High-Level Project Summary
Venus is called the twin sister of earth but turns out it’s the evil twin. As where Earth is heaven, Venus is hell. The challenge is to design a system that can reliably work in Venus’ hellish environment. To achieve this, the best solution is to use it's high air pressure to generate electricity. To do so we need a chamber with very low or zero pressure. To generate electricity from pressure differences, we have designed a system. Our system comprises a vacuum chamber, turbine, electricity generator, Battery Management System, battery and a valve. The air flow is generated which is controlled by the valve which is then controlled by the BMS.
Link to Final Project
Link to Project "Demo"
Detailed Project Description
The challenge is to design a system which can support a Venus lander for 60 days by providing electricity. The capacity of an energy storing system can be increased by increasing the size of the storing element. The bigger problem here is to sustain the system in Venus’ harsh atmosphere. There are three major factors to consider on Venus. Acid, Pressure and Temperature. All of these factors make our system less durable. To overcome these problems we must use materials that are unaffected by high temperatures, Acid and pressure. Batteries use chemicals to store energy but they are most likely to be affected by temperature and pressure. To avoid this we must minimize the use of chemicals and liquids in our system.
To overcome these factors, unlike any other energy storing system our system neither uses chemicals nor moving masses as main energy storage. Our system uses a vacuum chamber. The main energy storing unit doesn't need high pressure or temperature protection as it’s all made up of strong metals and has a rigid structure. Its working mechanism is explained below.
Initially the system powers the Venus’ lander by the energy stored in the battery. The Battery Management System checks the battery voltages and calculates the remaining energy. Once the battery gets discharged enough, BMS starts the electricity generation unit to recharge the battery.
The Electricity Generation Unit works by storing energy in the form of vacuum. We have a vacuum chamber with zero air in it . Now we take advantage of Venus’ high pressure (92 bar) environment to create airflow and generate mechanical energy by a turbine, which is then used to generate electricity by an electricity generator. The generated electricity is used to recharge the battery. Which is then used to power the rover.
As the Electricity Generation Unit generates electricity, pressure in the vacuum chamber increases, while decreasing the pressure difference between Venus atmosphere and the chamber. Once the chamber’s pressure becomes equal to the atmospheric pressure, the Energy Generation Unit becomes futile for energy purposes. After this, the chamber can be used as a laboratory to test Venusian air in stable conditions.
The mechanical energy or the turbine can also be utilized to power the rover’s motion.
Storing energy in the form of vacuum may seem a futile idea on earth but vacuum energy storage devices can work at very high efficiency in a high pressure environment like Venus. At 475°C battery efficiency decreases and chances of it failing increases, so we don’t want to store our energy in a chemical form. Secondly, storing the energy in the form of vacuum comes with multiple advantages, as we can directly convert it into mechanical energy which results in lower energy losses and the chamber is less affected by the temperature and radiation as compared to the battery.
By this system we hope to achieve higher efficiency and durability. By using this system we don’t need to worry about the radiation affecting the battery as we won’t need a bigger battery and small systems can be protected by using high density material to block radiation (e.g. lead) to protect the battery and circuitry.
The power generation Unit doesn't need much protective shielding as we can build the chamber, turbine and valve using stainless steel and titanium alloys because of its durability at 460° Celsius and in an acidic environment.
The battery we are using for this project is Li–FeS cell battery. Which NASA developed for long duration Venus missions. The reason to choose this battery is that it can tolerate the high Venus surface temperature of 465 °C and pressure of 92 bar. These batteries are based on lithium alloy anodes, transition metal sulfide cathodes, and molten salt electrolytes. Among the various cathode materials examined for thermal stability and for electrochemical activity, FeS has emerged as the most suitable cathode. With optimized cell components, cell design, and operational parameters, laboratory test cells were fabricated, which demonstrated continuous operation of ~26 days at 475 °C. These batteries will enable new long-duration surface missions for detailed surface exploration of Venus.[7]
The turbine converts air flow into mechanical energy. The energy generated by a turbine is 95 times greater than the energy consumed to create vacuum in the chamber. As the camber is vacuumed on earth the pressure difference will be 1.013bar on earth which will be increased by 95times on Venus as the Venus’ surface pressure is 95 times higher than the Earth. Pressure difference will be increased thus the energy.
