Abstract: A thermal energy storage system includes a heat exchange module having a quantity of phase change material and a quantity of reference gas in fluid communication with the phase change material. A sensor is provided for sensing the reference gas pressure and generating a pressure signal that is related to the reference gas pressure. The exchange of heat changes the heat of the phase change material, a change in the phase of the phase change material, and a change in the total volume of the phase change material. This changes the volume of the reference gas, and also changes the reference gas pressure. The sensor will detect and generate a signal of the reference gas pressure change and form this a change in the state of charge of the phase change material can be determined. A thermal energy storage system and method for storing thermal energy are also disclosed.

Abstract: A medium for energy storage includes a plurality of capsules. Each capsule contains a phase changing material (PCM) configured to undergo a liquid-solid phase transition at a solidification temperature, TS. The PCM undergoes a relative volume change due to the phase transition. A shell is filled with the PCM. The shell contains a first heat-conducting material, and is configured to comply to the relative volume change. The relative volume change is configured to cause a buoyancy force, which acts on the capsule when the capsule is disposed in water at a water temperature, TW, to be larger than the capsule's weight for Tw>Ts, and equal to or smaller than the capsule's weight for Tw<Ts. The Ts can be within ±5° F. of a design water temperature To at the outlet of a water tank. The capsule can be neutrally buoyant in water at To.

Abstract: A diffuser for a water heater fill tubes having a tube wall with an outside diameter. The diffuser includes an elongated flexible diffuser body for positioning at the outlet end of the fill tube. The diffuser body has a sealing end for sealing with an outside surface of the fill tube wall closest to the inlet end of the fill tube, and an open end for positioning at an end closest to the outlet end of the fill tube. The open end has a diameter larger than an outside diameter of the tube wall, thereby creating an diffuser water outlet opening between the diffuser body and the tube wall for redirecting radial water flow emanating from the fill tube water outlet opening(s) toward the diffuser outlet opening. A fill tube assembly for a water heater, a water heater, and a method for heating water are also disclosed.