Team Graviton

https://team-graviton.netlify.app/

https://youtu.be/_M3mTrWMx6E

Venus is called earth’s twin because of their similarity in size and structure. But with its sulfuric acid clouds, temperature of over 450°C, and surface pressure of 92 bar, is one of the most hostile planetary environments in the solar system[1]. Due to this, Venus is facing problems regarding the energy storage systems for a long-time surface mission. Previous missions to the surface of Venus have failed to operate for more than two hours. As the currently available batteries cannot operate in the extreme environment, our main 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.

Our Solution

Considering the surface conditions and different perspectives, we are bringing you a combined solution, Venus Hybrid Energy Storage System (VHESS) which will store energy by using IN SITU with supercritical CO2 power cycles. Our energy storage system, VHESS, consists of high-speed flywheel energy storage (FES) and a Sodium Nickel Chloride battery.

Supercritical CO2 Gas Turbine: 

For our power source, we have designed a gas power turbine that will take the supercritical (450 degree Celsius) CO2 by the inlet. This works on the Brayton cycle which highly depends on the inlet temperature and pressure.

The CO2 is sucked into the inlet by a supercharger and while going through the converging-diverging nozzle the gas pressure and temperature increase drastically. That high pressured supercritical CO2 is flown over the turbine and thus turbine rotates[2].

Unique approach to storing mechanical to mechanical energy:

Instead of connecting the turbine shaft directly with the generator, we have taken a different approach. We have designed the shaft which would go through the flywheel outer chamber. The chamber is kept sealed by using two O rings on the top and the bottom of the flywheel chamber to keep it vacuumed.

The shaft is designed through the flywheel vacuum chamber to transmit the rotational energy from the turbine shaft to the flywheel rotor by a conveyer belt. Instead of converting the rotational energy of the turbine to electrical energy by the generator directly, we designed the system so that it can avoid energy conversion by transmitting turbine rotational energy to the flywheel. Though it creates a high chance of failure in maintaining the vacuum of the flywheel chamber. But by doing this, the efficiency of our system increases.

Flywheel working principle:

Here we are using a hybrid composite of M46J/epoxy–T1000G/epoxy rim with a titanium hub for the flywheel that exhibits a higher energy density when compared to known existing flywheel hybrid composite materials such as boron/epoxy-graphite/epoxy.

The combination of M46J/epoxy andT1000G/epoxy gives the maximum energy density. It is about 18 times more than the boron/epoxy–graphite/epoxy. This is due to the current high modulus and high-strength carbon fibers[3].

The central part of the flywheel energy system is the flywheel rotor. When set in rotation the rotor acquires angular momentum and stores mechanical energy. As mentioned above, the flywheel rotor usually rotates at high angular velocities. Magnetic bearings and vacuum enclosures are used to minimize frictional losses that occur in the bearings and with the air surrounding rotating components. The typical components of advanced FES cells are shown in the Figure required the energy stored in the rotor can be released by operating the electrical machine in generator mode producing electricity. Conditioning of the electrical power to or from the generator unit is achieved by power electronic systems. The figure illustrates the power flow affecting flywheel rotor rotation for the charge and discharge cycle[4].

then the turbine shaft is connected to the generator where it produces the electrical energy. We store this electrical energy in the high-temperature sustaining Sodium Nickel Chloride battery[4]. 

Sodium Nickel Chloride as electrical power storage:

Sodium Nickel Chloride is used as the high-temperature rechargeable batteries which have an energy density of 143 W-h/kg and lower risk factor compared with alternative solutions. It is an improvement over the sodium-sulfur battery, with the sulfur cathode replaced with transition metal chlorides in contact with sodium tetra chloroaluminate melt for improved safety. The main benefit is it can operate in the 250°C–500°C temperature range, and thus solve the problem previous missions were facing with the Venus surface condition[5].

It has a round trip efficiency of 90%. Further, the long-term cycling of the 6 h duty cycle shows quite stable trends for SOC and temperature. The capacity shows a degradation rate of 0.0046%/cycle over 150 cycles (150 days). The module also can be put into a self-sustaining mode for over 70 h before most of the energy stored in the module is consumed via self-heating to maintain the operating temperature. Therefore the battery module shows quite a reliable performance than other existing batteries that can be in this hostile environment[6].

So in conclusion, we have updated the previous energy storage system with a combined approach using a Flywheel Energy Storage system having an M46J/epoxy–T1000G/epoxy rim with a titanium hub incorporating a supercritical CO2 gas turbine and Sodium Nickel Chloride battery module.

Requirements

A typical rover with a 4.5-meter diameter atmospheric entry aeroshell normally weighs about 850 kg and thus requires around 216 watts to operate. This power is produced by a 250-watt power capacity Super-critical CO2 gas turbine with a mass flow rate of 0.45-0.5 kg/s. The energy generated is stored in a flywheel having E/mass to be around 32 kJ/kg and NaNiCl2 battery with90-110 Wh/kg and having degradation of 0.0046% per cycle.

So, the mass of our total system would be 150kg totally with a volume of 0.5 cubic meters.

Why This Particular solution:

• Having an extremely long life cycle and round trip efficiency of more than 90% make the system more reliable to store and produce energy for spaceships and rovers.
• We are using in situ resources to generate energy, so we can store energy simultaneously in both mechanical and electrical system

Tools Used:

• Solidworks
• Adobe Premier Pro

Project Links:

GitHub Project

CAD Model

• Venus Resources – NASA Solar System Exploration – To get the atmospheric and surface value of different parameters.
• ·Energy Storage Technologies for Future Planetary Science Missions | NASA Solar System Exploration – To get data on present battery technology for planetary exploration.
• ·Automaton Rover for Extreme Environments (AREE) | NASA – To check the feasibility of a combined storage system.
• ·g2 flywheel module design - NASA Technical Reports Server (NTRS) – To develop the flywheel storage system for outer space.
• ·Venus Fact Sheet (nasa.gov) – To know about the material composition of Venus's surface.
• ·ESA - Past missions to Venus – To gather knowledge about the previous mission on the surface of Venus.
• Venus (nasa.gov) - Gaining brief information about the FUTURE mission to Venus.

We are a bunch of enthusiast who regard every project as an opportunity to learn, to invent and reinvent. NASA Space App Challenge is also an opportunity for us. This is the first time we have participated in this competition but this won’t be last time. However during solving the challenge we have gone through several papers and research that help us to learn and also to find a reliable solution. This inspired us to think renew and nevertheless explore the Venus. That idea has been refurbished over the past few days and this is what we have been pleased with.

Solving a real engineering problem is a really a fun and also it’s a dream for all engineering students to do such competition that gives them the opportunity. Thus the same thing goes for us too. We finally would like to thanks out dear senior Sumit Chandra vai from team Mohakash and the mentors from BASIS for helping us during the project.   

[1]Venus Air Pressure (nasa.gov)

[2] Study on the supercritical CO2 power cycles for landfill gas firing gas turbine bottoming cycle - ScienceDirect

[3] Composite flywheel material design for high-speed energy storage | Journal of Applied Research and Technology. JART (elsevier.es)

[4] Rotor Design for High-Speed Flywheel Energy Storage Systems | IntechOpen

[5]

[6] https://www.mdpi.com/1996-1944/14/9/2280

#Venus, #interplanetarimission, #energystoragesystem