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Solar assisted cooling with a multi-stage absorption chiller.

Author(s) : RIEPL M., GURTNER R., SCHWEIGLER C.

Summary

Commercially available solar thermal cooling installations are commonly based on hot water-driven single-effect absorption chillers. This configuration yields a considerable solar cooling performance, when solar heat is applied as driving heat source only. Yet, in commercial installations requiring reliable supply of cooling with no regard to the current availability of solar driving heat, fossil fired boilers are applied as back-up heat source. In this case a rather poor utilization of the driving heat is accomplished as measured by the exergetic content of the fossil driving heat. For improved utilization of the fossil fuel serving as backup driving energy input for the absorption chiller an integrated double/single-effect chiller can be applied. Solar driving heat is supplied to the conventional single-effect sub-cycle, whereas fossil back-up firing drives the double-effect stage of the chiller allowing for a more efficient utilization of the fossil energy. During the transitional period the plant can serve for simultaneous cooling and heating. In winter operation the system operates in heat pump mode for upgrading of low temperature heat from the solar collector system or with low-grade heat input from any other ambient heat source. In summer 2010 a pilot installation of such a system has been installed and commissioned. The system provides heating and cooling energy for an office building with flexible operational modes. The core of the system is formed by the double-/single-effect LiBr/water absorption chiller which is based on a commercially available single-effect hot water driven chiller which has been slightly adapted for the integration of the double-effect stage. This double-effect stage contains a direct gas-fired high temperature generator which has been designed as a natural convection steam generator with vertical boiling tubes. In this work the system and chiller design with its different operational modes for flexible provision of heating and cooling energy is presented. Also, a numerical model for the dynamic simulation of the system has been developed which promises a prediction of the energetic efficiency. The first monitoring data of the real system have been used to validate the numerical model. The performance of the innovative double-/single-effect plant in the system’s environment has been analyzed based on the consideration of the thermodynamic mechanisms of the internal absorption cycle depending on the availability of solar heat as driving source for the single-effect stage and the resulting need of additional fossil heat supplied to the double-effect stage.

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Pages: 923-930

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Details

  • Original title: Solar assisted cooling with a multi-stage absorption chiller.
  • Record ID : 30001297
  • Languages: English
  • Source: Sources/sinks Alternative to the Outside Air for Heat Pump and Air-conditioning Techniques (Alternative Sources - AS), Padua, Italy, April 5-7, 2011. / International Sorption Heat Pump Conference (ISHPC11), Padua, Italy, April 6-8, 2011.
  • Publication date: 2011/04/06

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