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Ballon-Gasspeicher 400 m³ - ARA Zirl |
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GAS HOLDER FOR DIGESTER GAS/BIOGAS
Why do we store digester gas?
The energy stored in the biogas cannot be used directly and
transformed into heat and electric current at all times. For
example the energy demand at night is usually lower as the one in
the daytime. But, of course, the digester gas will be also
generated at night and might be used to supply the higher energy
demand during the day.
But for that purpose storage of the gas is necessary.
Also for the operation of the digester a gas holder might be
necessary. The scum is often removed out of the digester by
opening the scum door: Because of taking out a larger amount of
liquid in this case, gas has to flow back from the gas holder into
the digester to avoid damages caused by a vacuum.
Limits of the digester gas storage
Digester gas is an energy form with a very low energy density. For
comparision:
1 m³ digester gas ≈ 0,6 l fuel oil
Therefore the storage of gas produced excessively in the summer to
supply the higher energy demand in the winter is not feasible for
practical and economic reasons.
Reasonably only the production of one day will be buffered. So the
energy not used at night or during the weekend is able to be
stored and utilized during the day. Especially for sewage plants
which use the gas in a combined heat and power unit this is
recommended. The produced electric energy can be used in the
daytime in far better economic way.
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