Economic analysis of the seasonal storage of electricity with liquid organic hydrides

A future alternative for generating winter electricity is the seasonal storage of surplus summer electricity in the form of chemically bound hydrogen in liquid organic hydrocarbons using the MTH-system (Methylcyclohexane–Toluene–Hydrogen). This paper compares the economics of the MTH-system with the conventional production of electricity from fossil fuel sources. Based on numerical modelling of the individual plants, simulations of several design alternatives of the MTH-system were performed for 1000 GWh of stored summer electricity and 80 MW output. The overall efficiencies ηtot and the economic results of these simulations are ηtot=0.40 and 0.26 $/kWh for the MTH-SOFC system alternative, ηtot=0.33 and 0.30 $/kWh for the MTH-MCFC and ηtot=0.25 and 0.36 $/kWh for the MTH-system with gas and steam turbines. Compared with the cost of electricity production using fossil fuels (0.05–0.1 $/kWh), the electricity produced by the MTH-system is expensive. Therefore an economic comparison including an assumed carbon tax was made to account for a possible scarcity of energy or the environmental impact due to the use of fossil energy resources. It concludes that the MTH-system is not competitive for the levels of carbon tax under discussion, but compares with options for providing electricity from new renewables. Due to the disparities in economics and carbon taxes, a best case study of the MTH-system was made to reduce its economic disadvantages. This results in a maximum efficiency of the MTH-system of 0.48 with corresponding winter electricity costs of 0.17 $/kWh.