Energy return on investment
[5][2] The energy analysis field of study is credited with being popularized by Charles A. S. Hall, a Systems ecology and biophysical economics professor at the State University of New York.
That's mainly because the "energy invested" critically depends on technology, methodology, and system boundary assumptions, resulting in a range from a maximum of 2000 kWh/m2 of module area down to a minimum of 300 kWh/m2 with a median value of 585 kWh/m2 according to a meta-study from 2013.
[16][clarification needed] Conventional sources of oil have a rather large variation depending on various geologic factors.
[17] Due to the process heat input requirements for oil shale harvesting, the EROI is low.
[17] Economically, oil shale might be viable due to the effectively free natural gas on site used for heating the kerogen, but opponents have debated that the natural gas could be extracted directly and used for relatively inexpensive transportation fuel rather than heating shale for a lower EROI and higher carbon emissions.
The weighted average standard EROI of all oil liquids (including coal-to-liquids, gas-to-liquids, biofuels, etc.)
[clarification needed] In a 2010 paper by Murphy and Hall, the advised extended ["Ext"] boundary protocol, for all future research on EROI, was detailed.
In order to produce, what they consider, a more realistic assessment and generate greater consistency in comparisons, than what Hall and others view as the "weak points" in a competing methodology.
[23][24] In the case of photovoltaic solar panels, the IEA method tends to focus on the energy used in the factory process alone.
Net energy describes the amounts, while EROI measures the ratio or efficiency of the process.
One can then use this to calculate the population of the Roman Empire required at its height, on the basis of about 2,500–3,000 calories per day per person.
Falling EROI due to depletion of high quality fossil fuel resources also poses a difficult challenge for industrial economies, and could potentially lead to declining economic output and challenge the concept (which is very recent when considered from a historical perspective) of perpetual economic growth.
[33] A full accounting would require considerations of opportunity costs and comparing total energy expenditures in the presence and absence of this economic activity.
It is in part for these fully encompassed systems reasons, that in the conclusions of Murphy and Hall's paper in 2010, an EROI of 5 by their extended methodology is considered necessary to reach the minimum threshold of sustainability,[22] while a value of 12–13 by Hall's methodology is considered the minimum value necessary for technological progress and a society supporting high art.
This might have an EROI of less than one, but could still be desirable due to the benefits of liquid fuels (assuming the latters are not used in the processes of extraction and transformation).
Calculations are done by summing all of the EROIs for domestically produced and imported fuels and comparing the result to the Human Development Index (HDI), a tool often used to understand well-being in a society.
Frequently in literature harvest factors are reported, for which the origin of the values is not completely transparent.
The bold numbers are those given in the respective literature source, the normal printed ones are derived (see Mathematical Description).
"[4] One of the notable outcomes of the Stanford University team's assessment on ESOI, was that if pumped storage was not available, the combination of wind energy and the commonly suggested pairing with battery technology as it presently exists, would not be sufficiently worth the investment, suggesting instead curtailment.
Many energy technologies are capable of replacing significant volumes of fossil fuels and concomitant green house gas emissions.
Research on the concept was conducted by Centre for Photovoltaic Engineering, University of New South Wales, Australia.
[46][47] The reported investigation establishes certain mathematical relationships for the solar breeder which clearly indicate that a vast amount of net energy is available from such a plant for the indefinite future.
