Energy returned on energy invested

Energy returned on energy invested In energy economics and ecological energetics, energy returned on energy invested (EROEI or ERoEI), or energy return on investment (EROI), is the ratio of the amount of usable energy (the exergy) delivered from a particular energy resource to the amount of exergy used to obtain that energy resource.[1][2] It is a distinct measure from energy efficiency as it does not measure the primary energy inputs to the system, only usable energy. Arithmetically the EROEI can be defined as:

.[3] When the EROEI of a source of energy is less than or equal to one, that energy source becomes a net "energy sink", and can no longer be used as a source of energy, but depending on the system might be useful for energy storage (for example a battery). A related measure Energy Store On Energy Invested (ESOEI)is used to analyse storage systems.[4][5] To be considered viable as a prominent fuel or ener gy source a fuel or energy must have an EROEI ratio of at least 3:1.[6][3]

Contents Non-manmade energy inputs Relationship to net energy gain Low carbon power Photovoltaic Wind turbines Economic influence Oil sands Criticism of EROEI Additional EROEI Calculations ESOEI EROEI under rapid growth See also References External links

Non-manmade energy inputs The natural or primary energy sources are not included in the calculation of energy invested, only the human-applied sources. For example, in the case of biofuels thesolar insolation driving photosynthesis is not included, and the energy used in the stellar synthesis of fissile elements is not included for nuclear fission. The energy returned includes only human usable energy and not wastes such as waste heat. Nevertheless, heat of any form can be counted where it is actually used for heating. However the use of waste heat in district heating and water desalination in cogeneration plants is rare, and in practice it is often excluded in EROEI analysis of ener gy sources.

Relationship to net energy gain EROEI and Net energy (gain) measure the same quality of an energy source or sink in numerically different ways. Net energy describes the amounts, while EROEI measures the ratio or ef ficiency of the process.They are related simply by

or

For example, given a process with an EROEI of 5, expending 1 unit of energy yields a net energy gain of 4 units. The break-even point happens with an EROEI of 1 or a net energy gain of 0. The time to reach this break-even point is called energy payback period (EPP) or energy payback time (EPBT).[7][8]

Low carbon power Photovoltaic The issue is still subject of numerous studies, and prompting academic argument. 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 .[9] Regarding output, it obviously depends on the local insolation, not just the system itself, so assumptions have to be made. Some studies (see below) include in their analysis that photovoltaic produce electricity, while the invested energy may be lower grade primary energy. A 2015 review in Renewable and Sustainable Energy Reviews assessed the energy payback time and EROI of solar photovoltaics. In this study, which uses an insolation of 1700/kWh/m²/yr and a system lifetime of 30 years, mean harmonized EROIs between 8.7 and 34.2 were found. Mean harmonized energy payback time varied from 1.0 to 4.1 years.[10] Raugei, Fullana-i-Palmer and Fthenakis found EROEI in the range of 5.9 to 11.8 and 19 to 39 for the major commercial PV types in South European installations.[11] The low range assumes that primary energy and electricity are of the same quality, whereas the high range (19-39) is calculated by converting the electricity output of PV to primary energy as recommended by the IEA PVPS Task 12 [12] Furthermore, Fthenakis determined the EROEI to be as high as 60 for the LCA Methodology Guidelines they contributed to write.

least energy consuming thin-film PV technologyinstallations in the U.S. Southwest.[13]

Wind turbines The EROI of wind turbines depends on invested energy in the turbine, produced energy and life span of a turbine. In the scientific [14] literature EROIs normally vary between 20 and 50.

Economic influence High per-capita energy use has been considered desirable as it is associated with a high standard of living based on energy-intensive machines. A society will generally exploit the highest available EROEI energy sources first, as these provide the most energy for the least effort. This is an example of David Ricardo's best-first principle. Then progressively lower quality ores or energy resources are used as the higher-quality ones are either exhausted or in use, for example, wind turbines positioned in the windiest areas.

