Water Purification Low Flow Rate Energy Recovery
From Army 17.1 SBIR Solicitation
17-089 TITLE: Low Flow Rate Energy Recovery
TECHNOLOGY AREA(S): Materials/Processes
OBJECTIVE: Under this topic, the Government invites proposals for the development and demonstration of a light weight low flow rate energy recovery module for enabling technology for the development of a small, man portable, sea water reverse osmosis water purification system.
DESCRIPTION: The Army currently lacks the capability to purify water at the small scale of contingency bases (<200 Soldiers), small units level (Company level and below), but still greater than individual Solider level. The smallest current Army water purification system consists of multiple pieces which weigh over 1500 pounds and requires a High Mobility Multipurpose Wheeled Vehicle (HMMWV) sized vehicle to transport. Current commercial off the shelf (COTS) systems which treat sea water do not produce enough water, require high power demands, and due to their high complexity require too much skilled maintenance. The Army would like to develop a small, man portable, energy efficient reverse osmosis (RO) system, but high energy requirements and low energy efficiencies are a current technological gap. In order to accomplish this goal, an energy recovery device which capture the energy lost due to the high pressure and high flow rate waste brine stream is required. Commercially available energy recovery devices do not exist in the flow ranges and low weights required. Hence, new technology is needed to develop or adapt a system to recover energy from the waste brine stream generated from high pressure RO membranes. Such devices recovery energy via mechanical, electrical, or hydraulic means for example.
Proposals should identify cutting edge energy recovery technologies that can be used to recover lost energy in the brine waste stream generated from reverse osmosis elements. Proposals should address energy recovery systems or devices that are able to operate using concentrated seawater (up to 55,000 ppm salt (Sodium Chloride)), if the device has contact with the RO product water be made from NSF-61 compatible materials, can operate using feed pressures up to 1200 psig, variable feed flow rates in the range of 75 GPH to 125 GPH, with a recovery of at least 70% of the energy from the waste brine stream.
PHASE I: Demonstrate feasibility of the core energy recovery technology in a laboratory setting. Verify the high pressure energy recovery technology can be integrated in a system with a high-pressure RO pump to reduce the system energy requirement while showing a pathway to meet the full scale integrated system weight (< 80 lbs) and energy metrics (15-20 watt-hr/gallon or less). Objectives also include completion of a conceptual design for a full scale energy recovery prototype that when combined with appropriately sized RO equipment, meets the production rate, weight (RO elements + pump+ energy recovery device =<80lbs), and energy requirements listed in the description above and is suitable for use by military units across the range of small unit operations.
PHASE II: Based on the design parameters elucidated in Phase I, design, fabricate and demonstrate a full scale prototype high pressure energy recovery system which can be used by various military and other defense and support organizations for military, humanitarian assistance, and disaster relief operations when integrated with a RO skid. The delivered prototype should be suitable for laboratory and field demonstration but the design does not need to be ready for manufacture, nor is military standard durability required. The prototype shall, in conjunction with an appropriately sized RO system, operate at the minimum energy recovery rate of 70%, at or below the 15-20 watt-hr/gallon energy metric and the reverse osmosis product flow rate of 10-15 GPH.
PHASE III DUAL USE APPLICATIONS: Commercialization – Technology developed under this SBIR could have an impact on military water purification with the intended transition path being into the planned Man Portable Water Purification System development effort. The development of this technology may also find application in the commercial water treatment industry, municipal water treatment applications and potentially in the residential arena.
1. von Gotberg, A. Pang, and J.L. Talavera. “Optimizing Water Recovery and Energy Consumption for Seawater RO Systems”, GE Power and Water, Water & Process Technologies, TP1021EN, 2012.
2. Liberman, “The Future of Desalination in Texas”, Vol 2, Report 363, Chapter 2, “The importance of energy recovery devices in reserve osmosis desalination”, 2004.
4. “Membrane Desalination Power Usage Put in Perspective”, American Membrane Technology Association, FS-7, April, 2016
5. “Seawater Desalination Power Consumption”, Watereuse Association, November 2011.
KEYWORDS: Water Treatment, Energy Recovery, Reverse Osmosis (RO), Light Weight
TPOC-1: Michael Anderson
TPOC-2: Jeremy Walker
Submitted Proposal: A171-089-1397
Note: Formatting changed to suite web page layout, page title blocks and disclosure restriction blocks have been removed from text.
Note2: Released on Internet 10/1/2017.
A new method for RO (Reverse Osmosis) brine water energy recovery, that can be used in a low volume water purification system, which reduces the per gallon of purified water output energy cost, is being developed. This allows the RO system to be sized for purified water volume output needs and/or also be sized for weight needs while, allowing for the higher efficiency of having brine water energy recovery in a small RO system.
1 Identification and Significance of the Problem or Opportunity.
In all areas that people are present, drinkable and potable water is needed. Sometimes carrying in water for short periods is feasible, but often using water sources that are present require some purification to be able to utilize the water. The most popular and energy efficient method of water purification is using RO (Reverse Osmosis) to purify the water. Large water purification facilities have made good improvements of reducing the amount of energy needed per gallon of water produced. The major portion of this energy reduction has been from reclaiming the energy of the high pressure brine water output, being released back into the low pressure environment.
