Greenhouse solar heating in the Argentinian northwest

LUIS SARAVIA; RICARDO ECHAZU; CARLOS CADENA; MIGUEL CONDORI

RENEWABLE ENERGY

Elsevier Science

Lugar: Great Britain; Año: 1996 vol. 11 p. 119 - 128

0960-1481

In the present paper a low cost solar active water heating system is proposedto increase the average night temperature and avoid freezing problems inside greenhouses.The system collects the excess of energy in the greenhouse during the day,and returns it at night. The most important part of the system is a plastic bag madeof two thin polyethylene films vertically hung inside the greenhouse, that works as asolar collector during the day and as a heat exchanger at night.The films are soldered in such a way that the water introduced at the top of the bagfalls by gravity following a zig-zag path. The warm water is stored in a pond directlybuilt in the ground and waterproofed with a polyethylene film.The system has been designed taking into account the meteorological conditions inSalta where 12 freezing days are expected each year with minimum temperaturesdown to - 8°C.A prototype was built in a 600 m 2 greenhouse covered with a single polyethylenefilm. It was located in the Province of Salta, Argentina, with a 24.5 ° South latitudeand an altitude of 1200 m. Tests were performed for three years beginning at the 1992winter, and a satisfactory thermal and operational behavior was obtained. Withoutside temperatures down to - 6°C at the end of the night, the system was able tokeep a temperature of 2°C inside the greenhouse.