IEA Solar Heating and Cooling Programm - NachhaltigWirtschaften.at

IEA SHC Task 38 Solar Air Conditioning and Refrigeration Subtask C1 Report, 31 October 2010
6 Thermo-mechanical chillers
Klaus Ellehauge (Ellehauge and Kildermoos, Denmark)
6.1 Brief description of the technology
Thermo-mechanical chillers are mechanically driven heat-pumps where the mechanical
driving forces are provided by conversion of low temperature heat to mechanical energy.
The idea of providing cooling by combining a mechanical heat pump with a machine for
conversion of low temperature heat to mechanical power has only been tried by very few
companies. To be successful it would seem desirable to integrate the mechanical structure
and the thermodynamics of the two processes.
Of course in separate processes, the mechanical driven heat pump is a well known
technology, while the applicable technology for the conversion of low temperature heat, e.g
from a solar collector, to mechanical power is not so well developed.
This technology is available only from a small number of larger companies, while a larger
amount of smaller companies are researching the technology.
The conversion of thermal power to mechanical power follows the Rankine cycle. In order to
keep the driving temperatures low it is most common to operate the Rankine machine with
an organic liquid as the working fluid. The technology making use of organic Rankine cycles
is often referred to as ORC technology. The temperature ranges in which the ORC machines
run efficiently are however not low enough to fully suit low temperature solar collectors.
However a Danish system under development that uses water at low pressure, operates at
temperatures suited for solar collectors and provides cooling as well.
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