John Morgan's argument (August issue, p. 22) that renewable energy and storage systems need an EROI of about 7 to be viable is clearly nonsense. As long as society is structured around getting its energy from burning fossil carbon -which has an EROI of about 30 at the moment but is dropping steadily as we have to move onto digging up progressively less-accessible fossil carbon - an EROI of 7 may look like the lowest return we can easily live with, but an EROI of 2 could be made to work in a society structured to devoting half its energy (in the strictly thermodynamic sense) to building replacement energy-generation equipment.
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