la tasa de retorno energética y el dilema de las energías renovables

EROI = Quantity of Energy Supplied ÷ Quantity of Energy Used in the Supply Process
  • The units are usually given in BTUs, kWhs or other units available to both energy supplied and used.
  • Quantity of Energy Used in the Supply Process includes: drilling, refining, construction, installation, smelting, operations, maintenance, decommissioning, transportation, roads, manufacture of specialized equipment and chemicals required for extraction
  • Quantity of Energy Supplied includes: electricity, useable heat, power for useful work

There is a minimum EROI, greater than 1, that is required for an energy source to be able to power society (The Energy Collective). “An energy system must produce a surplus large enough to sustain things like food production, hospitals, and universities to train the engineers to build the plant, transport, construct, and all the elements of the civilization in which it is embedded.”

Weißbach calculates that this minimum viable EROI is about 7 for the United States and the European Union. Lower EROIs cannot sustain our society at our level of complexity or our standard of living. So I ask – is a lower EROI fair for a developing country?

It is critical to understand these EROI values when making difficult decisions on energy policy. The many claims that renewables alone, or in the majority, can fuel our future are not consistent with their EROI. America’s present EROI averages about 40. A mix of 50% renewables, 30% fossil and 20% nuclear gives an average EROI of about 25.

I am not sure our economy can survive such a drop in surplus energy.

Energy Returned on Investment, or EROI, with and without energy storage (buffering or load following).  CCGT is combined-cycle natural gas turbine.  Nuclear is conventional Pressurized Water Reactors, fast reactors are several times higher.  Solar CSP is concentrated solar (á la Ivanpah), solar PV is photovoltaic solar cells like on rooftop solar. Energy sources must exceed the economic threshold of about 7 (blue line) in order to yield the surplus energy required to support a modern society. EROI is similar to Energy Returned on Energy Invested (EROEI). After Weißbach (2013)

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