Nanocomposite Materials Used for Ground Heat Exchanger Pipes

Abstract

This study compares the performance of single U-pipe, double U-pipe, and coaxial ground heat exchangers (GHE) equipped with standard HDPE and thermally enhanced (TE) pipes. Sizing calculations and 10-year hourly simulations were carried out with the GLHEPro software using as input a synthetic thermal load profile of a reference, heating-dominated, medium office building located in the U.S. climate zone 5B enclosing Colorado. Energy consumption by the ground heat and ground loop pumps were then calculated from the simulated outputs. Finally, a life-cycle cost analysis was performed to compare the total costs (construction and operation) net present value of the GHEs equipped with TE pipes with those equipped with standard HDPE pipes. Results showed that the double U-pipe with thermally enhanced pipes was the best option for the conditions considered in the study. Depending on the configuration, the use of TE pipes instead of standard HDPE pipes allowed a reduction of the GHE length between 9 and 14.8 % and a reduction of the construction cost between 3.3 and 8.6 %. For each configuration tested, the operation costs were similar between the GHEs equipped with HDPE and TE pipes. This study demonstrates that GHEs equipped with TE pipes can be a financially viable and environmentally beneficial solution, especially if secondary benefits are factored in such as saved footprints on available real estate.

Proceedings of the IGSHPA Research Track 2022

“…Increasing the GHE pipe diameter and/or using a double U-pipe configuration appear to be readily applicable improvements that are simple to implement, especially when compared to modifying the pipe material (Gosselin et al 2017) or opting for a coaxial GHE configuration requiring numerous pipe fusions in the field . GCHP system installers often prefer the ease of single and double loop installations that are compatible with a large pipe diameter and where pipes are rapidly lowered in boreholes for which there is no pipe fusion except for the bottom U-bend and the connection at surface.…”

“…Various options are available to increase the performance of GHE, which commonly includes (1) adjusting the borehole diameter (Luo et al, 2013), ( 2) increasing the thermal conductivity (TC) of the grout mixture (Desmedt et al, 2012;Lee et al, 2012Lee et al, , 2011) and ( 3) selecting proper pipe configuration and material . Besides, previous research specifically has been done to increase the TC of pipes by mixing high-density polyethylene (HDPE) with additives such as carbon-based nanoparticles (Gosselin et al, 2017). Moreover, coaxial pipe configurations have been extensively studied as it showed elevated GHE performances due to its large surface area and volume of water (Acuña et al, 2011;Acuña and Palm, 2013;Holmberg et al, 2016;Tago et al, 2005;Zanchini et al, 2010).…”

Ground heat exchangers with large diameter pipes: What are the benefits?

“…Increasing the GHE pipe diameter and/or using a double U-pipe configuration appear to be readily applicable improvements that are simple to implement, especially when compared to modifying the pipe material (Gosselin et al 2017) or opting for a coaxial GHE configuration requiring numerous pipe fusions in the field (Raymond et al, 2015). GCHP system installers often prefer the ease of single and double loop installations that are compatible with a large pipe diameter and where pipes are rapidly lowered in boreholes for which there is no pipe fusion except for the bottom U-bend and the connection at surface.…”

“…Various options are available to increase the performance of GHE, which commonly includes (1) adjusting the borehole diameter (Luo et al, 2013), (2) increasing the thermal conductivity (TC) of the grout mixture (Desmedt et al, 2012;Lee et al, 2012Lee et al, , 2011 and (3) selecting proper pipe configuration and material (Raymond et al, 2015). Besides, previous research specifically has been done to increase the TC of pipes by mixing high-density polyethylene (HDPE) with additives such as carbon-based nanoparticles (Gosselin et al, 2017). Moreover, coaxial pipe configurations have been extensively studied as it showed elevated GHE performances due to its large surface area and volume of water (Acuña et al, 2011;Acuña and Palm, 2013;Holmberg et al, 2016;Tago et al, 2005;Zanchini et al, 2010).…”

Comparative study on the thermal performance and economic efficiency of vertical and horizontal ground heat exchangers

“…Numerous studies Cui, Q., et al Advances in Geo-Energy Research, 2023, 7(1): 7-19 have focused on ground heat exchangers. For VGHE, Gosselin et al (2017) simulated the performance of single U, double U and coaxial ground heat exchanger pipes with high-density polyethylene and nanocomposite materials, and found that the performance of double U pipes with nanocomposite materials was superior to others. Javadi et al (2019) proposed eight new helical ground heat exchangers and compared them with a single U-tube heat exchanger.…”