  Storing electrical energy for long periods and transporting it over long
distances is an essential task of the necessary transition to a CO$_2$-free
energy economy. An oxidation-reduction cycle based on iron and its oxides
represents a very promising technology in this regard. The present work
assesses the potential of converting an existing modern coal-fired power plant
to operation with iron. For this purpose, a systematic retrofit study is
carried out, employing a model that balances all material and energy fluxes in
a state-of-the-art coal-fired power plant. Particular attention is given to
components of the burner system and the system$'$s heat exchanger. The analysis
provides evidence that main components such as the steam generator and steam
cycle can be reused with moderate modifications. Major modifications are
related to the larger amounts of solids produced during iron combustion, for
instance in the particle feeding and removal systems. Since the high particle
densities and lower demand for auxiliary systems improve the heat transfer, the
net efficiencies of iron operation can be one to two percentage points better
than coal operation, depending on operating conditions. This new insight can
significantly accelerate the introduction of this innovative technology by
guiding future research and the development of the retrofit option.
