In Support of a Physics-Based Energy Transition Planning: Sowing Our Future Energy Needs

Abstract

Main Text As fighting climate change becomes more and more urgent and important, the question of planning for an energy transition away from fossil fuels becomes critical. A recent controversy on the ability to reach 100% renewable and reliable energy supply for the US by the 2050s which involved a study by Jacobson et al. (2015) and a rebuttal by Clack et al. (2017) provides an instructive case in point on the difficulty of assessing the feasibility of the transition. Jacobson's team examined the feasibility issue using mostly physical assumptions to answer how such a future energy system might operate. But the main (and the most controversial) point of their paper was the estimate of the costs involved in the transition, something that led them to assert that the transition would not be stupendously expensive to achieve-on the contrary, it would be rather affordable and perhaps even cheaper than business-as-usual. This assertion and the fact that Jacobson implied relevance to the entire global energy system seem to have acted as the primary motivation for Clack et al. to initiate their critique which then focused on specific assumptions and methodological interpretations. Clack et al. argue that the 100% goal as described by Jacobson presents unrealistic requirements. That leads them to support a more conservative alternative approach involving nuclear energy but also a slower phase-out of fossil fuels through carbon capture and sequestration (CCS) and, eventually, negative emission technologies (NET) and greater reliance on biomass. However, these are also untested technologies that constitute a precarious global gamble (Fuss et al. 2014) that would similarly fail more than one of the criteria used by Clack et al. to structure their criticism. These were that "the required technologies have been commercially proven at scale at a cost comparable with alternatives; that the technologies Abstract Attaining the objectives set by the COP21 Paris agreement on climate involves not only phasing out fossil fuels from the world's energy mix but also replacing the energy services they provide with renewable energy and better efficiency, approximately by the mid-twenty-first century. A recent controversy on the viability of 100% renewable energy systems (Jacobson et al. in Proc Natl Acad Sci 112:15060-15065; Clack et al. in PNAS 114:6722-6727) brought forward the question of whether we can actually rely on renewable energy to replace conventional fossil resources. Focusing on the physical factors involved may offer us a currently underutilized method to reduce controversy showing that, in practical terms, the two parties are closer than immediately apparent. A physical perspective suggests that accelerated deployment of renewable energy sources makes attaining the Paris objectives feasible, although not without a major effort. A policy directed to increase capital investments in an early and fast expansion of the renewable energy and storage infrastructure is a crucial requirement for this purpose.