AccessO2 : An Innovative, Non-Electric, Life-Saving, Oxygen Concentrator

Summary

18 patients from the critical care unit died due to the lack of an oxygen supply system following a power failure” said Dr. Umesh Kumar, from MIOT Hospital in Chennai, India1. This news caught my attention and initiated my research on the importance of concentrated medical oxygen.

During research, I found that the concentrated oxygen is not available everywhere, requiring either importation of compressed oxygen cylinders or electricity to operate oxygen concentrators. To address this need, I have designed and constructed an innovative oxygen concentrator based on pressure swing adsorption that requires no electricity to operate. Under pedal power it is designed to generate oxygen concentration ranging from 30% to 80%, typical for use in hospitals, with flow rate sufficient to supply an incubator treating infant respiratory distress, the leading cause of death among premature infants.

My system achieves this by compressing air into pores in zeolite (a carbon-silicon-oxygen ceramic lattice with uniform pores 0.0000000005 meter diameter) that preferentially adsorbs nitrogen based on molecular size and chemical bonds. Because nitrogen is retained within the zeolite, oxygen passes through at higher concentration. The cycle is completed by purging nitrogen from the zeolite allowing repetition. Typical systems are powered electrically; my system is human powered, addressing the needs of clinics with unreliable electricity.

My system generated peak oxygen concentration of 88%, which declined to 42% steady state over time. This output is usable to treat neonates and infants who suffer from infant respiratory distress syndrome, and thereby reducing the mortality rate.

Question / Proposal

Can I design and build a human powered oxygen concentrator able to save lives in areas where concentrated oxygen is otherwise unavailable?

Hypothesis: An oxygen concentrator based on pressure swing adsorption will be designed and constructed that operates from human pedal power to supply 30% to 80% concentrated oxygen at 2L/min flow rate.

Hypoxemia, or low blood oxygen saturation, is a major fatal complication of several serious health conditions contributing to the global burden of maternal, infant, and child mortality. It is also the cause of death in infant respiratory distress: poorly functioning lungs resulting from premature birth. Millions suffering from these ailments live in underdeveloped countries without access to concentrated oxygen or stable electricity to run oxygen generators.

The expected application is installation in a clinic without reliable electricity, attached to a neonatal incubator, supplying continuous oxygen while the device is pedaled by family members and friends. The concentrator will require moderate physical power, which a person could sustain for two hours before alternating with another volunteer.

In my design phase I will research existing oxygen concentrators and adapt to human power, considering the gearing necessary to produce sufficient torque to drive a pump and synchronization to drive cams operating the valves. In the construction phase I will acquire components and assemble the system. During my experimentation phase, I will change independent variables such as type and quantity of zeolite, and volume and pressure of air, while monitoring oxygen concentration measured by an oxygen meter.

Research

Pneumonia is an illness caused by infection affecting all ages but is most serious among children and the elderly. Every year 1.9 million children under 5 years of age die from pneumonia2. Oxygen therapy is an important treatment for pneumonia; when employed, it could reduce the fatality rate by 35%. In addition to pneumonia, infant respiratory distress syndrome (in severe cases called bronchopulmonary dysplasia), which occurs primarily in premature infants, affects about 1% of newborns. The table below shows oxygen concentration needed for treating this syndrome3.

Figure 1: Effective oxygen concentrations for infant treating respiratory distress syndrome

During my research, I found references to two other non-electric oxygen concentrators. A group of scientists in Australia developed the Fully Renewable Energy Oxygen (FREO2)4,5, which for its power source, requires a stream with constant water flow. This system exploits the reduction in pressure of water flowing through a raised siphon to create a source of vacuum, which also generates pressure, through a coupled bellows system. The limitation is that in many places there is not flowing water to operate the system.

In 2016, Dr. Lara Brewer at University of Utah received a Gates Foundation grant to pursue an innovative global health and development research project titled “An Oxygen Conserving Oxygen Concentrator,” but no further information is available6.

To design a non-electric oxygen concentrator, I researched how a typical oxygen concentrator works. I reviewed many videos online and read articles from various institutions and companies that manufacture oxygen concentrators. I found that certain zeolites preferentially adsorb nitrogen when pressurized with atmospheric air, leaving concentrated oxygen. Afterward the nitrogen can be extracted from the zeolite by applying a vacuum, and then the cycle restarts. I learned that zeolites are a naturally occurring mineral that can also be produced on an industrial scale, and that synthetic zeolite infused with lithium cations is very effective for nitrogen adsorption.