In regard to fossil fuels, when oil was originally discovered, it

EROI

Fuel

1.3

Biodiesel

3.0

Bitumen tar sands

about 100 barrels of oil. The

80.0

Coal (United States)

ratio, for discovery of fossil

27.0

Coal (China) [15]

1.3

Ethanol corn

5.0

Ethanol sugarcane

1919 to only 5:1 in the

100.0

Hydro

2010s.[3][28]

35.0

Oil imports 1990

Although many qualities of an

18.0

Oil imports 2005

energy

12.0

Oil imports 2007

8.0

Oil discoveries

20.0

Oil production

the main sources of energy for

10.0

Natural gas 2005

an economy fall that energy

2.6–6.9 (external)

becomes more

1.1–1.8 (net)

took on average one barrel of oil to find, extract, and process

fuels in the United States, has declined steadily over the last century from about 1000:1 in

source

matter

(for

example oil is energy-dense and transportable, while wind is variable), when the EROEI of

difficult

to

Oil shale (surface mining/ex situ)

obtain and its relative price may increase. Since

2.4–15.8 (electric, external)

the

agriculture,

invention humans

of have

1.2–1.6 (electric, net)

Oil shale (in situ)[16][17]

6–7 (thermal, external)

increasingly used exogenous sources of energy to multiply

105

Nuclear (Centrifugal enrichment)[18]

10.0

Nuclear (with diffusion enrichment – Obsolete)[19][20][21]

2000 (estimate)

Dual fluid molten salt – molten lead nuclear[22][23]

sources, which is related to the

30.0

Oil and gas 1970

concept

14.5

Oil and gas 2005

15-25

Solar photovoltaic 2014 (crystalline silicon)[24]

5.0

Shale oil

one of the reasons for the

1.6

Hot water solar collector

collapse of the Western Empire

25.0

Concentrating Solar Electricity[25]

40.0

Wind [26]

that EROEI analysis provides a

9.5

Geothermal (without hot water heating)[27]

basis for the analysis of the rise

32.4

Geothermal (with hot water heating)[27]

human muscle-power. Some historians have attributed this largely to more easily exploited (i.e. higher EROEI) energy of

energy

slaves.

Homer-Dixon[29]

Thomas

argues that a falling EROEI in the Later Roman Empire was

in the fifth century CE. In "The Upside of Down" he suggests

and

fall

Looking

of at

civilisations. the

maximum

extent of the Roman Empire, (60 million) and its technological base the agrarian base of Rome was about 1:12 per hectare for wheat and 1:27 for alfalfa (giving a 1:2.7 production for oxen). 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. It comes out roughly equal to the area of food production at its height. But ecological damage (deforestation, soil fertility loss particularly in southern Spain, southern Italy, Sicily and especially north Africa) saw a collapse in the system beginning in the 2nd century, as EROEI began to fall. It bottomed in 1084 when Rome's population, which had peaked under Trajan at 1.5 million, was only 15,000. Evidence also fits the cycle of Mayan and

Cambodian collapse too. Joseph Tainter[30] suggests that diminishing returns of the EROEI is a chief cause of the collapse of complex societies, which has been suggested as caused by peak wood in early societies. Falling EROEI 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.[31] Tim Garrett links EROEI and inflation directly, based on a thermodynamic analysis of historical world energy consumption (Watts) and accumulated global wealth (US dollars). This economic growth model indicates that global EROEI is the inverse of global inflation over a given time interval. Because the model aggregates supply chains globally , local EROEI is outside its scope.[32]

Oil sands Because much of the energy required for producing oil from oil sands (bitumen) comes from low value fractions separated out by the upgrading process, there are two ways to calculate EROEI, the higher value given by considering only the external energy inputs and the lower by considering all energy inputs, including self generated. See: Oil sands#Input energy[33] "utilized detailed energy production and consumption data reported by oil sands producers from 1970 to 2010 to examine trends in historical energy returns from oil sands extraction. " They argued that by 2010, NERs (net energy returns) from oil sands mining and in situ operations had become significantly more energy efficient since 1970 although the NER remained significantly less efficient than conventional oil production. NERs from the oil sands, grew from "1.0 GJ/GJ in 1970 (entirely from the Suncor mining operation) to 2.95 GJ/GJ in 1990 and then to 5.23 GJ/GJ in 2010."[34]