However, energy recovery for small RO systems, with small GPH rates, in light weight systems have not been created that have energy efficiencies close to the heavy weight RO systems which must be carried by vehicle transportation and weighs over 1500 lbs. There is a need for lower weight system components, multiunit systems with unit adjustable capacities, which gives the reliability of continued RO production when one unit of the multiunit system fails and needs repair. With the ability to easily move units around to balance the needs across multiple areas, and the ability to not have the risk of losing all the RO production in located in one area that one shell hit could destroy during combat conditions. And with good unit efficiency that can be more easily moved, and for sizing that allows for a compact man portable RO unit to be carried to where it is needed for small Solider Units without always having the assistance of vehicle transport.
1.1 Terms Used in Document
RO: Reverse Osmosis
COTS: Commercial Off The Shelf (Commercial equipment that is currently available).
TBD: To Be Determined
Shown in Figure 1: RO System Without RO Output Energy Recovery, is the basic components for RO (Reverse Osmosis) water purification operation. An input pump pumps the input water to a very high pressure, as high as 1200 psi for single stage recovery. This high input pressure requires considerable energy to pump up to this pressure.
Figure 1: RO System Without RO Output Energy Recovery
The high pressure water enters the RO membrane module and pressure difference between input pressure and the low pressure clean water output allows the water to diffuse across the membrane leaving impurities inside. Since it is the pressure difference that allows the water to pass through the membrane, the purified output water will be at low pressure and does not any energy available for recovery.
As the water goes across the membrane, the remaining water becomes more concentrated with impurities and once impurities reach a high level, the impurities prevent any further RO operation without pumping to a higher pressure. The RO brine water with high impurity concentration flows out of the RO Membrane Module. A flow restriction of the brine output flow regulator keeps the pressure high in the RO module and allows for the pressure to drop from the high pressure to low pressure while allowing the needed volume of brine water to flow out.
The RO systems works on impurity levels of the water within the membrane. For lower levels of impurities in the source water, higher percentage of water will flow out as purified water, as compared to for source water with high concentrations of impurities, such as the salt in sea water. When high volumes of water, like brackish water, is available as source water, some trades-offs of water pressure, brine water output volume and impurity density, can be used to reduce the energy needed for each unit of purified water output. However, a common scenario is the purification of sea water where the primary impurity is salt, and the RO process typically gives about 30% purified water at 1200 psi and 70% goes out as brine water.
The brine water at the high RO pressure has considerable energy before being output as low pressure brine water. Dropping the pressure with a simple pressure relief valve will cause the high pressure to mechanically drop to the low pressure and the energy is lost as a small amount of heating of the low pressure output water. For large high volume RO plants, the high volume of output water can be used to run a generator to produce electricity which can be fed into the input pump motor to reduce the amount of energy the RO facility is using to purify the water. However, for a small portable, RO system, where the source of water and impurity level is unknown giving unknown RO brine water percentages, the volume rates are small, available energy source is limited, limited weight of the water purification solution, the loss of energy in converting to electricity and back to mechanical energy, this generator method of brine water energy recovery is impractical or infeasible. However, there is a possible low volume rate solution that can recover some of the energy of the RO brine water coming out of the water purifier.
1.3 RO Energy Recovery Overview
A high level diagram of the target solution is shown in Figure 2: RO System With RO Output Energy Recovery. In this solution, the high pressure brine water output is used to pump source water into the high pressure input side, bypassing the input water pump and any losses of energy from energy type conversion, such as a conversion to electricity and then back to mechanical energy at the input pump. An example of multiple energy conversion, would be the case of an electric generator hooked to the brine water output and then fed back to the source input pump.
Figure 2: RO System With RO Output Energy Recovery
Testing with the "law of conservation of energy", trying to pump a higher volume of input water at the same pressure then the outgoing brine water volume would fail since it would take more energy than is available in the output brine water energy. Trying to pump the same volume of input water as brine water going out, does not take into account potential energy losses in process and fluid pressure losses, so would also not be possible. However, the addition of more energy by adding another pump to account for the losses as a RecuperatorTM or DWEERTM system does, can work.
However, pumping a lower input volume then brine water going out, requires less energy than is going out and can take into account energy losses that occur in a real system. The input pressure can even be higher to account for pressure drops across the system, as long as the energy of the higher pressure input + overhead energy losses in pumping and fluid flow heating losses, is less than the energy going out as high pressure brine water. It is this basis of energy equalities that passes the "law of conservation of energy" that this brine energy recovery design, is based on.
From someone observing, they would just see water moving around the system and conservation of energy would be difficult to observe, since it is not different then just high pressure water. So where does the result of the conservation of energy end up at? Since the output is pumping some water into the input side bypassing the input pump, the input pump needs to pump lower volumes of water at high pressure to get the same amount of high pressure water input into the Reverse Osmosis Membrane Module. The input pump is pumping less water volume at high pressure to get the same net result as a system without the recovery pump at the full volume, which uses less input energy, which is the direct observable energy conservation. Since the new system for the same rate of purified water doesn't use as much input energy than the case without the energy recovery pump, it allows a limited energy supply to last longer, or uses less energy per gallon of water purified.
