Sustainability assessment of large-scale storage technologies for surplus electricity using group multi-criteria decision analysis

Power to gas (P2G)-methane, pumped hydroelectric storage (PHES) and compressed air energy storage (CAES) are three methods to store surplus electricity with high capacity and long discharge time. However, there is a few research included P2G-methane in comparing with other storage technologies in general and in terms of sustainability development. This paper explored and compared the cost, efficiency, position flexibility, storage capacity/discharge time, energy carrier vector and environmental issues of those storage technologies in terms of single criterion and group multi-criteria analysis. The single criterion data of each technology was reviewed from literature and compared with each other. The data from single criterion were normalised then used as inputs of the linear additive model. The weights of criteria were determined by sending out the weighting assessment form to 10 researchers. The comparison in terms of cost and efficiency showed that PHES is better than P2G and CAES. And P2G has many benefits such as: conversion of energy vector from electricity to gas which is available for renewable thermal and transport energy; longest storage time; and minimal impact on the environment. From sustainable development strategy perspective, the evaluation results of P2G, PHES and CAES are 4.03, 2.46 and 2.16, respectively. Which means P2G was assessed as preferable.