principle of the energy storage device with compressed air
The compressed air energy storage is based on the physical
principles of hydraulics and pneumatics. The disadvantages of
pneumatics (heat and cold losses) can be largely compensated in
connection with hydraulics. Hydraulic systems have a very high
efficiency of up to 90%.
The storage and provision of energy are based on the same working
principle. During the storage process (compression), the hydraulic
is pumped into several high-pressure cylinders by means of a
pump (hydraulic motor) using electrical energy. The pistons of the
high-pressure cylinders press and compress the air in the storage
up to a pressure of 300 bar. During unloading (decompression), the
high-pressure cylinders filled with oil are charged with the
pressure from the storage pressure tanks. Here, too, the oil drives
hydraulic motor, which in turn drives an electricity generator and
delivers the generated electrical energy to the consumer. In order
achieve continuous operation, several high-pressure cylinders are
in parallel and one behind the other. The parallel arrangement of
cylinders in connection with a corresponding control can compensate
the damaging heat development in compressors during charging and the
cold development leading to icing during unloading.
heat generated when air is compressed is transferred to the cooling
water tank of the system and is therefore not lost in terms of energy.
The heat stored in it can be used e.g. via a heat exchanger for the
heat requirement (domestic water, heating support) outside the system.
Likewise, the physical cold that occurs when the compressed air tanks
are unloaded can be used for cooling outside the system via a cold
The efficiency of electrical energy (electricity) and thermal energy
(heating and cooling) can be optimized and controlled within limits as
required in the system.
By including and using the thermal energy generated during compression
and the cold energy generated during decompression of compressed air,
very high overall efficiency can be achieved for the storage system.
Efficiency levels are shown in this overview (link
Commercially available 80 liter compressed air cylinders, in which the
air is compressed up to 300 bar, serve as storage containers. The
compression of the air by the hydraulic pump can be done with the
appropriate power (max. 20 kW for the pilot) from an external power
source. Power sources can be PV, wind generator or any other power
generator. When discharging the storage tank to generate electricity,
power of 10 kW can be continuously called up by the consumer. Charging
and withdrawal capacities are independent of the amount of energy
The compressed air generated during charging can also be used and fed
in as an energy carrier for use in companies' compressed air networks
(e.g. 10 bar low pressure). It is also possible to operate the system
only as an efficient compressor of compressed air with 50-60%
Another field of application is the compression of gases, in
biogas, which is generated in agricultural biogas plants and has to be
stored until the appropriate time of use. In addition, the highly
compressed gas can also be reused to generate electricity, which can
result in multiple uses. Digester gases in sewage treatment plants can
also be compressed and converted into electricity using this
The purely hydraulic-pneumatic mode of operation eliminates the risk
The stored energy can be called up at any time and without delay.
By providing additional compressed air cylinders, the energy storage
capacity of the system can be scaled as required.
The entire storage system consists of or is based on commercially
available components. The space requirement of the storage system is
approx. 3 square meters.
A pilot system with the functionality described above has been created
and is available for demonstration purposes.
Utility model protection and patents have been applied for for the
compressed air storage system designed here.