The sea in the desert

 By Sara Sangermani

Overcoming the limits of solar energy, generating clean, continuous, economical energy with a minimal environmental impact. It sounds impossible, but an ambitious South American project is succeeding in a venture that has as its principal player one of the most extreme places on earth…

There is a place in the world that is famous for being the most arid place in the planet planet, indeed it is 50 times drier than the famous Death Valley in California. It’s name is the Atacama Desert, in northern Chile, where the annual rainfall is never more than 3-4 millilitres. The mountain ranges and the Humboldt Current System prevent the formation of moisture and clouds, creating a natural barrier against atmospheric precipitation. Also temperature variations are extreme: from around 0° C, at night, to around 30° C during the day.
In a place where it never rains, about every 5 or 7 years, and only in the months between September and December, an incredible spectacle takes place that is only possible thanks to the phenomenon of El Niño which, by heating the Pacific Ocean, changes the air circulation across the region and contributes to the rare occurrence of rainfall. The desert fills with colourful flowers, giving rise to the phenomenon known as desierto florido, that attracts large numbers of tourists to this desolate place.

The Atacama Desert is the world’s most arid place and flowers only once every 5-7 years

The Atacama Desert also holds another record: of all the places in the world. it has the highest level of solar radiation. This makes it the perfect place for solar power plants that can provide energy, not only to Chile but also to other South American countries.
The opportunities are enormous, but there are also limits due to the need for space to install the solar panels and the impossibility of producing energy also during the night, which makes it impossible to guarantee a stable and continuous supply. Therefore, it is also necessary to find other sources for generating energy, and many countries are studying storage solutions, such as enormous batteries, which are very expensive, deplete rapidly and are not an ecological solution as they are difficult to dispose of. To overcome the lack of space, however, solar panels have been designed that can float on water and both functioning and abandoned industrial sites are being recovered.

A solution to this problem could in fact come from Chile.
The Atacama Desert is virtually uninhabited so it could be possible to use the area to create solar panel farms. Moreover, a the site with the world’s highest levels of radiation, a lower surface area could be used to produce the same amount of energy than would be required in other countries.
However, this would not solve the problem of storage, especially considering that, according to some data, peak electricity consumption in Chile is at 10 o’clock in the evening. So, how can electricity be guarantees at the moment of maximum demand?

A solution has been offered by Valhalla, a company founded in 2011 by two entrepreneurs with the aim of transforming the electricity sector to ensure economic development in the country, without having a negative impact on the planet.
Valhalla launched the Espejo de Tarapacá project, which aims to produce solar energy at all hours of the day and night, every day, that is economic (i.e. less than $1 per kWh), clean and abundant. Bit also using just 5% of the immense desert surface area to provide clean electricity for the whole of Chile.
Started in 2012 with a design and study phase to find the best place to build, after fundraising efforts to finance the work (a $500 million investment), the project’s operational phase operating began in 2017 and it is estimated that by 2020, in less than three and a half years, it will be able to produce clean electricity for the entire country.

The project is based in Caleta de San Marcos, a small town on the Pacific coast, around 100 km south of Iquique in the region of the Atacama Desert

How is all this possible? By combining the solar plant and a hydroelectric pumping plant.
During daylight hours, the solar panels produce electricity that is distributed according to demand. The surplus, meanwhile, is used to pump water into a natural reservoir, which is one of two hydroelectric power tanks used to generate electricity during the night.
The characteristics of the Atacama Desert make it ideal for this project, which is located in Caleta de San Marcos, about 100km south of Iquique. The high coastline near the ocean is full of natural shallow caves that are ideal for storing sea water without the need to build dams, a factor that, apart from reducing the environmental impact of the project, also significantly reduces the cost.

Two reservoirs, located at different altitudes, are connected with each other. Using excess solar energy, sea water is fed through pipes into the upper tank without the need to build dams as there are numerous natural shallow caves in the desert. The high coastline and the proximity to the ocean are key factors in the success of the project.

The way it works is similar to that of other hydroelectric pumping stations: two water reservoirs, at different heights, in this case with a difference of 535 metres, are connected by system of pipes and three turbines, each capable of generating 100 MW, and consequently guaranteeing an output of 300 MW.

During the daytime, when there is no demand for the energy produced by the hydroelectric power station, the water is pumped from the lower reservoir down to the top one where it is collected. Then, at night, when solar energy can not be used, the water is fed into the lower tank, generating energy. The hydroelectric power station transforms the hydraulic energy of water by exploiting the potential mechanical energy contained in the water mass in the upper reservoir. The flow of water makes it possible to operate the turbines that generate electricity.

During the day, excess solar energy is used to pump water into one of two reservoirs located at a higher altitude.
At night, the water is fed into the lower tank, generating energy.

The opportunities for Chile are amazing. The country could be one of the few in the world where the transition towards clean and sustainable energy first becomes a reality. This is why, in 2018, a parallel project by Valhalla, called Cielos de Tarapacá: will begin, which will link solar photovoltaic panels and a hydroelectric pumping system, to produce 600 MW by 2020, with two reservoirs with a 730-metre difference in altitude. The energy produced will then be used by a number of other countries in South America.

READ MORE: Unlocking Africa’s solar potential by Robin Wylie

about the author
Sara Sangermani