Getting more of your district heating network with geothermal storage options
Tuesday, 25 January 2022, 15:00 (CET/UTC+1), Claire Bossennec, TU Darmstadt
A heating district comprises several elements for which inputs and outputs fluctuate, depending on weather conditions and end-user consumption. The fluctuations lead, for example, to seasonally strongly varying utilization of combined heat and power (CHP) units, which produce electricity and capture heat thereby emitted. In winter, additional reheating by boilers usually takes place to cover peak loads. In summer, the output must be throttled due to the low demand for heat, reducing electricity generation and revenue.
The situation is similar with solar thermal collectors, a carbon-free heating option. While the generation potential is high in summer, the heat demand is low, whereas in winter, when the heat demand is high, the generation potential is low. Large-scale, seasonal heat storage is the only option to reduce heat generation potential and demand discrepancy. In this way, CHP units can continue to produce electricity efficiently under full load in summer, and solar thermal systems can also fully utilize the radiant heat potential of summer, replacing heat from conventional boilers.
Here, several geothermal storage options and experiences are presented, emphasizing medium-deep heat borehole heat exchangers, which require considerably less surface building space. This is of great advantage in urban areas, where heat consumption is concentrated. In addition, most of the heat is transferred to the deeper crystalline subsurface, which protects near-surface aquifers, compared to near-surface installations.