Energy Return (EROI) for Machines and Energy Harvesters

The formula

ER = E_delivered / (E_construction + E_operation + E_{decommissioning})

This follows the lifetime energy return on investment (EROI) protocol of Murphy and colleagues, which sets output boundaries at extraction, processing or end use (Murphy et al., 2011).

The lifecycle denominator is mandatory

Dividing operating output by operating input alone is called conversion efficiency, not Energy Return. For energy harvesters, where the ambient input is free, an operating-only ratio is meaningless.

Where it applies

Energy harvesters powering sensors and edge devices
On-site generation serving a facility
Research on biological power sources

Questions

Is Energy Return the same as efficiency?

No. Efficiency compares output with input during operation. Energy Return includes the energy to build and retire the system.

Sources

Murphy et al., 2011

Keep reading

The five ratiosThe five JL-26 ratios: Decision Yield, Overhead Ratio, Landauer Gap, Energy Return and Autonomy, with their formulas, units and which direction is better.Landauer GapThe Landauer Gap compares the energy per irreversible bit operation with the physical minimum, k_B·T·ln 2: the derivation, units, assumptions and evidence.The five accountsThe five accounts of the Joule Ledger: what each records, how it is measured, and why every joule entering a machine must land in exactly one of them.GlossaryPlain definitions of AI and data-center energy measurement terms, from PUE, WUE and meter points to the Landauer limit, Decision Yield and audit grades.

Take the next step.

The JL-26 Energy Return ratio: energy delivered over lifetime energy invested, with a declared boundary, following the EROI protocol of Murphy et al.

Get the textbook All ratios