My innovation is to generate concentrated oxygen using only human power, supplying 30% to 80% concentrated oxygen at a flow rate of 2 L/min. For comparison, the commercial electric oxygen concentrator Inogen G2 produces 85% concentrated oxygen at a flow rate of 1.2 L/min. Availability of human powered systems could save millions of lives who suffer from lung diseases but have no access to concentrated oxygen or electricity.

The problem is real: According to a survey of 231 African hospitals conducted by the World Health Organization(WHO), 150 lack a stable supply of electricity, 56 have no source of concentrated oxygen, and 38 have no electricity at all7.

Method / Testing and Redesign

Using the Google Sheets, I have programmed equations to iteratively calculate system parameters. The following screenshot shows the final calculation that I used to build my system.

Figure 2: Interactive calculations for system design

Based on the calculations in the figure above, the system requires about 17W of power to drive, which is ¼ of the power an average bicyclist can sustain for an hour. These calculations provided guidance for the size and cycling frequency of the air cylinder which is the pump that supplies pressure and vacuum. With the cylinder size determined, the rest of the system was designed as shown in the schematic diagram below.

Figure 3: Schematic diagram of the system

With the initial schematic drawn, I started gathering materials I would need to build the prototype. The major parts of the system are:

  • A double acting pneumatic air cylinder
  • Zeolite LiX
  • Four three-way valves
  • Eight check valves
  • Two variable pressure check valves
  • Chain and sprockets of various sizes
  • 20ft ¼” copper tubing with corresponding fittings
  • Bike pedals and mounting bearings
  • Modular aluminum channels
  • Zeolite canister made of PVC pipe
  • Capacitance manometer pressure gauge
  • Oxygen meter

Human power applied to pedals operates a compound chain and sprocket system that both increases torque and rotates a cam for proper timing of valves. The high torque sprocket drives a reciprocating arm connected to the piston in the pneumatic cylinder, to pressurize and evacuate the system in two compression strokes and two vacuum strokes. The compression stroke forces atmospheric air through the zeolite canister, and the vacuum stroke subsequently purges the canister to repeat the cycle. Figure 3 shows parallel zeolite canisters; the pneumatic cylinder is double-acting meaning that one zeolite canister can be pressurized while the other is evacuated, to double the flow rate. Figure 4 represents the pressure and vacuum cycles for one canister which is duplicated for the second canister.

Figure 4: Flow diagram of system - pressure and vacuum cycles.

Figure 5: System Components

The initial tests of the system produced almost no concentration of oxygen. My early research had led me to zeolite 13X as a nitrogen adsorber, but these poor results pushed me back to the literature where I found that zeolite 13X was used in high pressure industrial systems and not in smaller medical oxygen concentrators which instead used zeolite LiX, a lithium infused version. I contacted the manufacturer (Zeochem), explained my project, and received a free sample of LiX which I used in my system for testing.

Although the system was designed with two parallel channels, I tested with one, because zeolite canister volume and zeolite mass were independent variables in experiments measuring concentration, and modifying one canister was sufficient for the experiments.  

Results

I have hand pedaled the system for testing and measured the pressure, vacuum and concentration at various configurations. The human powered pressure-swing system I designed was able to pressurize and evacuate an empty canister with atmospheric air as shown below. The peak pressure achieved was 52 psi and the best vacuum was 21 inches Hg.

Figure 6: Pressure swing system performance without zeolite

The regular pressure profile depicted was the result of an extended iterative process of adjusting gearing, valves, and cam alignments to synchronize valve switching with the pump cylinder. After verifying pressures and vacuums in the empty canister, I added zeolite and recorded pressure, vacuum, and oxygen concentration levels. The results shown below were unexpected as there was a 42 psi reduction in pressure even though the free volume in the canister decreased.

Figure 7: Pressure swing system performance with Zeolite LiX

To establish a uniform initial condition, the zeolite canister was first evacuated using an electric  vacuum pump, resulting in higher initial oxygen concentration, and then the system was operated with only human power.  Pressure and vacuum alternated each cycle repeatably as shown. The oxygen concentration subsequently declined due to insufficient vacuum from the pressure-swing system. In this trial, representative of many others, the system achieved a peak concentration of 70% oxygen and reached a steady state of 42% oxygen. The highest concentration achieved by any trial was 88%, but concentration declined with subsequent cycles similar to Figure 6.

Flow rate was calculated by timing the pressure drop of the zeolite canister as gas is leaving the canister through the variable pressure check valve. Since the volume is known the flow rate can be estimated as 0.3 L/min.

