Abstract: A thermal energy store comprising a chamber having a gas inlet and a gas outlet and a plurality of successive, downstream, gas permeable thermal storage layers disposed between them, each layer comprising gas permeable thermal storage media, the store being configured for gas flow from the gas inlet to gas outlet through the layers for transfer of thermal energy to or from the thermal storage media, wherein at least one of the layers is a valved layer provided with at least one valve operable selectively to allow or prevent at least some gas flow through that layer via the valve so as to bypass the thermal storage media. A control system may selectively alter the flow path of the gas flowing from inlet to outlet in response to the progress of a thermal front, so as to bypass thermal storage layers upstream of the thermal front, where transfer is complete, or downstream thereof, where transfer is minimal.

Abstract: A thermal energy store comprising a chamber having a gas inlet and a gas outlet and a plurality of successive, downstream, gas permeable thermal storage layers disposed between them, each layer comprising gas permeable thermal storage media, the store being configured for gas flow from the gas inlet to gas outlet through the layers for transfer of thermal energy to or from the thermal storage media, wherein at least one of the layers is a valved layer provided with at least one valve operable selectively to allow or prevent at least some gas flow through that layer via the valve so as to bypass the thermal storage media. A control system may selectively alter the flow path of the gas flowing from inlet to outlet in response to the progress of a thermal front, so as to bypass thermal storage layers upstream of the thermal front, where transfer is complete, or downstream thereof, where transfer is minimal.