**2. Emerging agro-industrial companies specializing in solar desalination for irrigation**

Sundrop Farms is a leading company in high value-added horticulture. It is developing irrigated perimeters in arid areas of Australia with desalinated water from solar energy as the water source [25]. It is an agri-food company with the technological know-how to develop and operate hydroponic greenhouses (**Figure 1**).

Desalination is a long-term solution. But the high energy requirements of desalination are a drawback [27]. This is why Sundrops farms use solar desalination. The technology has given satisfactory technical results. In 2015, Sundrop Farms built a 20-hectare solar greenhouse in Port Augusta. A concentrated solar power plant (CSP) desalinates seawater taken from the Spencer Gulf to irrigate agricultural products [28].

#### **Figure 1.**

*An integrated desalination facility drawing its main electricity from an adjacent concentrating solar power plant [26].*

Tomato yields reached 850 tonnes/ha in hydroponic greenhouses [24]. A quantity of desalinated water of 335,103 m3 is used in the greenhouses. The financial cost of the project is estimated at the US \$ 205 million [29].

In the same context, a study carried out in 2017 in Spain showed that the supply of drinking water and irrigation water *via* a desalination plant increased resilience in the face of water shortages [30].

Another similar project was built in 2012 as part of the Norwegian agro-industry called the Sahara Forest Project in Qatar on an area of 300 ha. The Qatari installation can provide desalinated water for all crop irrigation needs [31] for a yield of 633 tonnes/ha of tomatoes and melons. This same agro-industrial project in the Sahara forest will initiate numerous activities in Tunisia over 10 ha [26]. In addition, an American blog called "sustainable business" specializing in sustainable development projects described a solar thermal project launched in 2014 in California [23].

A Californian start-up called WaterFX has set up a 14-hectare solar thermal desalination plant. It supplied 3.8 million m3 of water in 2014 from the saline drainage water of the San Joaquin Valley and turns it into freshwater for irrigation. The desalination unit recycles drainage water over an area of 2800 ha into a source of freshwater for nearby irrigated areas.

The success of the project convinced the Panoche Water District, in an arid agricultural region of California, to build a desalination plant [32]. WaterFX's operating cost is the US \$ 450 for 1.2103 m3 [33]. The price was deemed acceptable by the Panoche Water District.

A current price of US \$ 1/m3 is considered acceptable in some countries for domestic and industrial uses [34].
