An investigation of a ground thermal energy storage system, which includes storage units containing phase-change materials (PCM), is presented. This study is related to a large-diameter helical heat exchanger, which is placed vertically in the ground. The PCM storage units under consideration have a cylindrical shell shape and are located inside and/or outside the helix. A modified numerical scheme for the Solution of heat transfer in the ground, in the PCM units, and within the heat exchanger pipe, is presented. The theoretical results show that the thermal diffusivity of the PCM dominates the thermal performance of the system. Incorporation of PCM storage units containing paraffin wax results in a reduction of the thermal efficiency in comparison with a system not containing these units. However, incorporation of PCM having the same thermal diffusivity as of the soil results in a significant improvement of the thermal performance.

1.
Bar-On, B., Korin, E., Nir, A., and Tsang, C. F., 1991, “Seasonal Storage of Thermal Energy in Unsaturated Soils: Experimental Procedures and Technological Development,” Proceedings of THERMASTOCK 91 Fifth International Congress on Thermal Energy Storage, Scheveninge, Holland, May 13–16, pp. 4.3.1–4.3.6.
2.
Beck
M.
,
Reuss
H.
,
Schultz
J.
,
Spanning
B.
, and
Wagner
B.
,
1991
, “
Long-Term Storage of Low Temperature Solar Heat in the Ground
,”
Proceedings of the Biennial Congress of the International Solar Energy Society
, Vol.
2
, Part 1, Denver, CO, August 19–23, pp.
1499
1504
.
3.
Bensabat, J., Doughty, C., Korin, E., Nir, A., and Tsang, C. F., 1988, “Validation Experiments of Seasonal Thermal Energy Storage Models in Unsaturated Soils,” Proceedings of JIGASTOCK 88—Fourth International Conference on Energy Storage, Versailles, France, pp. 121–124.
4.
De Jong, A. G., and Hoogendoorn, C. J., 1980, “Improvement of Heat Transport in Paraffins for Latent Heat Storage System,” Proceedings of International Symposium on Thermal Storage and Solar Energy, Amsterdam, The Netherlands, November 5–6, pp. 123–133.
5.
Doughty, C., Korin, E., Nir, A., and Tsang, C. F., 1991, “Seasonal Storage of Thermal Energy in Unsaturated Soils: Modeling Simulation and Field Validation,” Proceedings of THERMASTOCK 91—Fifth International Congress on Thermal Energy Storage, Scheveningen, Holland, May 13–16, pp. 4.3.1–4.3.6.
6.
Doughty
C.
,
Korin
E.
,
Nir
A.
, and
Tsang
C. F.
,
1990
, “
Seasonal Storage of Thermal Energy in Unsaturated Soils: Simulation and Field Validation
,” Part 1,
STES
, Vol.
XII
No.
1
, pp.
1
5
; Part II, Vol. XII, No. 2, pp. 5–8.
7.
Korin, E., 1990, “Suggested Models for Studies of the Use of PCM Devices in UZTES,” Appendix C to the Final Report submitted to the U.S.A.-Israel Binational Sciences Foundation, Project No. 85-00129, Be’er-Sheva, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
8.
Nir
A.
,
Doughty
C.
, and
Tsang
C. F.
,
1986
, “
Seasonal Heat Storage in Unsaturated Soils: Example of Design Study
,”
Proceedings of 21st International Energy Conversion Engineering Conference
, Vol.
2
, San Diego, CA, pp.
669
675
.
9.
Nir
A.
,
Doughty
C.
, and
Tsang
C. F.
,
1992
, “
Validation of Design Procedure and Performance Modeling of a Heat and Fluid Transfer Field Experiment in the Unsaturated Zone
,”
Advances in Water Resources
, Vol.
15
, No.
3
, pp.
153
166
.
10.
Rabin, Y., 1991, “Long-Term Energy Storage in the Ground Using Heat Storage Elements Containing Phase Change Materials,” (in Hebrew), M.Sc. thesis, Ben-Gurion University, Beer-Sheva, Israel.
11.
Rabin, Y., Korin, E., and Sher, E., 1991, “Simplified Model for A Helical Heat Exchange for Long-Term Energy Storage in Soil,” Design and Operation of Heat Exchangers, eds., W. Roetzel, P. T. Heggs, and D. Butterworth, Springer Verlag, pp. 305–314.
12.
Rabin
Y.
, and
Korin
E.
,
1993
, “
An Efficient Numerical Solution for the Multidimensional Sohdification (or Melting) Problem Using a Microcomputer
,”
International Journal Heat and Mass Transfer
, Vol.
36
, No.
3
, pp.
673
683
.
13.
Rabin
Y.
, and
Korin
E.
,
1996
, “
Thermal Analysis of a Helical Heat Exchanger for Long-Term Thermal Energy Storage in the Ground
,”
International Journal Heat and Mass Transfer
, Vol.
39
, No.
5
, pp.
1051
1065
.
14.
Svec, O. J., 1991, “Design Evaluation of Ground Source Heat Pump with Horizontal Spiral Heat Exchangers,” Proceedings of THERMASTOCK 91—Fifth International Congress on Thermal Energy Storage, Scheveninge, Holland, May 13–16, pp. 4.15.1–4.15.6.
15.
Svec
O. J.
, and
Palmer
H. L.
,
1989
, “
Performance of Spiral Ground Heat Exchanger for Heat Pump Apphcation
,”
International Journal of Energy Research
, Vol.
13
, pp.
503
510
.
This content is only available via PDF.
You do not currently have access to this content.