A solar combi-system utilizing stable supercooling of sodium acetate trihydrate for heat storage: Numerical performance investigation

Gerald Englmair*, Christoph Moser, Hermann Schranzhofer, Jianhua Fan, Simon Furbo

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

To reduce the energy consumption of buildings significantly, a novel solar combi-system with short and longterm heat storage has been developed. A system prototype with 22.4m2 (aperture) evacuated tubular collectors, a 735 L water tank and 4 phase change material (PCM) units each containing 150 L sodium acetate trihydrate composite has been built. Experimental investigation has shown advantages of utilization of stable supercooling of sodium acetate trihydrate in spring and autumn. In this paper, a newly developed numerical model was used to investigate the performance potential of the system with combined utilization of the water tank and the PCM units, including on-demand crystallization of supercooled sodium acetate trihydrate composites. PCM units, the water tank and the collector circuit models were validated with measurement data from system demonstration. Space heating and hot water demand patterns of a Danish single-family Passive House with a yearly heat demand of 3723 kWh were applied. Results showed that a 56% annual solar fraction of heat supply was achieved with the prototype specifications. A 69% solar fraction could be achieved with an optimized scenario including a 15% increased hot water demand. Sensitivity analysis of component sizing showed that PCM units of 200 L can be more efficiently used with a 0.6m3 water tank. Optimal solar collector array tilt was 70°. Aperture areas between 12.8 and 22.4m2 were found adequate for frequent utilization of a PCM volume up to 1m3. Thus, the PCM heat storage capacity could be utilized at least 5.5 times a year. With a 22.4m2 collector area and 5 PCM units of 200 L each, a solar fraction of 71% was calculated for the annual heat supply. Assuming full charge of a 0.6m3 water tank and 2.8m3 of sodium acetate trihydrate composite by electricity at the beginning of the year, the system could run 18 days without need for auxiliary heating. Thus, in periods without solar collector power available, generation maxima of wind power could be utilized. In conclusion, building heat demand could be covered close to 100% by renewable energy resources.
Original languageEnglish
JournalApplied Energy
Volume242
Pages (from-to)1108-1120
ISSN0306-2619
DOIs
Publication statusPublished - 2019

Keywords

  • Solar heating system
  • Phase change material
  • Sodium acetate trihydrate
  • Stable supercooling
  • Passive House
  • Numerical simulation

Cite this

@article{9ed8580b0d0f4546a5358d3ea740a535,
title = "A solar combi-system utilizing stable supercooling of sodium acetate trihydrate for heat storage: Numerical performance investigation",
abstract = "To reduce the energy consumption of buildings significantly, a novel solar combi-system with short and longterm heat storage has been developed. A system prototype with 22.4m2 (aperture) evacuated tubular collectors, a 735 L water tank and 4 phase change material (PCM) units each containing 150 L sodium acetate trihydrate composite has been built. Experimental investigation has shown advantages of utilization of stable supercooling of sodium acetate trihydrate in spring and autumn. In this paper, a newly developed numerical model was used to investigate the performance potential of the system with combined utilization of the water tank and the PCM units, including on-demand crystallization of supercooled sodium acetate trihydrate composites. PCM units, the water tank and the collector circuit models were validated with measurement data from system demonstration. Space heating and hot water demand patterns of a Danish single-family Passive House with a yearly heat demand of 3723 kWh were applied. Results showed that a 56{\%} annual solar fraction of heat supply was achieved with the prototype specifications. A 69{\%} solar fraction could be achieved with an optimized scenario including a 15{\%} increased hot water demand. Sensitivity analysis of component sizing showed that PCM units of 200 L can be more efficiently used with a 0.6m3 water tank. Optimal solar collector array tilt was 70°. Aperture areas between 12.8 and 22.4m2 were found adequate for frequent utilization of a PCM volume up to 1m3. Thus, the PCM heat storage capacity could be utilized at least 5.5 times a year. With a 22.4m2 collector area and 5 PCM units of 200 L each, a solar fraction of 71{\%} was calculated for the annual heat supply. Assuming full charge of a 0.6m3 water tank and 2.8m3 of sodium acetate trihydrate composite by electricity at the beginning of the year, the system could run 18 days without need for auxiliary heating. Thus, in periods without solar collector power available, generation maxima of wind power could be utilized. In conclusion, building heat demand could be covered close to 100{\%} by renewable energy resources.",
keywords = "Solar heating system, Phase change material, Sodium acetate trihydrate, Stable supercooling, Passive House, Numerical simulation",
author = "Gerald Englmair and Christoph Moser and Hermann Schranzhofer and Jianhua Fan and Simon Furbo",
year = "2019",
doi = "10.1016/j.apenergy.2019.03.125",
language = "English",
volume = "242",
pages = "1108--1120",
journal = "Applied Energy",
issn = "0306-2619",
publisher = "Pergamon Press",

}

A solar combi-system utilizing stable supercooling of sodium acetate trihydrate for heat storage: Numerical performance investigation. / Englmair, Gerald; Moser, Christoph; Schranzhofer, Hermann; Fan, Jianhua; Furbo, Simon.

