Distillation is a process where water is heated until vapor is formed as steam which is then exposed to a cool surface which causes the steam to condense as liquid water. As the vapor rises, almost all of the elements dissolved in the water are left behind so the total dissolved solids (TDS) of the condensed steam is a small fraction (<5%) of the original water. The heat is often high enough and of sufficient duration to kill bacteria and other pathogens in the water thus the net result is a water quality that was often prescribed for medical application and in larger sizes used for desalinization of sea water.
The described process dates back to antiquity. More effective distillation equipment was developed during WWll. Then, the advent of better ion exchange resins and reverse osmosis membranes along with ever increasing energy cost gradually reduced the need for water distillation almost to the point of extinction. Because of chemical use, waste water streams and continued high energy costs and threatened fresh water sources, there is a good case to be made for a renewed look at distillation especially for turning seawater into drinking water.
Enter the brilliant research minds at MIT. On October 31, 2023 in a campus paper their researchers discovered (serendipitously?) that under certain conditions light will cause water to evaporate without the presence of heat in a process they called the photomolecular effect. Apparently, the water molecule-to-molecule hydrogen bond is broken and the singular molecules of water having a molecular weight less than that of air float away from the surface. A follow-up April 23, 2024 article by the same MIT publication indicates that green light is most effective and that the evaporation rate is up to four times that produced by heat. The angle of incidence light-to-water-surface is best at 450. We briefly described this process in an early 2024 blog hoping to see the information diffuse to a company or two in the water treatment industry or industry at large
I have actively looked on line, in newspapers and in technical publications since late 2023 to find any indication that this new technology has achieve any traction. Nothing as of January 2025. In the US and other developed nations where power and competent personnel are available, this photomolecular technology would probably create lower CAPEX and OPEX and allow for more rapid permitting because there is no discharge of extremely high TDS water back into the sea or ground. However, in much of the world where the population often is thirsty and unable to feed itself because of non-existent or extremely scarce usable water this technology may indeed be life-saving. As we envision a desal or highly brackish water distillation unit in its simplest form with this technology:
- Power requirements. Aside from low-head pumps to transfer water to and from the system there will need to be LED lights aimed at the water surface at a 450 angle, a fan to transfer vapor to the condensing chamber and a low delta T cooling surface to create the condensate. Undoubtedly a candidate for solar. All things considered; power needs will be 5% of that for reverse osmosis.
- Complexity. Aside from the fan and by incorporating mechanical fill/empty floats the only techy component would be a chiller and there a Peletier effect unit with only a fan could be employed. Compressors, refrigerants and controls eliminated. Compared to reverse osmosis it is probably 1/10 or less.
- Materials of construction. In the absence of high pressures, elevated temperatures and hardness scaling, many durable plastics, fiberglass and reasonably priced stainless steel alloys can be employed.
Hopefully, this technology will soon be picked up by a major player in the water treatment sphere and developed into a commercial product. In the meantime, let’s not lose sight of all of the new water beneath our feet as demonstrated by the incredible Stephan Riess 60+ years ago and brilliantly documented by Michael Salzman in his book New water for a thirsty world.
Spread the word!
