Phase change Materials (PCM) for passive thermal management in compressed hydrogen storage tank
Publication Date: 2016-Jan-19
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Phase change Materials (PCM) for passive thermal management in compressed hydrogen storage tank.
FIELD OF THE INVENTION
This invention relates to the field of compressed hydrogen storage. Compressed hydrogen gas at 700 bars at room temperature is considered today as the practical limit for a passenger car to run for 500 km without refueling. Today storage tanks made of reinforced polymer liners and metallic bottle necks are available commercially. However the long-term stability is an issue due to ageing of the polymer matrix of the liner. In order to support pressures of 700 bars and even higher with practically no permeability of the hydrogen, and to be able to maintain stability of performances in time the quality and time evolution of the polymer should be carefully controlled. As a matter of fact the temperature variation over 80-85°C that are currently obtained during rapid compression of the hydrogen tank are the principal cause of structural variations and ageing of the polymer liner implying an increase of the Hydrogen permeability due to free volume evolution of the polymer matrix.
The solution relates to use a Phase Change Material (PCM) for passive management of temperature variation during the refilling and use (discharging) of Hydrogen tank to the enhancement of the filling rate as well as improving the gas delivery during the use of the hydrogen and at the same time the added PCM will contribute to the protection of the polymer matrix of the liner as the PCM is positioned in the inner part of the bottle in contact with the polymer liner. PCM are materials that undergo phase change (melting and freezing) in the desired temperature range to store and release thermal energy. The PCM materials are selected to intercept the temperature variation for both refilling and discharge processes. Several configurations are considered to implement the PCM materials inside the hydrogen tank using at least two concentric 3D metal envelopes each of which is filled with an adequate PCM material. One of the PCM materials is selected for intercepting the temperature rise during tank refilling process and the other PCM material is selected for controlling the temperature during hydrogen usage (discharge of the tank).
The invention relates to disclosing optimal configurations in terms of PCM materials and their disposal in 3D metal envelopes integrated in the hydrogen storage tank in order to limit the instantaneous temperature increase during the filling and temperature decrease during discharging of compressed hydrogen storage tank by minimizing the added PCM weight to the storage cylinder.
Modern storage tanks can be made with carbon fiber composite materials, which are ultra light with a permeation resistant seamless liner and tough impact resistant reinforced shell. This makes them up to 10 times stronger than steel, allowing them to store hydrogen at pressures in excess of 350 bar, which can be safely used for over 100,000 refill cycl...