Articles
ENERGY SAVING METHODS IN THE ISRAELI INDUSTRY
The use of inflated double film of P.E. reduces the use of fuel by about 20 to 30 percent.
Heat distribution by perforated P.E. tubes located on the floor again reduces fuel consumption by about 10 percent.
Today these improvements and some other improvements such as the sealing of the greenhouses, have reduced fuel consumption for greenhouses at 18° C from 30 tons of diesel oil to about 20 tons per year, per 1000 sq. m.
The use of nonfossil fuel is only in a development stage.
Two projects are now being carried out in Israel.
In one, outside solar radiation is being collected by a film of water between two sheets of P.E. which covers the greenhouse, and the heated water then flows through P.E. pipes buried in the soil which in turn is used as a heat reservoir.
Results up to now indicate that the daily efficiency of the system, as a solar collector, is about 10%. The heat collected brings the indoor air temperature up to about 4° C above ambient.
In the other research project the greengouse itself is being used as a solar collector.
The excess heat developed in a completly closed greenhouse is transferred by direct contact of the inside air and cool water sprayed by specially designed nozzles in a heat exchange chamber built at the northern part of the greenhouse.
The warm water is collected in a reservoir which may be inside or outside the greenhouse.
During the night the system is operated in the same way, but then heat is transferred from the warm water to the cool air of the greenhouse.
Experiments show that the daily efficiency as a solar collector is about 50%. The absorbed heat enables to retain indoor air temperatures at about 6° C above ambient, with one P.E. cover.
With an inflated double layer of P.E. cover, the temperature difference between indoors and outside is increased to about 10°C. The relative humidity inside the house during the day is 80 to 85 percent and during the night about 100%.
Since the fuel crisis and the big increase of fuel prices all over the world, intensive research has been carried on to reduce energy costs in the greenhouse industry.
The research is being carried on in two complementary aspects: one is the "agricultural" aspect and the second is the "engineering" aspect.