https://github.com/paupumara/Positive-Energy

https://github.com/paupumara/Positive-Energy/blob/main/PPT%20DEMO%20-%20NASA%20-%20Positive%20Energy%202.pdf

1. Identifying the problem

The surface of Venus is completely inhospitable for life, barren, dry, crushed under an atmosphere of 90 bar and roasted by temperatures up to 453℃. Due to these conditions, prior explorations were able to last on the surface for less than two hours before the system failed.  

2. Record

In 1961, the Soviet space program began trying to explore Venus.In the decades that followed, it shot dozens of spacecraft toward the world sometimes known as Earth’s twin.In 1962, American spacecraft made it to Venus as well. Missions to Venus kept on happening and collecting information such as changes in temperature, images and composition of the surface, composition of atmosphere, geological processes, among many other groundbreaking data.Nevertheless, the last mission sent to Venus happened almost forty years ago and now we are looking to continue on the adventure

¿What did we develop?

We developed a hydrogen based power system that supports a rover in Venus for 60 Earth days. 

The objective of the challenge is to design an energy storage system that supports a surface lander or rover on the surface of Venus for at least 60 days. Therefore we came up with a system that is able to withstand the surface conditions such as extreme temperatures, high pressure atmosphere with caustic chemicals and unpredictable geological events.Besides, it would be sent with enough reactant to start and never stop until day 60.

¿How will energy be provided?

The energy will be provided by using hydrogen as fuel in proton exchange membrane fuel cells. We chose hydrogen because we believe it’s the future for energy sustainable obtaining, and nowadays it is the topic of investigators of the field. It’s the lightest element (molecular weight ¼ 2.016) with highest known energy content (calorific or heating value) of any fuel, has an awesome energy storage capacity and it has been shown from calculations that the energy contained in 1 kg of hydrogen is about 120 MJ (¼33.33 kWh), which exceeds double of most conventional fuels1. 

¿How will we transport hydrogen?

. Due to hydrogen’s low volumetric energy density in comparison to widely used fuels, storage at high pressures is required which in turn necessitates additional energy use for its compression.  Ammonia carries more hydrogen atoms per one mole than one mole of hydrogen (H2), and has higher energy density per volume than that of hydrogen.In terms of safety, ammonia has higher ignition temperature than hydrogen. In addition, cost per mass and per unit energy of ammonia is less than that of hydrogen due to widely implemented ammonia production infrastructures.2 There are several technical and economic reasons in support of NH3 decomposition for distributed H2 generation. First and foremost, NH3 decomposition has a single feed stream and is therefore accomplished in a single step. For this reason, there is a significant cost advantage as compared to the multi-step process inherent in steam reforming of hydrocarbons.3  For these reasons we chose ammonia as our hydrogen transporter.

¿How do we make it work?

Ammonia is easily transformed into Hydrogen and Nitrogen with the help of a catalyzer and high temperatures. There are many types of micro-reactors, to know which to choose, we picked as an example a rover design for a future Venus exploration. This design has a mass of 330 kg (plus a 7% margin) and a  daily energetic consumption of 500 W4. It includes basic on board instruments and since for our system we need an additional of thermal and pressure subsystems, we approximate a daily energetic consumption of 740 W and a mass of 500 kg (including a NaS battery to initiate our system).

After investigating, we observed that micro-reactors worked with a specific flow of ammonia each that produces a hydrogen flow way higher than necessary for our model (which may turn into a great advantage for other applications).