For an instrumented lab case, the rate of pumping of input water from the recovery pump energy verses the brine output rate, would give the observable energy recovery percentage and demonstrate the operation.
A possibly confusing aspect is when the input pump stops pumping, since the recovery pump pumps an input volume less than the output brine volume, and because the brine output also stops, the recovery pump would also immediately stop pumping. When the input pump starts pumping again, the pressure builds back up and the output brine starts flowing again, then the recovery pump would resume pumping, making it look like the input pump is directly running the output recovery pump, when it is indirectly running the pump through the brine water output.
1.4 Energy Recovery Pump
The brine output energy is recovered by using a piston pump as shown in Figure 3: RO Brine Energy Recovery Pump. The outgoing brine water flows into the side with the larger piston. One side of the large piston has RO brine water flowing into it from the output of the RO Membrane unit, while the other side has water flowing out through the brine water output control regulator/valve and out of the system. Sensors at both sides of the pump detect when the piston is getting close to the end of a stroke. Since the volumes are low, the stroke is moderately slow. When the piston gets to the end of the stroke, the controller detects the end of the stroke and runs a solenoid in the valving unit, that switches which side the high pressure brine water is flowing into and which side is being output to the brine output flow regulator, and then the piston is pushed the other direction.
This example of valving is done by a electronic controller and solenoid. A fully mechanical valve control mechanism could be used, but would also have to deal with additional high pressure water sealing for these additional mechanical parts.
The energy transferred to pump the input water is through the metal rod connecting the two pistons. The smaller piston is pulled and pushed by the larger brine output piston, which the pistons moving back and forth and using spring loaded check balls that control flow direction, pumps incoming water into the RO input. Since the input piston is smaller, the input pump can pump at a higher pressure then the brine output pump and can overcome pressure differences of pressure drops and check ball pressure drops, not requiring a booster pump, unlike a RecuperatorTM or DWEERTM, which each type requires an additional booster pump.
The energy used in this pump is from the seal friction on both the pistons and rod, and for leakage across the seals as water is pumping. Small leakage of the rod seal from the brine water into the input pumped water would result in some minor reduction in percent of pumped water which can be recovered with osmosis due to the higher impurity concentration, can also be thought of as energy loss or energy used by the pump. Another energy loss is hydraulic flow friction in pipes, components, and flow fiction across check and balls/valves. Any flexing of the metal components will also be absorbing energy from the pumping process.
Figure 3: RO Brine Energy Recovery Pump
Since the pump can pump at a lower pressure as well as a higher pressure, some form of brine output flow control must be used to maintain the correct pressure in the RO membrane units. This is shown in the diagram as the Output Pressure and Volume Control box, which essentially a flow regulator. The Output Pressure, to control the brine water output flow levels, is from the RO Output Brine Water feeding the energy transfer pump, not the pressure from the brine output of the pump. After the energy from the brine water has been transferred to the input water, the output pressure is low and cannot be used to tell what pressure is in the RO unit. However, by regulating the rate of brine water output flow, this controls the back pressure to the energy recovery pump, which can control the energy recovery pumping rate, which then controls the RO pressure being used for the osmosis process.
1.5 RO Flow Example with COTS Pump
This is a calculation of using the energy recovery pump to show purification rates of sea water of a system using the energy recovery pump and a common sea water input pump.
1.5.1 RO Purification Rate
Pump Volume Rate: VP = 1.5 GPM (Cat Pump 2SF15SEEL Specification)
Purification Percentage: PP = 30% = 0.3, Typical Single Stage Seawater Purification Rate
Brine Pump Recovery Rate: PR = 75% = 0.75, Set by Pump Design, 0.75 is Initial Target
Purification Volume Rate: VP = VT* PP
Volume Brine: VB = VT - VP = VT - VT* PP = VT( 1- PP)
Brine Recovery Rate: VR = PR * VB
RO Input Volume Total: VT = VP + VR, (Pump Rate + Brine Recovery Pump Rate)
VT = VP + VR = VP + PR * VB = VP + PR * VT( 1- PP)
VT - PR * VT( 1- PP) = VP Algebra to solve for VT
VT(1 - PR *( 1- PP)) = VP Extract VT and move remaining of equation to other side
VT = VP /(1 - PR *( 1- PP)) = 1.5/(1 - 0.75*(1-0.3)) = 1.5/(1 - 0.75*0.7) = 3.158 GPM
VP = VT* PP = 3.158 GPM * 30% = 0.947 GPM Purification Rate Per Minute
GH = 0.947 GPM = 0.947 GPM * 60 GPH/GPM = 56.84 GPH Purification Rate Per Hour
1.5.2 RO Purification Energy Usage Per Gallon
Energy Usage Rate: PP = 0.9 kW (Cat Pump 2SF15SEEL Specification)
Energy Usage Rate per Hour: PH = PP * H = 0.9 kW * 1.0 H = 0.9 kWh
Energy Use Per Gallon = PH/GH = 0.9 kWh/56.84 GPH = 0.0158 kWh/G = 15.8 Wh/G
Energy use per gallon of purified water meets the objective energy use goal.