Criticism of EROEI EROEI is calculated by dividing the energy output by the energy input. However, researchers disagree on how to determine energy input accurately and therefore arrive at different numbers for the same source of energy.[35] In addition, the form of energy of the input can be completely different from the output. For example, energy in the form of coal could be used in the production of ethanol. This might have an EROEI 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). How deep should the probing in the supply chain of the tools being used to generate energy go? For example, if steel is being used to drill for oil or construct a nuclear power plant, should the energy input of the steel be taken into account? Should the energy input into building the factory being used to construct the steel be taken into account and amortized? Should the energy input of the roads which are used to ferry the goods be taken into account? What about the energy used to cook the steelworkers' breakfasts? These are complex questions evading simple answers.[36] A full accounting would require considerations of opportunity costs and comparing total energy expenditures in the presence and absence of this economic activity. However, when comparing two energy sources a standard practice for the supply chain energy input can be adopted. For example, consider the steel, but don't consider the energy invested in factories deeper than the first level in the supply chain. Richards and Watt propose an Energy Yield Ratio for photovoltaic systems as an alternative to EROEI (which they refer to as Energy Return Factor). The difference is that it uses the design lifetime of the system, which is known in advance, rather than the actual lifetime. This also means that it can be adapted to multi-component systems where the components have dif ferent lifetimes.[37] Another issue with EROI that many studies attempt to tackle is that the ener gy returned can be in different forms, and these forms can have different utility. For example, electricity can be converted more efficiently than thermal energy into motion, due to electricity's lower entropy.

Additional EROEI Calculations There are three prominent expanded EROEI calculations, they are point of use, extended and societal. Point of Use EROEI expands the calculation to include the cost of refining and transporting the fuel during the refining process. Since this expands the bounds of the calculation to include more production process EROEI will decrease.[3] Extended EROEI includes point of use expansions as

well as including the cost of creating the infrastructure needed for transportation of the energy or fuel once refined.[38] Societal EROI is a sum of all the EROEIs of all the fuels used in a society or nation. A societal EROI has never been calculated and researchers believe it may currently be impossible to know all variables necessary to complete the calculation, but attempted estimates have been made for some nations. Calculations done by summing all of the EROEIs 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.[39] According to this calculation, the amount of energy a society has available to them increases the quality of life for the people living in that country and countries with less energy available also have a harder time satisfying citizens’ basic needs.[40] This is to say that societal EROI and overall quality of life are very closely linked.

ESOEI ESOEI (or ESOIe) is used when EROEI is below 1. "ESOIe is the ratio of electrical energy stored over the lifetime of a storage device to the amount of embodied electrical ener gy required to build the device."[5] Storage Technology

ESOEI[5]

Lead acid battery

5

Zinc bromide battery

9

Vanadium redox battery

10

NaS battery

20

Lithium ion battery

32

Pumped hydroelectric storage

704

Compressed air energy storage 792

EROEI under rapid growth A related recent concern is energy cannibalism where energy technologies can have a limited growth rate if climate neutrality is demanded. Many energy technologies are capable of replacing significant volumes of fossil fuels and concomitant green house gas emissions. Unfortunately, neither the enormous scale of the current fossil fuel energy system nor the necessary growth rate of these technologies is well understood within the limits imposed by the net energy produced for a growing industry. This technical limitation is known as energy cannibalism and refers to an effect where rapid growth of an entire energy producing or energy efficiency industry creates a need for energy that uses (or cannibalizes) the energy of existing power plants or production plants.[41] The solar breeder overcomes some of these problems.A solar breeder is a photovoltaic panel manufacturing plant which can be made energy-independent by using energy derived from its own roof using its own panels. Such a plant becomes not only energy selfsufficient but a major supplier of new energy, hence the name solar breeder. Research on the concept was conducted by Centre for Photovoltaic Engineering, University of New South Wales, Australia.[42][43] 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.[44] The solar module processing plant at Frederick, Maryland[45] was originally planned as such a solar breeder. In 2009 the Sahara Solar Breeder Projectwas proposed by the Science Council of Japan as a cooperation between Japan and Algeria with the highly ambitious goal of creating hundreds of GW of capacity within 30 years.[46] Theoretically breeders of any kind can be developed. In practice, nuclear breeder reactors are the only large scale breeders that have been constructed as of 2014, with the 600 MWe BN-600 and 800 MWe BN-800 reactor, the two largest in operation.