In: Applied Energy, Vol. 242, 2019, p. 1108-1120.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - A solar combi-system utilizing stable supercooling of sodium acetate trihydrate for heat storage: Numerical performance investigation

AU - Englmair, Gerald

AU - Moser, Christoph

AU - Schranzhofer, Hermann

AU - Fan, Jianhua

AU - Furbo, Simon

PY - 2019

Y1 - 2019

N2 - To reduce the energy consumption of buildings significantly, a novel solar combi-system with short and longterm heat storage has been developed. A system prototype with 22.4m2 (aperture) evacuated tubular collectors, a 735 L water tank and 4 phase change material (PCM) units each containing 150 L sodium acetate trihydrate composite has been built. Experimental investigation has shown advantages of utilization of stable supercooling of sodium acetate trihydrate in spring and autumn. In this paper, a newly developed numerical model was used to investigate the performance potential of the system with combined utilization of the water tank and the PCM units, including on-demand crystallization of supercooled sodium acetate trihydrate composites. PCM units, the water tank and the collector circuit models were validated with measurement data from system demonstration. Space heating and hot water demand patterns of a Danish single-family Passive House with a yearly heat demand of 3723 kWh were applied. Results showed that a 56% annual solar fraction of heat supply was achieved with the prototype specifications. A 69% solar fraction could be achieved with an optimized scenario including a 15% increased hot water demand. Sensitivity analysis of component sizing showed that PCM units of 200 L can be more efficiently used with a 0.6m3 water tank. Optimal solar collector array tilt was 70°. Aperture areas between 12.8 and 22.4m2 were found adequate for frequent utilization of a PCM volume up to 1m3. Thus, the PCM heat storage capacity could be utilized at least 5.5 times a year. With a 22.4m2 collector area and 5 PCM units of 200 L each, a solar fraction of 71% was calculated for the annual heat supply. Assuming full charge of a 0.6m3 water tank and 2.8m3 of sodium acetate trihydrate composite by electricity at the beginning of the year, the system could run 18 days without need for auxiliary heating. Thus, in periods without solar collector power available, generation maxima of wind power could be utilized. In conclusion, building heat demand could be covered close to 100% by renewable energy resources.

AB - To reduce the energy consumption of buildings significantly, a novel solar combi-system with short and longterm heat storage has been developed. A system prototype with 22.4m2 (aperture) evacuated tubular collectors, a 735 L water tank and 4 phase change material (PCM) units each containing 150 L sodium acetate trihydrate composite has been built. Experimental investigation has shown advantages of utilization of stable supercooling of sodium acetate trihydrate in spring and autumn. In this paper, a newly developed numerical model was used to investigate the performance potential of the system with combined utilization of the water tank and the PCM units, including on-demand crystallization of supercooled sodium acetate trihydrate composites. PCM units, the water tank and the collector circuit models were validated with measurement data from system demonstration. Space heating and hot water demand patterns of a Danish single-family Passive House with a yearly heat demand of 3723 kWh were applied. Results showed that a 56% annual solar fraction of heat supply was achieved with the prototype specifications. A 69% solar fraction could be achieved with an optimized scenario including a 15% increased hot water demand. Sensitivity analysis of component sizing showed that PCM units of 200 L can be more efficiently used with a 0.6m3 water tank. Optimal solar collector array tilt was 70°. Aperture areas between 12.8 and 22.4m2 were found adequate for frequent utilization of a PCM volume up to 1m3. Thus, the PCM heat storage capacity could be utilized at least 5.5 times a year. With a 22.4m2 collector area and 5 PCM units of 200 L each, a solar fraction of 71% was calculated for the annual heat supply. Assuming full charge of a 0.6m3 water tank and 2.8m3 of sodium acetate trihydrate composite by electricity at the beginning of the year, the system could run 18 days without need for auxiliary heating. Thus, in periods without solar collector power available, generation maxima of wind power could be utilized. In conclusion, building heat demand could be covered close to 100% by renewable energy resources.

KW - Solar heating system

KW - Phase change material

KW - Sodium acetate trihydrate

KW - Stable supercooling

KW - Passive House

KW - Numerical simulation

U2 - 10.1016/j.apenergy.2019.03.125

DO - 10.1016/j.apenergy.2019.03.125

M3 - Journal article

VL - 242

SP - 1108

EP - 1120

JO - Applied Energy

JF - Applied Energy

SN - 0306-2619

ER -