1.6 The Energy Conundrum
The above example shows that the energy recovery pump is pumping at a higher input rate than the input pump because the brine output rate is higher than the input pump rate. How can this be? Is this saying that a higher level of energy is being recovered then the input energy level? If so, it violates the conservation of energy. If this is true, solving for when 100% flow is going through the brine output, the balance point of energy recovery is at 50% brine pump rate, and the pump must pump less than 50% to overcome internal frictions of the pump, which the design can be adjusted to pump less than 50% of the brine output to overcome this case. Under this definition, 100% energy recovery would mean that the energy recovery pump is pumping the same amount as the input pump rate when the purification rate is 0. For 75% recovery of a 70% brine rate, the energy recovery pump would be pumping input water at: 0.7*0.75 = 0.525 pumping rate of the input pump rate. Would only need to solve from VT to get the correct input pump piston size.
However, this system is a circular feedback system. The energy in the brine water may be the accumulation of energy across multiple (infinite) circular cycles, and the system maybe an integration of this energy recovery. When you look at the balances of forces caused by the pressures, the pump should move the piston and the pump should pump the input water as long as the pumping friction is not too high compared to difference of force in each direction during the stroke. When you feed all water through brine output, pumping at a 0.75 rate, due to fluid feedback, the energy recovery pump will be pumping input water at 3 times the input pump rate. For 3/4 efficiency recovery, this means 3 energy units recovered for every 1 energy unit lost out of 4 units, and energy and high pressure water volume is interchangeable, so the equations are correct. Does this make sense? Where does the conservation of energy apply? The energy being lost is from the friction of seals, fluid flow friction energy lost, seal leakage, flexing of metals, and output of the piston pump pressure drop across the brine output regulator. This pumping energy loss could be less than the energy input, and from this point of view, conservation of energy is valid. In my opinion, I think this is the valid energy recovery viewpoint.
The pressure difference across the brine output regulator while operating, will allow the pumping friction energy consumption to be calculated. However, initial piston start force will be higher than when the piston is moving, so starting and stalling when switching directions must still be considered the high friction points. During the energy recovery pumps use and ageing process, wear, corrosion and/or salt build up might increase the friction and stall force levels.
If the feedback amplifies the pumping volume rate, it also amplifies the effect of seal friction, which complicates trying to calculate the seal friction loads correctly. This is why remaining at a conservative 0.75 rate is being used for initial demonstration and should overcome the seal friction. However, if test pump is built and it does not pump since the piston will be stalled, to determine if this problem is either a friction or a conservation of energy issue, a 50% case will be built and tested, and if it pumps with 0 purified water output rate, it is an amplified friction case, since if it is conservation of energy, the piston will not move due to real world frictions and the energy would be balanced on both sides. However, if the pump works at the 50% ratio case, then it would just be an amplified piston seal friction stalling condition.
The documentation of working RO systems seems to indicate that high efficiency brine energy recovery can be done. However, the RecuperatorTM or DWEERTM, which each type requires a additional booster pump, and might be used to hide the actual amount of input energy that is required, while claiming that the device itself is efficient. I look forward to finding out if 75% energy recovery pump rate means 75% energy recovery or 50% pump rate means 100% energy recovery. Either way, this will lead to valuable information about the possible small RO system efficiency and the correct formula to calculate brine water energy recovery rate efficiency, and the pump can be sized to work for either outcome.
2 Phase I Technical Objectives.
2.1 The Phase I Objectives
1. Research Metals and Materials Compatible with Saltwater.
2. Research Available COTS Saltwater RO Membranes.
3. Energy Recovery Pump Piston Sizing Tradeoff Study.
4. End of Piston Stroke Detection Development.
5. Design High Pressure Pistons and Rod.
6. Design High Pressure Pumping Cylinders.
7. Design Brine Water Valving Unit and Controller.
8. Design Brine Output Flow Regulator.
9. Do Lab Bench Testing and Demonstration.
10. Purchase Materials and Machine Work.
11. Portable Low Weight Conceptual Design.
12. Do Patent Search.
13. Do Project Management.
14. Write Phase I Monthly Status and Progress Reports.
15. Do CMRA Reporting.
16. Write Phase I Non-Proprietary Summary Report.
17. Write Phase I Final Report.
2.1 The Phase I Optional Objectives
1. Write Phase II Proposal.
2. Research Available COTS RO Saltwater Input Pumps.
3. Size Concept Design Small Volume Energy Recovery Pump.
4. Refine Portable Low Weight Conceptual Design.
5. Do Project Management.
6. Write Phase I Option Monthly Status and Progress Reports.
7. Do Phase I Option CMRA Reporting.
8. Write Phase I Option Non-Proprietary Summary Report.
9. Write Phase I Option Final Report.
3 Phase I Statement of Work
The work for Phase I is 6 Months Phase I Option is 4 Months in length and will be conducted at Lightning Fast Data Technology Inc. Headquarters (3419 NE 166th Ave, Vancouver, WA 98682). Note: Tasks are not listed in sequential work order since it covers multiple workers.
