A chemical heat pump includes a reactor part (1) that contains an active substance and an evaporator/condenser part (3) that contains that portion of volatile liquid that exists in a condensed state and can be absorbed by the active substance. A channel (4) interconnects the reactor part and the evaporator/condenser part. To heat the reactor part, a portion of this wall is arranged as a solar energy collector, which can result in a very compact structure. In at least the reactor part a matrix (13) is provided for the active substance so that the active substance both in its solid state and its liquid state or its solution phase is held or carried by or bonded to the matrix. The matrix is advantageously an inert material such as aluminium oxide and has pores, which are permeable for the volatile liquid and in which the active substance is located. In particular, a material can be used that has a surface or surfaces, at which the active substance can be bonded in its liquid state thereof. For example, the matrix can be a material comprising separate particles such as a powder or a compressed fibre material.