Drying is one of the most energy-intensive processes in agro-products industry.
For this reason, using solar energy appears as an attractive not polluting alternative
to be used in drying processes. However, the daily and seasonal fluctuations in
the radiation level require using energy accumulators with phase change materials
(paraffin wax), to have a continuous drying processes. In hybrid solar dryers with
energy accumulation system, a control system is essential to coordinate the control
valves that allow the income of air that comes from the solar panel or from the
energy accumulator. In this work, we implemented an advances multivariable control
system that uses fuzzy logic in the hybrid solar dryer. The dryer includes an energy
accumulator panel with paraffin wax as phase change material. The input variables
were ambient temperature and solar radiation, both not controllable. The controlled
variables were the opening level of the solar panel and accumulator energy valves.
The control program consisted in an algorithm implemented with the “Fuzzy” toolbox
in Matlab. Data were acquired with OPTO 22. The control system performed adequately
when used to dehydrate mushroom slices and plums. Closing or opening the respective
valves as a response to the variations of solar radiation and ambient air temperature
allowed optimizing the use of solar energy.