Heat storing device

A heat storing device for exchanging heat energy between a heat storing material and a fluid, comprising a heat storing module having heat storing material spaces filled with the heat storing material and fluid passages for the fluid to flow through adjacent to the heat storing material spaces, wherein:

• the heat storing module includes multiple flat plates in a stack;
• each of the plates has the fluid passages in a first face thereof and the heat storing material spaces in a second face thereof, the first face and the second face being on opposite sides of the plate;
• mutually adjacent pairs of the plates are stacked together so that the first faces thereof having the fluid passages face each other;
• the fluid passages of a first plate of the pair, and the fluid passages of a second plate of the pair, intersect substantially at right angles;
• and
• the fluid passages mutually intersecting at right angles communicate with each other at positions where they intersect.