Patent ID: 8881805

Claim:
A method of storing thermal energy comprising: pre-heating pressurized sub-critical fluids using geothermal heat sources; and injecting the pre-heated pressurized sub-critical fluids into a rock formation to create a pre-heated artificial geothermal reservoir containing the pre-heated fluids in a temperature range of 100 to 200 degrees C.; wherein the rock formation either is permeable, or is relatively impermeable but either has natural fractures or is artificially fractured to allow the pre-heated fluids to flow through the rock formation to displace fluids in the fractures, resulting in an accumulation of the pre-heated injected fluids; and wherein the pre-heated fluids are heated by geothermal heat sources comprising geothermal energy recovered from geothermal hot dry rock formations, or a geothermal brine removed from a geothermal power plant.