Since our goal is to make the reactor work non-stop, we chose the reactor with the lowest flow and a great efficiency: a Microfabricated Suspended-Tube Chemical Reactor .It consists of 4 thin-walled (2 mm) silicon nitride (SiN) tubes. The 4 tubes are essentially two U-shaped fluid channels where NH3 fuel enters the middle channels and exits on the outer channels in a heat recirculation strategy. The reaction zone is partially encased in silicon for thermal isolation and is 2 mm long. Prior to the Si reaction zone (hot), the SiN tubes are bundled in Si slabs that allow transverse heat transfer between processes .In this non-reaction length, NH3 fuel is preheated by the hot product stream. In their experimental work, 6 sccm of pure NH3 was fed into an electrically heated suspended-tube microreactor wash coated with an alumina (Al2O3)-supported iridium (Ir) catalyst. A conversion of 97% to produce up to 9 sccm of hydrogen fuel   was achieved at atmospheric pressure using an electric power input of 1.8 W (900 C) to use in the PEM cell fuel leaving a final energy production of 1.6 W .5

From this information we estimated the design of the reactor and the ammonia flow needed.

• Feed flow: 2 Nml/min 
• Temperature: 900°C 
• P= 1 bar 
• NH3 conversion : 97.0% 
• Energy  produced per day=  768 W por día
• Estimated volume: 0.000003 m3  or 30 cm3 ( 30 cm large, thickness and height)
• Estimated mass: 0.2 kg or 200 g  (  MicroTube of SiN, Si zone reaction and support)

¿How much ammonia do we need and how do we store it?

Using the total amount of the energy we need for 60 days we calculated how much ammonia we need (with redundancy) and decided to starge it in stainless steel: 

• NH3 required= 200 kg
• Stainless  recipient volumen: 0.00036 m3 or 360 cm3
• T= 49 °C
• Stainless steel 3.4 wall = 2 cm of thickness
• Estimated mass  wall =27 kg 
• Total mass storage = 227 kg 

Stainless steel recipient used in reference6

We then selected the PEM design of 45 cells that have an area, Ac, of 0.023 m2 and estimated the mass and volume with research data7 8.

→ Estimated volume= 0.16 m3  or 160000 cm3 ( 1 m of longitude, 0.4 m of thickness and height)

→ Estimated mass= 6.9 kg or 6900 g 

For this PEM we calculated the oxygen needed the same references: 

→ Vol O2  necessary = 0.5 m3

→ Mass O2 = 0.666 kg or 666 g 

We thought of a similar recipient as the ammonia storage but because of the quantity needed we did not consider it  relevant in the total mass.

¿How do we protect our system?

We designed a cube made of Aluminum Honeycomb Core Carbon Fiber Reinforced Polymer9 Composite Based Sandwich Structure, material used in spacecraft aeroshell:

• Edge : 56.5 cm 
• Volume: 0.18 m3 or 180000 cm3
• Wall thickness : 46 mm = 4.6 cm 
• Thickness AlPoras Foam = 3.68 cm 
• Thickness Carbon Fiber = 0.46cm
• Thickness Aramid Fiber= 0.46cm
• Vol AlPoras Foam face =11747.48 cc ( weight= 2.9 Kg)
• Vol Carbón fIber face =1468.44 cc ( weight 2.25 Kg)
• Vol Aramid Fiber face  =1468.44  cc( weight 2.11 Kg)
• Face weight= 7.26 kg
• Total faces= 8 units 
• Total weight=58.08 kg 

To regulate the pressure we cover the system with a Helium pressurant

Vol He estimated = 0.18 m3  

Mass He required = 0.03 Kg or 30 g 

Diagram of design:

Conclusion

We believe that our final mass works great with the rover model because the rate over the rover mass and the mass of our energy system mass is very much alike with other explorations.In addition, we have obtained a design with a very small volume which could be used in other projects.

We used open data from NASA about rover designs for future and old Venus explorations and stainless steel storages used in spacecraft. Among many others described in references and project description.

We found SpaceApp by chance one day while we were taking a walk through the city and since we heard about it, we got excited to be able to develop the project.

We love to be challenged, since it's a great way to learn about different fields that we may not be so familiar with. And also the 48 hour time frame adds an adrenaline rush that is very fun to expierience.

Browsing through the different challenges we knew right away that "Exploring Venus together" was the one for us ,since it presented such -at first read- impossible task and, as we said before, we love to be challenged and overcome our limits .

