ISHS Acta Horticulturae 148: III International Symposium on Energy in Protected Cultivation
DEVELOPMENTS IN SWEDISH GREENHOUSE PRODUCTION FOR THE PURPOSE OF LOWER ENERGY COSTS |
| Author: | B. Landgren |
| Abstract:
Many of the participants at the 1982 ISHS Congress in Hamburg heard about the developments in Sweden regarding reduction of energy-costs in protected cultivation. So these attending that meeting have already seen Table 1. Most of the measures in Table 1 are common in many North-European countries and they more or less have an influence on the greenhouse construction. The title in Hamburg was "Developments in Greenhouse Construction for the Purpose of Low Energy Requirements." This time, we shall call it "Developments in Swedish Greenhouse Production for the Purpose of Lower Energy Costs." In this paper, Swedish construction activities are especially emphasized. Artificial windbreaks have been evaluated in both full scale and wind-tunnel tests. A 5–10 percent heat-reduction is attainable, according to our tests at Alnarp. New efforts will be made with other kinds of windbreaks as can be seen on figure 1. The Swedish Board of Technical Development has shown interest, and has given us money to evaluate these ideas in more detail. As most of you probably know, different greenhouses have been tested in full scale at Alnarp and its surroundings, since the middle of the seventies. Double glass with CO2 in between gives a 30–40 percent heat-reduction in relation to single glass. Hortiplus-glass that is coated with tin-oxide on the outside can give 20 percent heat-reduction under dry conditions. Note that the tin-oxide (with its low emission factor) was on the outside since the inside is more permanently wet with condensation. Double acrylic (16 mm) is the dominant rigid sheet double glazing material in Sweden today, as well as in some other North-European or Scandinavian countries. Even triple acrylic is used as well as polycarbonate. Also, an Austrian made co-extruded plastics (Thermoclear) is being used where acrylic is coated on the outside surface of polycarbonate. This is done because acrylic has better long-term weathering properties, and polycarbonate is more resistant to fire. We have recently had some accidents with fire in acrylic houses due to the combination of artificial light and internal thermal screens. It should be pointed out, however, that polycarbonate has about 10–12 percent lower light transmission than acrylic even though the two materials appear to have the same clarity. | |
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