Water, Water, Everywhere, But Not a Drop to Drink

This may not be the Rime of the Ancient Mariner, but it has everything to do with seawater

By Frank Rovella
I read an interesting fact in an MIT publication the other day; they stated that by 2025, 1.8 billion people will have trouble getting clean drinking water; that’s over 20% of the world population. This is a number that until recently has not gotten much attention, however, the recent drought on the west coast has helped to drive it home. Cities like San Diego have been hit the hardest, currently 80% of San Diego’s water supply is imported. This has prompted state and county officials to move forward with a massive $1billion desalination plant. When completed it will be the largest in the western hemisphere.

Desalination is becoming the only option for many metropolitan areas with growing populations and increasingly arid climates. This is highlighted by the fact that since 2000 over 16,000 desalination plants have come online in over 120 countries. Seawater desalination is certainly proving to be a viable option, but it’s expensive. Water produced by desalination is measured in acre-foot units, one acre-foot being almost 360,000 gallons or the estimated amount used per year by two five-member American households. One of the reasons it is so costly is that seawater desalination is based on the Reverse Osmosis (RO) process. It takes a lot of energy to push that much water through this type of system. San Diego, for example, will be paying approximately $2,000 per acre-foot, which 80% more expensive than their current supply. As you can imagine, with that much public money at stake, there is a lot of pressure to reduce costs. Though RO technology has come a long way in recent years due to advances in materials and process control, it still has a long way to go.  To understand why it’s expensive, and why it is a prime candidate for enhancements from process improvements and materials technology, we have to first look at what an RO filter is and does.

The RO process used for desalination typically uses a spiral wound type of RO filter. This configuration is composed of two sheets of membrane that are glued back to back to form an envelope or a leaf. Membrane leaves contain two membrane sheets sandwiching a porous sheet that is the permeate collector. The leaf is glued on three sides; the fourth side is attached to a perforated permeate tube.  In this method, the water can only exit through the permeate tube. While the system is in operation, pressurized water flows over the surface of the membrane on both sides of the membrane leaf. Water permeating through the membrane flows on the permeate carrier to the open side of the leaf, it then exits through the permeate tube.

In large scale RO applications such as desalination, multiple leaves are connected to the permeate tube. It is set up so that the permeate from all of the leaves goes through the same tube. In the multiple membrane configurations, a mesh spacer is placed between the leaves. They are then wound around the permeate tube, hence the name “spiral wound”.

Advances in the understanding of RO flow have brought about design changes that have added higher levels of efficiency. Modern RO filters contain more leaves that are shorter; the decrease in the water path this creates has proven to be far more efficient. This means that fewer membranes and less overall equipment is needed to create even more water. However, this is just one area where improvements have been made. There has been a great deal of advancements in membrane materials, as well as efficiency to feed pumps and general operating systems.

We have to remember that desalination power consumption is very high because of the amount of force required to pump massive amounts of water through an RO filter. The power used for seawater desalination accounts for 20 to 30% of the cost but its far less expensive now than it was. In 1979 1,000 gallons of desalinated water required 114 kWh. Today that same 1,000 gallons needs only 14 kWh.

But solving the world’s water problem will take more than high-tech large-scale filtration of seawater. Its also going to take boots on the ground in areas that can’t afford the colossal outlay for a desalination plant. The 2030 Water Resources Group has been applying some very innovative solutions across the globe to solve water shortage problems, and most of it is through pure efficiency. For example, in a project in Cape Town South Africa, they identified widespread leakage problem that caused the loss of approximately 600,000 gallons per hour. There are also a number of other examples, mostly based around water management for areas such as power generation, groundwater conservation, distribution management, agriculture, and wastewater treatment. There are also a number of other technologies in development that could change the freshwater playing field. Research is currently underway that includes distillation, ion exchange, and biochemical desalination. Whatever the final solution is, if the problem is not solved or at least addressed adequately, fresh water will become a key issue in the years to come.

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3D Printing’s Silver Bullet

By Frank Rovella
Last week I wrote about a new process for the 3D printing of circuits, it was a big story with many implications. However; news reached me today that will make it seem like a side note in 3D printing development. This week, Redwood City, CA-based Carbon3D unveiled a new 3D printing technology called “Continuous Liquid Interface Production” or “CLIP” that will finally fulfill the promise that 3D printing has held since its inception. Until recently 3D printing had been relegated to short-run production and prototypes. It's slow cycle times, and depending on the process, not so great surface finishes have been the major stumbling blocks to widespread adoption. This has kept processes such as SLA, SLS, Polyjet, and many others at the periphery of large scale manufacturing. The big difference with CLIP is that it's a totally new process and does not resemble additive manufacturing as we know it.