Our field of knowledge was mostly chemistry and math, but on this hackathon we got to draw on the knowledge of different -way experienced- mentors, papers,videos, all type of resources! and learned so much about the importance of exploring other planets and space missions.

It is true that we had our setbacks, we started with a way different idea and then, after lots of work, we realised that it didn't work. We got very dissapointed but we pepped each other out and remembered that the important thing of this is to enjoy ,discover new things about science and each other. So we rolled up our sleeves and got to work again.

The mentors were a huge help encouraging us to keep going and were ready to ask any questions in the moment needed, without them we could not have made it; so very special thanks and appreciation to them.

• Landis, G. A. (2006). Robotic exploration of the surface and atmosphere of Venus. Acta Astronautica, 59(7), 570-579.
• Arana, L. R., Schaevitz, S. B., Franz, A. J., Jensen, K. F., & Schmidt, M. A. (2002, January). A microfabricated suspended-tube chemical reactor for fuel processing. In Technical Digest. MEMS 2002 IEEE International Conference. Fifteenth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No. 02CH37266) (pp. 232-235). IEEE.
• Sharma, P., & Pandey, O. P. (2022). Proton exchange membrane fuel cells: fundamentals, advanced technologies, and practical applications. In PEM Fuel Cells (pp. 1-24). Elsevier.
• Snyder, M. P. (2011). Design of a Lunar Rover Utilizing Hydrogen-Oxygen Fuel Cell Technologies (Doctoral dissertation, The Ohio State University).
• Flight Prototype Ammonia Storage And Feed System Final Report NASA-CR-91278, CONTRACT_GRANT: NAS5-10128, AVSSD-0100-67-RR.
• Marov, Mikhail Ya. (2004). «Mikhail Lomonosov and the discovery of the atmosphere of Venus during the 1761 transit». Proceedings of the International Astronomical Union (Cambridge University Press) 2004 (IAUC196): 209-219.
• Chiuta, S., Everson, R. C., Neomagus, H. W., Van der Gryp, P., & Bessarabov, D. G. (2013). Reactor technology options for distributed hydrogen generation via ammonia decomposition: A review. International journal of hydrogen energy, 38(35), 14968-14991.
• Abe, J. O., Popoola, A. P. I., Ajenifuja, E., & Popoola, O. M. (2019). Hydrogen energy, economy and storage: review and recommendation. International journal of hydrogen energy, 44(29), 15072-15086.
• Yao, J., Zhu, P., Guo, L., Duan, L., Zhang, Z., Kurko, S., & Wu, Z. (2020). A continuous hydrogen absorption/desorption model for metal hydride reactor coupled with PCM as heat management and its application in the fuel cell power system. International Journal of Hydrogen Energy, 45(52), 28087-28099.
• Dawood, F., Anda, M., & Shafiullah, G. M. (2020). Hydrogen production for energy: An overview. International Journal of Hydrogen Energy, 45(7), 3847-3869.
• Garvin, J. B., Getty, S. A., Arney, G. N., Johnson, N. M., Kohler, E., Schwer, K. O., ... & Zolotov, M. (2022). Revealing the Mysteries of Venus: The DAVINCI Mission. The Planetary Science Journal, 3(5), 117.
• Mateti, S., Zhang, C., Du, A., Periasamy, S., & Chen, Y. I. (2022). Superb storage and energy saving separation of hydrocarbon gases in boron nitride nanosheets via a mechanochemical process. Materials Today, 57, 26-34.
• Papila, M., & Atilgan, A. R. (2022). All-composite honeycomb core sandwich structures: Master curves for stiffness-based design. Forces in Mechanics, 6, 100066.
• Sun, Z., Jeyaraman, J., Shi, S., Sun, S., Hu, X., & Chen, H. (2014). Processing and property of carbon-fiber aluminum-foam sandwich with aramid-fiber composite adhesive joints. Journal of adhesion Science and Technology, 28(18), 1835-1845.

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