See also Embodied energy Emergy Energy balance Energy cannibalism

Exergy useful energy Jevons paradox — 1880s observation of the efficiency effect multiplier Khazzoom-Brookes Postulate— 1980s updating of Jevons paradox Cost of electricity by source— levelized cost of energy Social metabolism

References 1. Murphy, D.J.; Hall, C.A.S. (2010). "Year in review EROI or energy return on (energy) inves ted". Annals of the New York Academy of Sciences. 1185: 102–118. Bibcode:2010NYASA1185..102M (http://adsabs.harvard.edu/abs/2010N YASA1185..102M). doi:10.1111/j.1749-6632.2009.05282.x(https://doi.org/10.1111%2Fj.1749-6632.2009.05282.x) . 2. Cutler, Cleveland (2011-08-30)."Energy return on investment (EROI)"(http://www.eoearth.org/article/Energy_return_ on_investment_(EROI)). The Encyclopedia of Earth. Retrieved 2011-09-02. 3. Hall, CA; Lambert, JG; Balogh, SB (2013). "EROI of dif ferent fuels and the implications for society".Energy Policy: 141–52. doi:10.1016/j.enpol.2013.05.049(https://doi.org/10.1016%2Fj.enpol.2013.05.049) . 4. "Why energy storage is a dead-end industry - Energy Storage Report"(http://energystoragereport.info/eroi-energy-re turn-on-investment-energy-storage/). 15 October 2014. 5. http://pubs.rsc.org/en/content/articlepdf/2013/ee/c3ee41973h 6. Atlason, R; Unnthorsson, R (2014). "Ideal EROI (energy return on investment) deepens the understanding of energy systems". Energy: 241–45. doi:10.1016/j.energy.2014.01.096 (https://doi.org/10.1016%2Fj.energy.2014.01.096). 7. Marco Raugei, Pere Fullana-i-Palmer and V asilis Fthenakis (March 2012)."The Energy Return on Energy Investment (EROI) of Photovoltaics: Methodology and Comparisons with Fossil Fuel Life Cycles" (http://www.bnl.go v/pv/files/pdf/241_Raugei_EROI_EP_revised_II_2012-03_VMF .pdf) (PDF). http://www.bnl.gov/. Archived (https://ww w.webcitation.org/6XM2qJbIf?url=http://www .bnl.gov/pv/files/pdf/241_Raugei_EROI_EP_revised_II_2012-03_VMF.p df) (PDF) from the original on 28 March 2015.External link in |website= (help) 8. Ibon Galarraga, M. González-Eguino, Anil Markandya (1 January 2011). "Handbook of Sustainable Energy"(https://b ooks.google.com/books?id=N6rVrxV2ujMC&dq=Energy+payback+period&source=gbs_navlinks_s) . Edward Elgar Publishing. p. 37. ISBN 0857936387. Retrieved 9 May 2017 – via Google Books. 9. Dale, M.; et al. (2013). "Energy balance of the global photovoltaic (PV) industry -- is the PV industry a net electricity producer?. In". Environmental Science and Technology. 47 (7): 3482–3489. Bibcode:2013EnST...47.3482D (http://ad sabs.harvard.edu/abs/2013EnST...47.3482D). doi:10.1021/es3038824 (https://doi.org/10.1021%2Fes3038824). 10. Bhandari; et al. (2015). "Energy payback time (EPBT) and energy return on energy invested (EROI) of solar photovoltaic systems: A systematic review and meta-analysis . In". Renewable and Sustainable Energy Reviews. 47: 133–141. doi:10.1016/j.rser.2015.02.057 (https://doi.org/10.1016%2Fj.rser.2015.02.057). 11. "Raugei M., Fullana-i-Palmer P., Fthenakis V., The energy return on energy investment (EROI) of photovoltaics: Methodology and comparisons with fossil fuel life cycles. Energy Policy 45, 576-587, 2012". Energy Policy. 45: 576– 582. doi:10.1016/j.enpol.2012.03.008(https://doi.org/10.1016%2Fj.enpol.2012.03.008) . 12. "Fthenakis V., R. Frischknecht, M. Raugei, H. C. Kim, E. Alsema, M. Held and M. de Wild-Scholten, 2011, Methodology Guidelines on Life Cycle Assessment of Photovoltaic Electricity , 2nd edition, International Energy Agency, Report IEA-PVPS T12-03:2011, November 2011" (http://www.iea-pvps.org/). 13. "Fthenakis V., PV Energy ROI Tracks Efficiency Gains, Solar Today, American Solar Energy Society, 26(4), 24-26, 2012" (http://www.clca.columbia.edu/7B_SolarToday%20June12_c.pdf)(PDF). 14. Zimmermann (2013). "Parameterized tool for site specific LCAs of wind energy converters". The International Journal of Life Cycle Assessment. 18: 49–60. doi:10.1007/s11367-012-0467-y(https://doi.org/10.1007%2Fs11367-0 12-0467-y). 15. Hu; et al. "Energy Return on Investment (EROI) of china's conventional fossil fuels: Historical and future trends" (http s://www.sciencedirect.com/science/article/abs/pii/S036054421300100X). 16. University of Utah Institute for Clean and Secure Energy (November 6, 2013). "Clean and Secure Energy from Domestic Oil Shale and Oil Sands Resources"(https://www.netl.doe.gov/File%20Library/Research/Oil-Gas/enhance d%20oil%20recovery/fe0001243-qpr-jul-sept-2013.pdf)(PDF). 17. Cleveland, Cutler J.; O'Connor, Peter A. (2011). "Energy Return on Investment (EROI) of Oil Shale"(http://www.mdp i.com/2071-1050/3/11/2307/pdf). University of Utah Institute for Clean and Secure Energy . Sustainability.