The Generator is responsible for conversion or mechanical energy into electrical energy. It can be placed in or out of the protective enclosure based on its durability. To make it durable enough to withstand Venus weather without any protective enclosure we can build its outer body with stainless steel and titanium alloy. Internal metal can be relatively soft. AS they are not exposed to the atmosphere are the outer part. The energy generated by the generator is directly proportional to the mechanical energy generated by the turbine.
The valve is responsible for controlling the air flow, and the valve itself is controlled by BMS. To make it durable for Venus’ whether it must be made of strong alloy, like Stainless steel and titanium alloy. Which does not react to acids present on Venus and is strong enough to hold 92 bar of pressure.
The BMS (battery management system) will be responsible for controlling the air inlet valve. It will measure the battery voltage and will calculate how much the valve should be open to efficiently charge the battery. As the power generated by the turbine is directly proportional to the air flow, we can control how much electricity should be generated to recharge the battery efficiency as the battery has a maximum charge current limit. Due to Venus' harsh condition it’s impossible for normal electronics to work on Venus' surface for long periods of time. So we must use more durable electronics which can bear 92 bars of pressure for at least 60 days. So, the BMS should be based on the technology NASA developed for Venus' harsh weather, which is based on Silicon Carbide [9]. This technology is tested in GEER—the Glenn Extreme Environments Rig to work on Venus, in which they tested it for 521 hours (then GEER was shuted-down for some reason) and it showed no error or damage.
The formula to calculate the maximum energy which can be stored it the chamber is
Energy = K x volume K=7089.947
K is the constant of energy per volume of the Venus surface
The formula is derived using the equation available on Berkeley University of California’s website. ( https://ehs.berkeley.edu/sites/default/files/publications/stored-energy-calculator.xlsx )
The original formula calculates the energy stored in a pressurized chamber. We can also use this formula to calculate the energy our vacuum chamber can provide as the energy consumed to pressurize a chamber is equal to the energy consumed to vacuumize the chamber (theoretically), as in both cases we are creating pressure difference.
To power the rover (which consumes 100 watt per hour energy) for 60 days we must have 144000watt of energy stored in both battery and chamber combined. To store this much energy in vacuum chamber we need at least 20.31m 3 chamber. To have that much volume we need a cylinder of 1.5m radius and 2.87 meter high or cube with each side equal to 2.715m.
Space Agency Data
We used the data related to the Venus atmosphere, the data of a new battery developed by NASA and the data related to Silicon Carbide transistor technology available on NASA website. The data we used here is the surface temperature and Atmospheric composition and battery requirement to sustain the Venus atmosphere.
Hackathon Journey
If we summarize our journey of this Hackathon in one word, that word would be “AMAZING!”. Working and collaborating with international teammates and research was the best part.
By participating in this hackathon we learnt a lot. Remote collaboration, research, thinking style, problem solving and what not. We first selected a challenge of our interest and did a lot of research on the internet and some mathematics too. We love science and all of us wanted to contribute to the community and that’s what made us participate in this hackathon.
After we chose this challenge we thought about all aspects.
References
[1] https://ehs.berkeley.edu/sites/default/files/publications/stored-energy-calculator.xlsx
[3]https://www.popularmechanics.com/space/solar-system/a25099/nasa-develops-a-computer-chip-venus/
[4 ]https://ieeexplore.ieee.org/document/943813
[5] https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html
[6] https://www.sciencedirect.com/science/article/abs/pii/S0378775319314855?via%3Dihub
[7] https://www.nasa.gov/offices/nesc/articles/li-ion-batteries
[8]https://arc.aiaa.org/doi/pdf/10.2514/1.41886
[9]https://arstechnica.com/science/2017/02/venus-computer-chip/
Tags
#hardware, #vacuumenergystorage, #venus, #2monthpower, #surviveonvenus #teamwork,#3dmodels