Quite a while back we had a discussion of the idea of Energy Return On Energy Invested (EROEI) as a measure of the viability of solar and wind energy. I did the numbers for solar (including battery backup) and came to the conclusion that EROEI was at least 10 and therefore not a problem.
The issue has come up in an email discussion I’ve been having. Thinking about it, I concluded that using a ratio of energy generated to energy invested is incorrect. As a starting point, I assume that we want to consider energy separately from market goods in general. Producing new energy requires inputs of both energy and market goods (including labour and capital). Think about this example
Technology A uses 1 Mwh of energy input and $180 of market inputs to produce 10 MWh of energy output
Technology B uses 1 Mwh of energy input and $600 of market inputs to produce 20 MWh of energy output
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