Energy exchange system, comprising: a. an underground heat buffer for holding a medium for storing energy, comprising coupled wall parts, wherein - each wall part comprises ∘ a substantially plate-like body; ∘ a liquid throughflow circuit incorporated in or on the plate-like body, and ∘ one or more hydraulic couplings (5, 6, 7, 8) accessible from the outer side of the wall part for discharge and supply of liquid to the liquid throughflow circuit and configured for coupling to hydraulic couplings (5, 6, 7, 8) of a further wall part, and ∘ is coupled at a mutual angle about a substantially vertical axis to a similar wall part, and wherein; - the coupled wall parts are connected such that they enclose one space for contacting said medium; - the heat buffer also comprises a floor and/or cover part for closing the enclosed space on an upper and/or underside; said energy exchange system further comprising: b. a hydraulic heat exchange system connected to the liquid throughflow circuit of at least one of the wall parts of the heat buffer, the hydraulic heat exchange system comprising at least: i) a heat absorbing device for 1. absorbing heat such as solar heat; 2. relinquishing this heat to a liquid; 3. carrying the liquid to which the heat has been relinquished to the liquid throughflow circuit; and at least ii) a heat generating device for 1. receiving liquid carried through the liquid throughflow circuit; 2. generating heat, such as a heating system in a building. a. an underground heat buffer for holding a medium for storing energy, comprising coupled wall parts, wherein - each wall part comprises ∘ a substantially plate-like body; ∘ a liquid throughflow circuit incorporated in or on the plate-like body, and ∘ one or more hydraulic couplings (5, 6, 7, 8) accessible from the outer side of the wall part for discharge and supply of liquid to the liquid throughflow circuit and configured for coupling to hydraulic couplings (5, 6, 7, 8) of a further wall part, and ∘ is coupled at a mutual angle about a substantially vertical axis to a similar wall part, and wherein; - the coupled wall parts are connected such that they enclose one space for contacting said medium; - the heat buffer also comprises a floor and/or cover part for closing the enclosed space on an upper and/or underside; said energy exchange system further comprising: - each wall part comprises ∘ a substantially plate-like body; ∘ a liquid throughflow circuit incorporated in or on the plate-like body, and ∘ one or more hydraulic couplings (5, 6, 7, 8) accessible from the outer side of the wall part for discharge and supply of liquid to the liquid throughflow circuit and configured for coupling to hydraulic couplings (5, 6, 7, 8) of a further wall part, and ∘ is coupled at a mutual angle about a substantially vertical axis to a similar wall part, and wherein; ∘ a substantially plate-like body; ∘ a liquid throughflow circuit incorporated in or on the plate-like body, and ∘ one or more hydraulic couplings (5, 6, 7, 8) accessible from the outer side of the wall part for discharge and supply of liquid to the liquid throughflow circuit and configured for coupling to hydraulic couplings (5, 6, 7, 8) of a further wall part, and ∘ is coupled at a mutual angle about a substantially vertical axis to a similar wall part, and wherein; - the coupled wall parts are connected such that they enclose one space for contacting said medium; - the heat buffer also comprises a floor and/or cover part for closing the enclosed space on an upper and/or underside; b. a hydraulic heat exchange system connected to the liquid throughflow circuit of at least one of the wall parts of the heat buffer, the hydraulic heat exchange system comprising at least: i) a heat absorbing device for 1. absorbing heat such as solar heat; 2. relinquishing this heat to a liquid; 3. carrying the liquid to which the heat has been relinquished to the liquid throughflow circuit; and at least ii) a heat generating device for 1. receiving liquid carried through the liquid throughflow circuit; 2. generating heat, such as a heating system in a building. i) a heat absorbing device for 1. absorbing heat such as solar heat; 2. relinquishing this heat to a liquid; 3. carrying the liquid to which the heat has been relinquished to the liquid throughflow circuit; and at least 1. absorbing heat such as solar heat; 2. relinquishing this heat to a liquid; 3. carrying the liquid to which the heat has been relinquished to the liquid throughflow circuit; and at least ii) a heat generating device for 1. receiving liquid carried through the liquid throughflow circuit; 2. generating heat, such as a heating system in a building. 1. receiving liquid carried through the liquid throughflow circuit; 2. generating heat, such as a heating system in a building.