High-Level Project Summary
We designed an energy storage system that supports a surface lander or rover on the surface of Venus for <60 days. A Regenerative fuel cell system was designed to provide electric power for a probe operating on the surface of Venus. The fuel cell chosen was a CO/O2 fuel cell, using a doped zirconia solid electrolyte. Carbon dioxide is the main component of the Venus atmosphere. This allows the possibility of using ambient CO2 as the source material. The fuel cell can be made rechargeable by the addition of an electrolyzer. This electrolyzer will consume electricity produced from ASRG (Advanced Stirling Radioisotope Generator). The ASRG 130-Watt will go for electronics and electrolyzer
Link to Final Project
Link to Project "Demo"
Detailed Project Description
Our solution stores chemical energy in the form of CO and O2 in a solid oxide regenerative fuel cell. Solid oxide regenerative fuel cells are composed of a fuel cell stack and an electrolyzer stack. The fuel cell stack is where CO reaction with O2 occurs forming CO2. A massive amount of energy is released due to this reaction. In the electrolyzer stack, CO2 is reduced by reproducing CO and O2. This process requires electric current to operate. This current is generated using Advanced Stirling Radioisotope Generator (ASRG). The regenerated fuel resulting from CO2 electrolysis is then transferred to storage tanks for later usage. The ASRG is a device that converts the thermal energy released from the decay of the radioisotope fuel plutonium-238 to the high-speed motion of a small piston and its companion displacer through a copper wire coil generating electricity. The motion of the pistol is caused by the expansion and compression of helium gas as a result of the temperature difference between the two sides of the converter. What distinguishes our solution and makes it beneficial is its ability to make benefit from Venus's ambient conditions like the high temperature which is required for high solid Oxide regenerative fuel cell operation and the abundance of CO2 in Venus's atmosphere which enables the production of the used fuel.
More details:-
Generating system: -
The electric current will be generated by an Advanced Stirling Radioisotope Generator (ASRG). This generator utilizes the heat produced from the decay of the hot radioisotope fuel into the high-speed kinetic motion of a small piston and its companion displacer with an efficiency of 30%. In turn, this magnetized piston oscillates back and forth through a coil of wire, thereby generating an electric current. The fuel that we are using is PU-235 and every 1.3 kg of PU-235 generates 130 watts. The power generated is about 130 watts. The ASRG can last for 17 years.
Storage system: -
The storage system is a solid oxide Regenerative fuel cell which is composed of an electrolyzer and fuel cell.
The fuel cell: According to the “Venus surface power and cooling systems” pdf, fuel cells can use carbon monoxide (CO) and oxygen (O2) as fuel. The fuel cell achieved the requirements which are temperature and lifetime and power produced. It can produce from 250 to 400 mW/cm2 current and the voltage will be 1 V per fuel cell. The solid oxide fuel cell has an electrical efficiency of 60% and has a longer expected lifetime than the Proton Exchange Membrane (PEM) fuel cell. The average lifetime for SOFC is 56000 hours.
The electrolyzer: In order for a fuel cell to be regenerative, it must use an electrolyzer to dissociate the resulting compound from its previous reactants. These three types of electrolysis are alkaline electrolysis, solid Oxide electrolysis and PEM electrolysis. Solid Oxide electrolyzers are the best for a Venus surface mission fuel cell. This is a result of its capability of operating at high pressures and temperatures from 500c to 850c. And its high efficiency in the electrolysis of CO2 to produce CO and O2. Solid Oxide electrolyzers consist of a cathode, anode, and a membrane between the two electrodes. This membrane is usually made of O2- conductors mostly from yttria-stabilized zirconia. In the SOE process, CO2 is reduced at the cathode resulting in CO molecules and O2- ions transferring through the O2- conducting membrane to the anode. At the anode, it loses two electrons resulting in oxygen molecules. The electrolyzer will be powered by the electric current generated by the Stirling engine. The energy is stored as fuel which is CO and O2 to be used by the fuel cell.
Space Agency Data
We took data from the NASA pdf “Advanced Stirling Radioisotope Generator (ASRG)”. These data include the way of working and some specific information about the ASRG (including Power Output, Efficiency, and Total Mass).
Also “New Power Technologies for Venus Low-altitude and Surface Missions” pdf we took ideas from prior solutions. In addition, we took information about the temperature and the pressure relative to the altitude.
Some details about surface rovers and the mechanism of their work were taken from the Mars surface exploration website, this helped us to expect the power that the rover will need to obtain from the system.
Hackathon Journey
To work with a team and find a solution in just two days is an amazing experience. When we were told about this competition for the first time, we had doubts about its dynamics and how it is challenged. Fortunately, all the team liked to try this experience and take the adventure. It was an amazing experience which was full of benefits.