Power was estimated from a peak force of about 80 N on the pedals for about ½ of the total cycle and a speed of 15 rpm. The rest of the cycle does not require much significant force. The calculated power was 15 W.

Conclusion

My hypothesis is:

An oxygen concentrator based on pressure swing adsorption technique will be designed and constructed that operates from human pedal power to supply 30% to 80% concentrated oxygen at 2L/min flow rate”.

Results supporting the hypothesis:

  • Operable using only human power.
  • The system alternately generated pressure and vacuum
  • After testing zeolite LiX, it was determined to be the better version.
  • Peak oxygen concentration of 88%
  • Sustainable concentration of 42% at 0.3 L/min flow rate (with one canister and half pedaling rate)

The peak performance of the system was 88% oxygen at a flow rate of 0.3 L/min with 15 rpm of the pedals, half the original design speed, and 15 watts power. But the 88% was under the ideal conditions of the first cycle after evacuation by an electric vacuum pump, which purged residual nitrogen better than the pneumatic cylinder, suggesting that high vacuum was important for high concentration. The steady state performance without the vacuum pump was about 42% oxygen at the same flow rate and power.

To be completely instrumented, the experiment required an oxygen concentration meter, pressure gauge, vacuum gauge, flow meter, timer, and a force gauge. My electrochemical oxygen concentration meter was calibrated with 100% oxygen and atmospheric 21% oxygen. I used a capacitance manometer to measure pressure and vacuum, and a timer. Because I didn't have the flow meter or force gauge, I estimated the flow volumetrically and estimated the force on the pedals.

My system repeatedly achieves an initial concentration greater than 50% and declines to a steady state at 42%. This is usable for oxygen therapy for premature babies and neonates for which at least 30% is beneficial.

The measured flow rate for one canister was 0.3 L/min at half speed pedaling. The final system will drive both canisters simultaneously at full speed for a flow rate of 1.2 L/min.

Under various test conditions, my system achieved a steady state oxygen concentration of 42%, which, although usable, is lower than my 80% goal. I hypothesize the primary reason is that in the LiX zeolite, pores with more lithium ions hold N2 more vigorously while pores with fewer lithium ions attract N2 weakly. The second case purges with moderate vacuum but the first case requires vacuum higher than my system can generate. Residual nitrogen stuck in those pores lowers the efficiency of the zeolite. Therefore the system generates higher concentrations when evacuated with the electric vacuum pump.

A secondary reason is that I do not yet know optimal volumes for both the zeolite and the canister, despite reducing both through a sequence of experiments. Initial calculations assumed generating 30 psi in the cylinder would produce that much pressure in the canister. This did not happen because the zeolite adsorbed nitrogen in the canister resulting in lower pressure, by 42 psi as reported above. Since concentration is related to pressure, future experiments will further decrease the size of the zeolite canister to increase both pressure and vacuum and thereby increase concentration.

About me

My name is Sanjit Thangarasu and I am a sophomore at Poolesville High School, MD in the Science, Math, Computer Science(SMCS) Program. I am greatly motivated to help others and also driven by a passion for engineering and science. In this project, I combined my passion and drive together to help those who cannot help themselves in developing countries.

One of my greatest inspirations is Elon Musk. He was able to determine the three areas where humanity needed to improve: transportation, energy, and space exploration. This inspired me to look for problems within the world that affect many people and can be solved through engineering and science.

I love working with robots and I am a lead member of the First Tech Challenge (FTC) robotics team for over 4 years. I enjoy solving new challenges and building things that solve real-world problems, and being on a team with my friends has allowed me to fulfill my passion for engineering in a way that is fun and exciting. 

Winning the Google Science Fair is not just about receiving a reward for my project, it's about the knowledge that I have gained, the people I have met and the connections that I have made that would help me drive my innovations. Winning the Google Science Fair will also help me to take my Oxygen Concentrator project to the next level to futher improve the design and make production ready equipment that would save millions of lives.

Health & Safety

For the period of this project, I have been working in a farm workshop located in Frederick, Maryland. Throughout the construction and testing portions of my project, I was under the constant supervision of my Dad, Thanga Palanisamy(240-274-9814), and my mentor Glen Dunham(301-704-5691).

When working and handling power tools and machinery I was always under the supervision of either of the two adults and always wore the proper laboratory and workspace protection. I wore items like safety glasses, firm grip work gloves, tight fit cloths, etc. I made sure to always wear my gloves especially when working with metals and cutting materials. 

