Low Cost Desalination? Call Off the Hunt, We Are There
Apr 24, 2012
by Paul O`Callaghan
“If we could produce fresh water from salt water at a low cost, that would indeed be a great service to humanity, and would dwarf any other scientific accomplishment.”
- President John F. Kennedy, 1962
In many ways, we are already there . The ‘best-in-class’ desalination plants now have the same energy footprint as much of the ‘conventional water’ used in major cities like San Diego.
The mantra that desalination is ‘too energy intensive to be widely adopted‘ has been trotted out so often that it has become self-perpetuating. This used to be the case, but the reality today is somewhat different. Desalination energy costs have been dramatically reduced and are now half what they were ten years ago! Desalination is ready to go mainstream. The market is going to grow and this will drive further innovation as competition increases. New technologies to watch include aquaporin membranes, forward osmosis and capacitive deionization.
It is often reported that somewhere between 20-30% of the energy use in California is associated with moving water. This highlights that fact that collecting, treating and transporting water, not matter what way you go about it, consumes energy. As our cities continue to grow and we transport water every longer distances, that gap between the energy footprint of so called ‘conventional water’ and desalinated water is going to continue to narrow.
In Southern California, for example, the energy cost of pumping water from Northern California over the Sierra Nevada Mountains is 2.67kWhr per m3. That is essentially the same energy cost as ‘best-in-class’ state of the art desalination plants.
Expect Incremental Improvements in Desalination, not Breakthroughs
You may hear reports that we will be able reduce desalination energy use by 50%. In reality this is unlikely.
The next gains we are likely to see, will be very important, but will be incremental and not at the same scale as the gains over the past decade.
Bear in mind, you never get 100% efficiency in anything. So we can chip away and move from 65% efficiency to 70% to 75%, and but at some point the law of diminishing returns starts to apply. Unfortunately Moore’s Law does not apply in this case, as we bump our heads against what nature allows.
What we can do however, is use different sources of energy, waste heat, solar energy, wind energy, and that may be an important way in which we manage that energy-water nexus.
The Key Takeaway: Desalination is Ready to Go Mainstream
As the need for desalination increases, the incremental improvement gains we are likely to see, while they may not be game changing, will be critical to the success of new water technologies.
Three companies to watch which all have very different and innovative approaches to desalination are Porifera, Atlantis Technologies and Aquaporin.
Porifera Inc. is developing a breakthrough forward osmosis membrane that utilizes carbon nanotubes. The technology originated in Lawrence Livermore National Laboratory and has a range of applications including drinking water treatment, dewatering and desalination. Forward osmosis, is the reverse, of reverse osmosis, which makes it, well just plain osmosis. The idea is to use salinity gradients and various draw solutions to play around with thermodynamics and cause water molecules to move from one place to another.
Carbon nanontubes are exceptionally smooth, and they allow water to pass through them, in a kind of slippery slide type fashion, with very little frictional losses. The properties of carbon nanotubes are well known, the trick is to try and get a whole bunch of them to line up in a straight line, in parallel, which is the opposite of what they typically want to do .
Aquaporin A/S is a Danish company that uses a biomimetic technology (technology which mirrors nature) to embed Aquaporin proteins into membranes (Aquaporin Inside™). Aquaporin proteins are natures way of shuffling water in and out of our cells. These proteins are found in our kidneys and are also used in plants such as mangroves and are what allows them to have to grow in brackish swamps. The aquaporin protein is is naturally occurring and what the Danish Company, Aquaporin A/S
Scientists from Aquaporin travelled to the NASA Ames Research Center in Palo Alto (CA, US) to perform first real field tests with its Aquaporin Inside™ technology. Michael Flynn, Head of Advanced Human Support Technology Research Group at NASA Ames who is involved in the testing, indicated ” In NASA we are continuously working towards reducing the mass we need to transport into space on manned space missions. One way of doing so, is by re-circulating bodily fluids from our astronauts.” One of the unique features of an aquaporin protein is just how selective it is, it lets water through, and only water. This is very useful when trying to produce ultrapure water.
Atlantis Technologies, a short-listed company in the Imagine H2O Competition, uses capacitive deionization and supercapacitors to take the salt out of the water, as opposed to taking the water out of the salt. This is a subtle point, but there is a lot more water in seawater than there is salt. Seawater is 3% salt and 97% water by weight. So the logic is it makes sense to move the salt, not the water.
Radial deionization is a form of capacitive deionization (CDI) which was originally developed with over $3,000,000 of funding from the Defense Advanced Research Projects Agency (DARPA).
As the desalination market continues to grow, this will attract more entrants and increase competition. So expect more activity in this area in the next few years!
O2 Environmental is hosting the 3rd Annual BlueTech Forum May 30th in San Francisco where a number of the innovative desalination companies mentioned in this article will be presenting as part of the BlueTech Showcase.