Ugo Bardi: Photovoltaic Water

When we started working on producing water from atmospheric humidity, myself and my friend and colleague Toufic El Asmar thought it was a mad idea. Energy is expensive and water condensation requires a lot of it. Yet, as we kept working on the concept, we found that it made sense. Sure, it takes energy, but, with the progress of technology, renewable energy is becoming cheaper and cheaper. And at some moments, renewable energy really costs zero. At those moments, you should store it, but storage is the expensive part of renewable power. So, why not transform solar energy into something that you can store at little or no cost, for instance clean, drinkable water? After all, water is fast becoming a scarce commodity in many regions of the world.

So, the idea was born of a “solar water machine” which uses electric energy from photovoltaic panels to drive a water condenser which collects humidity from the air. The water is then filtered and made drinkable by adding a small amount of natural salts. The machine is more complex than this; it also collects rainfall and it can clean and purify water from almost any source, producing up to two hundred liters of pure water per day. Its solar panels make it completely self-sufficient: you may place it anywhere; it doesn’t need to be connected to the grid (although it may be). So, it is good for remote places, for emergency situations, and for a variety of needs. Here is the “Acqua dal Sole” system, the day of its official presentation in Capannori, Italy. The people involved in the project are lined up in front of the machine (including yours truly).

Now that I told you the essential, let me tell you some more details about this idea. It all started some years ago, when myself and Toufic El Asmar prepared a project about using solar collectors to produce air conditioning for North African and Mid-Eastern Countries. The idea was that these countries enjoy a high solar insulation, which could be collected using parabolic mirrors to heat up an absorption air conditioning system. The project was approved by the European Commission with the name of “REACT” and it led to the manufacturing of two prototypes, one in Morocco, the other in Jordan.

As time went by, however, the rapid fall of the price of photovoltaic panels made parabolic solar collectors obsolete. But while working on the React project, we noticed how solar refrigeration could produce a lot of water by condensation from the air. That led us to study the subject more in detail and the European Commission sponsored a project called “Aqua Solis“. Our idea was to study an approach completely different than the large scale desalination plants which are commonly used nowadays to produce water for dry countries. The idea was to develop “village scale” systems; improved versions of the old “solar still” idea. Cheap, simple, and with no need of the expensive pipeline systems needed for the conventional desalination plants. The basic idea was to create versatile systems which could use photovoltaic energy for water production, but also for any use needed at a particular moment

In time, this study evolved into a patent filed by me (Ugo Bardi) and Toufic El Asmar and to a working device: the “Acqua dal Sole” system, built by the Italian companies Sinapsi and Sinerlab, on a project by Archistudio. The “Acqua dal Sole” system is at present located in an area close to the airport of Capannori (near Lucca, in Italy) where a high tech aeronautics company, “Zefiro” has kindly offered space for a test. The water produced is free for anyone stopping by, although for bureaucratic reasons you will read on the tap the sign “not drinkable” (in Italian). But it is perfectly drinkable and very good, I can tell you that!

We are looking at practical applications and markets for this device. Of course, that depends on the cost but, as the prices of PV keep falling, it is likely that water from the air could be a revolution in the way water is produced in the world, especially in areas where it is badly needed. And also on the way renewable energy is stored.

Once you have seen the “photovoltaic camel” you can understand how fast the range of applications of PV panels is growing. Photovoltaics is an emergent technology which has the possibility of reshaping the world in ways which, at present, we can’t even imagine.

Acknowledgement: the people who worked on the “Acqua dal Sole” project

Ugo Bardi (University of Florence)
Eugenio Baronti (Zefiro s.r.l.)
Lorenzo Cardarella (Sinapsi s.r.l.)
Toufic El Asmar (Food and Agriculture Organization, FAO)
Filippo Niccolai (Sinerlab s.r.l.)
Francesco Niccolai (Sinerlab s.r.l.)
Michele Tosti (Sinapsi s.r.l.)