Evaluating a large geothermal absorber’s energy extraction and storage performance in a common geological condition

•Rapid simulation of a geothermal absorber thousands of meters in size.•Predicting over 500 tons of coal equivalent extraction heat within four months.•Showing a huge underground heat storage space by data post-processing. Geothermal exploitation generally requires extracting heat from “hot spots” associated with geothermal anomalies, which restricts geothermal projects to specific sites. The full potential of geothermal devices under normal geological conditions has not been recognized. This study used the finite element method to evaluate the heat extraction and storage performance of a deep fully enclosed geothermal absorber with a long horizontal section in a common basin geological structure with ordinary terrestrial heat flow. Calculations showed the average thermal power per unit was 0.84–1.54 MW, with a continuous supply lasting at least 4 months to meet winter heating demand for residential community. When this device played the role of energy storage, the corresponding underground heat storage capacity was 0.83–1.66 × 104 GJ. Therefore, it has the potential to adapt to the future multi-energy complementary and mutually adjustable energy application scenarios. The model proposed in this study provides a fast simulation method for this type of geothermal absorber, which combined huge-scale multi-layered stratigraphic structures with multi-physical fields. The data post-processing method provides a more reasonable approach for calculating underground heat storage capacity. Moreover, with this method, the macroscopic morphology of the entire underground heat storage is shown by the cloud map of heat storage density, which provides specific information that can facilitate the design of subsequent hot injection schemes.