18. Weissbach, D.; et al. (April 6, 2013). "Energy intensities, EROIs, and energy payback times of electricity generating power plants" (http://festkoerper-kernphysik.de/Weissbach_EROI_preprint.pdf) (PDF). 19. "Paducah enrichment plant to be closed"(http://www.world-nuclear-news.org/ENF_Paducah_enrichment_plant_to_b e_closed_2805132.html). www.world-nuclear-news.org. Retrieved 2015-12-04. 20. Wald, Matthew L. (2013-05-24)."USEC to Shut Uranium-Enrichment Plant in Kentucky"(https://www.nytimes.com/2 013/05/25/business/usec-to-shut-uranium-enrichment-plant-in-kentucky .html). The New York Times. ISSN 03624331 (https://www.worldcat.org/issn/0362-4331). Retrieved 2015-12-04. 21. "Paducah Site | Department of Energy"(https://energy.gov/pppo/paducah-site). energy.gov. Retrieved 2015-12-04. 22. "Institute for Solid-State Nuclear Physics"(http://festkoerper-kernphysik.de/dfr_eco). 23. "DFR – The Dual Fluid Reactor"(http://www.daretothink.org/dfr-the-dual-fluid-reactor/). 26 March 2014. 24. "Re-assessment of net energy production and greenhouse gas emissions avoidance after 40 years" (https://www.nat ure.com/articles/ncomms13728). 25. Burkhardt, J.; et al. "Life Cycle Assessment of a Parabolic Trough Concentrating Solar Power Plant and the Impacts of Key Design Alternatives"(https://pubs.acs.org/doi/pdf/10.1021/es1033266) . 26. "Karl R. Haapala; Preedanood Prempreeda. Comparative life cycle assessment of 2.0 MW wind turbines". International Journal of Sustainable Manufacturing . 45. doi:10.1504/IJSM.2014.062496(https://doi.org/10.1504%2FI JSM.2014.062496). 27. Atlason, R.S.; Unnthorsson, R. (1 March 2013)."Hot water production improves the energy return on investment of geothermal power plants"(https://www.researchgate.net/publication/257176671_Hot_water_production_improves_th e_energy_return_on_investment_of_geothermal_power_plants) . Energy. 51: 273–280. doi:10.1016/j.energy.2013.01.003 (https://doi.org/10.1016%2Fj.energy.2013.01.003). 28. Hall, Charles A.S. "EROI: definition, history and future implications"(http://www.esf.edu/efb/hall/talks/EROI6a.ppt) (PowerPoint). Retrieved 2009-07-08. 29. Homer-Dixon, Thomas(2007). The Upside of Down; Catastrophe, Creativity and the Renewal of Civilisation (https:// books.google.com/books?id=rvk6tsE4UDcC). Island Press. ISBN 978-1-59726-630-7. 30. Tainter, Joseph (1990). The Collapse of Complex Societies(https://books.google.com/books?id=M4H-02d9oE0C&pri ntsec=frontcover). Cambridge University Press. ISBN 052138673X. 31. Morgan, Tim (2013). Life After Growth. Petersfield, UK: Harriman House.ISBN 9780857193391. 32. Garrett, T. J. (2012). "No way out? The double-bind in seeking global prosperity alongside mitigated climate change". Earth System Dynamics. 3: 1. Bibcode:2012ESD.....3....1G (http://adsabs.harvard.edu/abs/2012ESD.....3....1G) . doi:10.5194/esd-3-1-2012 (https://doi.org/10.5194%2Fesd-3-1-2012). 33. Brandt 2013 34. Brandt, A. R.; Englander, J.; Bharadwaj, S. (2013). "The energy efficiency of oil sands extraction: Energy return ratios from 1970 to 2010".Energy. 55: 693. doi:10.1016/j.energy.2013.03.080 (https://doi.org/10.1016%2Fj.energy.2 013.03.080). "Current oil sands operations have mine mouth NERs (net energy returns) of about 6 GJ output per GJ of energy consumed and point of use energy returns of about 3 GJ/GJ." 35. Mason Inman. Behind the Numbers on Energy Return on Investment(https://www.scientificamerican.com/article/eroi -behind-numbers-energy-return-investment/). Scientific American, April 1, 2013. Archive (https://web.archive.org/we b/20171223202459/https://www.scientificamerican.com/article/eroi-behind-numbers-energy-return-investment/) 36. Richards, Michael; Hall, Charles (2014)."Does a Change in Price of Fuel Affect GDP Growth? An Examination of the US Data from 1950–2013"(http://www.mdpi.com/1996-1073/7/10/6558/htm). Energies. 7: 6558–6570. doi:10.3390/en7106558 (https://doi.org/10.3390%2Fen7106558). 37. Richards, B.S.; Watt, M.E. (2006). "Permanently dispelling a myth of photovoltaics via the adoption of a new net energy indicator" (http://www.inference.phy.cam.ac.uk/sustainable/refs/solar/Myth.pdf)(PDF). Renewable and Sustainable Energy Reviews. 11: 162–172. doi:10.1016/j.rser.2004.09.015 (https://doi.org/10.1016%2Fj.rser.2004.0 9.015). 38. Hall CA, Lambert JG, Balogh SB. 2013. EROEI of dif ferent fuels and the implications for society . Energy Policy. 141– 52 39. Lambert JG, Hall CA, Balogh S, Gupta A, Arnold M. 2014. Energy , EROI and quality of life. Energy Policy . 40. Lambert JG, Hall CA, Balogh S, Gupta A, Arnold M. 2014. Energy , EROI and quality of life. Energy Policy . 153–67 & Arvesen A, Hertwich EG. 2014. More caution is needed when using life cycle assessment to determine energy return on investment (EROI). Energy Policy. 1–6

