A new public report of TheGreefa project has been developed presenting the work motivated by the idea of developing and testing a new concept for extremely water-efficient and intensive production of agricultural goods in closed greenhouses. The basic idea is to keep water in a closed cycle or to use impure water (like pre-treated wastewater) in irrigation and to produce pure condensed water for external uses.

The main problem in running a closed greenhouse, especially in hot and arid climates is overheating. TheGreefa works on a new cooling method, based on the heat-pipe principle, using the phase change of water for heat dissipation from the greenhouse to day/night storage. Thermochemical technology for improved heat transfer and storage is used to solve the problem. Besides, more conventional concepts, like improving the heat storage capacity of the greenhouse soil and increase of the total greenhouse cover surface for improved heat conduction are used to support the cooling strategy.

In TheGreefa, a lab greenhouse was realized at INRGREF’s Tunis demonstrator for testing and evaluating the principle. The first tests are running and in September 2022, the first batch of tests including vegetation will start. In parallel, a larger greenhouse demonstrator will be realized at the village of Cherfech in the Ariana region near Tunis. Here, learnings from the planning and testing already did contribute to technical improvements of the overall system. However, the new concept will also include elements for simplification and cost reduction using intelligent low-tech solutions and means of reducing energy consumption, mainly in terms of ventilation.

The tests still need more time to reach the required goals, but once the system is in an operational state and water circulation can be approved, the idea already can be demonstrated in a rather realistic environment. Dramatically rising problems in water supply for agriculture, even in Central European regions, will give specific attention to this technology, once it will be in the envisaged demonstration mode.

As soon as the report has been accepted by the European Commission, it will be made available on TheGreefa website.