Specifying boundary conditions for economical closed loop deep geothermal heat production

László Kalmár, Tamás Medgyes and János Szanyi

Energy, 2020, vol. 196, issue C

Abstract: Geothermal energy utilization does not depend on weather conditions. Among the various types of heat supplies, ground source heat pumps are the most widely used in the geothermal sector; however, their utilization rate is considerably less than the growth rate of other renewable energy sources. This paper reports an overview of a deep borehole heat exchanger (DBHE) with high-grade vacuum insulated tubing (VIT). Using a computational software, wells with various depths and geothermal gradients are evaluated in the same lithology. The calculation method’s outputs are compared with analytical, semi-analytical and experimental steady state results to show reliability of the developed software. DBHEs are evaluated based on calculated theoretical natural convective mass flow rates (NCMFRs). Considering extended typical well structures with 7″ production casings to surface, the heat performance is evaluated, and revenue requirement (RR) is calculated by employing the theoretical NCMFR. In the calculation depth range of 1200 m–3000 m, geothermal gradient ranges from 40 °C/km to 60 °C/km, and inlet temperatures are 12 °C and 40 °C are considered. Based on the results, reliably profitable depths and geothermal gradient ranges are declared and district heating networks with promising wells are identified. It is concluded that DBHE can be financially viable if integrated into the existing local heat market and infrastructure.

Keywords: Geothermal energy; Renewable energy; Deep borehole heat exchanger; Revenue requirement; Natural convective mass flow rate; High-grade vacuum insulated tubing; Closed loop; Concentric heat exchanger (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:196:y:2020:i:c:s0360544220301754

DOI: 10.1016/j.energy.2020.117068

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