Presentation of a prototype solar Striling motor project: the STHELIO
This project was carried out by the Engineering Physics department of the University of Clermont-Ferrand.
Project Team: 42 Engineering Physics Students / Teachers Engineering Physics industry.
Duration of the study: September 2003 to May 2005
Partners: ANVAR, ADEME, ENERIA, Solar Oven Development Association La Rose des Dunes.
Objective of the project
The goal of this project is to realize a converter of solar energy into electrical energy by means of a Stirling type engine.
Cahier des charges
Main characteristics of the solar motor are:
- Solar collector area: 2.5 m²
- power output: 250 500 to W
- autonomous operation
- automatic position follow the sun
- data management via Labview software (r)
- Beta Stirling engine
- Working gas: nitrogen
- 1 10 pressure in bars
- temperature of the hot source 600 900 ° C to ° C
- temperature of the cold source to 20 50 ° C
- speed: 500 900 to rev / min.
Stirling engine operating principle
Robert Stirling (1790-1878) imagined an engine using a liquid or gaseous fluid, contained in a closed chamber, heated by a heat source outside the chamber, and subjected to high pressures: the “Stirling engine”.
The Stirling engine is a thermal machine that converts thermal energy into mechanical energy and which theoretically operates according to the thermodynamic Stirling cycle.
The engine has a "hot spot" and a "cold spot". A gas circulates between these two points and thus undergoes alternately compression and expansion. This gas pulsation is used to drive a piston which recovers mechanical energy. Theoretical transformations of the Stirling cycle impose discontinuous movements of the displacer and the driving piston.
The concentrator and the architecture of the building.
The concentrator, of parabolic geometry, concentrates the sun's rays in a focal spot five centimeters in diameter located at the focus of the parabola. In order to reflect the maximum of rays mainly in the visible range, the surface of the concentrator is covered with a layer of vacuum deposited aluminum protected by a varnish.
The parable on its support
The hub of the concentrator is azimuthal type, driven by two stepper motors. Mechanically, the azimuthal movement is provided by a gear motor, that of elevation by an electric cylinder.
The linear motor mechanical coupling (beta architecture).
The gas pulsation is recovered by a piston coupled, via a double linkage (mechanical coupling), to a generator which thus produces electrical energy.
Beta engine and generator
The collector (hot source) made of refractory steel is located at the focus of the parabola while the main cylinder (cold source) is cooled by circulating water.
The linear motor electromagnetic coupling.
In addition to the Beta type engine, we have studied a linear type stirling engine with electromagnetic coupling. The reciprocating linear motion of the displacer is achieved by a linear stepping motor. The gas pulsation is recovered by a piston which sets in motion a linear alternator producing electric current. This engine is therefore completely devoid of mechanical coupling except for the spring of the linear alternator.
The linear motor
The solar tracking.
The system is equipped with a solar tracking allowing to continuously maintain the axis of the dish in the direction of the sun
The system operates autonomously using a program developed in Labview (r) which takes into account the data supplied by the various sensors (temperature, position and solar flux, pressure, etc.). This program manages the automation of solar monitoring.
GUI control program