The design refers to the Phase I energy recovery demonstration pump design, but hoping to be able to apply as much as possible of the design work to the Phase II energy recovery pump for the low weight, small output volume, concept design.
3.1 Phase I Tasks
3.1.1 Task 1: Research Metals and Materials Compatible with Saltwater
Research parts and materials that can be used to build components for the sea water pump, valving unit, and high pressure tubing. Determine sources, availability, and issues. It is desirable to build a demonstration energy recovery pump out of target saltwater compatible materials, however, this is a very low budget project. If the cost is prohibitive, or machining issues, or material availability issues, then prototype demonstration unit, might be built using available low cost materials and saltwater compatibility will be a Phase II issue. Saltwater tests can still be done with non saltwater compatible materials If using non-saltwater compatible materials, after the saltwater tests, the salt is neutralized and/or equipment is thoroughly cleaned. However, the system will probably have a shortened life cycle, and damaging corrosion can easily set in. But the system does not need to last long to prove the energy recovery concept.
3.1.2 Task 2: Research Available COTS Saltwater RO Membranes
This is to research the availability of USA sourced small form factor RO Membrane Module products for sea water purification which supports the high target pressure of 1200 psi. Look into size and weight needed for the low volume application. If no products can be found, try and negotiate with the RO manufacturers for a RO product module with the needed size and weight. Look into cutting, resizing, and repackaging the larger commercial sea water RO products, to the needed size, but this is a Phase II project to do so. RO Membrane Module will not be used in the energy recovery pump bench demonstration, however, this is to get information for the conceptual design.
3.1.3 Task 3: Energy Recovery Pump Piston Sizing Tradeoff Study
The energy recovery pump can be built in different combinations of piston size and piston movement speeds. Bigger pistons requires heavier pistons and cylinders, but has slower piston movement rates might have some friction and energy use advantages. This is to create a list of issues, advantages, and piston size combination ranges that can work for the target brine output water rates for the demonstration unit. Part of this study might be done in conjunction with piston, rod and cylinder design cycle.
3.1.4 Task 4: End of Piston Stroke Detection Development
For better reliability it is desirable to use a passive method to detect the end of the piston stroke through the metal casing, since switches and/or mechanical rods require seals that increase the odds of leakage at 1200 psi pressures. Methods such as a coil used for a oscillator that changes frequency when the piston is near the end, detection of magnets that might be on the head and the piston to change the polarity of the magnet flux of the head when the piston gets close to the end, etc. can be evaluated. However, for the high pressure, the cylinder cover/head might be too thick to effectively detect the end of the stroke, so mechanical methods or switches might be employed.
3.1.5 Task 5: Design High Pressure Pistons and Rod
Although the basic design is simple, due to the high 1200 psi pressure multiplied by the piston area, these forces can be large depending on piston diameter. When the piston force is inward, the connecting rod must be strong enough not to flex significantly and hold the pistons apart. However, a more difficult case is when the pump is pumping the other direction, and this large force is outward and the threaded nuts and rod must withstand this large force. The volume pumped and pump ratio is affected by the connecting rod moderate diameter and so the piston force area and volume pumped is different in each stroke direction. The piston also has to be designed so that fluid will always be able to apply force across most of the area when the piston is against the cylinder head or the center plate to prevent a fluid area force locking condition.
The percentage of energy recovered is controlled by the ratios of piston areas, (inside area and ratios is different than outside due to connecting rod presence). These ratios only needs to be large enough to reliably overcome friction and other losses. However, this is going to be tested with an average of 75% piston area ratios for a target 75% energy recovery for reliable demonstrations. Some energy is used by the valving unit, which should be less than 5% for a better than net 70% recovery. The fluid dynamics and fluid friction losses plus seal friction losses have a very high probably of being substantially below 25%, however, the balance point of pumping ratios where the pump becomes unreliable will be a Phase II study, the Phase I test is just to validate the basis of the energy recovery operation.
3.1.6 Task 6: Design High Pressure Pumping Cylinders
The design of the cylinders and heads will be done together as a set. The cylinder shape has an advantage over the flat head due to the redial fluid pressures and the strong tensile strength of the metals. The heads surface is moderately flat, although some curvature might be used in the design, the high pressure fluid pressure on the flat surface results in other force directions and the need to control energy loss from warping the metal on every pumping stroke, the metal has to be much thicker then the cylinder walls. The lighter weight design would be to machine the cylinders and head from one piece of metal. Although welding of head to cylinder might be able to be used, it will be weaker than a fully machined design. If material is not readily available or cost is prohibitive, the head will be designed to be bolted on at the cost of a heavier design, and the more costly single metal block and/or welded head consideration will be resolved in Phase II.
3.1.7 Task 7: Design Brine Water Valving Unit and Controller
Output from the RO units is brine water that needs to be input into the Energy Recovery Pump. However, which side of the piston is being fed with RO brine input water and which side is being pumped out as low energy brine output, needs to be quickly switched at the end of each piston stroke. This switching of fluid flow direction is done in the Input/Output Brine Water Valving Unit. At this time, the primary plan is to use a controller which detects near end of stroke conditions and will run one or two solenoids to switch the flows, however, a full mechanical design may be considered as a possible design. Controller design will be part of valving unit and end stroke detection design and might just use a general PC computer and some interfaces for the bench tests, whatever is easiest to do at the time, actual design is TBD.
