Seasonal storage of hydrogen in liquid organic hydrides: description of the second prototype vehicle

Abstract

The MTH-system ( methyl cyclohexane, toluene, hydrogen) has been proposed for the seasonal storage of electricity. It consists of two closed loops: in the outer loop hydrogen is produced by electrolysis of water and later burned to give water again. In the inner loop the hydrogen is combined with toluene to give methyl cyclohexane. In this form the energy can be easily stored, transported and finally used throughout the year. At the moment of end use the hydrogen is liberated by splitting the methyl cyclohexane into hydrogen and toluene, and the toluene is recharged with hydrogen later. The most appropriate application of the seasonally stored hydrogen seems to be its use as fuel for heavy vehicles in combustion engines of fuel cells. The exhaust gas of a combustion engine powered by hydrogen consists of water vapour, N 2 and NO x . There are no emissions of carbohydrates, carbon monoxide, carbon dioxide or dust particles. The system thus constitutes an important contribution to the protection of the environment. The on-board splitting reaction of methyl cyclohexane to toluene and hydrogen as well as its combination with the hydrogen-fueled combustion engine have been realized and investigated in full scale at our institute. In the present paper we describe the results obtained with the second prototype MTH 2 and we sketch the perspectives for the near future.