Inflated Greenhouses / Technical Report

Heat loss can be reduced by separating two coverings by air pressure maintained by a small continuously running fan. An air-inflated double layer of plastic has shown a fuel savings of 25 to 40 percent over the use of a single layer of plastic. The total worldwide area of inflated greenhouses in 2003 was estimated at 3,000 square miles. Approximately 65% of all commercial greenhouses in the United States use the air-inflated system. Double-layer polyethylene covered greenhouses can consume 40% less fuel than single polyethylene covered greenhouses. Double polycarbonate panels will have approximately 50% lower heat requirements than single layer greenhouses. Four demonstration plots were set up in Albania to introduce inflated greenhouses as an energy-efficient alternative. The plots were located in Berat, Fier, and Lushnje, with two different sites in Lushnje. Each plot had a 1000 sq. m greenhouse, and a set of data loggers was installed in each inflated and a common control greenhouse. The expected outcomes of the proposed technology included improved operational efficiency, expanded market opportunity, increased farmer's revenues, and increased profit due to price premium. The planned parameters to be recorded included temperature and humidity fluctuations, days to first flowering, days to first/last harvest, the incidence of pests and diseases, marketable yield, and respective prices. The analysis focused on dark hours, where due to significant energy losses, plants might be threatened in cold nights. There was no significant difference in air humidity between the two types of greenhouses. However, the differences regarding air temperatures were significant, with the inflated greenhouses maintaining a higher temperature throughout the night. The heat required for a given construction, shape, and covering material of a greenhouse can be calculated. Considering a difference of 2 to 4 Celsius degree between common and double plastic greenhouses, the heat losses can be significantly reduced in inflated greenhouses, ranging from 19,000 to 39,000 kcal per hour. This means that due to better energy conservation inside the inflated greenhouses, a similar effect of burning 2 to 4 l/hr of heating oil was naturally obtained. The total benefit throughout the growing season would be equal to the burning effect of 19,000 to 39,000 liters of heating oil per 1000 sq. m greenhouse.