3.1.8 Task 8: Design Brine Output Flow Regulator
Output from the pump must be controlled to prevent most all of the fluid going out at a lower pressure, bypassing the RO Elements and directly running the pump with most of the water. This uses pressure of the RO fluid to manage system output since pump output will be at a much lower pressure and unneeded backpressure when Brine water should be flowing out, will prevent the pump from working. Some control of operation for varying input water conditions may allow some flexibility in controlling needed operational pressures and associated energies per unit of purified water output. The energy recovery will work just as well at lower pressures as it will at higher pressures and automatically adapts to the pressure. More pure water going in will have higher RO rates at lower pressures and the input RO pressure is close to the RO output pressure, so it is the output flow regulator that determines the RO pressures and output rates, but there are tradeoffs depends on the quality of water being purified. The controller might be able to do some smart management, but full system design and evaluation will need to be done for this to be considered, and so smart management will be a Phase II consideration.
3.1.9 Task 9: Lab Bench Testing and Demonstration
This task designs and assembles lab bench test unit shown in Figure 4: Lab Bench Test, Evaluation, and Demonstration Unit. This will use a COTS high pressure saltwater pump (Cat Pump 2SF15SEEL). This will have fluid rate metering for input pump rate, recovery pump input water rate, brine output water rate, and simulated RO output water rate with metering placed on the low pressure side to allow use of lower cost, low pressure meters. A watt meter is used for pump power input, and pressure meter for RO high pressure area, and a pressure meter at the brine control regulator valve to determine the recovery pump and fluid flow energy loss/usage.
Figure 4: Lab Bench Test, Evaluation, and Demonstration Unit
A pressure relief value is present to keep from overloading the input pump while the valves (made for slow changing of fluid rates) are slowly being adjusted to set various simulated purified water and brine output flow rates at close to the target 1200 psi operating pressure. This will allow tests for energy usage, input pumping rates, and energy recovery pumping rates for simulated purified flow rates of 0% to 100% allowing the test points to be measured across the full operating range.
A small very low pressure pump (not shown) will be used to get the water to the Source Water Input manifold at close to atmospheric pressure for labor saving convenience.
Moderate/good accuracy rate meters will be used, however, if higher accuracy measurement is needed beyond the rate meter's accuracy, brine output and purified water quantities can be carefully measured for a period of operation time after flow equalization has been established. Excellent accuracy watt meters can obtained at low costs.
Lab bench demonstrations will be at Lightning Fast Data Technology Head Quarters, as needed and coordinated by contract officer.
Note: Selection of parts and materials is part of this task, however, purchasing and obtaining materials for the lab bench unit is part of the Materials and Machining task.
3.1.10 Task 10: Purchase Materials and Machine Work
This task is to manage material purchase, contact and work with machine shops, and get the parts manufactured. The material costs are included in this as a block sum to be used for material purchase, machining work purchase, and may also include Mechanical CAD software tool cost but might be able to get by with lower value tools, such as open source tools, to do the work, so the CADs cost is TBD at project time. It would require a completed design to get accurate machining costs, so this is used and billed as needed and may not use the full material amount in the cost estimate. Time also includes some assembly and some basic testing.
This task also includes buying gauges, meters, pipes, input pump, valves, and a pressure relief valve, to create the lab bench test unit. However all the high pressure saltwater resistant 316 stainless steel components are expensive. The flow and pump demonstration will probably be done with regular water, and 316 stainless steel only used if sufficient budget is available to cover the cost of everything. Using 316 stainless steel to allow saltwater test and demonstration is more desirable then using plain water, and demonstrations beyond Phase I may also be desirable.
3.1.11 Task 11: Portable Low Weight Conceptual Design
Conceptual design of a portable light weight reverse osmosis sea water purification system based on the energy recovery pump design discussed in this document. The objective is that combined weight of the input pump, energy recovery pump, RO Membrane Module(s), RO brine output regulator, piping and framing will be < 80 lbs and organized to allow it to be carried on the back like a backpack, as a man portable equipment for use by a small military unit. Energy requirement objective will be < 20 watt-hr/gallon of purified water from sea water at a rate of 10-15 GPH. Power source, probably small gasoline generator, will be a separate unit and not part of the design.
3.1.12 Task 12: Patent Search
Patent search for the RO energy recovery pump for use and design. If no patents are found, apply for patent.
3.1.13 Task 13: Project Management
General project support and management. Work scheduling, planning, and progress tracking and review. SBIR, government contracting compliance review and planning.
3.1.14 Task 14: Phase I Monthly Status and Progress Reports
Status and Progress Reports document the status of overall project, the projects objectives for the month, the progress of each task, results obtained, and any concerns. Provided within 15 days after the completion of each month, but excludes the last month which is included in the Final Report.
3.1.15 Task 15: CMRA Reporting
Create Non-Proprietary Summary Report as described in ARMY 17.1 Small Business Innovative Research (SBIR) Proposal Submission Instructions.
!!! OPPS !!!
