Switching to renewable energy systems may not represent a net decline in energy

Energy researchers have been trying to understand the consequences of moving to fully renewable energy for decades. Some previous research has suggested that renewable energy technologies, such as solar panels and wind turbines, may not generate as much net energy (i.e., the energy left after accounting for the energy used to produce the energy) as their long-standing renewable energy counterparts. fossil fuels.

Scientists at the University of Leeds recently conducted a study to further investigate how true this theory is, by comparing the estimated net energy produced by burning fossil fuels with that produced by renewable energy technologies. The results of their analyses, published in Energy of Naturesuggest that the transition to renewable energy systems may not actually represent a net decline in energy.

“For a given energy system, energy return on investment (EROI) refers to the ratio of energy delivered to society divided by energy invested,” Emmanuel Aramendia, co-author of the paper, told Tech Xplore. “The common and persistent view is that fossil fuels have a higher EROI than renewable energy and therefore return significantly more net energy to society than renewable energy systems. This view questions whether it is possible to transition to a low-carbon economy without drastic reductions in living standards.”

Previous studies have typically quantified the energy return from fossil fuels at the first stage of extraction (i.e., energy extracted from oil wells or elsewhere). In contrast, the returns from renewable energy systems are typically quantified at the final stage of energy generation (i.e. energy delivered to users in the form of electricity).

These studies suggest that fossil fuels produce significantly more usable energy than renewable energy sources. Recent works, including an article published in Energy of Nature in 2019 found that when comparing the energy returns at the end of power generation, the energy returns from fossil fuels and renewables were not that different. However, even these works did not take into account factors that can only be estimated by conducting analyzes at the useful energy stage.

“Previous work has not taken into account the fact that renewable energy systems such as photovoltaics and wind power provide electricity that is, on average, used with a much higher end-to-use efficiency (i.e. the efficiency with which the final energy carrier is converted into valuable for society’s energy flow, e.g. heat, mobility, etc.) than media based on fossil fuels,” Aramendia said.

“For example, the efficiency of an internal combustion engine (e.g. a gasoline or diesel vehicle) is in the range of 25-35%, while the efficiency of an electric car is around 80%. In our work, we extend the analysis boundary to the useful energy stage to account for end-to-use efficiency effects.”

In a recent study, Aramendia and his colleagues analyzed data collected by the International Energy Agency to determine direct energy consumption (i.e., in situ energy consumption) in the fossil fuel industry. They also used the Exiobase input-output model, a database of monetary and energy data from 43 countries around the world, to determine the indirect use of energy produced from fossil fuels (i.e. energy consumption in the supply chain).

“This gives us the final stage of fossil fuel EROI from 1971 to 2019,” Aramendia explained. “We then used an energy database recently developed at the University of Leeds, describing energy flows up to the useful energy stage and therefore clearly showing the efficiency (ultimate to useful) of energy carriers. Using average yields from the database, we were able to determine a useful EROI step for fossil fuels.”

Finally, researchers compared the energy efficiency of fossil fuels with that of renewable energy systems (i.e., photovoltaics and wind turbines). The comparison was based on the EROI values ​​they identified for fossil fuels, adjusted for the final-to-useful yield impact, and the EROI values ​​they obtained from existing literature focusing on solar panels and wind energy.

“Our work dispels the long-held narrative that fossil fuels provide a much higher net energy return than renewables and that the transition to renewables can only be accompanied by a decline in living standards,” Aramendia said. “In fact, our findings show that the EROI of fossil fuels is on average very low at the useful stage (3.5:1 compared to 8.5:1 at the final stage), which is due to the very low average final to useful efficiency of fossil fuels. “

The results of this team’s analysis strongly challenge previous arguments regarding the high net energy efficiency of fossil fuels. Instead, they suggest that renewable energy systems could ultimately provide society with similar levels of net energy, especially if quantified at the useful energy stage.

“Investing energy in building renewable energy infrastructure is very beneficial to society, not only in terms of climate change mitigation, but also in terms of future energy availability,” Aramendia said. “The energy efficiency of renewable energy sources exceeds that of fossil fuels. This is particularly important in the context of rapidly growing global energy demand, particularly in developing countries, where renewable energy sources have the highest potential to deliver the desired increase in energy demand.”

The findings gathered by Aramendia and his colleagues could inspire governments and policymakers to further introduce measures to support the deployment of renewable energy systems. Additionally, they could promote new initiatives to facilitate the implementation of these systems in lower-income developing geographic regions.

“Future research should focus on identifying mitigation pathways that ensure both the rapid phase-out of fossil fuels and sufficient net energy supplies to ensure a good standard of living for all,” Aramendia added. “Aspects requiring particular attention are inequalities within and internationally in access to energy services and the initial upfront energy investments required for the energy transition, which may temporarily reduce the net energy available to society in the early stages of the transition.”

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