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A sustainable and environmentally alternative to commonly used air conditioning systems can be the solar cooling system due to the use of renewable and clean energy. Solar absorption systems can be used for greenhouse cooling in areas with high outdoor temperatures and solar radiation levels. These systems take advantage of the simultaneity between the solar energy availability and the greenhouse cooling demand allowing the reduction of conventional electricity and water consumption. This paper presents the results of the application of a solar cooling plant for the climate control of a greenhouse at the University of Bari, Italy. The experimental plant consists of a Mediterranean greenhouse, having a surface of 300 m2, and of a single effect LiBr-H2O absorption chiller fed by evacuated-tube solar collectors. Two different localized systems were chosen for the distribution of cold inside the greenhouse: the first system presents pipes placed centrally on the cultivation vessels; the second consists of pipes in contact with aluminium plates and of a transparent EVA film, used to border an area close to plants. The distribution system of cold with pipes, plate and EVA film provided a slightly higher cooling capacity due to the presence of the plates which increases the ability to dissipate energy.

The installation of PV panels on the greenhouse’s roof reduces solar radiation that passes through roof glazing and falls to the plants inside the greenhouse, affecting their lighting and therefore crop growing. In this paper, performance results of energy production and plant growing from installed PV panels on greenhouse roof, are presented. The results are obtained from a cultivation period of lettuce crop inside two greenhouses, one with fixed roof installed photovoltaics and another unit without photovoltaics. Regarding electrical output, PV panels produced 50.83 kWhm −2 for the characteristic cultivation period of Feb-Mar-Apr, creating also a 20% greenhouse shading. Plant growing results under shading effect were satisfactory, as they were at same level with those of reference greenhouse without PV covered roof. Extending the results for three PV installation modes to 1 ha greenhouse, theoretical results were calculated. The considered PV installation modes are the fixed one, with panels placed on south facing greenhouse roof and two sun tracking modes, with PV panels in rows and axis on east-west and north-south direction. The calculations showed that sun tracking PV panels produce more electricity than fixed mode and can result to solar control of the interior space of the greenhouse.

The advantages of Infra-Red (IR) heating is verified and demonstrated in a full-scale production greenhouse for vegetable seedlings, heated by gas-fired IR radiators. Temperature distributions data collected during a 62-day period during the winter showed that the seedlings could be kept at the optimum thermal conditions while the greenhouse air was maintained at a 2°C-3°C lower temperature, indicating a significant reduction in energy requirements. These results were also supported by Liquefied Petroleum Gas (LPG) consumption data collected over a period of two consecutive years, in relation to climatic conditions.

The performance of an Infra-Red heating system using gas fired IR radiators is demonstrated in a full scale production greenhouse for vegetable seedlings. Outside meteorological data and the greenhouse thermal conditions have been monitored for a heating period of 60 days, to assess the quality of the canopy climate and the potential in energy savings. Results indicate that the seedlings are kept at optimum thermal conditions while the greenhouse air is maintained at lower temperature, by 2-3 °C, indicating a significant reduction in energy requirements. During operation, plant growth seemed to be positively affected by the IR radiation, whereas no plant infections by pests and / or diseases were observed.