A chemical heat pump including an active substance and a volatile liquid that can be absorbed by the substance at a first temperature and be desorbed by the substance at a second higher temperature, including: - a reactor part containing the active substance and arranged to be heated and cooled by an external medium, - an evaporator/condenser part containing the portion of the volatile liquid that exists in a condensed state, and arranged to be heated and cooled by an external medium, and - a channel for the vapour phase of the volatile liquid, the channel connecting the reactor part and the evaporator/condenser part to each other, wherein the reactor part includes - a vessel or a container having an area of a side wall arranged as a solar energy collector or having an area of a side wall in direct contact with a solar energy collector, and - a matrix for the active substance, said matrix being in contact with said side wall, - the active substance and the volatile liquid being selected, so that the active substance at the first temperature has a solid state from which the active substance when absorbing volatile liquid and the vapour phase thereof immediately or directly partly changes to a liquid state or a solution phase and at the second temperature has a liquid state or exists in a solution phase, from which the active substance when releasing the volatile liquid, in particular the vapour phase thereof, directly changes partly to a solid state, and - the active substance both in its solid state and in its liquid state or in its solution phase is held in and/or is bonded to the matrix, characterized in that the chemical heat pump is arranged in a box with a separating wall for circulating the ambient air either around the reactor part or the evaporator/condenser part, and that the box is open at two opposite sides, which are connected by the separating wall, the box being provided with a flap, which is articulated at a free edge of the separating wall and which can be opened forwards and backwards, allowing ambient air to cool surfaces of the reactor part or surfaces of the evaporator/condenser part. - a reactor part containing the active substance and arranged to be heated and cooled by an external medium, - an evaporator/condenser part containing the portion of the volatile liquid that exists in a condensed state, and arranged to be heated and cooled by an external medium, and - a channel for the vapour phase of the volatile liquid, the channel connecting the reactor part and the evaporator/condenser part to each other, - a vessel or a container having an area of a side wall arranged as a solar energy collector or having an area of a side wall in direct contact with a solar energy collector, and - a matrix for the active substance, said matrix being in contact with said side wall, - the active substance and the volatile liquid being selected, so that the active substance at the first temperature has a solid state from which the active substance when absorbing volatile liquid and the vapour phase thereof immediately or directly partly changes to a liquid state or a solution phase and at the second temperature has a liquid state or exists in a solution phase, from which the active substance when releasing the volatile liquid, in particular the vapour phase thereof, directly changes partly to a solid state, and - the active substance both in its solid state and in its liquid state or in its solution phase is held in and/or is bonded to the matrix, characterized in that the chemical heat pump is arranged in a box with a separating wall for circulating the ambient air either around the reactor part or the evaporator/condenser part, and that the box is open at two opposite sides, which are connected by the separating wall, the box being provided with a flap, which is articulated at a free edge of the separating wall and which can be opened forwards and backwards, allowing ambient air to cool surfaces of the reactor part or surfaces of the evaporator/condenser part.