How it Works

ORC is similar to steam cycle used in big power plants to produce electricity but, in this case, an organic fluid is used instead of water as working fluid. Organic fluid is similar to air-conditioning fluids and allows to perform the Rankine cycle at lower temperatures. The working fluid in a closed cycle gathers heat from a heating source or a hot reservoir and generates a hot gaseous stream that expands through a volumetric expander to generate power.



The working fluid is pumped (ideally isentropically) from a low pressure to a high pressure by a pump. While the current technology in large and medium-scale ORC installations is represented by centrifugal feed pumps, this solution is not suitable for smaller systems: in fact, the concurrent requirements of low flow rates and high differential pressures can be satisfied by a centrifugal machine only if multi-stage architectures are considered, but this option entails excessive costs. Positive displacement pumps are then a more suitable alternative for small-scale ORCs, but they involve some drawbacks such as a relatively low efficiency. Kaymacor machine utilize a proprietary solution for the pump whose efficiency is 55% (compare to 15% of commercial solutions).



The high-pressure liquid stream enters the evaporator where it is heated at constant pressure by an external heat source to become a saturated vapor stream. Common heat sources for organic Rankine cycles are exhaust gases from combustion systems (power plants or industrial processes), hot liquid or gaseous streams from industrial processes or renewable thermal sources such as geothermal, solar thermal or biomass. Down-scaling of ORC technology has required utilization of plate heat exchangers instead of shell and tube exchangers used in big ORC machines.



The superheated or saturated vapor stream expands through the expander to generate power output. The expansion decreases the temperature and pressure of the vapor stream. Machines of small size, in order to take advantage of the same enthalpy jump of larger machines must be structurally different from those currently developed. Kaymacor system implements a volumetric expander whose main features are: low weight, high efficiency, lower noise level, reduced vibrations and high reliability. Efficiency of the volumetric expander integrated in MORGANA system is 70%. Kaymacor system implements a very efficient electrical machine. In fact, the low enthalpic content of heat source requires optimization of all the components and high electrical conversion efficiency.



The vapor stream enters the condenser where it is cooled to generate a saturated liquid stream. In this phase heat is produced for cogeneration application. Temperature of such heat can be selected in a large range.


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