  Planning the appropriate renewable energy 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 renewable energy 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 renewable energy technologies. The
easiest pathway requires installation of renewable energy plants to accelerate
from 0.12TWp/year in 2013 to peak between 6.6 and 10.4 TWp/year, for an early
or a late fossil-fuel phase-out respectively in order for emissions to stay
within the recommended CO2 budget.
