The most usual hydroponics system consists of plant cultivation into gutter pipe or other containers through which the nutrient solution circulates intermittently. This system requires continuous electricity supply for pumping nutrient solution, so it is highly vulnerable to prolonged failures in the electricity supply. Two auxiliary systems were evaluated for pumping. In one, the solution movement is promoted by compressed air. The electric buoys and pneumatics valves controllers perform several cycles of nutrient solution, using the air accumulated into the cylinder's compressor. The other system consists of a set of 12-volt pumps fed by batteries which are supplied by a charger. The tested system had a compressor with a motor of one hp, a cylinder of 45 L, and two solution tanks. One tank had 60 L, which allows pressurization. Specifically for the used compressor, it was obtained, on average, four cycles of solution transference for each full cylinder of the compressor, without electricity. The total volume of solution transference for each cylinder was 200 L, which corresponds to the movement of approximately 5 L of solution per liter of compressed air. The other system consists of three 12-volt pumps model 500 gph with capacity for 1890 L h-1 of liquid transference and consumption of 2.5 amps h-1, supplied by an automotive battery. The set worked, on average, for 3 hours and 20 minutes for each battery charge. The volume of pumped solution was approximately 500 L h-1. With these parameters it is possible to make projects of systems for auxiliary pumping according to the volume of solution to be pumped and the convenient intervals, since there are many models of air compressors, automotive batteries, chargers and 12-volts pumps.
Hydroponics; safety pumping; circulation of solution
