Dehumidifier for photovoltaic modules, of a series of photovoltaic concentration modules, formed by a common air inlet and outlet access that communicates all the modules, and which passes through a bed of moisture absorbing material, having an electrical self-adjusted resistance (15) installed therein. The circuit is completed with a solenoid valve (13), a flow switch (19), a non-return valve (12); a pressure switch (16) and a timer relay (20). The process is based on pressure differences existing within the photovoltaic modules throughout the day, and consists of two steps: drying air by passing through the bed of absorbent material before entering into the photovoltaic modules and the regeneration of the drying system, which can be automatically or manually by connecting a compressor or fan.