Presentation of a draft solar Striling engine prototype: the STHELIO
This project was directed by Genie Physics Department of the University of Clermont-Ferrand.
Project Team: 42 Engineering Physics Students / Teachers Engineering Physics industry.
Study duration: September 2003 May 2005
Partners: ANVAR, ADEME, ENERIA, Solar Oven Development Association La Rose des Dunes.
Objective of the project
The aim of this project is to provide a solar energy converter into electrical energy through a Stirling 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) devised an engine using a liquid or gaseous fluid, contained in a closed enclosure, heated by a source of heat outside the enclosure, and subjected to high pressures: the "Stirling engine".
The Stirling engine is a heat engine converting thermal energy into mechanical energy and which theoretically operates on the Stirling thermodynamic cycle.
The motor has a "hot spot" and a "cold spot". A gas flows between these two points and thus undergoes alternating compression and expansion. This gas pulsation is used to drive a piston which allows the mechanical energy to be recovered. The theoretical transformations of the Stirling cycle impose discontinuous movements of the displacer and the engine piston.
The hub and the architecture of the frame.
The concentrator parabolic shape focuses the sunlight into a focal spot five centimeters in diameter located at the focus of the parabola. To reflect maximum radiation mainly in the visible range, the surface of the hub is covered with a layer of aluminum vacuum deposited protected by a varnish.
The parable on its support
The setting of concentrator azimuth type driven by two stepper motors. Mechanically, the azimuthal motion is assured by a geared motor, the elevation through an electric jack.
The linear motor mechanical coupling (beta architecture).
The pulsation of the gas is recovered by a piston coupled via a dual linkage (mechanical coupling) to a generator and produces electrical energy.
Beta engine and generator
The collector (hot source) made of refractory steel is located in the focus of the parabola as the main cylinder (heat sink) is cooled by water circulation.
The linear motor electromagnetic coupling.
Alongside the type of motor Beta we studied a stirling engine linear electromagnetic coupling types. The reciprocating linear motion of the displacer is performed by a linear stepper motor. The pulsation of the gas is recovered by a piston which moves a linear alternator producing electric current. This engine is completely free of any mechanical coupling with the exception of the linear alternator spring.
The linear motor
The solar tracking.
The system is equipped with a solar monitoring to continually maintain the axis of the parabola towards the sun
The system operates autonomously using a program developed Labview (r) which takes into account the data from the various sensors (temperature, position and solar flow, pressure, ...). This program manages the automation of solar tracking.
GUI control program