A heat-transferring device comprising: a buffer tank, a reactor vessel in thermal contact with the buffer tank, wherein an active substance is held inside the reactor vessel, a burner, a reactor heating loop adapted to transfer heat from the burner to the active substance in the reactor vessel, a reactor cooling loop adapted to transfer heat from the active substance in the reactor vessel to the buffer tank, a volatile liquid reservoir in fluid contact with the reactor vessel, an evaporator in fluid contact with the volatile liquid reservoir, a volatile liquid in the enclosed space formed by the reactor vessel, the volatile liquid reservoir, and the evaporator, the volatile liquid is selected together with the active substance so that the volatile liquid has the ability to be absorbed by the active substance at a first temperature and the ability to be desorbed by the active substance at a second higher temperature, an exhaust gas pipe (10, 11, 12) leading from the burner to a first space at least partially surrounding the volatile liquid reservoir adapted so that heat can be transferred from burner exhaust gas in the first space to the volatile liquid reservoir, a reactor heat exchanger inside the reactor vessel, the reactor heat exchanger having an inside and an outside, wherein the active substance is at least partially applied on the outside of the reactor heat exchanger, the reactor heating loop comprises a boiler at least partially surrounding the burner, a boiler conduit (5, 16) leads from the boiler to the inside of the reactor heat exchanger, which is in thermal contact with the active substance applied on the outside of the reactor heat exchanger, a burner fluid supply tube leading from the inside of the reactor heat exchanger to the boiler, and a communication pipe leading from the burner fluid supply tube to the buffer tank, the reactor cooling loop comprises a reactor cooling inlet pipe leading from the buffer tank via a pump and a valve to the inside of the reactor heat exchanger, and the communication pipe leading from the burner fluid supply tube to the buffer tank, wherein the enclosed space formed by the buffer tank, the boiler, the boiler conduit (5, 16), the inside of the reactor heat exchanger, an optional boost pipe, the reactor cooling inlet pipe, the communication pipe, the burner fluid supply tube is at least partially filled with a heat-transferring fluid, the exhaust gas pipe (10, 11, 12) is at least partially in thermal contact with the buffer tank. a buffer tank, a reactor vessel in thermal contact with the buffer tank, wherein an active substance is held inside the reactor vessel, a burner, a reactor heating loop adapted to transfer heat from the burner to the active substance in the reactor vessel, a reactor cooling loop adapted to transfer heat from the active substance in the reactor vessel to the buffer tank, a volatile liquid reservoir in fluid contact with the reactor vessel, an evaporator in fluid contact with the volatile liquid reservoir, a volatile liquid in the enclosed space formed by the reactor vessel, the volatile liquid reservoir, and the evaporator, the volatile liquid is selected together with the active substance so that the volatile liquid has the ability to be absorbed by the active substance at a first temperature and the ability to be desorbed by the active substance at a second higher temperature, an exhaust gas pipe (10, 11, 12) leading from the burner to a first space at least partially surrounding the volatile liquid reservoir adapted so that heat can be transferred from burner exhaust gas in the first space to the volatile liquid reservoir, a reactor heat exchanger inside the reactor vessel, the reactor heat exchanger having an inside and an outside, wherein the active substance is at least partially applied on the outside of the reactor heat exchanger, the reactor heating loop comprises a boiler at least partially surrounding the burner, a boiler conduit (5, 16) leads from the boiler to the inside of the reactor heat exchanger, which is in thermal contact with the active substance applied on the outside of the reactor heat exchanger, a burner fluid supply tube leading from the inside of the reactor heat exchanger to the boiler, and a communication pipe leading from the burner fluid supply tube to the buffer tank, the reactor cooling loop comprises a reactor cooling inlet pipe leading from the buffer tank via a pump and a valve to the inside of the reactor heat exchanger, and the communication pipe leading from the burner fluid supply tube to the buffer tank, wherein the enclosed space formed by the buffer tank, the boiler, the boiler conduit (5, 16), the inside of the reactor heat exchanger, an optional boost pipe, the reactor cooling inlet pipe, the communication pipe, the burner fluid supply tube is at least partially filled with a heat-transferring fluid, the exhaust gas pipe (10, 11, 12) is at least partially in thermal contact with the buffer tank.