Quantifying the Narrowing Net-energy Pathways to a Global Energy Transition

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Figure 1. SET-compliant primary energy supply evolution (in PWh) for providing 2000 W average net power per capita by 2100 to a population of 10.8 billion. Fossil fuel emissions comply with a 990 Gt CO 2 cap peaking in 2020 and phased-out by 2075. The dashed line represents the net available energy while the values above it the energy investment in building and operating the energy system (‘seed’).

The above image shows one of many possible runs with a given CO2 cap (Carbon Budget), transition time, and various mixes of measures (with EROIs >=20 as a weighted average). Runs need not include particular sources, such as nuclear power or CSP (Concentrated Solar Power), especially if the EROI is less than 20.

This image may be compared with that in 'Three Years to Save the Climate', which does not address the energy transition.
It may also be compared with the images in 'Avoiding Climate Change Disaster'. These show a Business As Usual scenario and a Sustainable Energy Transition with the same Carbon Budgets.

The Abstract includes:

Planning the appropriate renewable energy (RE) installation rate should balance two partially contradictory objectives: substituting fossil fuels fast enough to stave-off the worst consequences of climate change while maintaining a sufficient net energy flow to support the world’s economy. The upfront energy invested in constructing a RE infrastructure subtracts from the net energy available for societal energy needs, a fact typically neglected in energy projections. Modeling feasible energy transition pathways to provide different net energy levels we find that they are critically dependent on the fossil fuel emissions cap and phase-out profile and on the characteristic energy return on energy invested of the RE technologies. The easiest pathway requires installation of RE plants to accelerate from 0.12 TW p yr –1 in 2013 to peak between 7.3 and 11.6 TW p yr –1 in the late 2030s, for an early or a late fossil-fuel phase-out respectively, in order for emissions to stay within the recommended CO 2 budget.

So the early fossil-fuel phase-out requires the installation of RE plants to accelerate by 7.3/0.12 = 61-fold and the late phase-out by 11.6/0.12 = 97-fold. Further delay would mean that there is no solution.

Paper: 2016-09-07, ‘The sower’s way: quantifying the narrowing net-energy pathways to a global energy transition’, Sgouridis et al., http://iopscience.iop.org/article/10.1088/1748-9326/11/9/094009/pdf and
http://iopscience.iop.org/1748-9326/11/9/094009/media/erl094009_suppdata.pdf

However, in the light of two papers by Cullen and Allwood et al, 2010 and 2010, runs could include not just Supply Measures, but also 'Demand Measures', which may be able to reduce the demand by up to 80% with measures having EROIs >=20. This could greatly reduce the accelerations from 60-fold or 97-fold, to more like 60/5 = 12-fold or 100/5 = 20-fold. These could be far less challenging for supply and demand, and keep the renewable energy supply capacities below the global limits.

See: 2010-12-14, ‘Reducing Energy Demand: What Are the Practical Limits?’, Jonathan M. Cullen, Julian M. Allwood, and Edward H. Borgstein, http://pubs.acs.org/doi/abs/10.1021/es102641n and
http://pubs.acs.org/doi/suppl/10.1021/es102641n

2010-03-05, ‘Theoretical efficiency limits for energy conversion devices’, Jonathan M. Cullen, Julian M. Allwood, http://www.sciencedirect.com/science/article/pii/S0360544210000265

For the global limits of renewable energy, see: Climate and Energy Topics

Article date: 2017-07-10

Quantifying the Narrowing Net-energy Pathways to a Global Energy Transition
'Planning the appropriate renewable energy (RE) installation rate should balance two partially contradictory objectives: substituting fossil fuels fast enough to stave-off the worst consequences of climate change while maintaining a sufficient net energy flow to support the world’s economy. The upfront energy invested in constructing a RE infrastructure subtracts from the net energy available for societal energy needs, a fact typically neglected in energy projections. Modeling feasible energy transition pathways to provide different net energy levels we find that they are critically dependent on the fossil fuel emissions cap and phase-out profile and on the characteristic energy return on energy invested of the RE technologies. The easiest pathway requires installation of RE plants to accelerate from 0.12 TW p yr –1 in 2013 to peak between 7.3 and 11.6 TW p yr –1 in the late 2030s, for an early or a late fossil-fuel phase-out respectively, in order for emissions to stay within the recommended CO 2 budget’.

So the early fossil-fuel phase-out requires the installation of RE plants to accelerate by 7.3/0.12 = 61-fold and the late phase-out by 11.6/0.12 = 97-fold. Further delay would mean that there is no solution.

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