Energy Return On Energy Invested

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Energy is required in building, operating, maintaining and eventual decommissioning any power generating plant. As long as the plant generates more energy in its lifetime than it consumes it will provide a surplus for useful purposes. The greater the surplus the more it allows society to provide other goods and services – to grow food, to build, heat and cool homes and workplaces, run water and sewerage services, provide education, health care, transport, recreation etc – besides building, maintaining and decommissioning its energy generators. The ratio of energy generated to energy consumed is known as Energy Return On Energy Invested (EROEI or EROI) and it is estimated that for a modern civilisation to function the EROEI of its energy supplies in aggregate must be in the region of 10 or more.

Even an EROEI less than unity – a system that consumes more energy than it produces – may be useful if it provides services such as storing energy for use when and where it is needed but unavailable, such as to supply energy when demand temporarily exceeds supply, or to convey energy from fixed generators to electric vehicles. However the overall, aggregate, EROEI of the system of generators and storage systems must still be high enough to allow for a functioning civilisation.

There is further discussion of ERoEI in the Wikipedia article, and in Euan Mearns' article ERoEI for Beginners on his Energy Matters blog (with many more references in the comments section).

Justin Bowles gives a discussion from an economist's perspective in "One Reason We Struggle to Grow: Energy Return on Investment (EROI)" on his Risk and Well-Being blog.

Both Euan Mearns and Justin Bowles credit Professor Charles Hall as "the father of EROI". Hall was one of the speakers at the 3rd Science and Energy Seminar at Ecole de Physique des Houches in March 2016 where he gave a talk on EROI: Ecological, anthropological and industrial perspective (slides)


Stanford scientists calculate the carbon footprint of grid-scale battery technologies

Stanford scientists have developed a novel way to calculate the energetic cost of building large batteries and other storage technologies for the electrical grid.

Solar energy in the context of energy use, energy transportation and energy storage David MacKay; Philosophical Transactions of the Royal Society

In a decarbonized world that is renewable-powered, the land area required to maintain today's British energy consumption would have to be similar to the area of Britain.

The Energy Return of Solar PV Euan Mearns; Energy Matters; 9 May 2016

A new study by Ferroni and Hopkirk estimates the ERoEI of temperate latitude solar photovoltaic (PV) systems to be 0.83.

The Energy Return of Solar PV – a response from Ferroni and Hopkirk Euan Mearns; Energy Matters; 20 May 2016

Last week’s post on The Energy return of Solar PV caused quite a stir. Yesterday I received a response to some of the comments from Ferroccio Ferroni and Robert Hopkirk addressing some of the queries raised by readers. Their response is given below the fold. But first I have a few comments to add.

Energy payback time (EPBT) and energy return on energy invested (EROI) of solar photovoltaic systems: A systematic review and meta-analysis Khagendra P. Bhandari, Jennifer M. Collier, Randy J. Ellingson, Defne S. Apul; Renewable and Sustainable Energy Reviews; 28 Feb 2015

There is a fast growing interest in better understanding the energy performance of PV technologies as evidenced by a large number of recent studies published on this topic. The goal of this study was to do a systematic review and a meta-analysis of the embedded energy, energy payback time (EPBT), and energy return on energy invested (EROI) metrics for the crystalline Si and thin film PV technologies published in 2000–2013. A total of 232 references were collected of which 11 and 23 passed our screening for EPBT/EROI and embedded energy analysis, respectively. Several parameters were harmonized to the following values: Performance ratio (0.75), system lifetime (30 years), insolation (1700 kWh m2 yr1), module efficiency (13.0% mono-Si; 12.3% poly-Si; 6.3% a:Si; 10.9% CdTe; 11.5% CIGS). The embedded energy had a more than 10-fold variation due to the variation in BOS embedded energy, geographical location and LCA data sources. The harmonization narrowed the range of the published EPBT values. The mean harmonized EPBT varied from 1.0 to 4.1 years; from lowest to highest, the module types ranked in the following order: cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), amorphous silicon (a:Si), poly-crystalline silicon (poly-Si), and mono-crystalline silicon (mono-Si). The mean harmonized EROI varied from 8.7 to 34.2. Across different types of PV, the variation in embedded energy was greater than the variation in efficiency and performance ratio suggesting that the relative ranking of the EPBT of different PV technology today and in the future depends primarily on their embedded energy and not their efficiency.

The Destruction of Scottish Power Posted on January 6, 2016 by Euan Mearns

How Long Does It Take to Pay Off a Tesla Powerwall?

The ERoEI of Mining Uranium Euan Mearns; Energy Matters; 21 Feb 2018

In 2009, in the comments to this post on The Oil Drum we stumbled upon a mine of information on the operation of the Rossing uranium mine in Namibia. The data table provided numbers for the amount of energy used on site together with the amount of uranium mined. This provided an opportunity to calculate the energy return of the mining operation. Simply put ERoEI = energy contained in the U / the energy used to mine and refine it. There are some complexities but back then I calculated an ERoEI of 1200:1 The data has been updated and fresh calculations are presented below.

Kite generator / high altitude

The ERoEI of High Altitude Wind Power Euan Mearns; Energy Matters; 29 Jun 2016 For several weeks I have been researching and writing a review post on high altitude wind power. It has grown into a 6000 word monster that should hopefully fly on Monday. While doing this it has been difficult to find time to write other posts. Hence this is a preview of one section on Energy Return on Energy Invested (ERoEI) which makes a nice post in its own right. KiteGen have presented a back of the envelope style ERoEI calculation for their 3 MW stem indicating a value of 562 which is incredibly high. I have done my own calculation using a variant of their methodology and my own input variables. The idea is to try and estimate the energy intensity of a wind turbine structure and to interpolate that into a KiteGen stem. This involves making many weak assumptions but should be good for arriving at a ball park number.