When comparing CLIP to standard 3D printing processes keep in mind that current methods are basically 2D printing. Layer after layer stacked on each other to create a three-dimensional object.  With layers come uneven surfaces, one of the most striking advantages of the CLIP process can be seen in the image on the right. CLIP can produce surface finishes that no other 3D technology can match but, what is really amazing is the speed.  Depending on process and materials, CLIP provides cycle times that are 25 to 100 times faster than standard 3D printing technology. In addition, it is also designed to be used with polymeric materials that open the doors to almost limitless possibilities.

The CLIP printing process starts with a pool of UV curable resin. The print head drops into the pool and begins projecting UV light through a special window into the resin, forming the base and subsequently the entire object.  As the form builds, the head raises in conjunction with object growth. UV light makes this all happen, but the window that it transmits through has to be completely transparent to the UV rays and permeable to oxygen, similar to a contact lens. The system controls the oxygen flow through the window creating a dead zone in the adjacent resin pool.  The dead zone is just tenths of a micron thick which delivers incredible resolution. The image of the part being printed is projected through the window, much the same as a movie is projected and creates the item from the bottom up.

This all sounds like a post grads project at MIT but its real and ready for prime time. In fact, Carbon3D just announced that they have raised $40 million to commercialize the technology, too bad they are still privately held. How this technology changes the landscape of plastics manufacturing and 3D printing is anyone’s guess, but one thing is for sure; we’ll be hearing a lot more CLIP 3D printing technology in the coming years.

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3D Printing & the End of the Circuit Board

By Frank Rovella
3D Printing also known as Additive Manufacturing has been around since the 1980s since then there has been a lot of positive and negative hype depending on your perspective. We’ve all heard the fear-mongering from uninformed media sources touting the end of manufacturing as we know it. Until recently it’s only been the end of rapid prototyping as we know it. However, a number of recent developments may indicate that this is about to change.

In a quiet turn of the century factory turned industrial park northwest of Boston, a small group, of academics and engineers, has developed a system that can 3D print electronics.

In conjunction with Harvard University, Voxel8 has developed a 3D printer and highly conductive silver printer inks that allow the circuit board to be printed in process.

As revolutionary as this sounds we have to remember that this is new technology; the developers at Voxel8 aren’t even sure about the potential applications.  At first glance, it looks more like a proof of concept that a production model. Their initial offering utilizes fused filament fabrication (FFF) technology, an established 3D process that is dependable with good repeatability, but not known for high precision.  From a production standpoint, there are several drawbacks. For example, when changing from standard

thermoplastics to conductive inks the ink cartridge must be manually changed. Voxel8’s conductive inks can print the circuit board, but the operator must still manually place the electronic components.
But all this manual labor doesn’t take the wind out of my sails; think about the level of automation, speed, and precision of modern PCB insertion systems. Then combine that with the very low operating costs of the typical FFF 3D system and it’s not hard to imagine large scale production using this technology in the near future.

Its common knowledge that for 3D printing to make a dent in manufacturing metals have to be firmly in the picture. Enter Selective Laser Melting (SLM), this 3D printing process can create products composed of metals such as aluminum, stainless steel, Titanium, and Cobalt Chrome alloys.

SLM was originally employed to produce prototypes and low volumes of dental applications and medical implants and found some high profile applications with NASA.  However its ability to produce complex geometries, hidden voids, and channels has not been lost on the manufacturing community. Tolerances to ±0.02 mm, surface finishes of 20 μm, with close to 100% density make this a very attractive technology.

General Electric is pretty confident in the technology and has invested over $125 million building the first high volume 3D printing facility in the world.  The plant is designed to manufacture fuel nozzles for GE’s LEAP jet engines; they will be using SLM 3D printing technology with Ceramic Metal Composites (CMC). To get an idea of the scale of production, GE currently has orders for more than 6000 LEAP engines, each requires 20 fuel nozzles. As the facility ramps up, GE is expecting production of up to 40,000 SLM printed fuel nozzles by the year 2020.

These developments by themselves may not be cause for alarm, but when taken as a whole they represent a real shift in the way products are manufactured. According to a recent Forbes article, the U.S. 3D printing market grew by 23% from 2009 to 2014 and is expected to continue with growth of 16% from 2015 to 2019.

Though it’s doubtful that 3D printing will ever totally take the place of processes such as machining and stamping, it is certainly poised to make a profound impact on manufacturing as a whole.

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