Used Solar Panels * https://www.bloomberg.com/opinion/articles/2021-08-25/used-solar-panels-are-powering-the-developing-world

Used solar panel block-chain for trade * https://asia.nikkei.com/Business/Technology/Blockchain-to-power-Marubeni-s-market-for-used-solar-panels-in-Japan

Used solar panel b2b market for reselling solar * https://energybin.com/

There's potentially a large market for reselling used solar panels now that solar has been around for a while.