Advanced energy recovery systems from liquid hydrogen

The realization and connection to the electrical grid of large scale generating plants exploiting renewable sources such as solar or wind can be prevented by problems of grid stability and power management. This problem can be solved by introducing adequately large energy storage systems. One of the most promising and studied technologies for large storage of energy in chemical form is the production of hydrogen by water electrolysis, which can be stored and transported in compressed or liquid form. Liquefaction is a high energy consuming process, but allows higher storage densities and can represent the appropriate solution when large scale hydrogen storage and long range transport is needed. For similar reasons, today, increasing quotas of natural gas are transported in liquid form. Current vaporization systems directly provide heat absorbed from the environment or produced by burning part of the output of gasified fuel. Advanced systems aimed at recovering part of the energy spent for liquefaction of natural gas have been proposed and tested. In this paper, we consider achievable advantages of realizing recovery systems in view of the future use of liquid hydrogen (LH2) as energy vector. The maximum outcomes of ideal thermal systems is evaluated. Then, different gas turbine (GT), magnetohydrodynamic (MHD) generator and combined systems are considered and compared, both with ideal recovery systems and with conventional vaporizing and power generating systems.