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Ground-source heat pump with recharging of the borehole.

Bergvärmepump med borrhålsåterladdning.

Author(s) : FAHLÉN P.

Type of article: Article

Summary

Vertical bore-holes in dry bed-rock are commonly used as heat source in Swedish heat pump installations. Indeed, the winners of the Swedish heat pump competition in 1996 have this as the first alternative. Calculations as well as measurements have shown that currently used design depths of bore-holes result in minimum brine temperatures in the range -3 to -5 °C. Performance of a heat pump system typically improves with 2-4%/K and hence it is important to increase inlet brine temperature. There are two basic options for improvement: a deeper borehole or recharging from an alternative heat source (e.g. exhaust-air or a solar system). The article discusses thermo-economic optimisation of the combination bore-hole/exhaust-air heat-recovery. In situ measurements confirm calculated brine temperatures. Furthermore, calculations as well as measurements underline the importance of minimizing power input to pumps and fans that are used in the distribution systems. With recharging and heat-recovery, the brine temperature never goes below zero and hence defrosting of the exhaust-air coil will not be necessary. Also, a much smaller amount of anti-freeze suffices and this will both improve heat transfer and decrease electric input to the brine pump.

Details

  • Original title: Bergvärmepump med borrhålsåterladdning.
  • Record ID : 2004-2479
  • Languages: Danish
  • Source: ScanRef - vol. 32 - n. 6
  • Publication date: 2003/11
  • Document available for consultation in the library of the IIR headquarters only.

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