Energy Storage

Battery type - Lithium Thionyl Chloride battery (liquid)

Operational temperature. - 180 degrees C

Why Lithium Thionyl Chloride battery?

Due to its relatively high operational temperature the battery will not face any trouble during any malfunction. And as it will be inside the tesseract we will not need to worry about this part. It has a very high energy content coming in at 480 Wh/kg and meaning it can store a lot of energy.

Compared to the lithium ion battery’s 250 Wh/kg meaning it can store almost double the energy. The self discharge rate of Lithium Thionyl Chloride batteries is very slow and comes in at 1% per year. Meaning it loses about 1% of its power every year while doing nothing. Lithium ion has a self discharge rate of 5%. This means if we take a battery weighing 25 kgs we can estimate the amount of power it can store. This means we can store 12000 Wh worth of electricity.

The Tesseract Isolation System

Due to the harsh environmental conditions on Venus most batteries don't last for more than a few hours let alone 90 days. There are 3 main factors that inhibit batteries from performing optimally on venus. These 3 factors are the surface temperature, Atmospheric pressure and high speed of winds where even a small rock can completely eradicate the rovers battery pack. To combat these 3 issues we have carefully handcrafted a case to encapsulate the battery. This design will not only thermally insulate the battery and shield it from the high atmospheric pressure but it will also protect the battery from wear and tear.

The battery case is in the shape of a Tesseract for structural rigidity which can help protect the battery from debris coming in contact with it at high speeds. The main chassis of the tesseract is from Platinum. The reason we specifically chose to use platinum is due to its rigidity, high heat insulation and its non reactiveness with compounds found on venus such as carbon dioxide and sulfuric acid. Moreover the platinum layer of the tesseract is only 2.8mm thick so that Infrared rays with 1022 nm (frequency) can pass through which can be used to charge the battery (You can learn more about this process in the energy transmitting sector of our project).

Inside the platinum layer of the tesseract we have cross sections between the main cube on the inside and the pieces that connect it with the outside cube made out of platinum. These cross sessions are filled with pressurized argon. Pressurized argon ensures that the cube has a higher pressure than the pressure of the outside atmosphere mimicking the inner workings of spacecraft in space thus leading the tesseract to stay intact and not collapse on itself. We specifically chose Argon, because argon is a good heat insulator and because argon is a noble gas ensuring that it does not react with any substances present on venus causing the entire system to fail.

When we go a stage deeper we then enter the main cube level of the tesseract. This level is covered with silicone to add another level of heat insulation and to hold the next 2 stages in place. The next stage is a hollow block of aerogel, aerogel is 98% air because of which it has a high specific surface area and a low thermal conductivity. Due to this, aerogel is the most suitable layer of thermal insulation before the battery. Then at last comes the main battery which powers the rover

Battery - Now that we have a protective shield around the battery which is completely heat insulating. This allows us to use whatever battery we want. The main objective now is to find a battery which is energy dense, a battery with at least 500 Wh/kg this will help us to have a smaller battery with a lot of capacity. With which we also need something that has a fairly high operational temperature. This narrows down the battery options.

We finally chose a Lithium Thionyl Chloride battery. This battery has a fairly high operational temperature and is one of the most energy dense battery types out there. If done right it is very stable as well. As for charging, multiple research teams are coming close to making it stable during charging. The battery is made out of volatile materials, hence the need for care. It reacts with our skin. But once on Venus we don’t require that level of care and incase of emergency the battery still has a high operational temperature.