What happened

Shares of alternative energy fuel cell stocks Ballard Power Systems (BLDP -7.78%) and Bloom Energy (BE -4.12%) are off to the races in end-of-week trading Friday, with Ballard exploding 9% higher and Bloom coming along for a 3.2% ride (as of 12:55 p.m. EDT). At the same time, however, shares of their shared rival Plug Power (PLUG 0.51%) are plunging -- down 4.3%.

What's up with that?

A red arrow swoops up, while a blue arrow swoops down

Image source: Getty Images.

So what

Today looks to be a tale of two cities for fuel cell stocks. For Ballard, in particular, today is the best of times, with analysts at Roth Capital forecasting a "material catalyst" that should boost Ballard shares.

Specifically, reports TheFly.com, Roth believes that the Chinese government is about to reinstate its subsidies on the production of trucks and buses powered by hydrogen fuel cells. And because Ballard has deals in place to produce fuel cell buses in China, the company would be a logical beneficiary of such a move.

Roth sees this as providing both a "short- and medium-term revenue" boost to Ballard, but why is Bloom Energy stock going up, too? Bloom, as you know, focuses its efforts on stationary fuel cell sites to produce on-site power. However, because Bloom is also getting into the business of hydrogen gas production (to power both on-site and mobile fuel cells), it's possible that an uptick in fuel cell use of any sort in China could benefit Bloom as well.

Now what

While it might not be exactly the worst of times for Plug Power, it is the odd man out in today's race higher for fuel cell stocks.

And Plug's declining stock price today is rather odd. Plug produces both hydrogen for fuel cells and fuel cells that power vehicles, so the company actually has two ways to potentially benefit from Chinese subsidy largesse. But here's why Plug's rally short-circuited today:

Elsewhere on Wall Street, at the same time Roth was singing Ballard's praises, noted short-seller Citron Research was tweeting out a warning that Plug is likely to "miss 2020 revenue guidance by 40%." Reminding investors that Plug is a company that has "never generated a profit," Citron labeled Plug stock "the Anti-Tesla" -- overpriced, unprofitable, and run by a CEO who "has sold 95% of his [Plug stock]" already.  

Needless to say, Citron is not enthused with the stock, predicting that Plug shares will fall "back to $7." So far today, that's the direction they're heading in.