Abstract
The main objective of the present research work is to propose an innovative transient model of a solar collector. Here, the collector is modelled as a discrete time linear dynamic system of the first order, with average temperature of the collector as state variable and, direct radiation, diffused radiation, ambient temperature and inlet temperature of heat transfer fluid, as a set of input to the system. Useful thermal energy transferred to the heat transfer fluid is the output. The parameters of the model have been determined using Kalman filter method. Kalman filter is a recursive method of system identification, thus it is possible to have on line simulation that permits the use of advanced methods of systems control.
The necessity to introduce tests in transient conditions depends essentially on the facts that the collector testing under steady state requires stringent conditions (tests to be conducted under mid-day without sun following surface, clear sky and very low diffused radiation, fixed inlet flow rate and the temperature) and hence lengthy test period and high cost. Transient method enables testing to be extended over the entire day (with possible acquisition of much higher numbers of experimental data on the daily basis in comparison to the steady state method) without any strict condition of a clear sky. On the contrary, for an accurate and precise determination of different parameters it is necessary to test a collector under cloudy days, as well. Testing under transient conditions takes into account the dynamic behaviour of collector through proper use of its thermal capacity or equivalent parameters thus making the model workable under real conditions. To avert problems and the limitations associated with the collector testing under steady state conditions, a test under transient conditions called QDT (EN, 12975-2) has been introduced in the existing norms. A series of models and methodologies already proposed and, in most of the cases validated, as well, are reported in reference (E. H. Amer, 1997). In this paper is implemented an innovative dynamic model for solar collector based on Kalman Filter (Sergio Bittanti, 2002). The starting point to
Keywords
Dynamic Model, Solar Collector, Kalman Filter Method
References
E. H. Amer, J. K. Najak and G. K. Sharma (1997) Transient test methods for flate plate collectors: review and experimental evaluation, Solar Energy, 60(5): 229-243. EN (12975-2) Thermal solar systems and components - Solar collectors- part 2: Test methods. J. A. Duffle, W. A. Beckman (1990) Solar Engineering of Thermal Processes, second edition, John Wiley and Ruberti, A. Isidori, Teoria del Sistemi, Bollati Boringhieri, Torino. Sergio Bittanti (2002) Teoria della Predizione e del Filtraggio, Pitagora editrice Bologna, Milano. J. A. Duffle, W. A. Beckman (1991) Solar Engineering of Thermal Processes, second edition, John Wiley and Sons.