The isentropic expansion energy of compressed and cryogenic hydrogen

Abstract

CryogenicsOnboard storage a b s t r a c t Pressure is often perceived as the single most important parameter when considering the safety of a storage system, for example when calculating the pneumatic energy that could be released in the event of a sudden accidental failure (or burst energy). In this paper, we investigate the role of temperature as another degree of freedom for minimizing the burst energy. Results are first presented for ideal gases, for which the relationship between burst energy as a function of initial and final volumes, temperature and pressures can be expressed analytically. Similar analysis is then derived for the specific case of H 2 using real gas equations of state. Assuming the expansion is isentropic, which holds for an adiabatic and sudden release as in a burst, it is shown that the energy released during a sudden burst is a weak function of pressure, revealing that the effect of increasing pressure is negligible beyond a certain value (~100 bar); whereas the burst energy is a linear function of temperature. This suggests that temperature controls the burst energy in a much greater way.This analysis is carried out in the frame of onboard H 2 storage systems, for which it is shown that the use of cryogenic temperature for hydrogen vehicles, where risks of collision and impact on the surroundings are high, appears as a safety feature since burst energy is up to 18 times less than room temperature, high pressure storage.

Hydrogen Storage in Cryogenic, Cybernetic, and Catalytic Vessels for Transport Vehicles

“…The CcH2 and CaH2 storage models also present certain limitations and drawbacks, which are mainly related to the cost, maintenance, losses and safety concerns [38][39][40][41][42][43]. A major component of the cost (approximately 75% of the total cost of the pressure vessel) is the carbon fiber composite wrapping of the pressure vessels, which serves as a strong factor for both safety and operating pressure requirements [44][45].…”

“…Mechanical containment: Since the retro-action container delays a huge portion of heat flowing inside the vessel, the internal pressure of the hydrogen storage container is limited. The netting analyses have demonstrated that decreasing the design pressure from 700 bar to 100 bar results in a total vessel mass decrease (composite and liner) by a factor of 2.4 [39][40][41][42][43]. Therefore, the gravimetry of the hydrogen vessels operating at pressures below 150 bar might be over 10%.…”

Electrochemical hydrogen compression and purification versus competing technologies: Part I. Pros and cons

“…According to Petitpas et al [32], the ideal gas law is valid until 100 bar for hydrogen (23 °C). At 23 °C between 100 to 800 bar, the isentropic coefficient γ increases.…”