I have handled zeolites with care and carefully returned the unused zeolites to its original air tight container. Used laboratory gloves when handing zeolites and disposed any spilled zeolites to the appropriate dust bins.

Bibliography, references, and acknowledgements

References

1. Johnson, T. A. Chennai floods: 48 hours at the MIOT hospital where 18 died. The Indian Express (2015). Available at: https://indianexpress.com/article/india/india-news-india/chennai-48-hrs-in-hospital-where-18-died/. 

2. Scott, J. A. G., Abdullah Brooks, W., Peiris, J. S. M., Holtzman, D. & Kim Mulhollan, E. Pneumonia research to reduce childhood mortality in the developing world. J. Clin. Invest. 118, 1291–1300 (2008).

3. Hermansen, C. L. & Mahajan, A. Newborn Respiratory Distress. AFP 92, 994–1002 (2015).

4. FREO2 Aqua — FREO2 Foundation. FREO2 Foundation Available at: http://freo2.org/aquaculture/. 

5. Sobott, B. A., Peake, D. J., Black, J. F. P. & Rassool, R. P. FREO2: An electricity free oxygen concentrator. Pneumonia 6, 115–119 (2015).

6. Explorations Grant. Available at: https://healthcare.utah.edu/publicaffairs/news/2015/07/07-31-2015_research-globalhealth.php. 

7. Belle J, E. al. Influenza preparedness in low-resource settings: a look at oxygen delivery in 12 African countries. - PubMed - NCBI. Available at: https://www.ncbi.nlm.nih.gov/pubmed/20818088. 

8. Jee, J.-G., Lee, S.-J., Moon, H.-M. & Lee, C.-H. Adsorption Dynamics of Air on Zeolite 13X and CMS Beds for Separation and Purification. Adsorption 11, 415–420 (2005).

9. Rege, S. U. & Yang, R. T. Limits for Air Separation by Adsorption with LiX Zeolite. Ind. Eng. Chem. Res. 36, 5358–5365 (1997).

10. Global Health Observatory | Visualizations | Child mortality. Available at: https://www.who.int/gho/en/

11. Onyango, D., Kikuvi, G., Amukoye, E. & Omolo, J. Risk factors of severe pneumonia among children aged 2-59 months in western Kenya: a case control study. Pan Afr. Med. J. 13, (2012).

12. Home - UNICEF DATA. UNICEF DATA Available at: https://data.unicef.org/. 

13. Technical Specification for Oxygen Concentrators. Available at: http://apps.who.int/iris/bitstream/handle/10665/199326/9789241509886_eng.pdf; 

14. La Vincente SF, E. al. The functioning of oxygen concentrators in resource-limited settings: a situation assessment in two countries. - PubMed - NCBI. Available at: https://www.ncbi.nlm.nih.gov/pubmed/21756524. (Accessed: 11th December 2018)

15. Kingham, T. P., Kamara, T. B., Cherian, M. N., Gosselin, R. A., Simkins, M., Meissner, C., et al. (2009). Quantifying surgical capacity in Sierra Leone: a guide for improving surgical care. Archives of Surgery, 144(2), 122-127.

Acknowledgements

I am thankful to the following persons who helped me to conceive and execute the project providing timely help and advise:

Mr. Glen Dunham - My mentor, guide, teacher, and a simple man with lots of knowledge.  With his extensive knowledge of physics, engineering, and chemistry, he was able to provide me a concrete foundation to start this project as well as new information to keep me innovating. He helped me with the research topic, understand the core concepts, chemical structure of the zeolites and global challenges. Whenever I was stuck, he would guide me in the right direction, and whenever I made a new discovery he questioned more which helped to research further and fully understand the subject. He happily provided all the tools and machinaries required to buid the project from his farm toolset. He taught me how to handle the power tools safety and provided help where needed.

Dr. Milton Axley - provided a set of fresh eyes to this project. Gave valuable feedback and new insights to improve and further develop my project. 

Mr. Alex Hawkins - ZeoChem LLC for providing the sample of zeolite. After explaining my project he was kind enough to send me a sample of the zeolite that was the basis of my project. Without Alex's help, I would have had to order 200 pounds of zeolite which would have costed me thousands of dollars.

My Parents - My first source of inspiration. Being STEM professionals, they showed me what STEM can do to improve the world and provided me an environment to learn and grow.  They provided financial and moral support, encouraged me to continue to work when I hit the roadblock on the project. They tirelessly drove me everywhere I need to go to complete the project successfully. Thank you Mom & Dad!