the tubes and connected to the positive pole of a direct voltage, while the negative pole is connected to the tubes. The corrosion is thereby diverted to the anode.
The floor surrounding the storage pipes is used to absorb the heat generated by compressing the gas when the storage unit is charged. This buffering of the temperature rise in the storage tank saves pumping energy. Conversely, when gas is withdrawn from the storage tank, the temperature of the contents drops, then of the pipe, and heat is transferred from the floor to the storage tank.
Economic function of tube storage systems
The most important function of tube storage tanks for natural gas nowadays is the peak shaving. Households use more gas in the morning and in the evening than during the day or at night, and consumption peaks are particularly high on cold days. Since the gas is delivered from the production fields in a relatively constant flow, appropriate storage facilities are required in order to react to these fluctuations in demand and to be able to provide peak gas.
Fluctuations in demand can basically be balanced out with different gas storage facilities. Small, flexible containers such as tubular storage tanks are ideal for daily fluctuations. Storage service providers are able to use tubular storage systems to help municipal utilities and power plants obtain more even gas supplies and thus reduce their gas procurement costs:
“The surplus of reference power from the customer's full supply contract is used to refill the storage tank during the low-load night and midday hours. The load peaks in the morning and in the evening afterwards are capped by gas from the storage facility. Thanks to this compensation within one day, an above-ground storage facility can provide a performance that is adequate to that of a much larger underground storage facility, despite its low storage capacity. "
List of tube memories
Austria
In 2011 Wiener Erdgasspeicher GmbH put a pipe storage facility for natural gas into operation in Vienna-Leopoldau with a geometric storage volume of approx. 15,000 m³. The accumulator is currently operated with a maximum pressure of approx. 45 bar, the output pressure (support pressure) is approx. 4 bar. This means that approx. 675,000 m³ of gas can be stored and a maximum of approx. 600,000 m³ of this can be withdrawn. The extraction rate is up to 100,000 m³ / h.