500W - 1500W Cogenerative Stirling engine
El.Ma has realized several Stirling engines from 500 W up to 1500 W, connected to an electric generator for the production of electrical energy that currently is in the testing phase thanks to the interface to a process controller and appropriate sensors.
The Stirling engine is based on the continuous and controlled external combustion principle that is characterized by low pollution and, from a theoretical point of view, high efficiency emissions; it isn't equipped with any valve or iniection system, and in this way it allows long time-breaking and low service costs.
There are different configurations of the Stirling engine: the version realized by El.Ma. through manufactures with numerical control machines (CNC) is a gamma one, and comprises two cylinders, one rigenerator, a piston and a displacer that is 90° ahead than power piston.
The fuel, of any kind (flame, radiation, etc.), supplies thermal energy (heat) to the engine from outside in order to keep the high temperature in the upper side of the cylinder, while in the opposite side the low temperature is obtained through an appropriate cooling circuit.
The power factor comes from the differences of pressure inside a certain gas mass that is alternatively heated, cooled and moved from side to side of the engine between two areas with different temperature by the displacer.
The thermal efficiency is increased by the the rigenerator and this differentiates the Stirling engine from a hot fluid engine made by a thin mesh, which work as a deposit for the heat extracted from the fluid carrier during the passage to the cool side in order to return in the following passage to the hot side.
In order to generate electrical energy, the engine is connected to a permanent magnet electric generator that is connected in turn to a smart load; moreover, thanks to the fluid cooling circuit and to a heat exchanger, it is possible to remove the thermal energy produced by the cycle as heat.
Thanks to a driver developed ad hoc, the generator works also as an electric motor for the automated start-up.
In order to improve the efficiency, a combustion chamber and cooling system have been realized to produce hot water for domestic use.
The testing of the engine and the check of parameters of the Stirling cycle are carried on with the assistance of the process control, developed by El.Ma., and connected to an appropriate system of sensors, for the survey and the logging of all useful data such as rounds, pressures, temperatures, vibrations, electrical sizes, etc.