Purafy Portage Portable Water Purification System

Portage is a durable, reliable, go-anywhere water filtration system to provide safe drinking water anywhere in the world. Its novel graphene ultrafilter technology cleans the dirt and bacteria from the water, and when used in a brackish or sea water environment, an optional reverse-osmosis stage removes the salt. It is transported by disaster relief or military personnel by truck or helicopter to remote locations or places where the local infrastructure has been destroyed. It can be powered by an external battery bank supplied by solar power.

The Challenge:

Purafy had developed a proof of concept prototype that filtered water through brute force. It had the right kind of filters, but the plumbing architecture to generate the pressure and flow needed to drive the reverse osmosis was all wrong. They didn’t know it yet, but there device was consuming far more power than the competitors for the same amount of freshwater flow rate. For a product that is intended to be solar powered, this was a big problem. They were under the impression it was only slightly worse, and could be resolved by a bit of tuning.

The system was highly manual. There was a long set of instructions that the user must follow in the operating manual to startup the machine, and failure to follow the instructions could cause permanent damage to the graphene filters or RO membranes. There was an analog flow meter on one side of the case, and a manual value inside the case. The user had to fully open this valve before startup, and then after running the machine for several minutes, slowly close this valve while watching the analog gauge to achieve the correct operating condition for the RO membranes.

Purafy had no clear customer – initially it was pitched toward disaster relief, but there seemed to be more actual interest from military applications. It was not clear if the design should evolve into a small, man portable, solar powered device, or a large truck-based machine powered by a military generator with NATO standard power terminals.

The Approach:

The initial ask from the customer was

Design for safety
Design for market needs (right sizing)
Ruggedize
Improve user experience

The first focus of the work was to benchmark the current design against the competitors to see how we stack up against them with respect to various performance metrics, pick a niche that will make this product competitive, and focus our efforts to optimize for that.

The technical specs for the prototype device were limited and of dubious reliability, so we started by instrumenting the current design and evaluating it over a wide range of operating conditions to quantify its performance. This was when it became clear that this device was using more than double the power consumption of the competitors, so it becomes unviable for any solar/battery powered application. There would be much more redesign than we initially signed up for.

The focus of the project shifted from design to R&D. We reverse engineered the working principles of the competitors, reviewed academic literature on the latest technology in water filtration, and developed detailed system models. We identified different hydraulic pressure conversion devices (they key to an efficient reverse osmosis system) and search for one that would be the right size for our device. We proposed different designs to the Purafy “runabout” vs “workhorse” so they could survey their prospective customers for interest.

Once a desired water throughput target was locked down and the core piece of technology identified (a ‘clark pump’ by Electromaax), we finally shifted back into design mode.

At this point we brought on board a mechanical engineer to lay out the plumbing in space to package all the components in a rugged case, and a mechanical designer to polish up the details.

Meanwhile the electrical team designed the electronics. First we defined the architecture – an IP67 box inside the main case housing the main control PCB with the power electronics, and a separate front panel PCB for the buttons, LEDs and screen. A cable running between the second case (that houses the reverse osmosis) provides CAN communication to the sensors that monitor the high-pressure system.

The Outcome:

What was delivered was a system that is durable and intuitive. A great deal of effort went into the software controls to automate the operation so any untrained operator can use the device. This included automating the startup procedure, priming, periodic backflushing, and cleaning modes of operation. The intuitive ease of use of the machine is one of the main selling points over the competition.

The device has a high degree of sensing. It monitors the power consumed by all 3 motors, and it measures the pressure and flow at various stages in the water filtration process. The feedback control system ensures that the system operates at the ideal operating point to maximize efficiency, and gracefully shuts down when air enters the system to prevent permanent damage to the reverse osmosis membranes.

The system is optimized to balance cost, weight, size, and power consumption. Compared to the original device that consumed 36.1 kJ of energy per liter of fresh water produced, the new system needs only 15.5 kJ – a 57% reduction.

Services Provided

Market Research

Concept Development & Validation

Requirements Definition

Technology Feasibility

User Needs Development

System Architecture

Assumption Validation

Concept Prototyping

R&D

Prototyping & Rapid Builds

Human Factors & Usability

Mechanical Design

User Interface Design

Software & Firmware Design

Electronics Design

System Design

Analysis & Simulation

Low Volume Manufacturing & Pilot Builds

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