Hiroshima

Japan - Air-source heat pump

 
Summary
The Hiroshima Kita local office of the Chugoku Electric Power Co. implemented a heat-pipe ice thermal storage system (l’stock) for its air-conditioning needs. Initially the company increased the temperature differential between the supply and return chilled/hot water to 10ºC by using low temperature chilled water, characteristic of ice thermal storage. This large water temperature differential permitted the circulating water flow rate to be cut in half and, hence, the capacity of primary and secondary circulating pumps and the diameter of chilled and hot water pipes to be reduced.  		 

 

l' stock installed in the Hiroshima Kita office.

These measures allowed significant reduction in the initial investment and running costs of the l’stock system.


Building and design values

 
Building type: Office
Location: Hiroshima, Japan
Year of construction: No data
Number of storeys: 4
Heated floor area (m2): 4 351
% of total floor area (%): No data
Design values: No data


Heating and cooling

 
Application: Space heating and cooling
Heat pump type(s): Air
Heat pump installed capacity (kW) Heating: 105.5 Cooling: -
Refrigerant: R22
Heat source Air
Details: The l’stock is a compact ice storage system consisting of an air-source heat pump, an ice storage tank using a heat-pipe for ice production, and a control panel. The secondary side of the system has adopted a close circulation system to save pumping power.
Distribution system(s): Fan coils
Supply and return temperature (ºC)
Summer (S) and winter (W) operation		 Heating: No data Cooling: No data
Auxiliary system: No data
Heat pump design: No data
Supplementary system: No data
Heat pump system completion date: No data


Additional information

The l’stock can operate in various modes:

Ice making using the heat pipe.

  • Ice thermal storage (storing ice) and air-conditioning for cooling (supplying chilled water) in the cooling season.

  • Heat storage (storing hot water) and air-conditioning for heating (supplying hot water) in the heating season. The control panel automatically switches the mode of operation between the thermal storage and the airconditioning modes. The system is set to operate in thermal storage mode for 7.5 h and in air-conditioning mode for 16 h.

     

    The company increased the temperature differential between the supply and return chilled/hot water to 10ºC by using low-temperature chilled water, characteristic of ice thermal storage. This temperature differential permitted the circulating water flow rate to be cut in half and, hence, the capacity of primary and secondary circulating pumps and the diameter of chilled and hot water pipes to be reduced.


    Performance

     
    Heating energy Heat pump Aux. heating system Auxiliaries
    Energy input (kWh/year): 39 296 - -
    Energy output (kWh/year): No data - n/a


    Cooling energy Heat pump Aux. heating system Auxiliaries
    Energy input (kWh/year): 97 471 - -
    Energy output (kWh/year): No data - n/a
    Note:
    The load shifting ratio by the l’stock in the cooling and heating seasons was 36% and 29%, respectively.

    Coefficient of performance (COP)
    Heating: 3.29 (2.72 heat storage)
    Test conditions: No data
    Cooling: 3.08 (2.79 ice storage)
    Test conditions: No data


    Heat pump cost breakdown
    Heat pump only (JPY): Total investment JPY 9 920 000 higher than for a 122 kW air-source heat pump air-conditioning system without thermal storage
    Installation (JPY):
    Capital cost (excluding heat pump) (JPY):
    Maintenance: No data


    Alternative system (if has been considered) Comparisons made to a corresponding 122 kW air-source heat pump without thermal storage. Annual savings with the current system are about JPY 2 140 000. There are additional cost savings by the reduced power consumption of the circulating pumps.


    Fuel cost No data


    Payback 4.6 years for the incremental investments


    CO2 emissions No data


    Operational experience and other comments
    The system does not require significant amounts of time and labour for installation and needs only little space.

    Contacts
    This case study is presented on Caddet website at http://www.caddet.org.

     

     
    Last updated: 1 March 2004
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