41. Pearce, J.M. (2008). "Limitations of Greenhouse Gas Mitigation T echnologies Set by Rapid Growth and Energy Cannibalism" (https://web.archive.org/web/20090817071517/http://www .climate2008.net/?a1=pap&cat=1&e=61). Klima. Archived from the original (http://www.climate2008.net/?a1=pap&cat=1&e=61) on 2009-08-17. Retrieved 2011-04-06. 42. "The Azimuth Project: Solar Breeder"(http://www.azimuthproject.org/azimuth/show/Solar+breeder). Retrieved 2011-04-06. 43. Lindmayer, Joseph (1978). The solar breeder. Proceedings, Photovoltaic Solar Energy Conference, Luxembourg, September 27–30, 1977. Dordrecht: D. Reidel Publishing. pp. 825–835.Bibcode:1978pvse.conf..825L (http://adsab s.harvard.edu/abs/1978pvse.conf..825L). ISBN 9027708894. OCLC 222058767 (https://www.worldcat.org/oclc/2220 58767). 44. Lindmayer, Joseph (1977). The Solar Breeder (https://www.researchgate.net/publication/23885550_Solar_breeder_ Energy_payback_time_for_silicon_photovoltaic_systems) . NASA. 45. "The BP Solarex Facility Tour in Frederick, MD" (http://scodpub.wordpress.com/2010/03/29/2003-bp-solarex-tour/) . Sustainable Cooperative for Organic Development . Retrieved 28 February 2013. 46. Koinuma, H.; Kanazawa, I.; Karaki, H.; Kitazawa, K. (Mar 26, 2009),Sahara solar breeder plan directed toward global clean energy superhighway, Science Council of Japan

External links World-Nuclear.org, World Nuclear Association study on EROEIwith assumptions listed. Web.archive.org, Wayback Archive of OilAnalytics.org, "EROIas a Measure of Energy Availability" EOearth.org, Energy return on investment (EROI) EOearth.org, Net energy analysis H2-pv.us, Essay on H2-PV Breeder Synergies Retrieved from "https://en.wikipedia.org/w/index.php?title=Energy_returned_on_energy_invested&oldid=868696016 " This page was last edited on 13 November 2018, at 21:12(UTC). Text is available under theCreative Commons Attribution-ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of theWikimedia Foundation, Inc., a non-profit organization.