A thermal energy store capable of accepting, storing and releasing thermal energy at a range of more than one temperature to/from at least one thermal energy source and/or sink, said thermal energy store comprising: a configuration of three or more thermal energy storage banks (102a, 102b, 102c, 102d, 102e, 102f, 102g, 102h) each of said thermal energy storage banks having an operating temperature range; at least three or more of the thermal energy storage banks contains thermal energy storage material comprising a single material or a mixture of materials; a control system capable of choosing and/or switching a source and/or destination of thermal energy transfer in succession and/or in parallel amongst one or more thermal energy sources/sinks and one or more thermal energy storage banks of the thermal energy store and wherein the control system is capable of adapting the thermal energy transfers within and to/from the thermal energy store; wherein said thermal energy storage material in at least one bank contains at least some of one or more types of thermal energy storage material that undergoes at least one energy absorbing and/or releasing phase transition at one or more temperatures or one or more sub- ranges of temperatures within the operating temperature ranges of each bank; wherein each phase transition is associated with a change in physical and/or chemical properties of said thermal energy storage material; one or more thermal energy transfer connections, wherein each connection comprises one or more devices for transferring heat from a lower temperature body to a higher temperature body, each connection linking two or more banks; wherein the source or destination of thermal energy transfers are switchable in succession or between internal and external energy transfers in parallel; wherein the source is a location where energy is being transferred from and the destination is a location where energy is being transferred to; wherein internal energy transfer is where energy is transferrable between storage banks within the thermal energy store and wherein one or more of the thermal energy storage banks act as a thermal energy source and one or more of the thermal energy storage banks act as a thermal energy sink; and wherein external energy transfer is transferred to or from the thermal energy storage banks and wherein the thermal energy source or a thermal energy sink is external to the thermal energy storage banks. a configuration of three or more thermal energy storage banks (102a, 102b, 102c, 102d, 102e, 102f, 102g, 102h) each of said thermal energy storage banks having an operating temperature range; at least three or more of the thermal energy storage banks contains thermal energy storage material comprising a single material or a mixture of materials; a control system capable of choosing and/or switching a source and/or destination of thermal energy transfer in succession and/or in parallel amongst one or more thermal energy sources/sinks and one or more thermal energy storage banks of the thermal energy store and wherein the control system is capable of adapting the thermal energy transfers within and to/from the thermal energy store; wherein said thermal energy storage material in at least one bank contains at least some of one or more types of thermal energy storage material that undergoes at least one energy absorbing and/or releasing phase transition at one or more temperatures or one or more sub- ranges of temperatures within the operating temperature ranges of each bank; wherein each phase transition is associated with a change in physical and/or chemical properties of said thermal energy storage material; one or more thermal energy transfer connections, wherein each connection comprises one or more devices for transferring heat from a lower temperature body to a higher temperature body, each connection linking two or more banks; wherein the source or destination of thermal energy transfers are switchable in succession or between internal and external energy transfers in parallel; wherein the source is a location where energy is being transferred from and the destination is a location where energy is being transferred to; wherein internal energy transfer is where energy is transferrable between storage banks within the thermal energy store and wherein one or more of the thermal energy storage banks act as a thermal energy source and one or more of the thermal energy storage banks act as a thermal energy sink; and wherein external energy transfer is transferred to or from the thermal energy storage banks and wherein the thermal energy source or a thermal energy sink is external to the thermal energy storage banks.