Temperature Control of a Solar Furnace with Exact Linearization and Off-Line Identification
The ability to predict the behavior of materials is crucial in several industries due to safety aspects, such as in high temperature furnaces for the production of glass, in the nuclear energy industry or in the high concentrated thermal solar systems. Solar furnaces use concentrated solar radiation that can be used to perform material stress tests with high temperatures. These devices have nonlinear dynamics that are caused by the actuator, the shutter, and by the interaction between the solar energy and the properties of the material. The contribution of this paper consists in the design of a controller for practical use based on the exact linearization method with off-line identification. The aim is to improve the controller performance to track the temperature profile. In this context it is assumed that the thermodynamic properties of the sample material to be tested are unknown.
Control of a Solar Furnace using MPC with Integral Action
Abstract Solar furnaces are devices employed in high temperature material stress tests that use concentrated solar energy. This process has a nonlinear dynamics caused by a fourth power temperature term and by the nonlinear behavior of the shutter. Sun power variability due to weather conditions may affect the operation of a solar furnace if it is not compensated by adjusting the shutter aperture. The contribution of this paper is to explore and to evaluate the application of model predictive control with integral action to a nonlinear process. Off-line identification is employed to characterize the temperature dynamics. This methodology avoids the use of online adaptation mechanisms that may cause stability problems during temperature stress tests that may melt the material sample. The aim is to design a controller with a good performance, able to track the temperature cycling profile without overshooting to avoid melting the material sample. Active cooling is also explored to improve the temperature tracking during the decrease of the temperature profile. Experimental results obtained from the closed loop control of the plant are presented.
Melting and casting of alloys in a solar furnace
A feasibility study conducted using a small working model of a solar furnace is reported in which the melting and casting of various alloys was tested. The prototype furnace had either a spun copper or aluminum hemispherical concentrator, and was manually tracked. A later self-tracking version consisted of a paraboloidal cofiguration fabricated from a wire mesh antenna covered with aluminized polyester. The experimental results show that a simple and inexpensive solar furnace could be commercialized in the near future. (SPH)