Design and thermal performance of an innovative greenhouse

The study presents the design and thermal performance evaluation of a novel solar greenhouse with humidification-dehumidification unit, water-cooled heat exchanger and variable mixing ratio in the Mediterranean climate. The greenhouse is designed to provide proper microclimatic conditions for crops, produce fresh water through condensing water vapor released from the plants, and save energy using the semitransparent PV panels. Results showed that on a typical summer day, the solar greenhouse ensures proper microclimatic conditions all day long by reducing the temperature by 11.14 °C compared to conventional greenhouses, while maintaining acceptable values of relative humidity and producing 70 L of fresh water per day. An operation schedule was established based on varying return-to-fresh air ratio to ensure optimal system performance. The operation schedule showed that proper microclimatic conditions can be reached through ventilation for 13 h per day. To enhance the net-energy performance, the produced water can be used for irrigation and the return air can be used for cooling the PV panels.