Desolenator machine purifies water using only solar energy

The Desolenator uses energy and heat from the sun to turn dirty or salt water into distilled drinking water. It is entirely self-contained and can provide water stressed towns and villages with a cheap, reliable and convenient source of hydration. Currently still in the development stage, the device could be put to use by the end of 2015.

We spoke to the inventor, William Janssen, about the inspiration and technology behind his machine, and some of its more unusual benefits…

What first inspired you to create the Desolenator?

I was visiting Thailand and I saw that people had a lot of water heaters on their roofs that used solar energy. They are very simple contraptions that warm up water for their showers using sunlight. I observed these units and I noticed that they just use a black surface to collect heat from the sun, and I thought why would you not install a photovoltaic (PV) solar panel instead of the black surface because the PV panel is also hot and black?

The solar panels that we have in Europe and North America are very suitable for temperate climates but actually they are not so suitable for places where the sun shines abundantly, like Dubai. If you were to place a solar panel on your house in Dubai in the summer, you would notice that the surface temperature of the solar panel would actually get extremely high. Temperatures of 80°C are quite normal but the productivity of the solar panel actually goes down if the surface temperature is over 50°C.

So I was thinking, if you think about this idea in Thailand where they use solar heat to warm up water, and if you replace the black surface with a PV panel and insulate the whole thing, then the PV panel would get even hotter. Then you could flow a thin film of water over the top of the solar panel to cool it down. That means you can manage the surface temperature of the PV panel, but you can also warm the water up on top of it to almost boiling temperature, about 95°C. That is of course something quite wonderful because if you want to efficiently distill water then you have to get the water to boiling temperature.

How does the machine work?

We warm the water up on top of the solar panel, to about 95°C, then the water runs off into a small vessel that is an actual boiler vessel, like a kettle. We take the electricity that the PV panel has created and we insert the electricity into the boiler via a simple spiral heater. This leads the water to evaporate and the eureka moment when I finally put the whole thing together was realizing that it is actually the vapour that contains the most energy. Because water takes relatively little energy to warm up but takes a lot of energy to change state, from liquid to gas.

So what we did was take the vapour off the top of the boiler, collect it in a tube and feed the vapour back into the cavity that was created on top of the solar panel. We then heat exchange the latent energy of the vapour back to distilled water and the water that is at the same time warming up, is absorbing all this energy. So we have effectively created a circular system where we insert water over PV cells, the water warms up from ambient temperature to 95°C, we take the water into a boiler where we make it constantly boil, and we take the vapor and we heat exchange the vapor over the PV panel to condense it back to distilled water. So we have created a thermodynamically efficient way of distilling water in a relatively small, compact unit. Which leads us to believe that we can achieve a yield of 15 litres per day from a simple family-sized unit.

How much does it cost to make one Desolenator?

We are currently in the process of product development for a one square meter exposed surface, so the unit is the same size as a large flat screen television and would cost about 500 US dollars.

What is the next step?

We would like to accelerate the product development and be able to do field tests. Once we have successfully field-tested the product with families around the world, NGOs (Non Governmental Organisations) who are active in the water spectrum will then also be able to use our product. The other thing that we would like to do is see what the upper limit of the technology is. If we were to try to build a community sized unit with 30 or 50 square meters of exposed surface, how far we could go in up-scaling the technology and creating one little water factory in every arid coastal village?

As well as providing drinking water for people in water stressed areas, what are the other benefits of the Desolenator?

There are a few groups of people who might want access to this technology. The main one is military application. For example, airborne units that go to certain places where there is trouble obtaining drinking water might find it useful. Another interesting one that we were not aware of but that we found out about through our crowd-funding campaign is people known as ‘preppers’. Preppers are people who are preparing for some sort of a doomsday scenario. They collect a certain amount of food and water and medical supplies etc. They have very active forums on the internet and these people are quite interested in our product because it would mean that if there is a situation where there is no more fresh water supply, they could simply go to a location where they have access to water and sun and they can use the Desolenator.

Learn more about the Desolenator and discover lots of other renewable energy innovations that could power tomorrow in Issue 70 of How It Works magazine. Pick up a copy from all good retailers, or order it online from the ImagineShop. If you have a tablet or smartphone, you can also download the digital version onto your iOS or Android device. To make sure you never miss an issue of How It Works magazine, make sure you subscribe today!