EROI
Chapter 2 - Society
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Welcome to the EROI page
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EROI (Energy Return On energy Invested) is a measure of the energy efficiency of a particular activity, calculated by dividing the energy produced (or 'output') by the energy required (or 'invested') for that production. This calculation makes EROI an economic figure.
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Core idea
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Definition of EROI
Mathematically, EROI is defined as:
EROI = Energy delivered / Energy required to deliver that energy
- Positive EROI values indicate that an activity is an energy source because it produces net energy that can be used for other activities
- EROI values below 1 indicate that the activity consumes more energy than it produces, making it an energy consumer rather than an energy source.
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The Importance of EROI for the Energy Transition
The EROI (Energy Return On energy Invested) is crucial to the energy transition. It determines how much energy is needed to produce a certain amount of usable energy. A low EROI means much energy is required for extraction and processing, reducing the net energy yield.
During the energy transition, when we switch from fossil fuels to renewable energy sources, it is essential to consider the EROI. This is because many renewable energy sources have a lower EROI than fossil fuels.
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Deep dive
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Three Main Types of EROI analysis
The three types of EROI analyses differ in their limits on the energy inputs included in the calculation. The Standard EROI has the narrowest possible limits, while the Extended EROI has the most comprehensive limits. As the limits become broader, the EROI value generally becomes lower.
The choice of a specific EROI analysis depends on the purpose of the study.
- The standard EROI is the most appropriate analysis if the purpose is to compare different energy sources based on their net energy yield.
- The Extended EROI is the most appropriate analysis for determining the total energy costs of an energy source for society.
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Standard EROI (EROISt)
This analysis divides a project's, region's, or country's energy output by the sum of the direct (on-site) and indirect (energy required to make the products used on-site) energy used to generate that output.
It excludes the energy associated with supporting labour, financial services, etc.
For example, the EROI calculation is applied to fuel when it leaves the extraction or production facility (wellhead, mine mouth, farm gate, etc.). This approach allows for comparing different fuels even when analysts disagree on the rest of the methodology to be used.
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Point of Use EROI (EROIPOU)
Point of Use EROI is a more comprehensive EROI that includes the costs of refining and transporting the fuel. As the boundaries of the analysis are expanded, the energy costs to get the fuel to that point increase, resulting in a lower EROI.
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Extended EROI (EROIEXT)
This extended analysis considers the energy required not only to obtain a unit of energy but also to use it. For example, the EROI of the power at the mine mouth is required to make that energy minimally usable by society, for example, to drive a truck.
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Important factors determining EROI
The EROI of the available energy sources influences the optimal energy mix, the ideal combination of energy sources for a particular region or country.
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Energy density of the source
Sources with high energy density, such as fossil fuels, generally require less energy to extract and process than sources with low energy density, such as biomass.
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Source location and accessibility
The location and accessibility of an energy source significantly impact EROI. For example, offshore wind farms require more energy to build and maintain than onshore wind farms. Oil and gas reserves that are difficult to reach require more energy to extract than reserves that lie close to the surface.
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Technology used for extraction and processing
Technological advances can improve the EROI of energy sources. For example, improved drilling techniques and refining processes can increase the EROI of fossil fuels. More efficient solar panels and wind turbines can increase the EROI of renewable energy sources.
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Required infrastructure
Building infrastructure, such as pipelines, power grids, and refineries, requires energy that impacts EROI.
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Lifespan and efficiency of installations
The lifespan and efficiency of energy conversion systems, such as power plants and wind farms, play a role in the EROI. Longer lifespans and higher efficiency lead to higher EROI.
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Influence of EROI on the optimal energy mix
The EROI is an essential factor in determining the optimal energy mix. A mix of energy sources with a high EROI is desirable, but other factors, such as sustainability, environmental impact and energy security, should also be considered. The optimal energy mix differs per region and country, depending on the available energy sources, the energy demand and the policy objectives.
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Renewable Energy Sources
Although renewable energy sources often have lower EROI values than fossil fuels, they are more sustainable and have fewer adverse environmental impacts.
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Energy Storage
The intermittent nature of renewable energy sources requires energy storage. The EROI of energy storage systems is essential to determine the overall EROI of renewable energy systems.
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Dynamic EROI
The EROI of energy sources can change over time due to technological progress and resource depletion. A dynamic approach to EROI is vital to determine the optimal energy mix in the long term.
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Some EROI figures
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| Standard EROI (EROISt) | Extended EROI (EROIEXT) | |
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| Oil (in 2050) | 6.5 | |
| Solar (photovoltaic) | 7.8 | 1.7 |
| Wind energy (offshore) | 8.7 | 2.3 |
| Wind energy (onshore) | 13.2 | 2.9 |
| Hydropower (large power stations) | 28.4 | 6.5 |
| Content source |
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| C. de Castro - Standard, Point of Use, and Extended Energy Return on Energy Invested (EROI) from Comprehensive Material Requirements of Present Global Wind, Solar, and Hydro Power Technologies - 2020 |
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Challenges in determining EROI
Calculating EROI, especially on a national scale, poses several challengesː
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Defining system boundaries
Which energy inputs and outputs are included in the calculation?
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Data collection
Obtaining accurate data on all energy inputs and outputs of the energy sector is crucial.
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Changes over time
The EROI of energy sources can change over time, which makes the analysis complex.
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EROI is an essential concept for the energy transition. It helps us to understand the energy efficiency of different energy sources and to determine the optimal energy mix.
To make the energy transition successful, investing in renewable energy sources with the highest possible EROI and technologies that can improve the EROI of renewable energy is essential.
In addition, it is crucial to consider the dynamic nature of EROI and the need for energy storage for intermittent energy sources.
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Do you want to know more?
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| Sources | Links |
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| Wikipedia | https://en.wikipedia.org/wiki/Energy_return_on_investment |
| Science Direct | https://www.sciencedirect.com/topics/engineering/energy-return-on-investment |
| Investopedia | https://www.investopedia.com/terms/e/energy-return-on-investment.asp |
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