Patent ID: 7337838

Claim:
A plant for tempering a building, comprising: an in-ground energy storage unit formed by a plurality of ground heat exchangers coupled in parallel, each ground heat exchanger including a first tube-shaped leg surrounded by heat insulation and a second leg in thermal connection with surrounding soil, the energy storage unit having a continuously varying temperature in a depth direction between a cold end and a warm end; at least one room temperature keeping device for at least one room; a circulation pump for circulating circulation fluid through a circulation circuit, which includes the circulation pump, the first and second legs of the ground heat exchangers, and the at least one room temperature keeping device, and in which the circulation fluid flows down one leg and up the other leg in each of the ground heat exchangers; and a valve device for controlling a flow direction of the circulation fluid in the ground heat exchangers such that when keeping a warm temperature in the at least one room, circulation fluid is directed to the at least one room temperature keeping device from the warm end of the energy storage unit and when keeping a cool temperature in the at least one room, circulation fluid is directed to the at least one room temperature keeping device from the cold end, wherein the circulation pump is controlled such that a temperature difference S between an inlet and an outlet of the ground heat exchangers at all operating conditions has a constant value equal to at least 50% of a fixed value S MIN for the plant, wherein S MIN =F+U+L where: F is a temperature difference between a required feeding temperature to the at least one room temperature keeping device at a maximum warm keeping power at cool ambient temperature and at maximum cool keeping power at warm ambient temperature; U is a required driving temperature difference at a ground surface between the ground and the circulation fluid in the second leg at maximum heat power outlet from the ground at cool ambient temperature; and L is a required driving temperature difference at the ground surface between the ground and the circulation fluid in the second leg at maximum cool power outlet from the ground at warm ambient temperature.