A rotary shutter valve 500 is used for geothermal reservoir stimulation. The valve 500 includes a pressure chamber 520 for holding a working fluid (F) under pressure. A rotatable shutter 532 is turned with a powering device 544 to periodically align one or more windows 534 with one or more apertures 526 in a bulkhead 524. When aligned, the pressurized working fluid (F) flows through the bulkhead 524 and enters a pulse cavity 522, where it is discharged from the pulse cavity 522 as pressure waves 200. The pressure wave propagation 200 and eventual collapse of the bubbles 202 can be transmitted to a target rock surface 204 either in the form of a shock wave 206, or by micro jets 208, depending on the bubble-surface distance. Once cavitation at the rock face begins, fractures are initiated in the rock to create a network of micro-fissures for enhanced heat transfer.

A cooling system for a subterranean power line may include a cooling tube configured to house a fluid. Heat generated by the subterranean power line may be radiated and/or conducted to the cooling tube and absorbed by the fluid within the cooling tube. As the fluid heats up, it may change phase from a liquid to a gas. The hot gas may rise to a heat-exchanging condenser configured to dissipate the heat and condense the fluid back into a liquid. The cool, condensed liquid my return from the heat-exchanging condenser to the cooling tube. Risers, gas transport tubes, pressure regulation systems, fluid storage tanks, and other components described herein may increase the efficiency of the cooling system and/or otherwise improve the viability of the cooling system for subterranean power lines.

A geothermal pump includes a lineshaft, an internal casing disposed concentrically around the lineshaft and configured to form a lubrication-space between the lineshaft and the internal casing, an external casing disposed concentrically around the internal casing and configured to form a brine-space between the internal casing and the external casing, a piping network connected to an above-ground end of the internal casing, and a seal assembly disposed on a down-hole end of the lineshaft and connected to the piping network and the lubrication-space, such that a fluid circuit is formed, the seal assembly being configured to enable a lubrication fluid to flow from the piping network to the lubrication-space in a direction toward the above-ground end of the lineshaft while restricting the lubrication fluid from flowing toward the down-hole end of the lineshaft.

A thermal energy storage system includes a container positioned within a surrounding body of water and comprising a container wall. The wall has an interior surface exposed to and defining an internal volume of the container and has an exterior surface opposite the interior surface and exposed to the surrounding body of water. The internal volume is substantially full of water, and the container is configured to thermally separate water within the internal volume along the interior surface from water of the surrounding body of water along the exterior surface. A thermal source in thermal communication with the water within the internal volume is configured to transfer a thermal potential to the water within the internal volume.

A geothermal energy system comprising a plurality of borehole heat exchangers, each borehole heat exchanger containing a working fluid and comprising an elongate tube having a closed bottom end and first and second adjacent elongate conduits interconnected at the bottom end, a manifold for the working fluid to which the plurality of borehole heat exchangers is connected, and a plurality of valves connected between the plurality of borehole heat exchangers and the manifold, whereby the first and second conduits of the plurality of borehole heat exchangers are selectively connectable to the manifold by operation of the valves.

A collector for a heat pump installation includes a pipe to circulate a heat transfer liquid between a heat source and a heat pump. An inner surface of the pipe has an uneven surface structure that includes at least one of indentations or elevations extending helically in a longitudinal direction. The indentations or elevations are arranged to create a turbulent flow of the heat transfer liquid in the pipe.

A geothermal loop in-ground heat exchanger for energy extraction including an outer tubular casing and an inner tubular portion spaced from the outer tubular casing to define an injection space wherein a working fluid is injected into the injection space at a first temperature, T.sub.1 while the heat exchanger is located in a geothermal heat reservoir and the working fluid exits through the inner tubular portion at a second temperature, T.sub.2 which is greater than T.sub.1.