Sub-hourly simulation of residential ground coupled heat pump systems

Michael Kummert, Michel Bernier

Research output: Contribution to journalArticle

19 Citations (Scopus)
42 Downloads (Pure)

Abstract

Residential Ground Coupled Heat Pump systems are usually characterised by an ON/OFF behaviour of the heat pump with typical cycling frequencies of 1 - 4 cycles per hour. The ground loop fluid pump has the same ON/OFF behaviour and the borehole heat exchanger operates either in full flow or no flow conditions. Typical hourly simulations of GCHP systems use steady-state models for the heat pump and the borehole fluid (transient models being used for buildings and heat transfer in the ground). This paper reviews the models used in typical hourly simulations as well as transient models that are available and compares the results obtained using the two classes of models within the TRNSYS simulation environment. Both the long-term energy performance and the optimum system design are compared. It is shown that using steady-state models leads to an overestimation of the energy use that ranges from a few percents with oversized borehole heat exchangers to 75% for undersized exchangers. A simple Life Cycle Cost analysis shows that using steady-state models can lead to selecting a very different design than the one that would have been selected using dynamic models.
Original languageEnglish
Pages (from-to)27-44
Number of pages17
JournalBuilding Services Engineering Research and Technology
Volume29
Issue number1
DOIs
Publication statusPublished - 2008

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Heat pump systems
Boreholes
Pumps
Heat exchangers
Fluids
Life cycle
Dynamic models
Systems analysis
Heat transfer
Costs

Keywords

  • pumps
  • pump systems
  • building engineering
  • energy
  • cost analysis

Cite this

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title = "Sub-hourly simulation of residential ground coupled heat pump systems",
abstract = "Residential Ground Coupled Heat Pump systems are usually characterised by an ON/OFF behaviour of the heat pump with typical cycling frequencies of 1 - 4 cycles per hour. The ground loop fluid pump has the same ON/OFF behaviour and the borehole heat exchanger operates either in full flow or no flow conditions. Typical hourly simulations of GCHP systems use steady-state models for the heat pump and the borehole fluid (transient models being used for buildings and heat transfer in the ground). This paper reviews the models used in typical hourly simulations as well as transient models that are available and compares the results obtained using the two classes of models within the TRNSYS simulation environment. Both the long-term energy performance and the optimum system design are compared. It is shown that using steady-state models leads to an overestimation of the energy use that ranges from a few percents with oversized borehole heat exchangers to 75{\%} for undersized exchangers. A simple Life Cycle Cost analysis shows that using steady-state models can lead to selecting a very different design than the one that would have been selected using dynamic models.",
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note = "Also published in Proceedings of the 7th International Conference on System Simulation in Buildings. University of Liege, pp. 34-46, 2006.",
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}

Sub-hourly simulation of residential ground coupled heat pump systems. / Kummert, Michael; Bernier, Michel.

In: Building Services Engineering Research and Technology , Vol. 29, No. 1, 2008, p. 27-44.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Sub-hourly simulation of residential ground coupled heat pump systems

AU - Kummert, Michael

AU - Bernier, Michel

N1 - Also published in Proceedings of the 7th International Conference on System Simulation in Buildings. University of Liege, pp. 34-46, 2006.

PY - 2008

Y1 - 2008

N2 - Residential Ground Coupled Heat Pump systems are usually characterised by an ON/OFF behaviour of the heat pump with typical cycling frequencies of 1 - 4 cycles per hour. The ground loop fluid pump has the same ON/OFF behaviour and the borehole heat exchanger operates either in full flow or no flow conditions. Typical hourly simulations of GCHP systems use steady-state models for the heat pump and the borehole fluid (transient models being used for buildings and heat transfer in the ground). This paper reviews the models used in typical hourly simulations as well as transient models that are available and compares the results obtained using the two classes of models within the TRNSYS simulation environment. Both the long-term energy performance and the optimum system design are compared. It is shown that using steady-state models leads to an overestimation of the energy use that ranges from a few percents with oversized borehole heat exchangers to 75% for undersized exchangers. A simple Life Cycle Cost analysis shows that using steady-state models can lead to selecting a very different design than the one that would have been selected using dynamic models.

AB - Residential Ground Coupled Heat Pump systems are usually characterised by an ON/OFF behaviour of the heat pump with typical cycling frequencies of 1 - 4 cycles per hour. The ground loop fluid pump has the same ON/OFF behaviour and the borehole heat exchanger operates either in full flow or no flow conditions. Typical hourly simulations of GCHP systems use steady-state models for the heat pump and the borehole fluid (transient models being used for buildings and heat transfer in the ground). This paper reviews the models used in typical hourly simulations as well as transient models that are available and compares the results obtained using the two classes of models within the TRNSYS simulation environment. Both the long-term energy performance and the optimum system design are compared. It is shown that using steady-state models leads to an overestimation of the energy use that ranges from a few percents with oversized borehole heat exchangers to 75% for undersized exchangers. A simple Life Cycle Cost analysis shows that using steady-state models can lead to selecting a very different design than the one that would have been selected using dynamic models.

KW - pumps

KW - pump systems

KW - building engineering

KW - energy

KW - cost analysis

U2 - 10.1177/0143624407087286

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JO - Building Services Engineering Research and Technology

JF - Building Services Engineering Research and Technology

SN - 0143-6244

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