The recent harsh winter period was a good stress test for heating systems and especially for heat pumps. From some customers with a geothermal heat pump we received questions about the (seemingly) low temperature in the BTES. For example, on Friday, Feb. 12, 2 customers signaled regimes of 4 degrees Celsius at the inlet of the heat pump and 0.5 and 0 degrees return temperature, respectively. For another customer, the BTES indicated a regime of 4.2°C/0.7°C on Saturday, Feb. 13 - after a week with only frost days.
These values are perfectly normal at the end of a (very) cold period and indicate that the BTES is well utilized. During the winter, heat is slowly extracted from the soil. By the end of summer, (passive) cooling of the building has reheated the soil to about 12 degrees.
In past years, frost days were scarce or completely absent during winters. Bottom temperatures then dropped to 6 to 7 degrees. However, the 4 degrees in mid-February this year was not at all problematic, quite the contrary. Because the water in the pipes of the BTES is mixed with glycol, there is even an additional margin of 10 degrees. The efficiency of the geothermal heat pumps also remained very good in these conditions, with a COP (coefficient of performance) of more than 4 (4 units of indoor heat is extracted from 3 units of ground heat and 1 unit of electricity).
A heat pump works in cycles that naturally intensify when outdoor temperatures are extreme. At the end of such a cycle, the temperature in the wells may drop a bit, because the soil cannot always fully follow the demand from the wells. Between 2 cycles, however, the soil has time to release its energy again to the water in the BTES . So the fact that the input temperature at the heat pump had dropped to about 4 degrees on Friday, Feb. 12 and Saturday, Feb. 13, was perfectly normal. On Monday, February 15, our customers already recorded temperatures above 5 degrees again.
Ingenium remains a great advocate of heat pumps to ensure a comfortable indoor climate in buildings all year round. The fact that they continue to work perfectly even during the past ice week at the end of winter underlines their added value in the sustainable energy transition. If the coming summer has a few more heat waves in store, we will be happy to let you know in the fall how the geothermal heat pumps responded to that stress test.
If you want more info, be sure to contact our expert Raf De Herdt at 050 40 45 30 or raf.deherdt@ingenium.be