3.1.16 Task 16: Phase I Non-Proprietary Summary Report
Create Non-Proprietary Summary Report as described in ARMY 17.1 Small Business Innovative Research (SBIR) Proposal Submission Instructions.
17: Phase I Final Report
Contains detailed information for project objectives, work performed, results obtained, and estimates of technical feasibility. Provided within 30 days of Phase I completion.
3.2 Phase I Option Tasks
3.2.1 Option Task 1: Phase II Proposal
Write a Phase II proposal for "Low Flow Rate Energy Recovery".
3.2.2 Optional Task 2: Research Available COTS RO Saltwater Input Pumps
Research the throughput and power usage of available 1200 psi capable saltwater piston and diaphragm pumps. Note: This is for low volume low rate pumping which does not have the advantage of a huge turbo pump which has low energy use when water is not moving (not being pumped) since the fluid acts as a lubricant as the turbine spins which keep the energy use low for non-moving fluid, the primary energy used into the fluid actually being pumped. Small pumps do not have this advantage.
Will also look for low flow rate turbine pumps and consider the issues needed to get low flow volumes at high 1200 psi pressures, but the liquid friction per pumped volume may be a bigger consideration of small pumps compared to big pumps, research is required.
3.2.3 Optional Task 3: Size Small Volume Energy Recovery Pump for Concept Pump
The energy recovery pump was sized for the available high pressure saltwater pump to do a valid lab bench tests. This evaluates the energy recovery pump size, including estimate of piston sizes, needed for the 10 to 15 GPH concept design.
3.2.4 Optional Task 4: Refine Portable Low Weight Conceptual Design
Refines the Portable Low Weight Concept Design. Due to the primary focus being on creating a proof of concept energy recovery pump, the schedules was tight. Some of the needed research was not done and the concept design was not given as much work time as desired. This work is to refine the concept design to include more information learned in Phase I, the new information about available saltwater pumps, optimally sized energy recovery pumps, and other potential concept design refinements.
3.2.5 Option Task 5: Project Management
General project support and management. Work scheduling, planning, and progress tracking and review. SBIR, government contracting compliance review and planning.
3.2.6 Option Task 6: Phase I Option Monthly Status and Progress Reports
Same as described in Phase I, but for the Phase I Option time period.
3.2.7 Option Task 7: Phase I Option CMRA Reporting
Create Non-Proprietary Summary Report as described in ARMY 17.1 Small Business Innovative Research (SBIR) Proposal Submission Instructions.
!!! Double OPPS !!!
3.2.8 Option Task 8: Phase I Option Non-Proprietary Summary Report
reate Non-Proprietary Summary Report as described in ARMY 17.1 Small Business Innovative Research (SBIR) Proposal Submission Instructions.
3.2.9 Option Task 9: Phase I Option Final Report
Contains detailed information for project objectives, work performed, results obtained, and estimates of technical feasibility. Provided within 30 days of Phase I Option completion.
3.3 Invention Reporting
The invention has been defined, and there is no knowledge of an equivalent system. However it has not yet been proven to operate under the RO operation conditions (although the probability is very high). Once it is shown to pump an input water rate of 50% or better of the brine output rate, and a patent search has been made, the invention will be reported within 2 months of these findings on the Edison Invention Reporting System.
If it is determined that actual 100% energy recovery occurs at 50% pump rate due to the system's fluid feedback, as discussed earlier in the document, and 70% energy recovery occurs at less than 50% pump rate, then patent application and Edison invention reporting will proceed.
The lab bench test system will be used for demonstrations and internal testing. It will be an asset to use beyond the Phase I project and considered a prototype to be kept at Lightning Fast Data Technology Inc. unless otherwise requested by the Contracting Officer.
4 Related Work.
I, Mike Polehn, grew up and worked on our families' high production/volume cherry farm. This dealt with many types of equipment, repair of equipment, and occasional needs to solve issues with unique solutions. Went to OSU (Oregon) for Electrical and Computer Engineering, which included mechanical engineering statics, dynamics, strengths and materials, thermal dynamics, etc.
This a basic project that only requires a good quality engineering education to do. With my real world experience and extended knowledge across multiple disciplines, it allowed me to see a solution for this energy recovery problem with very little effort.
5 Relationship with Future Research or Research and Development.
(a) The anticipated results of Phase I and Phase I Option will show that a small mechanical energy recovery pump can be used to recover energy from the brine water output and transfer the energy to input water by pumping additional source water into the system in parallel with the source input pump. This will reduce the energy requirement from pumping a larger quantity of input water to using a smaller input pump with lower power use and reduce the energy usage per gallon of purified water for the smaller RO systems.
(b) The significance of the Phase I objective is to develop and prove the basic brine energy transfer pump will work at better than 70% energy recovery. This will set the foundation for the pump's internal energy usage and system load analysis in Phase II, to determine the balance point for pump input and output ratio sizing for reliable system operation. The Phase I results will also provide sizing experience and a solid foundation for optimal sizing rules for the lower rate and lower weight energy recovery pump for the Phase II man portable RO system. No development of membrane material is planned, but if a suitable sea water membrane package size cannot be found, nor will a RO manufacturer negotiate to provide a small membrane module suitable for a man portable system, a large sea water membrane element might be cut and repackage into a small format package for the Phase II prototype.
