Embodiments of the present invention relate to
heat transfer fluids (e.g. molten-salt) as a thermal buffer for heating, by
thermal energy derived from wind-generated
electricity, at least one of (i) a subsurface
hydrocarbon-containing formation or (ii) a
bed of
hydrocarbon-containing rocks. During times when wind is plentiful, wind
electricity is used to heat the
heat transfer fluid—e.g. by means of an electrically resistive heater immersed in the
heat transfer fluid. At any time,
thermal energy from the wind
electricity may be transferred to the
hydrocarbon-containing rocks or subsurface formation by the
heat transfer fluid. In some embodiments, the fluid is heated both by wind-generated electricity and by solar
radiation. Some embodiments relate to a subsurface
molten salt heater (e.g. powered by wind-generated electricity) having a non-thermally insulation portion through which
molten salt flows. The heater is configured to maintain a temperature of the circulating
molten salt, throughout the substantially non-thermally-insulated portion, at a temperature significantly above a
melt temperature of the molten salt.