A fast approximate method for simulating thermal pile heat exchangers. (December 2022)

• Record Type: Journal Article
• Authors: Loveridge, Fleur; Woodman, Nicholas; Javed, Saqib; Claesson, Johan
• Is Part Of: Geomechanics for energy and the environment. Volume 32(2022)
• Publication Date: 2022-12
• Subjects: Ground source energy -- Energy piles -- Thermal piles -- Pile foundations -- Heat transfer -- Renewable energy; Engineering geology -- Periodicals; Power resources -- Periodicals; Energy development -- Technological innovations -- Periodicals; Engineering geology -- Environmental aspects -- Periodicals; Energy development -- Technological innovations; Engineering geology; Engineering geology -- Environmental aspects; Power resources; Geology -- Periodicals; Energy-Generating Resources -- Periodicals; Periodicals; Electronic journals; 621.042
• DOI: 10.1016/j.gete.2022.100368
• Languages: English
• ISSNs: 2352-3808

Abstract

Abstract: Ground source heat pump systems, operating in conjunction with vertical ground heat exchangers, will play a key role in decarbonising heating and cooling of buildings. Design of traditional borehole heat exchangers relies on tools which implement routine analytical relationships between heat transferred and the temperature change in the ground and circulating thermal fluid. However, for novel piled foundations used as ground heat exchangers, there are few such analytical solutions available that are practical for routine implementation. This paper examines the use of a radial approximation to simulate the dynamic thermal behaviour of pile heat-exchangers. Originally developed for small diameter and high aspect ratio borehole heat exchangers, the approach is more challenging for piles since unsteady heat transfer within the pile material is more significant over typical timescales. Nonetheless, we demonstrate that for pile diameters between 300 mm and 1200 mm, generally the error is <1 °C with centrally placed heat transfer pipes or four or more pipes placed near the edge with circumferential spacing less than 550 mm. The radial model is therefore practical for most pile configurations. The strong performance of the model is demonstrated for a year of hypothetical heating and cooling cycles, and also against a field-scale thermal response test. Highlights: A fast analysis method for energy piles is evaluated for a range of conditions. For common pile geometries temperature prediction is within 1 degree. Based on real geometries, with few parameters, the method is robust.