(c): Regarding clearances, certifications, and approvals, no requirements were posted in the DoD SBIR BAA for Phase I and Phase II R& work of this topic. However, only materials that will not contaminate product water and not contaminate the brine water will be used. The Phase II man portable prototype will use 316 stainless steel for the high pressure liquid management components and metal in energy recovery pump, and NSF-16 compatible materials for the seals, gaskets, and low pressure liquid management components. Evaluation for general energy recovery production pump and for non-sea-water energy recovery pumps using metals other then 316 stainless steel may be considered in Phase II R&D. Certification will be a Phase III project work.
6 Commercialization Strategy.
The large capacity RO systems have improved brine energy recovery over several generations with good high pressure brine energy recovery. Since the energy recovery systems are bulky and require extra water pumps, they are suitable for stationary facilities. The brine energy recovery system presented in this document is probably only competitive on systems that can be moved with a fork lift and smaller more portable units. Since the pumping unit does not require the additional, expensive saltwater pumps, that are required to be to handle the high pressure, even though they are not pumping from low pressure up to high pressure, some of the smaller facility sized systems might be more economical to use this energy recovery pump. Phase II pump maximum efficiency evaluations will help determine if it can compete with the current larger brine energy recovery systems.
The use primary commercial applications for the new RO brine energy recovery is man portable RO systems useful for small military groups, for reduced weight RO systems for use in small sea going boats that serve a small crew, for humanitarian assistance, and disaster relief support. Since single systems can have single point failures, this system is good for multiple small units allowing considerably higher reliability of deployment and deployment balancing without total failure, which has a higher value then single large bulky systems.
The small system would be more economical for small use cases, such as isolated facilities and farms where bringing in water or the distance of piping for good water is not practical and only poor quality water sources are available.
The primary strategy at this time is to pursue both development for the more limited military needs of manufacturing of small volumes of man portable and small water purification systems, and licensing the energy recovery pump for commercial manufacture and to some of the other military equipment manufacturers. However, a more detailed market analysis is to be done in the Phase II time frame, which might change the commercialization strategy and result in brine water pump production for some of the small use cases and more limited licensing. This also has the chance of also capturing some of the sea water pump, brackish water pump, and small RO system market for boats, isolated facilities, and farms. However, the final strategy is TBD.
7 Key Personnel.
PRINCIPLE INVESTIGATOR: Mike Polehn
Oregon State University, BS in Electrical and Computer Engineering, 1983
Engineering education included mechanical engineering statics, dynamics, strengths of materials, thermal dynamics , etc. I grew up on a very large cherry orchard and learned many diverse things from farming. Spent considerable time working on and fixing different types of equipment, spent time modifying engines, transmissions, and bodies with gear head friends, resulting in practical experience that reinforced my engineering education, especially the mechanical engineering portions, and would apply to designing, creating components, and building the energy recovery prototype for this system.
Senior computer development engineer with 30 years experience with Digital Signal Processor (DSP) development, Device Driver development, Infrared Sensor digital signal processing and sensor analysis, and embedded development. Have both SW (primary C/C++) and HW development experience for the full development cycle of definition, document, design, development, debug, and test. Combining HW, SW and analytical experience, provides superior computer engineering capabilities over any of these skills by themselves. Flexible, self directed, and an independent thinker, capable of doing very complex work with little or no supervision.
Note: Extremely abbreviated resume. Full resume available on request.
8 Foreign Citizens.
No foreign citizens or individuals holding dual citizenship, working as a direct employee, contractor, or consultant, will be working on or involved with this Phase I or Phase I Option project.
The physical facilities and equipment to carry out Phase I is just office space, PC computers, garage space, and hand tools. Other than simple manufacture and assembly, part manufacturing will be carried out in machine shops not part of the facility. The energy recovery tests will be using tap water, unless specific requests to use sea water are requested, which arrangements will be made at that time. For Phase I, doing tests at a sea location with easily available sea water sources, or hauling, handling, and disposal of a moderate quantity of sea water for use at the test bench has not been included in this project.
The facilities meets all environmental laws and regulations of Federal, Washington State, and local Governments for, but not limited to, the following groupings: airborne emissions, waterborne effluents, external radiation levels, outdoor noise, solid and bulk waste disposal practices, and handling and storage of toxic and hazardous materials.
No Subcontractor or Consultants are required for Phase I and Phase I Option.
11 Prior, Current or Pending Support of Similar Proposals or Awards.
No prior, current, or pending support for proposed work.
12 Discretionary Technical Assistance.
No Discretionary Technical Assistance (DTA) required for Phase I and Phase I Option.
Post Proposal Comments
The proposal was not selected for funding. Although a debrief was requested, no debrief was provided. Writing reasonable proposals is expensive and is lost time since nothing was learned or nothing gained for the effort, which could have been spent doing something else. This is a fairly trivial project that a junior engineer can easily understand and do. This leaves me wondering about the real basis of the analysis of SBIR proposal evaluation. Is it really about invention, fact and technology, or primary conjecture formed from social interactions of knowing you better than the other proposal writers, or some combination of the two?