Negative Electricity Prices Are Not A Sign Of Renewable Success Michael Lynch; Forbes; 19 Feb 2016

Advocates of wind and solar power often point to low or negative prices for electricity in wholesale markets with a heavy reliance on those sources as representing success, but this reflects their ignorance of the utility system and basic economics and is misleading as to the true cost of power from these sources.
a report from Der Spiegel in September 2013: “For society as a whole, the costs have reached levels comparable only to the euro-zone bailouts. This year, German consumers will be forced to pay €20 billion ($26 billion) for electricity from solar, wind and biogas plants — electricity with a market price of just over €3 billion.”
In Texas, problems caused by excess windpower were reduced by construction of $7 billion worth of new transmission lines

Germany's Energy Poverty: How Electricity Became a Luxury Good staff; Der Speigel; 4 Sep 2013

Germany's agressive and reckless expansion of wind and solar power has come with a hefty pricetag for consumers, and the costs often fall disproportionately on the poor


Energy Analysis of Power Systems (World Nuclear Association)

  • Life Cycle Analysis, focused on energy, is useful for comparing net energy yields from different methods of electricity generation.
  • Nuclear power shows up very well as a net provider of energy, and only hydro electricity is closely comparable.
  • External costs, evaluated as part of life cycle assessment, strongly favour nuclear over coal-fired generation.
  • Energy Return on (energy) Investment is a way of measuring relative inputs and outputs.

A claim which has been made by opponents of nuclear energy is that it takes more energy to build a nuclear power plant than the plant ever generates it. David MacKay addressed this claim in the (now defunct) "metafaq" to his Sustainable Energy - Without The Hot Air:

Q: I heard it takes more energy to build a nuclear power plant than you ever get back from it... is that true?
A: No, of course not! Why would France and Finland and Sweden build so many power plants if that were true? They could just use the energy directly. The energy cost of uranium enrichment is described in my book, along with figures for the amount of concrete and steel used in the materials of the power station. The exact figures vary from country to country, but as a ballpark figure the carbon footprint of enrichment, building, decommisioning, and waste management is about 20 grams CO2 per kWh (compare with coal power stations at 1000 g CO2 per kWh) and raw petrol and gas at about 250 grams per kWh. Nuclear power stations produce at least ten times as much energy as it takes to make them, make their fuel, and decommision them.


The Catch-22 of Energy Storage John Morgan; Brave New Climate; 22 Aug 2014

Several recent analyses of the inputs to our energy systems indicate that, against expectations, energy storage cannot solve the problem of intermittency of wind or solar power. Not for reasons of technical performance, cost, or storage capacity, but for something more intractable: there is not enough surplus energy left over after construction of the generators and the storage system to power our present civilization.
The problem is analysed in an important paper by Weißbach et al.

Energy intensities, EROIs, and energy payback times of electricity generating power plants D. Weißbach, G. Ruprecht, A. Huke, K. Czerski, S. Gottlieb, A. Hussein; ; 6 Apr 2013 [preprint]

The Energy Returned on Invested, EROI, has been evaluated for typical power plants representing wind energy, photovoltaics, solar thermal, hydro, natural gas, biogas, coal and nuclear power. The strict exergy concept with no ”primary energy weighting”, updated material databases, and updated technical procedures make it possible to directly compare the overall efficiency of those power plants on a uniform mathematical and physical basis. Pump storage systems, needed for solar and wind energy, have been included in the EROI so that the efficiency can be compared with an ”unbuffered” scenario. The results show that nuclear, hydro, coal, and natural gas power systems (in this order) are one order of magnitude more effective than photovoltaics and wind power.

A Framework for Incorporating EROI into Electrical Storage Graham Palmer; BioPhysical Economics and Resource Quality; Jun 2017

The contribution from variable renewable energy (VRE) to electricity generation is projected to increase. At low penetration, intermittency can usually be accommodated at low cost. High-penetration VRE will displace conventional generation, and require increased grid flexibility, geographic and technology diversity, and the use of electrical storage. Energy return on investment (EROI) is a tool that gives greater weight to the principles of energetics over market prices, and may provide a long-term guide to prospective energy transitions. The EROI of electrical storage may be critical to the efficacy of high-penetration renewable scenarios. However, there is no generally agreed upon methodology for incorporating storage into EROI. In recent years, there have been important contributions to applying net-energy analysis to storage, including the development of storage-specific net-energy metrics. However, there remains uncertainty as to how to apply these metrics to practical systems to derive useful or predictive information. This paper will introduce a framework for evaluating storage at a system level. It introduces the surplus energy-storage synergy hypothesis as a general principle for exploring the role of storage. It is argued that the useful energy available to society is determined by both the net-energy of the energy source and the stored energy as stocks. This hypothesis is translated across to electricity systems with the use of electrical reliability indices to evaluate the value of storage. A case study applies the framework to a suite of VRE simulations. The case study was modelled as a limiting case of VRE plus storage, and is therefore not intended as a comprehensive cost-optimised solution to high-penetration VRE. A shift from an electrical system based mostly on energy stocks to one based mostly on natural flows is constrained by the quantity of storage required, and the quantity of VRE overbuild to charge the stores. The application of the framework shows that the value of electrical storage and overbuild exhibits a marked diminishing returns behaviour at rising VRE penetration and therefore the first units of storage are the most valuable. The framework is intended to stimulate further research into using EROI to better understand the role of VRE and storage in prospective energy transitions.