The disclosure relates to a hydraulic accumulator, in particular in the form of a piston-type accumulator, having a separating element which is arranged in an accumulator housing and separates two fluid chambers from one another in a fluid-tight manner, in particular a closed accumulator chamber comprising a working gas from a liquid chamber comprising an operating liquid such as hydraulic oil, wherein a fluid connector is fluidically connected to one of the fluid chambers, wherein outside the accumulator housing and fixed thereto is an attachment part with a magnetic field generating device which acts on a fluid connection between the fluid connector of the accumulator housing and a fluid connector of the attachment part in such a way that magnetisable particles can be separated in a cleaning manner from the fluid passing through the fluid connection.

An apparatus for determining the position of a movable separation element which is arranged within an accumulator as a separator between a gas space and a fluid space, wherein the determination apparatus comprises at least one pressure sensor for the detection of pressure data, at least one ultrasonic sensor for the detection of ultrasonic data and at least one calculation unit for the evaluation of the data with the aid of which determination apparatus the position of the separation element can be determined.

The invention relates to an external pressure fluid reservoir which has: an interior for receiving a fluid; an external wall to which, during operation, pressure is applied by an external pressure from the external environment and which separates the interior from the external environment in a fluid-tight manner; and a connection, which is provided between the interior and the external environment, for selectively exchanging fluid between the interior and the external environment; wherein the interior is formed by a bulk material filling and the wall is designed such that, during operation, said wall absorbs an external pressure exceeding the pressure in the interior and introduces it into the bulk material filling which in turn supports said wall, in its operating position, against the excess external pressure.

A device for isothermal compression, constant-pressure power generation and physical energy storage includes an air storage tank, a weight, a piston and a piston rod. An inner cavity of the air storage tank is divided into first to third chambers by first and second heat conducting baffles. The piston is arranged in the second chamber. The piston rod has a lower end connected with the piston and an upper end connected with the weight. First and second elastic sealing belts are arranged in the first and third chambers, respectively. The first chamber includes a first water injection port and a first water outlet above the first elastic sealing belt, and the third chamber includes a second water injection port and a second water outlet above the second elastic sealing belt. A bottom of the air storage tank includes an air injection port and a compressed air outlet.