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Solar assisted absorption cooling machine with optimized utilization of solar energy



The state of the art of solar driven cooling devices is the combination of a single effect absorption chiller (SE-AC) and conventional furnaces using gas or oil as a fuel. If the available solar heat supply is not enough for the chiller operation, heat from the furnace supplies the absorption machine. This operation change causes an abrupt decrease of the system efficiency (COP). Due to the low efficiency in the gas driven mode a substantial solar contribution of 30 to 50% is necessary to save primary energy compared to an efficient electrically driven compression chiller.
For this reason the main objective of this project is to develop an absorption cooling machine, which can use either solar energy from thermal collectors or natural gas with a higher COP than standard single effect chillers.

Technical Approach

The concept of this project is to set up a double effect absorption chiller (DE-AC) which is gas fired but modified allowing it to be driven directly by hot water from thermal collectors. Essentially this machine acts as a highly efficient DE-AC when driven by gas and as a SE-AC when using solar energy. Compared with the system described above (only SE-AC, solar collector, furnace as a backup), this would lead to an additional saving of about 40% of the fuel consumption for cooling. The solar contribution necessary to reduce the primary energy demand compared to the compression chiller is in this case only 10% -
which can easily be reached in Southern Europe.

The pilot unit will be in the range of 25 kW cooling capacity typical for small size office buildings, restaurants etc. The reasons for this choice are firstly to have a machine which is not far from the very low capacities needed for residential houses and secondly a machine which can be scaled up or used in a modular way to cover the range necessary for hotels, hospitals, food storage etc. Moreover this is a range which is not well covered by existing manufacturers. As the available area for solar collectors is in general limited, this also favours the low to medium capacity range.

Expected Achievements and Exploitation

The outputs of this project will be:
evaluation of the feasibility and economy of the system
development of software tools for the simulation of solar cooling installations
definition of the layout and the control strategy
design, dimensioning and construction of the components
setup of the laboratory prototype and extended tests

Within 18 months a prototype will be developed, constructed and tested. The results will allow to decide if there is a chance to build and market a solar assisted absorption chiller, which is not only highly efficient but also economical.

Call for proposal

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EU contribution
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Am Hubland

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Total cost
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Participants (4)