M. Grafiadellis, S. Kyritsis
During the last two years considerable efforts have been expended to explore the possibilities of using solar energy to meet part or all of the heating energy requirements of greenhouses in Greece. Emphasis has been given to the development of relatively low-cost heating systems. Two different systems have been studied.

The first system consists of three major elements. These are: (i) the external solar energy collector, (ii) an underground water reservoir and (iii) plastic tubes of black polyethylene through which warm water is circulated to heat the greenhouse. Beside these three major elements water pumps, thermostats and water pipes are needed. On cold nights the solar heated greenhouse had 6,5°C higher air temperature and 8–10°C higher soil temperature than the non heated greenhouse.

The second system is much simpler. It consist of an under-ground water reservoir, a fun and a pump and is under investigation in the Agricultural Research Center of North Greece.

The solar heating systems were found to be very useful for plastic greenhouses in Greece, since they protect the crop from low temperature conditions in nonheated greenhouses. A solar heated greenhouse gave 2–3 weeks earliness and 30–50 % increase of tomato production.

Grafiadellis, M. and Kyritsis, S. (1981). HEATING GREENHOUSES WITH SOLAR ENERGY. Acta Hortic. 115, 553-564
DOI: 10.17660/ActaHortic.1981.115.62

Acta Horticulturae