Renewables Have a Higher EROI than Fossil Fuels
Discussion
when measured properly, Renewables already seem to have a higher EROI than fossil fuels
Nafeez Ahmed:
"The concept of energy return on investment (EROI) has become an important metric to understand the efficiency of an energy system. It comes in the form of a simple ratio that reflects how much energy is used to extract a single unit of energy from any given resource. The challenge with producing accurate assessments of the EROI of any resource is in ensuring correct assumptions about that resource, including exactly how and where the energy inputs and outputs are measured to derive the most accurate figures.
EROI is an important measure to the extent that it can provide useful insights into the amount of net energy available to society beyond the energy used to extract energy in the first place. The higher the ratio, the more surplus net energy available to support other social and economic activities. But the lower the ratio, the less surplus net energy. A decline in EROI, then, implies economic decline.
There is now a compelling body of scientific literature showing that the EROI of the global fossil fuel energy system has been in decline for several decades and, as a result, is experiencing a vicious cycle of diminishing returns from which there is no prospect of recovery.
Yet it’s often argued that while EROI decline is inevitable with fossil fuels, renewable energy represents a further decline in EROI which means they cannot accomplish the same levels of societal and economic complexity.
But this view was significantly challenged in a recent study led by Professor Paul Brockway at the University of Leeds, published in Nature Energy. It found that as fossil fuels are becoming 'harder to reach', they 'require more energy to extract and, hence, are coming at an increasing "energy cost."' The study noted that fossil fuel EROI is typically vastly overestimated because it is measured right at the wellhead, and not at the most relevant point when energy enters the economy as electricity or petrol. EROI for fossil fuels, they conclude, is 'very low… around 6:1 and declining.' It has already declined by at least 10% over the last 25 years.
The second crucial conclusion of the paper is that when measured properly, renewables already seem to have a higher EROI than fossil fuels. As most fossil fuel EROI studies are undertaken at the wrong stage, they are not directly comparable with wind and solar generation which immediately produce electricity. And while fossil fuels exhibit a declining EROI trend with escalating costs and diminishing returns, wind and solar are experiencing the opposite: an increasing EROI trend with increasing returns and declining costs. Therefore, Brockway et. al conclude that 'the renewables transition may actually halt – or even reverse – the decline in global EROI at the final energy stage.'
The Nature Energy findings are corroborated by a more recent RethinkX study of the levelized cost of electricity (LCOE), which measures the average cost of generating electricity across the entire lifetime of a power plant, including its building and operating costs. That study found that conventional LCOE estimates by the International Energy Agency and Energy Information Administration underestimate the per-kilowatt hour cost of coal, gas and large-scale hydropower by up to 400%. This would suggest that their EROI is significantly lower than usually believed.
Meanwhile, as even conventional LCOE figures show that solar, wind and batteries (SWB) have already reached parity with fossil fuels, these RethinkX findings indicate that SWB is already much cheaper, consistent with higher EROI.
Despite the findings of the Brockway paper, the idea that renewables represent a significant decline in EROI relative to fossil fuels is a persistent misconception that has plagued numerous other studies which tend to repeat the same mistakes largely due to a failure to understand these technologies.
These mistakes can be found in many places, not least in the famous feature documentary by Michael Moore, Planet of the Humans. More recently, the Geological Survey of Finland has published a paper repeating such errors, as has the journal Energies.
Yet there are significant problems with these approaches. One of the most egregious is the statement that solar panels have a life span of around 20 to 30 years. Conventional conservative EROI calculations for solar therefore put EROI calculations at around 10:1 for somewhere like Switzerland. This is already higher than the 6:1 of fossil fuels demonstrated by Brockway et. al.
But the assumptions here are completely false. Solar panels do not spontaneously combust after two or three decades. Rather their efficiency declines over time by a very small amount every year. This means that after 20 years, most solar panels will still operate at 90% capacity. This suggests that their life span is likely to extend many decades beyond 30 years–as much as 40-50 years if not more–with a gradual decline in efficiency, suggesting that even the 10:1 estimate is far too low, and closer to something like 20:1 at least.
Similarly, research by Imperial College London confirms that the life span of wind turbines will extend to at least 25 years, most likely lasting beyond that for newer turbines. Today, some of the most important design components for wind power such as transformers, copper ground cables and the towers they are positioned on, among others, last for 50 years or more. Once again, the trajectory is for a higher EROI value, particularly as these technologies continue to improve in performance.
The energy payback from solar and wind is also phenomenal, and comes at a fraction of the carbon footprint of fossil fuels, even if the latter included carbon capture and storage. A study in Nature Energy in 2017 found that the lifetime carbon footprints of solar and wind are about 1/20th of coal and gas, including manufacturing and construction. Solar and wind installations also produce respectively 26 and 44 times more energy than the energy used to build them."