  Fusion energy is often regarded as a long-term solution to the world's energy
needs. However, even after solving the critical research challenges,
engineering and materials science will still impose significant constraints on
the characteristics of a fusion power plant. Meanwhile, the global energy grid
must transition to low-carbon sources by 2050 to prevent the worst effects of
climate change. We review three factors affecting fusion's future trajectory:
(1) the significant drop in the price of renewable energy, (2) the
intermittency of renewable sources and implications for future energy grids,
and (3) the recent proposition of intermediate-level nuclear waste as a product
of fusion. Within the scenario assumed by our premises, we find that while
there remains a clear motivation to develop fusion power plants, this
motivation is likely weakened by the time they become available. We also
conclude that most current fusion reactor designs do not take these factors
into account and, to increase market penetration, fusion research should
consider relaxed nuclear waste design criteria, raw material availability
constraints and load-following designs with pulsed operation.
