Geothermal heat exchanger, geothermal heat arrangement and method for charging thermal energy into ground

A method for charging thermal energy into ground, the method comprises:

• circulating a primary working fluid in a geothermal heat exchanger comprising a piping arrangement having a rise pipe arranged into a ground hole and a drain pipe, the rise pipe and the drain pipe being arranged in fluid communication with each other for circulating a primary working fluid in the ground hole for geothermal heat exchange in the ground hole, the rise pie is arranged inside the drain pipe in the ground hole, the ground hole extending from the ground surface into the ground and having a lower end, the depth of the ground hole is at least 300 m;
• the rise pipe being provided with a first thermal insulation surrounding the rise pipe along at least part of the length of the rise pipe;
• and
• providing heat exchange between the primary working fluid circulating in the geothermal heat exchanger and a secondary working fluid with a heat pump,
• wherein the method comprises:
• operating the heat pump in cooling mode in which the primary working fluid receives thermal energy from the secondary working fluid in the heat pump in the heat exchange between the primary working fluid circulating in the geothermal heat exchanger and the secondary working fluid for heating primary working fluid;
• and
• operating the geothermal heat exchanger in a charging mode in which the heated primary working fluid is circulated in a downwards direction in the rise pipe and in a direction upwards in the drain pipe for transporting thermal energy to the lower end of the ground hole and for releasing thermal energy from the heated primary working fluid to the ground at the lower end of the ground hole for storing thermal energy to the ground at the lower end of the ground hole.