During the competition, we developed a couple of essential skills and knowledge for our future. Teamwork and leadership are the skills of the future and this competition taught us a lot about teamwork practically not just some words. We collaborated in reading research papers to understand deeply. In addition, we shared opinions and modifications. We as a 6-members team could gain a good background in astronomy and planets, especially Venus. We learnt many technologies that are used to store energy.
Why we chose the "exploring Venus together” challenge specifically? We reviewed the list of challenges offered on the Space app website and we felt inclined toward “Exploring Venus together”. We felt inclined toward that challenge due to our passion for working on energy projects. So, finding an energy storage system that survives in the harsh environment of Venus is an exciting challenge for us.
During the competition, we modified our initial idea many times before the Hackathon. First, we decided to use batteries to store energy but the problem was there aren't Batteries that survive in the harsh Venus environment. In addition, batteries are used for short and low-power missions. So, it can't be a solution. We researched and found about rechargeable batteries and fuel cells. CO/O2 fuel cell was the suitable one for our challenge, but it is Efficiency is too low. Thus, we decided to modify this technology by using an electrolyzer to be a regenerative fuel cell. Another modification was to add a radioisotope power system to supply the electrolyzer with its needed power. After these modifications, we could find an initial successful idea for our challenge. This solution exploits the conditions on Venus to regenerate and recharge.
We faced many difficulties since there were topics beyond our current understanding, but we were able to work on them by researching and trying to collect data from different references.
References
1. D.M. Hunten, L. Colin, T.M. Donahue, V.I. Moroz, Venus, University of Arizona Press, Tucson, AZ, 1983.
2. S. Vougher, D. Hunten, R. Phillips (Eds.), Venus II, University of Arizona Press, Tucson, AZ, 1997.
3. D.H. Grinspoon, Venus Revealed, Perseus Publishing, Cambridge, MA, 1997.
4. J.B. Pollack, Atmospheres of the terrestrial planets, in: J.K. Beatty, A. Chaikin (Eds.), The New Solar System, third ed., Cambridge University Press, Cambridge, 1990, pp. 91–103.
5. K. R. Sridhar and R. Förstner, “Regenerative CO/O2 Solid Oxide Fuel Cells for Mars Exploration,” AIAA Paper 98-0650, Reston, VA (1998).
6. I. Nann, H. Weydahl, “Technical Note 4 – System
7. Design and System Study”, ESA project: Fuel Cells for Telecom Systems – System Study, ESA contract (AO/1-5525/07/NL/LvH), September 2008 Prime contractor: Thales Alenia Space (Cannes) Sub-contractor: CMR Prototech
8. Farnes, Jarle, et al. “Optimized High Temperature PEM Fuel Cell & High Pressure PEM Electrolyser for Regenerative Fuel Cell Systems in GEO Telecommunication Satellites.” E3S Web of Conferences, vol. 16, 2017, p. 10004, 10.1051/e3sconf/20171610004. Accessed 6 Jan. 2022.
9. Jet Propulsion Laboratory, California Institute of Technology. “Regenerative Solid Oxide Fuel Cells for Venus Interior Probe Energy Storage.” ECS Meeting Abstracts, 2019, 10.1149/ma2019-02/57/2459. Accessed 23 Apr. 2020.
10. Landis, Geoffrey A. “Robotic Exploration of the Surface and Atmosphere of Venus.” Acta Astronautica, vol. 59, no. 7, Oct. 2006, pp. 570–579, ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110016033.pdf, 10.1016/j.actaastro.2006.04.011. Accessed 22 Jan. 2020.
11. Landis, Geoffrey A., and Kenneth C. Mellott. “Venus Surface Power and Cooling Systems.”Acta Astronautica, vol. 61, no. 11-12, Dec. 2007, pp.995–1001,zenodo.org/record/895250/files/article.pdf, 10.1016/j.actaastro.2006.12.031.
12. NASA. Advanced Stirling Radioisotope Generator (ASRG). 2013, rps.nasa.gov/resources/65/archival-content-advanced-stirling-radioisotope-generator-asr/.---. Space Radioisotope Power Systems Advanced Stirling Radioisotope Generato. Aug. 2008.
13. R. Mercer, Carolyn, et al. Energy Storage Technology Development for Space Exploration. 2011, www.researchgate.net/publication/267688656_Energy_Storage_Technology_Development_for_Space_Exploration.
14. Sjölin, Kristofer, and Emil Holmgren. A Proton Exchange Membrane & Solid Oxide Fuel Cell Comparison. 2019,odr.chalmers.se/bitstream/20.500.12380/301883/1/A%20Proton%20Exchange%20Membrane%0%20Solid%20Oxide%20Fuel%20Cell%20comparison.pdf.