The green energy company is down 97% from its high point in 2021. Here's what you should know before buying it today.Plug Power's (PLUG -6.99%) hydrogen fuel cell solutions could help usher in a newer, cleaner, sustainable energy source. With some estimates projecting that the green hydrogen energy market could grow to $30 billion by 2030, Plug Power's long-term opportunity is huge.However, despite being a leading hydrogen energy stock, the company has struggled mightily over the past several years. The sto ...