Modelling and control of solar thermal system with borehole seasonal storage

The paper addresses the problem of controlling a solar thermal storage system with the purpose of achieving a desired thermal comfort level and energy savings. A solar thermal power plant is used for heating district houses with borehole seasonal energy storage. As the energy output from the solar thermal plant with borehole seasonal storage varies, the control system maintains the thermal comfort by using a servo controller. In this work, the modelling of the solar thermal system with borehole seasonal storage is inspired by the Drake Landing Solar Community in Okotoks, Alberta, Canada [1]. The discrete model of the integrated energy system is obtained by using energy preserving Cayley-Tustin discretization. A simple and easily realizable servo control algorithm is designed to regulate the system operating at desired thermal comfort level despite disturbances from the solar thermal plant system, the borehole geo-thermal energy storage system and/or the district heating loop system. Finally, the performance of the servo controller and frequency analysis of the plant is given in simulation results section.