Continuation of the Heat-Accumulator mod by aster26.

The Heat Capacitor could be used as a standalone mod, but I ported it specifically to use in combination
with brilliant "RealisticReactors" and "Nuclear Fuel" mods. Highly recommended!

This capacitor is a structure in the game, which could be heated and cooled - just like the heat pipes.
A heat capacitor has specific heat of 10MJ, which is ten times larger than that of a heat pipe (don't ask why specific heat is measured in Joules).

There are several ways to store energy in Factorio: electric accumulators is the most obvious way,
but you can also use steam and various fuels for these purposes. Much less obvious is
using heat pipes. They store energy that was already produced by your nuclear plant but is not yet consumed (or rather converted) by the
heat exchangers. You'd need a rather large field of them though to match your reactor output.

This mod lets you have a dedicated element to store the heat energy.
With that you can reach at least two goals: store energy and decrease the rate at which temperature
of your reactor changes. In some mods, like RealisticReactors this might be critical.

Known Issues

• You can walk on heat capacitors. It would be better to replace the image with something
  that supports walking upon, however I'm not an artist. Volunteers?