Temperature control of a greenhouse heated by renewable energy sources

The paper proposes a system developed to provide heat for a greenhouse using parabolic trough collectors (GHPTC). The GHPTC control system has the goal to maintain the temperature inside the greenhouse at a desired level, with the actuating variable the flow of the conducting fluid through collector pipes. Considering this aspect, the proposed model takes into account as an output variable the internal temperature of the greenhouse as it influences directly the growth of the plants. The GHTPC model consists of two individual parts: the greenhouse model and the collector´s model. Both were validated using real data, considering the maxim error between the real and simulated data on a period of one day. A nonlinear and linear model were deducted for the complex GHPTC system. Based on the linearized model, a PID controller was tuned and used to control the internal temperature in the greenhouse. The control method is suited for the system according to the obtained stationary and transient response performances.