I cant say for certain, but I can definitely speculate. I do know cotton requires a fair amount of water to grow, but I don't think it would use as many petrochemicals in the production. Though it would still use some, even if that is just in the supply chain through things like diesel for trucks and ships. The chemicals they use (like pesticides) may be derived from petrochemicals, but even if they aren't they could be damaging to the environment in many other ways. So I think polyester could have the greatest emissions of the two.
I guess it could depend on the scale of production too. Like if we were to try and replace all polyester clothing with cotton, that could have a massive impact due to the amount of land and water needed to produce such quantities of cotton clothing and such. But at the same time, creating clothes out of plastic isn't going so well either.
Ultimately we will probably still have to have some diversity materials for sustainable clothing production. It will really come down to a balance of land use, water use, what uses the least amount of chemicals, and probably a lot of other considerations.
As other people have said, this seems sus. I work for a PV, inverter and battery manufacturer and that flier has left a lot of things unclear. Like what brand the modules are from? what is the kW rating of the PV array? what is the throughput of the inverter (both ac and dc)? how many batteries? what the kWh storage of each battery?
Even things like: what is the weatherproof (IP) rating on the inverter and battery, this will impact where you install it. What are the warranty periods on the solar modules and battery and inverter.
If you were to even consider going with that you should definitely call and seek clarification on some of the above questions.
If you are generally interested in getting some installed, a good resource to know is Solar Quotes (https://www.solarquotes.com.au/). It is run by an electrical engineer who doesn't seem to be a representative of any of the manufacturers, so it's pretty unbiased. He rates all the different manufacturers for each product too.